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-rw-r--r--sys-kernel/boest-v4.4.198/0018-block-introduce-the-BFQ-v7r11-I-O-sched-for-4.7.0.patch7089
1 files changed, 7089 insertions, 0 deletions
diff --git a/sys-kernel/boest-v4.4.198/0018-block-introduce-the-BFQ-v7r11-I-O-sched-for-4.7.0.patch b/sys-kernel/boest-v4.4.198/0018-block-introduce-the-BFQ-v7r11-I-O-sched-for-4.7.0.patch
new file mode 100644
index 00000000..83913f6f
--- /dev/null
+++ b/sys-kernel/boest-v4.4.198/0018-block-introduce-the-BFQ-v7r11-I-O-sched-for-4.7.0.patch
@@ -0,0 +1,7089 @@
+From 543df267778243321eddaf17f981a1cb758dd8e7 Mon Sep 17 00:00:00 2001
+From: Paolo Valente <paolo.valente@unimore.it>
+Date: Thu, 9 May 2013 19:10:02 +0200
+Subject: [PATCH 18/20] block: introduce the BFQ-v7r11 I/O sched for 4.7.0
+
+The general structure is borrowed from CFQ, as much of the code for
+handling I/O contexts. Over time, several useful features have been
+ported from CFQ as well (details in the changelog in README.BFQ). A
+(bfq_)queue is associated to each task doing I/O on a device, and each
+time a scheduling decision has to be made a queue is selected and served
+until it expires.
+
+ - Slices are given in the service domain: tasks are assigned
+ budgets, measured in number of sectors. Once got the disk, a task
+ must however consume its assigned budget within a configurable
+ maximum time (by default, the maximum possible value of the
+ budgets is automatically computed to comply with this timeout).
+ This allows the desired latency vs "throughput boosting" tradeoff
+ to be set.
+
+ - Budgets are scheduled according to a variant of WF2Q+, implemented
+ using an augmented rb-tree to take eligibility into account while
+ preserving an O(log N) overall complexity.
+
+ - A low-latency tunable is provided; if enabled, both interactive
+ and soft real-time applications are guaranteed a very low latency.
+
+ - Latency guarantees are preserved also in the presence of NCQ.
+
+ - Also with flash-based devices, a high throughput is achieved
+ while still preserving latency guarantees.
+
+ - BFQ features Early Queue Merge (EQM), a sort of fusion of the
+ cooperating-queue-merging and the preemption mechanisms present
+ in CFQ. EQM is in fact a unified mechanism that tries to get a
+ sequential read pattern, and hence a high throughput, with any
+ set of processes performing interleaved I/O over a contiguous
+ sequence of sectors.
+
+ - BFQ supports full hierarchical scheduling, exporting a cgroups
+ interface. Since each node has a full scheduler, each group can
+ be assigned its own weight.
+
+ - If the cgroups interface is not used, only I/O priorities can be
+ assigned to processes, with ioprio values mapped to weights
+ with the relation weight = IOPRIO_BE_NR - ioprio.
+
+ - ioprio classes are served in strict priority order, i.e., lower
+ priority queues are not served as long as there are higher
+ priority queues. Among queues in the same class the bandwidth is
+ distributed in proportion to the weight of each queue. A very
+ thin extra bandwidth is however guaranteed to the Idle class, to
+ prevent it from starving.
+
+Signed-off-by: Paolo Valente <paolo.valente@unimore.it>
+Signed-off-by: Arianna Avanzini <avanzini@google.com>
+---
+ block/Kconfig.iosched | 6 +-
+ block/bfq-cgroup.c | 1182 +++++++++++++
+ block/bfq-ioc.c | 36 +
+ block/bfq-iosched.c | 3754 +++++++++++++++++++++++++++++++++++++++++
+ block/bfq-sched.c | 1200 +++++++++++++
+ block/bfq.h | 801 +++++++++
+ 6 files changed, 6975 insertions(+), 4 deletions(-)
+
+diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
+index 0ee5f0f78b7b..f78cd1a9fc1b 100644
+--- a/block/Kconfig.iosched
++++ b/block/Kconfig.iosched
+@@ -51,14 +51,12 @@ config IOSCHED_BFQ
+ applications. If compiled built-in (saying Y here), BFQ can
+ be configured to support hierarchical scheduling.
+
+-config CGROUP_BFQIO
++config BFQ_GROUP_IOSCHED
+ bool "BFQ hierarchical scheduling support"
+ depends on CGROUPS && IOSCHED_BFQ=y
+ default n
+ ---help---
+- Enable hierarchical scheduling in BFQ, using the cgroups
+- filesystem interface. The name of the subsystem will be
+- bfqio.
++ Enable hierarchical scheduling in BFQ, using the blkio controller.
+
+ choice
+ prompt "Default I/O scheduler"
+diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
+new file mode 100644
+index 000000000000..8610cd65afa1
+--- /dev/null
++++ b/block/bfq-cgroup.c
+@@ -0,0 +1,1182 @@
++/*
++ * BFQ: CGROUPS support.
++ *
++ * Based on ideas and code from CFQ:
++ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
++ *
++ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
++ * Paolo Valente <paolo.valente@unimore.it>
++ *
++ * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
++ *
++ * Licensed under the GPL-2 as detailed in the accompanying COPYING.BFQ
++ * file.
++ */
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++
++/* bfqg stats flags */
++enum bfqg_stats_flags {
++ BFQG_stats_waiting = 0,
++ BFQG_stats_idling,
++ BFQG_stats_empty,
++};
++
++#define BFQG_FLAG_FNS(name) \
++static void bfqg_stats_mark_##name(struct bfqg_stats *stats) \
++{ \
++ stats->flags |= (1 << BFQG_stats_##name); \
++} \
++static void bfqg_stats_clear_##name(struct bfqg_stats *stats) \
++{ \
++ stats->flags &= ~(1 << BFQG_stats_##name); \
++} \
++static int bfqg_stats_##name(struct bfqg_stats *stats) \
++{ \
++ return (stats->flags & (1 << BFQG_stats_##name)) != 0; \
++} \
++
++BFQG_FLAG_FNS(waiting)
++BFQG_FLAG_FNS(idling)
++BFQG_FLAG_FNS(empty)
++#undef BFQG_FLAG_FNS
++
++/* This should be called with the queue_lock held. */
++static void bfqg_stats_update_group_wait_time(struct bfqg_stats *stats)
++{
++ unsigned long long now;
++
++ if (!bfqg_stats_waiting(stats))
++ return;
++
++ now = sched_clock();
++ if (time_after64(now, stats->start_group_wait_time))
++ blkg_stat_add(&stats->group_wait_time,
++ now - stats->start_group_wait_time);
++ bfqg_stats_clear_waiting(stats);
++}
++
++/* This should be called with the queue_lock held. */
++static void bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg,
++ struct bfq_group *curr_bfqg)
++{
++ struct bfqg_stats *stats = &bfqg->stats;
++
++ if (bfqg_stats_waiting(stats))
++ return;
++ if (bfqg == curr_bfqg)
++ return;
++ stats->start_group_wait_time = sched_clock();
++ bfqg_stats_mark_waiting(stats);
++}
++
++/* This should be called with the queue_lock held. */
++static void bfqg_stats_end_empty_time(struct bfqg_stats *stats)
++{
++ unsigned long long now;
++
++ if (!bfqg_stats_empty(stats))
++ return;
++
++ now = sched_clock();
++ if (time_after64(now, stats->start_empty_time))
++ blkg_stat_add(&stats->empty_time,
++ now - stats->start_empty_time);
++ bfqg_stats_clear_empty(stats);
++}
++
++static void bfqg_stats_update_dequeue(struct bfq_group *bfqg)
++{
++ blkg_stat_add(&bfqg->stats.dequeue, 1);
++}
++
++static void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg)
++{
++ struct bfqg_stats *stats = &bfqg->stats;
++
++ if (blkg_rwstat_total(&stats->queued))
++ return;
++
++ /*
++ * group is already marked empty. This can happen if bfqq got new
++ * request in parent group and moved to this group while being added
++ * to service tree. Just ignore the event and move on.
++ */
++ if (bfqg_stats_empty(stats))
++ return;
++
++ stats->start_empty_time = sched_clock();
++ bfqg_stats_mark_empty(stats);
++}
++
++static void bfqg_stats_update_idle_time(struct bfq_group *bfqg)
++{
++ struct bfqg_stats *stats = &bfqg->stats;
++
++ if (bfqg_stats_idling(stats)) {
++ unsigned long long now = sched_clock();
++
++ if (time_after64(now, stats->start_idle_time))
++ blkg_stat_add(&stats->idle_time,
++ now - stats->start_idle_time);
++ bfqg_stats_clear_idling(stats);
++ }
++}
++
++static void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg)
++{
++ struct bfqg_stats *stats = &bfqg->stats;
++
++ stats->start_idle_time = sched_clock();
++ bfqg_stats_mark_idling(stats);
++}
++
++static void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg)
++{
++ struct bfqg_stats *stats = &bfqg->stats;
++
++ blkg_stat_add(&stats->avg_queue_size_sum,
++ blkg_rwstat_total(&stats->queued));
++ blkg_stat_add(&stats->avg_queue_size_samples, 1);
++ bfqg_stats_update_group_wait_time(stats);
++}
++
++static struct blkcg_policy blkcg_policy_bfq;
++
++/*
++ * blk-cgroup policy-related handlers
++ * The following functions help in converting between blk-cgroup
++ * internal structures and BFQ-specific structures.
++ */
++
++static struct bfq_group *pd_to_bfqg(struct blkg_policy_data *pd)
++{
++ return pd ? container_of(pd, struct bfq_group, pd) : NULL;
++}
++
++static struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg)
++{
++ return pd_to_blkg(&bfqg->pd);
++}
++
++static struct bfq_group *blkg_to_bfqg(struct blkcg_gq *blkg)
++{
++ struct blkg_policy_data *pd = blkg_to_pd(blkg, &blkcg_policy_bfq);
++ BUG_ON(!pd);
++ return pd_to_bfqg(pd);
++}
++
++/*
++ * bfq_group handlers
++ * The following functions help in navigating the bfq_group hierarchy
++ * by allowing to find the parent of a bfq_group or the bfq_group
++ * associated to a bfq_queue.
++ */
++
++static struct bfq_group *bfqg_parent(struct bfq_group *bfqg)
++{
++ struct blkcg_gq *pblkg = bfqg_to_blkg(bfqg)->parent;
++
++ return pblkg ? blkg_to_bfqg(pblkg) : NULL;
++}
++
++static struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
++{
++ struct bfq_entity *group_entity = bfqq->entity.parent;
++
++ return group_entity ? container_of(group_entity, struct bfq_group,
++ entity) :
++ bfqq->bfqd->root_group;
++}
++
++/*
++ * The following two functions handle get and put of a bfq_group by
++ * wrapping the related blk-cgroup hooks.
++ */
++
++static void bfqg_get(struct bfq_group *bfqg)
++{
++ return blkg_get(bfqg_to_blkg(bfqg));
++}
++
++static void bfqg_put(struct bfq_group *bfqg)
++{
++ return blkg_put(bfqg_to_blkg(bfqg));
++}
++
++static void bfqg_stats_update_io_add(struct bfq_group *bfqg,
++ struct bfq_queue *bfqq,
++ int rw)
++{
++ blkg_rwstat_add(&bfqg->stats.queued, rw, 1);
++ bfqg_stats_end_empty_time(&bfqg->stats);
++ if (!(bfqq == ((struct bfq_data *)bfqg->bfqd)->in_service_queue))
++ bfqg_stats_set_start_group_wait_time(bfqg, bfqq_group(bfqq));
++}
++
++static void bfqg_stats_update_io_remove(struct bfq_group *bfqg, int rw)
++{
++ blkg_rwstat_add(&bfqg->stats.queued, rw, -1);
++}
++
++static void bfqg_stats_update_io_merged(struct bfq_group *bfqg, int rw)
++{
++ blkg_rwstat_add(&bfqg->stats.merged, rw, 1);
++}
++
++static void bfqg_stats_update_dispatch(struct bfq_group *bfqg,
++ uint64_t bytes, int rw)
++{
++ blkg_stat_add(&bfqg->stats.sectors, bytes >> 9);
++ blkg_rwstat_add(&bfqg->stats.serviced, rw, 1);
++ blkg_rwstat_add(&bfqg->stats.service_bytes, rw, bytes);
++}
++
++static void bfqg_stats_update_completion(struct bfq_group *bfqg,
++ uint64_t start_time, uint64_t io_start_time, int rw)
++{
++ struct bfqg_stats *stats = &bfqg->stats;
++ unsigned long long now = sched_clock();
++
++ if (time_after64(now, io_start_time))
++ blkg_rwstat_add(&stats->service_time, rw, now - io_start_time);
++ if (time_after64(io_start_time, start_time))
++ blkg_rwstat_add(&stats->wait_time, rw,
++ io_start_time - start_time);
++}
++
++/* @stats = 0 */
++static void bfqg_stats_reset(struct bfqg_stats *stats)
++{
++ if (!stats)
++ return;
++
++ /* queued stats shouldn't be cleared */
++ blkg_rwstat_reset(&stats->service_bytes);
++ blkg_rwstat_reset(&stats->serviced);
++ blkg_rwstat_reset(&stats->merged);
++ blkg_rwstat_reset(&stats->service_time);
++ blkg_rwstat_reset(&stats->wait_time);
++ blkg_stat_reset(&stats->time);
++ blkg_stat_reset(&stats->unaccounted_time);
++ blkg_stat_reset(&stats->avg_queue_size_sum);
++ blkg_stat_reset(&stats->avg_queue_size_samples);
++ blkg_stat_reset(&stats->dequeue);
++ blkg_stat_reset(&stats->group_wait_time);
++ blkg_stat_reset(&stats->idle_time);
++ blkg_stat_reset(&stats->empty_time);
++}
++
++/* @to += @from */
++static void bfqg_stats_merge(struct bfqg_stats *to, struct bfqg_stats *from)
++{
++ if (!to || !from)
++ return;
++
++ /* queued stats shouldn't be cleared */
++ blkg_rwstat_add_aux(&to->service_bytes, &from->service_bytes);
++ blkg_rwstat_add_aux(&to->serviced, &from->serviced);
++ blkg_rwstat_add_aux(&to->merged, &from->merged);
++ blkg_rwstat_add_aux(&to->service_time, &from->service_time);
++ blkg_rwstat_add_aux(&to->wait_time, &from->wait_time);
++ blkg_stat_add_aux(&from->time, &from->time);
++ blkg_stat_add_aux(&to->unaccounted_time, &from->unaccounted_time);
++ blkg_stat_add_aux(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
++ blkg_stat_add_aux(&to->avg_queue_size_samples, &from->avg_queue_size_samples);
++ blkg_stat_add_aux(&to->dequeue, &from->dequeue);
++ blkg_stat_add_aux(&to->group_wait_time, &from->group_wait_time);
++ blkg_stat_add_aux(&to->idle_time, &from->idle_time);
++ blkg_stat_add_aux(&to->empty_time, &from->empty_time);
++}
++
++/*
++ * Transfer @bfqg's stats to its parent's dead_stats so that the ancestors'
++ * recursive stats can still account for the amount used by this bfqg after
++ * it's gone.
++ */
++static void bfqg_stats_xfer_dead(struct bfq_group *bfqg)
++{
++ struct bfq_group *parent;
++
++ if (!bfqg) /* root_group */
++ return;
++
++ parent = bfqg_parent(bfqg);
++
++ lockdep_assert_held(bfqg_to_blkg(bfqg)->q->queue_lock);
++
++ if (unlikely(!parent))
++ return;
++
++ bfqg_stats_merge(&parent->dead_stats, &bfqg->stats);
++ bfqg_stats_merge(&parent->dead_stats, &bfqg->dead_stats);
++ bfqg_stats_reset(&bfqg->stats);
++ bfqg_stats_reset(&bfqg->dead_stats);
++}
++
++static void bfq_init_entity(struct bfq_entity *entity,
++ struct bfq_group *bfqg)
++{
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++
++ entity->weight = entity->new_weight;
++ entity->orig_weight = entity->new_weight;
++ if (bfqq) {
++ bfqq->ioprio = bfqq->new_ioprio;
++ bfqq->ioprio_class = bfqq->new_ioprio_class;
++ bfqg_get(bfqg);
++ }
++ entity->parent = bfqg->my_entity;
++ entity->sched_data = &bfqg->sched_data;
++}
++
++static void bfqg_stats_exit(struct bfqg_stats *stats)
++{
++ blkg_rwstat_exit(&stats->service_bytes);
++ blkg_rwstat_exit(&stats->serviced);
++ blkg_rwstat_exit(&stats->merged);
++ blkg_rwstat_exit(&stats->service_time);
++ blkg_rwstat_exit(&stats->wait_time);
++ blkg_rwstat_exit(&stats->queued);
++ blkg_stat_exit(&stats->sectors);
++ blkg_stat_exit(&stats->time);
++ blkg_stat_exit(&stats->unaccounted_time);
++ blkg_stat_exit(&stats->avg_queue_size_sum);
++ blkg_stat_exit(&stats->avg_queue_size_samples);
++ blkg_stat_exit(&stats->dequeue);
++ blkg_stat_exit(&stats->group_wait_time);
++ blkg_stat_exit(&stats->idle_time);
++ blkg_stat_exit(&stats->empty_time);
++}
++
++static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
++{
++ if (blkg_rwstat_init(&stats->service_bytes, gfp) ||
++ blkg_rwstat_init(&stats->serviced, gfp) ||
++ blkg_rwstat_init(&stats->merged, gfp) ||
++ blkg_rwstat_init(&stats->service_time, gfp) ||
++ blkg_rwstat_init(&stats->wait_time, gfp) ||
++ blkg_rwstat_init(&stats->queued, gfp) ||
++ blkg_stat_init(&stats->sectors, gfp) ||
++ blkg_stat_init(&stats->time, gfp) ||
++ blkg_stat_init(&stats->unaccounted_time, gfp) ||
++ blkg_stat_init(&stats->avg_queue_size_sum, gfp) ||
++ blkg_stat_init(&stats->avg_queue_size_samples, gfp) ||
++ blkg_stat_init(&stats->dequeue, gfp) ||
++ blkg_stat_init(&stats->group_wait_time, gfp) ||
++ blkg_stat_init(&stats->idle_time, gfp) ||
++ blkg_stat_init(&stats->empty_time, gfp)) {
++ bfqg_stats_exit(stats);
++ return -ENOMEM;
++ }
++
++ return 0;
++}
++
++static struct bfq_group_data *cpd_to_bfqgd(struct blkcg_policy_data *cpd)
++ {
++ return cpd ? container_of(cpd, struct bfq_group_data, pd) : NULL;
++ }
++
++static struct bfq_group_data *blkcg_to_bfqgd(struct blkcg *blkcg)
++{
++ return cpd_to_bfqgd(blkcg_to_cpd(blkcg, &blkcg_policy_bfq));
++}
++
++static void bfq_cpd_init(struct blkcg_policy_data *cpd)
++{
++ struct bfq_group_data *d = cpd_to_bfqgd(cpd);
++
++ d->weight = BFQ_DEFAULT_GRP_WEIGHT;
++}
++
++static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, int node)
++{
++ struct bfq_group *bfqg;
++
++ bfqg = kzalloc_node(sizeof(*bfqg), gfp, node);
++ if (!bfqg)
++ return NULL;
++
++ if (bfqg_stats_init(&bfqg->stats, gfp) ||
++ bfqg_stats_init(&bfqg->dead_stats, gfp)) {
++ kfree(bfqg);
++ return NULL;
++ }
++
++ return &bfqg->pd;
++}
++
++static void bfq_group_set_parent(struct bfq_group *bfqg,
++ struct bfq_group *parent)
++{
++ struct bfq_entity *entity;
++
++ BUG_ON(!parent);
++ BUG_ON(!bfqg);
++ BUG_ON(bfqg == parent);
++
++ entity = &bfqg->entity;
++ entity->parent = parent->my_entity;
++ entity->sched_data = &parent->sched_data;
++}
++
++static void bfq_pd_init(struct blkg_policy_data *pd)
++{
++ struct blkcg_gq *blkg = pd_to_blkg(pd);
++ struct bfq_group *bfqg = blkg_to_bfqg(blkg);
++ struct bfq_data *bfqd = blkg->q->elevator->elevator_data;
++ struct bfq_entity *entity = &bfqg->entity;
++ struct bfq_group_data *d = blkcg_to_bfqgd(blkg->blkcg);
++
++ entity->orig_weight = entity->weight = entity->new_weight = d->weight;
++ entity->my_sched_data = &bfqg->sched_data;
++ bfqg->my_entity = entity; /*
++ * the root_group's will be set to NULL
++ * in bfq_init_queue()
++ */
++ bfqg->bfqd = bfqd;
++ bfqg->active_entities = 0;
++}
++
++static void bfq_pd_free(struct blkg_policy_data *pd)
++{
++ struct bfq_group *bfqg = pd_to_bfqg(pd);
++
++ bfqg_stats_exit(&bfqg->stats);
++ bfqg_stats_exit(&bfqg->dead_stats);
++
++ return kfree(bfqg);
++}
++
++/* offset delta from bfqg->stats to bfqg->dead_stats */
++static const int dead_stats_off_delta = offsetof(struct bfq_group, dead_stats) -
++ offsetof(struct bfq_group, stats);
++
++/* to be used by recursive prfill, sums live and dead stats recursively */
++static u64 bfqg_stat_pd_recursive_sum(struct blkg_policy_data *pd, int off)
++{
++ u64 sum = 0;
++
++ sum += blkg_stat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_bfq, off);
++ sum += blkg_stat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_bfq,
++ off + dead_stats_off_delta);
++ return sum;
++}
++
++/* to be used by recursive prfill, sums live and dead rwstats recursively */
++static struct blkg_rwstat bfqg_rwstat_pd_recursive_sum(struct blkg_policy_data *pd,
++ int off)
++{
++ struct blkg_rwstat a, b;
++
++ a = blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_bfq, off);
++ b = blkg_rwstat_recursive_sum(pd_to_blkg(pd), &blkcg_policy_bfq,
++ off + dead_stats_off_delta);
++ blkg_rwstat_add_aux(&a, &b);
++ return a;
++}
++
++static void bfq_pd_reset_stats(struct blkg_policy_data *pd)
++{
++ struct bfq_group *bfqg = pd_to_bfqg(pd);
++
++ bfqg_stats_reset(&bfqg->stats);
++ bfqg_stats_reset(&bfqg->dead_stats);
++}
++
++static struct bfq_group *bfq_find_alloc_group(struct bfq_data *bfqd,
++ struct blkcg *blkcg)
++{
++ struct request_queue *q = bfqd->queue;
++ struct bfq_group *bfqg = NULL, *parent;
++ struct bfq_entity *entity = NULL;
++
++ assert_spin_locked(bfqd->queue->queue_lock);
++
++ /* avoid lookup for the common case where there's no blkcg */
++ if (blkcg == &blkcg_root) {
++ bfqg = bfqd->root_group;
++ } else {
++ struct blkcg_gq *blkg;
++
++ blkg = blkg_lookup_create(blkcg, q);
++ if (!IS_ERR(blkg))
++ bfqg = blkg_to_bfqg(blkg);
++ else /* fallback to root_group */
++ bfqg = bfqd->root_group;
++ }
++
++ BUG_ON(!bfqg);
++
++ /*
++ * Update chain of bfq_groups as we might be handling a leaf group
++ * which, along with some of its relatives, has not been hooked yet
++ * to the private hierarchy of BFQ.
++ */
++ entity = &bfqg->entity;
++ for_each_entity(entity) {
++ bfqg = container_of(entity, struct bfq_group, entity);
++ BUG_ON(!bfqg);
++ if (bfqg != bfqd->root_group) {
++ parent = bfqg_parent(bfqg);
++ if (!parent)
++ parent = bfqd->root_group;
++ BUG_ON(!parent);
++ bfq_group_set_parent(bfqg, parent);
++ }
++ }
++
++ return bfqg;
++}
++
++/**
++ * bfq_bfqq_move - migrate @bfqq to @bfqg.
++ * @bfqd: queue descriptor.
++ * @bfqq: the queue to move.
++ * @entity: @bfqq's entity.
++ * @bfqg: the group to move to.
++ *
++ * Move @bfqq to @bfqg, deactivating it from its old group and reactivating
++ * it on the new one. Avoid putting the entity on the old group idle tree.
++ *
++ * Must be called under the queue lock; the cgroup owning @bfqg must
++ * not disappear (by now this just means that we are called under
++ * rcu_read_lock()).
++ */
++static void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
++ struct bfq_entity *entity, struct bfq_group *bfqg)
++{
++ int busy, resume;
++
++ busy = bfq_bfqq_busy(bfqq);
++ resume = !RB_EMPTY_ROOT(&bfqq->sort_list);
++
++ BUG_ON(resume && !entity->on_st);
++ BUG_ON(busy && !resume && entity->on_st &&
++ bfqq != bfqd->in_service_queue);
++
++ if (busy) {
++ BUG_ON(atomic_read(&bfqq->ref) < 2);
++
++ if (!resume)
++ bfq_del_bfqq_busy(bfqd, bfqq, 0);
++ else
++ bfq_deactivate_bfqq(bfqd, bfqq, 0);
++ } else if (entity->on_st)
++ bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
++ bfqg_put(bfqq_group(bfqq));
++
++ /*
++ * Here we use a reference to bfqg. We don't need a refcounter
++ * as the cgroup reference will not be dropped, so that its
++ * destroy() callback will not be invoked.
++ */
++ entity->parent = bfqg->my_entity;
++ entity->sched_data = &bfqg->sched_data;
++ bfqg_get(bfqg);
++
++ if (busy) {
++ if (resume)
++ bfq_activate_bfqq(bfqd, bfqq);
++ }
++
++ if (!bfqd->in_service_queue && !bfqd->rq_in_driver)
++ bfq_schedule_dispatch(bfqd);
++}
++
++/**
++ * __bfq_bic_change_cgroup - move @bic to @cgroup.
++ * @bfqd: the queue descriptor.
++ * @bic: the bic to move.
++ * @blkcg: the blk-cgroup to move to.
++ *
++ * Move bic to blkcg, assuming that bfqd->queue is locked; the caller
++ * has to make sure that the reference to cgroup is valid across the call.
++ *
++ * NOTE: an alternative approach might have been to store the current
++ * cgroup in bfqq and getting a reference to it, reducing the lookup
++ * time here, at the price of slightly more complex code.
++ */
++static struct bfq_group *__bfq_bic_change_cgroup(struct bfq_data *bfqd,
++ struct bfq_io_cq *bic,
++ struct blkcg *blkcg)
++{
++ struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0);
++ struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1);
++ struct bfq_group *bfqg;
++ struct bfq_entity *entity;
++
++ lockdep_assert_held(bfqd->queue->queue_lock);
++
++ bfqg = bfq_find_alloc_group(bfqd, blkcg);
++ if (async_bfqq) {
++ entity = &async_bfqq->entity;
++
++ if (entity->sched_data != &bfqg->sched_data) {
++ bic_set_bfqq(bic, NULL, 0);
++ bfq_log_bfqq(bfqd, async_bfqq,
++ "bic_change_group: %p %d",
++ async_bfqq, atomic_read(&async_bfqq->ref));
++ bfq_put_queue(async_bfqq);
++ }
++ }
++
++ if (sync_bfqq) {
++ entity = &sync_bfqq->entity;
++ if (entity->sched_data != &bfqg->sched_data)
++ bfq_bfqq_move(bfqd, sync_bfqq, entity, bfqg);
++ }
++
++ return bfqg;
++}
++
++static void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
++{
++ struct bfq_data *bfqd = bic_to_bfqd(bic);
++ struct blkcg *blkcg;
++ struct bfq_group *bfqg = NULL;
++ uint64_t id;
++
++ rcu_read_lock();
++ blkcg = bio_blkcg(bio);
++ id = blkcg->css.serial_nr;
++ rcu_read_unlock();
++
++ /*
++ * Check whether blkcg has changed. The condition may trigger
++ * spuriously on a newly created cic but there's no harm.
++ */
++ if (unlikely(!bfqd) || likely(bic->blkcg_id == id))
++ return;
++
++ bfqg = __bfq_bic_change_cgroup(bfqd, bic, blkcg);
++ BUG_ON(!bfqg);
++ bic->blkcg_id = id;
++}
++
++/**
++ * bfq_flush_idle_tree - deactivate any entity on the idle tree of @st.
++ * @st: the service tree being flushed.
++ */
++static void bfq_flush_idle_tree(struct bfq_service_tree *st)
++{
++ struct bfq_entity *entity = st->first_idle;
++
++ for (; entity ; entity = st->first_idle)
++ __bfq_deactivate_entity(entity, 0);
++}
++
++/**
++ * bfq_reparent_leaf_entity - move leaf entity to the root_group.
++ * @bfqd: the device data structure with the root group.
++ * @entity: the entity to move.
++ */
++static void bfq_reparent_leaf_entity(struct bfq_data *bfqd,
++ struct bfq_entity *entity)
++{
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++
++ BUG_ON(!bfqq);
++ bfq_bfqq_move(bfqd, bfqq, entity, bfqd->root_group);
++ return;
++}
++
++/**
++ * bfq_reparent_active_entities - move to the root group all active
++ * entities.
++ * @bfqd: the device data structure with the root group.
++ * @bfqg: the group to move from.
++ * @st: the service tree with the entities.
++ *
++ * Needs queue_lock to be taken and reference to be valid over the call.
++ */
++static void bfq_reparent_active_entities(struct bfq_data *bfqd,
++ struct bfq_group *bfqg,
++ struct bfq_service_tree *st)
++{
++ struct rb_root *active = &st->active;
++ struct bfq_entity *entity = NULL;
++
++ if (!RB_EMPTY_ROOT(&st->active))
++ entity = bfq_entity_of(rb_first(active));
++
++ for (; entity ; entity = bfq_entity_of(rb_first(active)))
++ bfq_reparent_leaf_entity(bfqd, entity);
++
++ if (bfqg->sched_data.in_service_entity)
++ bfq_reparent_leaf_entity(bfqd,
++ bfqg->sched_data.in_service_entity);
++
++ return;
++}
++
++/**
++ * bfq_destroy_group - destroy @bfqg.
++ * @bfqg: the group being destroyed.
++ *
++ * Destroy @bfqg, making sure that it is not referenced from its parent.
++ * blkio already grabs the queue_lock for us, so no need to use RCU-based magic
++ */
++static void bfq_pd_offline(struct blkg_policy_data *pd)
++{
++ struct bfq_service_tree *st;
++ struct bfq_group *bfqg;
++ struct bfq_data *bfqd;
++ struct bfq_entity *entity;
++ int i;
++
++ BUG_ON(!pd);
++ bfqg = pd_to_bfqg(pd);
++ BUG_ON(!bfqg);
++ bfqd = bfqg->bfqd;
++ BUG_ON(bfqd && !bfqd->root_group);
++
++ entity = bfqg->my_entity;
++
++ if (!entity) /* root group */
++ return;
++
++ /*
++ * Empty all service_trees belonging to this group before
++ * deactivating the group itself.
++ */
++ for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) {
++ BUG_ON(!bfqg->sched_data.service_tree);
++ st = bfqg->sched_data.service_tree + i;
++ /*
++ * The idle tree may still contain bfq_queues belonging
++ * to exited task because they never migrated to a different
++ * cgroup from the one being destroyed now. No one else
++ * can access them so it's safe to act without any lock.
++ */
++ bfq_flush_idle_tree(st);
++
++ /*
++ * It may happen that some queues are still active
++ * (busy) upon group destruction (if the corresponding
++ * processes have been forced to terminate). We move
++ * all the leaf entities corresponding to these queues
++ * to the root_group.
++ * Also, it may happen that the group has an entity
++ * in service, which is disconnected from the active
++ * tree: it must be moved, too.
++ * There is no need to put the sync queues, as the
++ * scheduler has taken no reference.
++ */
++ bfq_reparent_active_entities(bfqd, bfqg, st);
++ BUG_ON(!RB_EMPTY_ROOT(&st->active));
++ BUG_ON(!RB_EMPTY_ROOT(&st->idle));
++ }
++ BUG_ON(bfqg->sched_data.next_in_service);
++ BUG_ON(bfqg->sched_data.in_service_entity);
++
++ __bfq_deactivate_entity(entity, 0);
++ bfq_put_async_queues(bfqd, bfqg);
++ BUG_ON(entity->tree);
++
++ bfqg_stats_xfer_dead(bfqg);
++}
++
++static void bfq_end_wr_async(struct bfq_data *bfqd)
++{
++ struct blkcg_gq *blkg;
++
++ list_for_each_entry(blkg, &bfqd->queue->blkg_list, q_node) {
++ struct bfq_group *bfqg = blkg_to_bfqg(blkg);
++
++ bfq_end_wr_async_queues(bfqd, bfqg);
++ }
++ bfq_end_wr_async_queues(bfqd, bfqd->root_group);
++}
++
++static u64 bfqio_cgroup_weight_read(struct cgroup_subsys_state *css,
++ struct cftype *cftype)
++{
++ struct blkcg *blkcg = css_to_blkcg(css);
++ struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
++ int ret = -EINVAL;
++
++ spin_lock_irq(&blkcg->lock);
++ ret = bfqgd->weight;
++ spin_unlock_irq(&blkcg->lock);
++
++ return ret;
++}
++
++static int bfqio_cgroup_weight_read_dfl(struct seq_file *sf, void *v)
++{
++ struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
++ struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
++
++ spin_lock_irq(&blkcg->lock);
++ seq_printf(sf, "%u\n", bfqgd->weight);
++ spin_unlock_irq(&blkcg->lock);
++
++ return 0;
++}
++
++static int bfqio_cgroup_weight_write(struct cgroup_subsys_state *css,
++ struct cftype *cftype,
++ u64 val)
++{
++ struct blkcg *blkcg = css_to_blkcg(css);
++ struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
++ struct blkcg_gq *blkg;
++ int ret = -EINVAL;
++
++ if (val < BFQ_MIN_WEIGHT || val > BFQ_MAX_WEIGHT)
++ return ret;
++
++ ret = 0;
++ spin_lock_irq(&blkcg->lock);
++ bfqgd->weight = (unsigned short)val;
++ hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
++ struct bfq_group *bfqg = blkg_to_bfqg(blkg);
++ if (!bfqg)
++ continue;
++ /*
++ * Setting the prio_changed flag of the entity
++ * to 1 with new_weight == weight would re-set
++ * the value of the weight to its ioprio mapping.
++ * Set the flag only if necessary.
++ */
++ if ((unsigned short)val != bfqg->entity.new_weight) {
++ bfqg->entity.new_weight = (unsigned short)val;
++ /*
++ * Make sure that the above new value has been
++ * stored in bfqg->entity.new_weight before
++ * setting the prio_changed flag. In fact,
++ * this flag may be read asynchronously (in
++ * critical sections protected by a different
++ * lock than that held here), and finding this
++ * flag set may cause the execution of the code
++ * for updating parameters whose value may
++ * depend also on bfqg->entity.new_weight (in
++ * __bfq_entity_update_weight_prio).
++ * This barrier makes sure that the new value
++ * of bfqg->entity.new_weight is correctly
++ * seen in that code.
++ */
++ smp_wmb();
++ bfqg->entity.prio_changed = 1;
++ }
++ }
++ spin_unlock_irq(&blkcg->lock);
++
++ return ret;
++}
++
++static ssize_t bfqio_cgroup_weight_write_dfl(struct kernfs_open_file *of,
++ char *buf, size_t nbytes,
++ loff_t off)
++{
++ /* First unsigned long found in the file is used */
++ return bfqio_cgroup_weight_write(of_css(of), NULL,
++ simple_strtoull(strim(buf), NULL, 0));
++}
++
++static int bfqg_print_stat(struct seq_file *sf, void *v)
++{
++ blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_stat,
++ &blkcg_policy_bfq, seq_cft(sf)->private, false);
++ return 0;
++}
++
++static int bfqg_print_rwstat(struct seq_file *sf, void *v)
++{
++ blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_rwstat,
++ &blkcg_policy_bfq, seq_cft(sf)->private, true);
++ return 0;
++}
++
++static u64 bfqg_prfill_stat_recursive(struct seq_file *sf,
++ struct blkg_policy_data *pd, int off)
++{
++ u64 sum = bfqg_stat_pd_recursive_sum(pd, off);
++
++ return __blkg_prfill_u64(sf, pd, sum);
++}
++
++static u64 bfqg_prfill_rwstat_recursive(struct seq_file *sf,
++ struct blkg_policy_data *pd, int off)
++{
++ struct blkg_rwstat sum = bfqg_rwstat_pd_recursive_sum(pd, off);
++
++ return __blkg_prfill_rwstat(sf, pd, &sum);
++}
++
++static int bfqg_print_stat_recursive(struct seq_file *sf, void *v)
++{
++ blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
++ bfqg_prfill_stat_recursive, &blkcg_policy_bfq,
++ seq_cft(sf)->private, false);
++ return 0;
++}
++
++static int bfqg_print_rwstat_recursive(struct seq_file *sf, void *v)
++{
++ blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
++ bfqg_prfill_rwstat_recursive, &blkcg_policy_bfq,
++ seq_cft(sf)->private, true);
++ return 0;
++}
++
++static u64 bfqg_prfill_avg_queue_size(struct seq_file *sf,
++ struct blkg_policy_data *pd, int off)
++{
++ struct bfq_group *bfqg = pd_to_bfqg(pd);
++ u64 samples = blkg_stat_read(&bfqg->stats.avg_queue_size_samples);
++ u64 v = 0;
++
++ if (samples) {
++ v = blkg_stat_read(&bfqg->stats.avg_queue_size_sum);
++ v = div64_u64(v, samples);
++ }
++ __blkg_prfill_u64(sf, pd, v);
++ return 0;
++}
++
++/* print avg_queue_size */
++static int bfqg_print_avg_queue_size(struct seq_file *sf, void *v)
++{
++ blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
++ bfqg_prfill_avg_queue_size, &blkcg_policy_bfq,
++ 0, false);
++ return 0;
++}
++
++static struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
++{
++ int ret;
++
++ ret = blkcg_activate_policy(bfqd->queue, &blkcg_policy_bfq);
++ if (ret)
++ return NULL;
++
++ return blkg_to_bfqg(bfqd->queue->root_blkg);
++}
++
++static struct blkcg_policy_data *bfq_cpd_alloc(gfp_t gfp)
++{
++ struct bfq_group_data *bgd;
++
++ bgd = kzalloc(sizeof(*bgd), GFP_KERNEL);
++ if (!bgd)
++ return NULL;
++ return &bgd->pd;
++}
++
++static void bfq_cpd_free(struct blkcg_policy_data *cpd)
++{
++ kfree(cpd_to_bfqgd(cpd));
++}
++
++static struct cftype bfqio_files_dfl[] = {
++ {
++ .name = "weight",
++ .flags = CFTYPE_NOT_ON_ROOT,
++ .seq_show = bfqio_cgroup_weight_read_dfl,
++ .write = bfqio_cgroup_weight_write_dfl,
++ },
++ {} /* terminate */
++};
++
++static struct cftype bfqio_files[] = {
++ {
++ .name = "bfq.weight",
++ .read_u64 = bfqio_cgroup_weight_read,
++ .write_u64 = bfqio_cgroup_weight_write,
++ },
++ /* statistics, cover only the tasks in the bfqg */
++ {
++ .name = "bfq.time",
++ .private = offsetof(struct bfq_group, stats.time),
++ .seq_show = bfqg_print_stat,
++ },
++ {
++ .name = "bfq.sectors",
++ .private = offsetof(struct bfq_group, stats.sectors),
++ .seq_show = bfqg_print_stat,
++ },
++ {
++ .name = "bfq.io_service_bytes",
++ .private = offsetof(struct bfq_group, stats.service_bytes),
++ .seq_show = bfqg_print_rwstat,
++ },
++ {
++ .name = "bfq.io_serviced",
++ .private = offsetof(struct bfq_group, stats.serviced),
++ .seq_show = bfqg_print_rwstat,
++ },
++ {
++ .name = "bfq.io_service_time",
++ .private = offsetof(struct bfq_group, stats.service_time),
++ .seq_show = bfqg_print_rwstat,
++ },
++ {
++ .name = "bfq.io_wait_time",
++ .private = offsetof(struct bfq_group, stats.wait_time),
++ .seq_show = bfqg_print_rwstat,
++ },
++ {
++ .name = "bfq.io_merged",
++ .private = offsetof(struct bfq_group, stats.merged),
++ .seq_show = bfqg_print_rwstat,
++ },
++ {
++ .name = "bfq.io_queued",
++ .private = offsetof(struct bfq_group, stats.queued),
++ .seq_show = bfqg_print_rwstat,
++ },
++
++ /* the same statictics which cover the bfqg and its descendants */
++ {
++ .name = "bfq.time_recursive",
++ .private = offsetof(struct bfq_group, stats.time),
++ .seq_show = bfqg_print_stat_recursive,
++ },
++ {
++ .name = "bfq.sectors_recursive",
++ .private = offsetof(struct bfq_group, stats.sectors),
++ .seq_show = bfqg_print_stat_recursive,
++ },
++ {
++ .name = "bfq.io_service_bytes_recursive",
++ .private = offsetof(struct bfq_group, stats.service_bytes),
++ .seq_show = bfqg_print_rwstat_recursive,
++ },
++ {
++ .name = "bfq.io_serviced_recursive",
++ .private = offsetof(struct bfq_group, stats.serviced),
++ .seq_show = bfqg_print_rwstat_recursive,
++ },
++ {
++ .name = "bfq.io_service_time_recursive",
++ .private = offsetof(struct bfq_group, stats.service_time),
++ .seq_show = bfqg_print_rwstat_recursive,
++ },
++ {
++ .name = "bfq.io_wait_time_recursive",
++ .private = offsetof(struct bfq_group, stats.wait_time),
++ .seq_show = bfqg_print_rwstat_recursive,
++ },
++ {
++ .name = "bfq.io_merged_recursive",
++ .private = offsetof(struct bfq_group, stats.merged),
++ .seq_show = bfqg_print_rwstat_recursive,
++ },
++ {
++ .name = "bfq.io_queued_recursive",
++ .private = offsetof(struct bfq_group, stats.queued),
++ .seq_show = bfqg_print_rwstat_recursive,
++ },
++ {
++ .name = "bfq.avg_queue_size",
++ .seq_show = bfqg_print_avg_queue_size,
++ },
++ {
++ .name = "bfq.group_wait_time",
++ .private = offsetof(struct bfq_group, stats.group_wait_time),
++ .seq_show = bfqg_print_stat,
++ },
++ {
++ .name = "bfq.idle_time",
++ .private = offsetof(struct bfq_group, stats.idle_time),
++ .seq_show = bfqg_print_stat,
++ },
++ {
++ .name = "bfq.empty_time",
++ .private = offsetof(struct bfq_group, stats.empty_time),
++ .seq_show = bfqg_print_stat,
++ },
++ {
++ .name = "bfq.dequeue",
++ .private = offsetof(struct bfq_group, stats.dequeue),
++ .seq_show = bfqg_print_stat,
++ },
++ {
++ .name = "bfq.unaccounted_time",
++ .private = offsetof(struct bfq_group, stats.unaccounted_time),
++ .seq_show = bfqg_print_stat,
++ },
++ { } /* terminate */
++};
++
++static struct blkcg_policy blkcg_policy_bfq = {
++ .dfl_cftypes = bfqio_files_dfl,
++ .legacy_cftypes = bfqio_files,
++
++ .pd_alloc_fn = bfq_pd_alloc,
++ .pd_init_fn = bfq_pd_init,
++ .pd_offline_fn = bfq_pd_offline,
++ .pd_free_fn = bfq_pd_free,
++ .pd_reset_stats_fn = bfq_pd_reset_stats,
++
++ .cpd_alloc_fn = bfq_cpd_alloc,
++ .cpd_init_fn = bfq_cpd_init,
++ .cpd_bind_fn = bfq_cpd_init,
++ .cpd_free_fn = bfq_cpd_free,
++
++};
++
++#else
++
++static void bfq_init_entity(struct bfq_entity *entity,
++ struct bfq_group *bfqg)
++{
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++ entity->weight = entity->new_weight;
++ entity->orig_weight = entity->new_weight;
++ if (bfqq) {
++ bfqq->ioprio = bfqq->new_ioprio;
++ bfqq->ioprio_class = bfqq->new_ioprio_class;
++ }
++ entity->sched_data = &bfqg->sched_data;
++}
++
++static struct bfq_group *
++bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
++{
++ struct bfq_data *bfqd = bic_to_bfqd(bic);
++ return bfqd->root_group;
++}
++
++static void bfq_bfqq_move(struct bfq_data *bfqd,
++ struct bfq_queue *bfqq,
++ struct bfq_entity *entity,
++ struct bfq_group *bfqg)
++{
++}
++
++static void bfq_end_wr_async(struct bfq_data *bfqd)
++{
++ bfq_end_wr_async_queues(bfqd, bfqd->root_group);
++}
++
++static void bfq_disconnect_groups(struct bfq_data *bfqd)
++{
++ bfq_put_async_queues(bfqd, bfqd->root_group);
++}
++
++static struct bfq_group *bfq_find_alloc_group(struct bfq_data *bfqd,
++ struct blkcg *blkcg)
++{
++ return bfqd->root_group;
++}
++
++static struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
++{
++ struct bfq_group *bfqg;
++ int i;
++
++ bfqg = kmalloc_node(sizeof(*bfqg), GFP_KERNEL | __GFP_ZERO, node);
++ if (!bfqg)
++ return NULL;
++
++ for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
++ bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
++
++ return bfqg;
++}
++#endif
+diff --git a/block/bfq-ioc.c b/block/bfq-ioc.c
+new file mode 100644
+index 000000000000..fb7bb8f08b75
+--- /dev/null
++++ b/block/bfq-ioc.c
+@@ -0,0 +1,36 @@
++/*
++ * BFQ: I/O context handling.
++ *
++ * Based on ideas and code from CFQ:
++ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
++ *
++ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
++ * Paolo Valente <paolo.valente@unimore.it>
++ *
++ * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
++ */
++
++/**
++ * icq_to_bic - convert iocontext queue structure to bfq_io_cq.
++ * @icq: the iocontext queue.
++ */
++static struct bfq_io_cq *icq_to_bic(struct io_cq *icq)
++{
++ /* bic->icq is the first member, %NULL will convert to %NULL */
++ return container_of(icq, struct bfq_io_cq, icq);
++}
++
++/**
++ * bfq_bic_lookup - search into @ioc a bic associated to @bfqd.
++ * @bfqd: the lookup key.
++ * @ioc: the io_context of the process doing I/O.
++ *
++ * Queue lock must be held.
++ */
++static struct bfq_io_cq *bfq_bic_lookup(struct bfq_data *bfqd,
++ struct io_context *ioc)
++{
++ if (ioc)
++ return icq_to_bic(ioc_lookup_icq(ioc, bfqd->queue));
++ return NULL;
++}
+diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
+new file mode 100644
+index 000000000000..f9787a65bb93
+--- /dev/null
++++ b/block/bfq-iosched.c
+@@ -0,0 +1,3754 @@
++/*
++ * Budget Fair Queueing (BFQ) disk scheduler.
++ *
++ * Based on ideas and code from CFQ:
++ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
++ *
++ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
++ * Paolo Valente <paolo.valente@unimore.it>
++ *
++ * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
++ *
++ * Licensed under the GPL-2 as detailed in the accompanying COPYING.BFQ
++ * file.
++ *
++ * BFQ is a proportional-share storage-I/O scheduling algorithm based on
++ * the slice-by-slice service scheme of CFQ. But BFQ assigns budgets,
++ * measured in number of sectors, to processes instead of time slices. The
++ * device is not granted to the in-service process for a given time slice,
++ * but until it has exhausted its assigned budget. This change from the time
++ * to the service domain allows BFQ to distribute the device throughput
++ * among processes as desired, without any distortion due to ZBR, workload
++ * fluctuations or other factors. BFQ uses an ad hoc internal scheduler,
++ * called B-WF2Q+, to schedule processes according to their budgets. More
++ * precisely, BFQ schedules queues associated to processes. Thanks to the
++ * accurate policy of B-WF2Q+, BFQ can afford to assign high budgets to
++ * I/O-bound processes issuing sequential requests (to boost the
++ * throughput), and yet guarantee a low latency to interactive and soft
++ * real-time applications.
++ *
++ * BFQ is described in [1], where also a reference to the initial, more
++ * theoretical paper on BFQ can be found. The interested reader can find
++ * in the latter paper full details on the main algorithm, as well as
++ * formulas of the guarantees and formal proofs of all the properties.
++ * With respect to the version of BFQ presented in these papers, this
++ * implementation adds a few more heuristics, such as the one that
++ * guarantees a low latency to soft real-time applications, and a
++ * hierarchical extension based on H-WF2Q+.
++ *
++ * B-WF2Q+ is based on WF2Q+, that is described in [2], together with
++ * H-WF2Q+, while the augmented tree used to implement B-WF2Q+ with O(log N)
++ * complexity derives from the one introduced with EEVDF in [3].
++ *
++ * [1] P. Valente and M. Andreolini, ``Improving Application Responsiveness
++ * with the BFQ Disk I/O Scheduler'',
++ * Proceedings of the 5th Annual International Systems and Storage
++ * Conference (SYSTOR '12), June 2012.
++ *
++ * http://algogroup.unimo.it/people/paolo/disk_sched/bf1-v1-suite-results.pdf
++ *
++ * [2] Jon C.R. Bennett and H. Zhang, ``Hierarchical Packet Fair Queueing
++ * Algorithms,'' IEEE/ACM Transactions on Networking, 5(5):675-689,
++ * Oct 1997.
++ *
++ * http://www.cs.cmu.edu/~hzhang/papers/TON-97-Oct.ps.gz
++ *
++ * [3] I. Stoica and H. Abdel-Wahab, ``Earliest Eligible Virtual Deadline
++ * First: A Flexible and Accurate Mechanism for Proportional Share
++ * Resource Allocation,'' technical report.
++ *
++ * http://www.cs.berkeley.edu/~istoica/papers/eevdf-tr-95.pdf
++ */
++#include <linux/module.h>
++#include <linux/slab.h>
++#include <linux/blkdev.h>
++#include <linux/cgroup.h>
++#include <linux/elevator.h>
++#include <linux/jiffies.h>
++#include <linux/rbtree.h>
++#include <linux/ioprio.h>
++#include "bfq.h"
++#include "blk.h"
++
++/* Expiration time of sync (0) and async (1) requests, in jiffies. */
++static const int bfq_fifo_expire[2] = { HZ / 4, HZ / 8 };
++
++/* Maximum backwards seek, in KiB. */
++static const int bfq_back_max = 16 * 1024;
++
++/* Penalty of a backwards seek, in number of sectors. */
++static const int bfq_back_penalty = 2;
++
++/* Idling period duration, in jiffies. */
++static int bfq_slice_idle = HZ / 125;
++
++/* Minimum number of assigned budgets for which stats are safe to compute. */
++static const int bfq_stats_min_budgets = 194;
++
++/* Default maximum budget values, in sectors and number of requests. */
++static const int bfq_default_max_budget = 16 * 1024;
++static const int bfq_max_budget_async_rq = 4;
++
++/*
++ * Async to sync throughput distribution is controlled as follows:
++ * when an async request is served, the entity is charged the number
++ * of sectors of the request, multiplied by the factor below
++ */
++static const int bfq_async_charge_factor = 10;
++
++/* Default timeout values, in jiffies, approximating CFQ defaults. */
++static const int bfq_timeout_sync = HZ / 8;
++static int bfq_timeout_async = HZ / 25;
++
++struct kmem_cache *bfq_pool;
++
++/* Below this threshold (in ms), we consider thinktime immediate. */
++#define BFQ_MIN_TT 2
++
++/* hw_tag detection: parallel requests threshold and min samples needed. */
++#define BFQ_HW_QUEUE_THRESHOLD 4
++#define BFQ_HW_QUEUE_SAMPLES 32
++
++#define BFQQ_SEEK_THR (sector_t)(8 * 1024)
++#define BFQQ_SEEKY(bfqq) ((bfqq)->seek_mean > BFQQ_SEEK_THR)
++
++/* Min samples used for peak rate estimation (for autotuning). */
++#define BFQ_PEAK_RATE_SAMPLES 32
++
++/* Shift used for peak rate fixed precision calculations. */
++#define BFQ_RATE_SHIFT 16
++
++/*
++ * By default, BFQ computes the duration of the weight raising for
++ * interactive applications automatically, using the following formula:
++ * duration = (R / r) * T, where r is the peak rate of the device, and
++ * R and T are two reference parameters.
++ * In particular, R is the peak rate of the reference device (see below),
++ * and T is a reference time: given the systems that are likely to be
++ * installed on the reference device according to its speed class, T is
++ * about the maximum time needed, under BFQ and while reading two files in
++ * parallel, to load typical large applications on these systems.
++ * In practice, the slower/faster the device at hand is, the more/less it
++ * takes to load applications with respect to the reference device.
++ * Accordingly, the longer/shorter BFQ grants weight raising to interactive
++ * applications.
++ *
++ * BFQ uses four different reference pairs (R, T), depending on:
++ * . whether the device is rotational or non-rotational;
++ * . whether the device is slow, such as old or portable HDDs, as well as
++ * SD cards, or fast, such as newer HDDs and SSDs.
++ *
++ * The device's speed class is dynamically (re)detected in
++ * bfq_update_peak_rate() every time the estimated peak rate is updated.
++ *
++ * In the following definitions, R_slow[0]/R_fast[0] and T_slow[0]/T_fast[0]
++ * are the reference values for a slow/fast rotational device, whereas
++ * R_slow[1]/R_fast[1] and T_slow[1]/T_fast[1] are the reference values for
++ * a slow/fast non-rotational device. Finally, device_speed_thresh are the
++ * thresholds used to switch between speed classes.
++ * Both the reference peak rates and the thresholds are measured in
++ * sectors/usec, left-shifted by BFQ_RATE_SHIFT.
++ */
++static int R_slow[2] = {1536, 10752};
++static int R_fast[2] = {17415, 34791};
++/*
++ * To improve readability, a conversion function is used to initialize the
++ * following arrays, which entails that they can be initialized only in a
++ * function.
++ */
++static int T_slow[2];
++static int T_fast[2];
++static int device_speed_thresh[2];
++
++#define BFQ_SERVICE_TREE_INIT ((struct bfq_service_tree) \
++ { RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
++
++#define RQ_BIC(rq) ((struct bfq_io_cq *) (rq)->elv.priv[0])
++#define RQ_BFQQ(rq) ((rq)->elv.priv[1])
++
++static void bfq_schedule_dispatch(struct bfq_data *bfqd);
++
++#include "bfq-ioc.c"
++#include "bfq-sched.c"
++#include "bfq-cgroup.c"
++
++#define bfq_class_idle(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
++#define bfq_class_rt(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_RT)
++
++#define bfq_sample_valid(samples) ((samples) > 80)
++
++/*
++ * We regard a request as SYNC, if either it's a read or has the SYNC bit
++ * set (in which case it could also be a direct WRITE).
++ */
++static int bfq_bio_sync(struct bio *bio)
++{
++ if (bio_data_dir(bio) == READ || (bio->bi_rw & REQ_SYNC))
++ return 1;
++
++ return 0;
++}
++
++/*
++ * Scheduler run of queue, if there are requests pending and no one in the
++ * driver that will restart queueing.
++ */
++static void bfq_schedule_dispatch(struct bfq_data *bfqd)
++{
++ if (bfqd->queued != 0) {
++ bfq_log(bfqd, "schedule dispatch");
++ kblockd_schedule_work(&bfqd->unplug_work);
++ }
++}
++
++/*
++ * Lifted from AS - choose which of rq1 and rq2 that is best served now.
++ * We choose the request that is closesr to the head right now. Distance
++ * behind the head is penalized and only allowed to a certain extent.
++ */
++static struct request *bfq_choose_req(struct bfq_data *bfqd,
++ struct request *rq1,
++ struct request *rq2,
++ sector_t last)
++{
++ sector_t s1, s2, d1 = 0, d2 = 0;
++ unsigned long back_max;
++#define BFQ_RQ1_WRAP 0x01 /* request 1 wraps */
++#define BFQ_RQ2_WRAP 0x02 /* request 2 wraps */
++ unsigned wrap = 0; /* bit mask: requests behind the disk head? */
++
++ if (!rq1 || rq1 == rq2)
++ return rq2;
++ if (!rq2)
++ return rq1;
++
++ if (rq_is_sync(rq1) && !rq_is_sync(rq2))
++ return rq1;
++ else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
++ return rq2;
++ if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META))
++ return rq1;
++ else if ((rq2->cmd_flags & REQ_META) && !(rq1->cmd_flags & REQ_META))
++ return rq2;
++
++ s1 = blk_rq_pos(rq1);
++ s2 = blk_rq_pos(rq2);
++
++ /*
++ * By definition, 1KiB is 2 sectors.
++ */
++ back_max = bfqd->bfq_back_max * 2;
++
++ /*
++ * Strict one way elevator _except_ in the case where we allow
++ * short backward seeks which are biased as twice the cost of a
++ * similar forward seek.
++ */
++ if (s1 >= last)
++ d1 = s1 - last;
++ else if (s1 + back_max >= last)
++ d1 = (last - s1) * bfqd->bfq_back_penalty;
++ else
++ wrap |= BFQ_RQ1_WRAP;
++
++ if (s2 >= last)
++ d2 = s2 - last;
++ else if (s2 + back_max >= last)
++ d2 = (last - s2) * bfqd->bfq_back_penalty;
++ else
++ wrap |= BFQ_RQ2_WRAP;
++
++ /* Found required data */
++
++ /*
++ * By doing switch() on the bit mask "wrap" we avoid having to
++ * check two variables for all permutations: --> faster!
++ */
++ switch (wrap) {
++ case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
++ if (d1 < d2)
++ return rq1;
++ else if (d2 < d1)
++ return rq2;
++ else {
++ if (s1 >= s2)
++ return rq1;
++ else
++ return rq2;
++ }
++
++ case BFQ_RQ2_WRAP:
++ return rq1;
++ case BFQ_RQ1_WRAP:
++ return rq2;
++ case (BFQ_RQ1_WRAP|BFQ_RQ2_WRAP): /* both rqs wrapped */
++ default:
++ /*
++ * Since both rqs are wrapped,
++ * start with the one that's further behind head
++ * (--> only *one* back seek required),
++ * since back seek takes more time than forward.
++ */
++ if (s1 <= s2)
++ return rq1;
++ else
++ return rq2;
++ }
++}
++
++/*
++ * Tell whether there are active queues or groups with differentiated weights.
++ */
++static bool bfq_differentiated_weights(struct bfq_data *bfqd)
++{
++ /*
++ * For weights to differ, at least one of the trees must contain
++ * at least two nodes.
++ */
++ return (!RB_EMPTY_ROOT(&bfqd->queue_weights_tree) &&
++ (bfqd->queue_weights_tree.rb_node->rb_left ||
++ bfqd->queue_weights_tree.rb_node->rb_right)
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ ) ||
++ (!RB_EMPTY_ROOT(&bfqd->group_weights_tree) &&
++ (bfqd->group_weights_tree.rb_node->rb_left ||
++ bfqd->group_weights_tree.rb_node->rb_right)
++#endif
++ );
++}
++
++/*
++ * The following function returns true if every queue must receive the
++ * same share of the throughput (this condition is used when deciding
++ * whether idling may be disabled, see the comments in the function
++ * bfq_bfqq_may_idle()).
++ *
++ * Such a scenario occurs when:
++ * 1) all active queues have the same weight,
++ * 2) all active groups at the same level in the groups tree have the same
++ * weight,
++ * 3) all active groups at the same level in the groups tree have the same
++ * number of children.
++ *
++ * Unfortunately, keeping the necessary state for evaluating exactly the
++ * above symmetry conditions would be quite complex and time-consuming.
++ * Therefore this function evaluates, instead, the following stronger
++ * sub-conditions, for which it is much easier to maintain the needed
++ * state:
++ * 1) all active queues have the same weight,
++ * 2) all active groups have the same weight,
++ * 3) all active groups have at most one active child each.
++ * In particular, the last two conditions are always true if hierarchical
++ * support and the cgroups interface are not enabled, thus no state needs
++ * to be maintained in this case.
++ */
++static bool bfq_symmetric_scenario(struct bfq_data *bfqd)
++{
++ return
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ !bfqd->active_numerous_groups &&
++#endif
++ !bfq_differentiated_weights(bfqd);
++}
++
++/*
++ * If the weight-counter tree passed as input contains no counter for
++ * the weight of the input entity, then add that counter; otherwise just
++ * increment the existing counter.
++ *
++ * Note that weight-counter trees contain few nodes in mostly symmetric
++ * scenarios. For example, if all queues have the same weight, then the
++ * weight-counter tree for the queues may contain at most one node.
++ * This holds even if low_latency is on, because weight-raised queues
++ * are not inserted in the tree.
++ * In most scenarios, the rate at which nodes are created/destroyed
++ * should be low too.
++ */
++static void bfq_weights_tree_add(struct bfq_data *bfqd,
++ struct bfq_entity *entity,
++ struct rb_root *root)
++{
++ struct rb_node **new = &(root->rb_node), *parent = NULL;
++
++ /*
++ * Do not insert if the entity is already associated with a
++ * counter, which happens if:
++ * 1) the entity is associated with a queue,
++ * 2) a request arrival has caused the queue to become both
++ * non-weight-raised, and hence change its weight, and
++ * backlogged; in this respect, each of the two events
++ * causes an invocation of this function,
++ * 3) this is the invocation of this function caused by the
++ * second event. This second invocation is actually useless,
++ * and we handle this fact by exiting immediately. More
++ * efficient or clearer solutions might possibly be adopted.
++ */
++ if (entity->weight_counter)
++ return;
++
++ while (*new) {
++ struct bfq_weight_counter *__counter = container_of(*new,
++ struct bfq_weight_counter,
++ weights_node);
++ parent = *new;
++
++ if (entity->weight == __counter->weight) {
++ entity->weight_counter = __counter;
++ goto inc_counter;
++ }
++ if (entity->weight < __counter->weight)
++ new = &((*new)->rb_left);
++ else
++ new = &((*new)->rb_right);
++ }
++
++ entity->weight_counter = kzalloc(sizeof(struct bfq_weight_counter),
++ GFP_ATOMIC);
++ entity->weight_counter->weight = entity->weight;
++ rb_link_node(&entity->weight_counter->weights_node, parent, new);
++ rb_insert_color(&entity->weight_counter->weights_node, root);
++
++inc_counter:
++ entity->weight_counter->num_active++;
++}
++
++/*
++ * Decrement the weight counter associated with the entity, and, if the
++ * counter reaches 0, remove the counter from the tree.
++ * See the comments to the function bfq_weights_tree_add() for considerations
++ * about overhead.
++ */
++static void bfq_weights_tree_remove(struct bfq_data *bfqd,
++ struct bfq_entity *entity,
++ struct rb_root *root)
++{
++ if (!entity->weight_counter)
++ return;
++
++ BUG_ON(RB_EMPTY_ROOT(root));
++ BUG_ON(entity->weight_counter->weight != entity->weight);
++
++ BUG_ON(!entity->weight_counter->num_active);
++ entity->weight_counter->num_active--;
++ if (entity->weight_counter->num_active > 0)
++ goto reset_entity_pointer;
++
++ rb_erase(&entity->weight_counter->weights_node, root);
++ kfree(entity->weight_counter);
++
++reset_entity_pointer:
++ entity->weight_counter = NULL;
++}
++
++static struct request *bfq_find_next_rq(struct bfq_data *bfqd,
++ struct bfq_queue *bfqq,
++ struct request *last)
++{
++ struct rb_node *rbnext = rb_next(&last->rb_node);
++ struct rb_node *rbprev = rb_prev(&last->rb_node);
++ struct request *next = NULL, *prev = NULL;
++
++ BUG_ON(RB_EMPTY_NODE(&last->rb_node));
++
++ if (rbprev)
++ prev = rb_entry_rq(rbprev);
++
++ if (rbnext)
++ next = rb_entry_rq(rbnext);
++ else {
++ rbnext = rb_first(&bfqq->sort_list);
++ if (rbnext && rbnext != &last->rb_node)
++ next = rb_entry_rq(rbnext);
++ }
++
++ return bfq_choose_req(bfqd, next, prev, blk_rq_pos(last));
++}
++
++/* see the definition of bfq_async_charge_factor for details */
++static unsigned long bfq_serv_to_charge(struct request *rq,
++ struct bfq_queue *bfqq)
++{
++ return blk_rq_sectors(rq) *
++ (1 + ((!bfq_bfqq_sync(bfqq)) * (bfqq->wr_coeff == 1) *
++ bfq_async_charge_factor));
++}
++
++/**
++ * bfq_updated_next_req - update the queue after a new next_rq selection.
++ * @bfqd: the device data the queue belongs to.
++ * @bfqq: the queue to update.
++ *
++ * If the first request of a queue changes we make sure that the queue
++ * has enough budget to serve at least its first request (if the
++ * request has grown). We do this because if the queue has not enough
++ * budget for its first request, it has to go through two dispatch
++ * rounds to actually get it dispatched.
++ */
++static void bfq_updated_next_req(struct bfq_data *bfqd,
++ struct bfq_queue *bfqq)
++{
++ struct bfq_entity *entity = &bfqq->entity;
++ struct bfq_service_tree *st = bfq_entity_service_tree(entity);
++ struct request *next_rq = bfqq->next_rq;
++ unsigned long new_budget;
++
++ if (!next_rq)
++ return;
++
++ if (bfqq == bfqd->in_service_queue)
++ /*
++ * In order not to break guarantees, budgets cannot be
++ * changed after an entity has been selected.
++ */
++ return;
++
++ BUG_ON(entity->tree != &st->active);
++ BUG_ON(entity == entity->sched_data->in_service_entity);
++
++ new_budget = max_t(unsigned long, bfqq->max_budget,
++ bfq_serv_to_charge(next_rq, bfqq));
++ if (entity->budget != new_budget) {
++ entity->budget = new_budget;
++ bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu",
++ new_budget);
++ bfq_activate_bfqq(bfqd, bfqq);
++ }
++}
++
++static unsigned int bfq_wr_duration(struct bfq_data *bfqd)
++{
++ u64 dur;
++
++ if (bfqd->bfq_wr_max_time > 0)
++ return bfqd->bfq_wr_max_time;
++
++ dur = bfqd->RT_prod;
++ do_div(dur, bfqd->peak_rate);
++
++ return dur;
++}
++
++/* Empty burst list and add just bfqq (see comments to bfq_handle_burst) */
++static void bfq_reset_burst_list(struct bfq_data *bfqd, struct bfq_queue *bfqq)
++{
++ struct bfq_queue *item;
++ struct hlist_node *n;
++
++ hlist_for_each_entry_safe(item, n, &bfqd->burst_list, burst_list_node)
++ hlist_del_init(&item->burst_list_node);
++ hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list);
++ bfqd->burst_size = 1;
++}
++
++/* Add bfqq to the list of queues in current burst (see bfq_handle_burst) */
++static void bfq_add_to_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq)
++{
++ /* Increment burst size to take into account also bfqq */
++ bfqd->burst_size++;
++
++ if (bfqd->burst_size == bfqd->bfq_large_burst_thresh) {
++ struct bfq_queue *pos, *bfqq_item;
++ struct hlist_node *n;
++
++ /*
++ * Enough queues have been activated shortly after each
++ * other to consider this burst as large.
++ */
++ bfqd->large_burst = true;
++
++ /*
++ * We can now mark all queues in the burst list as
++ * belonging to a large burst.
++ */
++ hlist_for_each_entry(bfqq_item, &bfqd->burst_list,
++ burst_list_node)
++ bfq_mark_bfqq_in_large_burst(bfqq_item);
++ bfq_mark_bfqq_in_large_burst(bfqq);
++
++ /*
++ * From now on, and until the current burst finishes, any
++ * new queue being activated shortly after the last queue
++ * was inserted in the burst can be immediately marked as
++ * belonging to a large burst. So the burst list is not
++ * needed any more. Remove it.
++ */
++ hlist_for_each_entry_safe(pos, n, &bfqd->burst_list,
++ burst_list_node)
++ hlist_del_init(&pos->burst_list_node);
++ } else /* burst not yet large: add bfqq to the burst list */
++ hlist_add_head(&bfqq->burst_list_node, &bfqd->burst_list);
++}
++
++/*
++ * If many queues happen to become active shortly after each other, then,
++ * to help the processes associated to these queues get their job done as
++ * soon as possible, it is usually better to not grant either weight-raising
++ * or device idling to these queues. In this comment we describe, firstly,
++ * the reasons why this fact holds, and, secondly, the next function, which
++ * implements the main steps needed to properly mark these queues so that
++ * they can then be treated in a different way.
++ *
++ * As for the terminology, we say that a queue becomes active, i.e.,
++ * switches from idle to backlogged, either when it is created (as a
++ * consequence of the arrival of an I/O request), or, if already existing,
++ * when a new request for the queue arrives while the queue is idle.
++ * Bursts of activations, i.e., activations of different queues occurring
++ * shortly after each other, are typically caused by services or applications
++ * that spawn or reactivate many parallel threads/processes. Examples are
++ * systemd during boot or git grep.
++ *
++ * These services or applications benefit mostly from a high throughput:
++ * the quicker the requests of the activated queues are cumulatively served,
++ * the sooner the target job of these queues gets completed. As a consequence,
++ * weight-raising any of these queues, which also implies idling the device
++ * for it, is almost always counterproductive: in most cases it just lowers
++ * throughput.
++ *
++ * On the other hand, a burst of activations may be also caused by the start
++ * of an application that does not consist in a lot of parallel I/O-bound
++ * threads. In fact, with a complex application, the burst may be just a
++ * consequence of the fact that several processes need to be executed to
++ * start-up the application. To start an application as quickly as possible,
++ * the best thing to do is to privilege the I/O related to the application
++ * with respect to all other I/O. Therefore, the best strategy to start as
++ * quickly as possible an application that causes a burst of activations is
++ * to weight-raise all the queues activated during the burst. This is the
++ * exact opposite of the best strategy for the other type of bursts.
++ *
++ * In the end, to take the best action for each of the two cases, the two
++ * types of bursts need to be distinguished. Fortunately, this seems
++ * relatively easy to do, by looking at the sizes of the bursts. In
++ * particular, we found a threshold such that bursts with a larger size
++ * than that threshold are apparently caused only by services or commands
++ * such as systemd or git grep. For brevity, hereafter we call just 'large'
++ * these bursts. BFQ *does not* weight-raise queues whose activations occur
++ * in a large burst. In addition, for each of these queues BFQ performs or
++ * does not perform idling depending on which choice boosts the throughput
++ * most. The exact choice depends on the device and request pattern at
++ * hand.
++ *
++ * Turning back to the next function, it implements all the steps needed
++ * to detect the occurrence of a large burst and to properly mark all the
++ * queues belonging to it (so that they can then be treated in a different
++ * way). This goal is achieved by maintaining a special "burst list" that
++ * holds, temporarily, the queues that belong to the burst in progress. The
++ * list is then used to mark these queues as belonging to a large burst if
++ * the burst does become large. The main steps are the following.
++ *
++ * . when the very first queue is activated, the queue is inserted into the
++ * list (as it could be the first queue in a possible burst)
++ *
++ * . if the current burst has not yet become large, and a queue Q that does
++ * not yet belong to the burst is activated shortly after the last time
++ * at which a new queue entered the burst list, then the function appends
++ * Q to the burst list
++ *
++ * . if, as a consequence of the previous step, the burst size reaches
++ * the large-burst threshold, then
++ *
++ * . all the queues in the burst list are marked as belonging to a
++ * large burst
++ *
++ * . the burst list is deleted; in fact, the burst list already served
++ * its purpose (keeping temporarily track of the queues in a burst,
++ * so as to be able to mark them as belonging to a large burst in the
++ * previous sub-step), and now is not needed any more
++ *
++ * . the device enters a large-burst mode
++ *
++ * . if a queue Q that does not belong to the burst is activated while
++ * the device is in large-burst mode and shortly after the last time
++ * at which a queue either entered the burst list or was marked as
++ * belonging to the current large burst, then Q is immediately marked
++ * as belonging to a large burst.
++ *
++ * . if a queue Q that does not belong to the burst is activated a while
++ * later, i.e., not shortly after, than the last time at which a queue
++ * either entered the burst list or was marked as belonging to the
++ * current large burst, then the current burst is deemed as finished and:
++ *
++ * . the large-burst mode is reset if set
++ *
++ * . the burst list is emptied
++ *
++ * . Q is inserted in the burst list, as Q may be the first queue
++ * in a possible new burst (then the burst list contains just Q
++ * after this step).
++ */
++static void bfq_handle_burst(struct bfq_data *bfqd, struct bfq_queue *bfqq,
++ bool idle_for_long_time)
++{
++ /*
++ * If bfqq happened to be activated in a burst, but has been idle
++ * for at least as long as an interactive queue, then we assume
++ * that, in the overall I/O initiated in the burst, the I/O
++ * associated to bfqq is finished. So bfqq does not need to be
++ * treated as a queue belonging to a burst anymore. Accordingly,
++ * we reset bfqq's in_large_burst flag if set, and remove bfqq
++ * from the burst list if it's there. We do not decrement instead
++ * burst_size, because the fact that bfqq does not need to belong
++ * to the burst list any more does not invalidate the fact that
++ * bfqq may have been activated during the current burst.
++ */
++ if (idle_for_long_time) {
++ hlist_del_init(&bfqq->burst_list_node);
++ bfq_clear_bfqq_in_large_burst(bfqq);
++ }
++
++ /*
++ * If bfqq is already in the burst list or is part of a large
++ * burst, then there is nothing else to do.
++ */
++ if (!hlist_unhashed(&bfqq->burst_list_node) ||
++ bfq_bfqq_in_large_burst(bfqq))
++ return;
++
++ /*
++ * If bfqq's activation happens late enough, then the current
++ * burst is finished, and related data structures must be reset.
++ *
++ * In this respect, consider the special case where bfqq is the very
++ * first queue being activated. In this case, last_ins_in_burst is
++ * not yet significant when we get here. But it is easy to verify
++ * that, whether or not the following condition is true, bfqq will
++ * end up being inserted into the burst list. In particular the
++ * list will happen to contain only bfqq. And this is exactly what
++ * has to happen, as bfqq may be the first queue in a possible
++ * burst.
++ */
++ if (time_is_before_jiffies(bfqd->last_ins_in_burst +
++ bfqd->bfq_burst_interval)) {
++ bfqd->large_burst = false;
++ bfq_reset_burst_list(bfqd, bfqq);
++ return;
++ }
++
++ /*
++ * If we get here, then bfqq is being activated shortly after the
++ * last queue. So, if the current burst is also large, we can mark
++ * bfqq as belonging to this large burst immediately.
++ */
++ if (bfqd->large_burst) {
++ bfq_mark_bfqq_in_large_burst(bfqq);
++ return;
++ }
++
++ /*
++ * If we get here, then a large-burst state has not yet been
++ * reached, but bfqq is being activated shortly after the last
++ * queue. Then we add bfqq to the burst.
++ */
++ bfq_add_to_burst(bfqd, bfqq);
++}
++
++static void bfq_add_request(struct request *rq)
++{
++ struct bfq_queue *bfqq = RQ_BFQQ(rq);
++ struct bfq_entity *entity = &bfqq->entity;
++ struct bfq_data *bfqd = bfqq->bfqd;
++ struct request *next_rq, *prev;
++ unsigned long old_wr_coeff = bfqq->wr_coeff;
++ bool interactive = false;
++
++ bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq));
++ bfqq->queued[rq_is_sync(rq)]++;
++ bfqd->queued++;
++
++ elv_rb_add(&bfqq->sort_list, rq);
++
++ /*
++ * Check if this request is a better next-serve candidate.
++ */
++ prev = bfqq->next_rq;
++ next_rq = bfq_choose_req(bfqd, bfqq->next_rq, rq, bfqd->last_position);
++ BUG_ON(!next_rq);
++ bfqq->next_rq = next_rq;
++
++ if (!bfq_bfqq_busy(bfqq)) {
++ bool soft_rt, in_burst,
++ idle_for_long_time = time_is_before_jiffies(
++ bfqq->budget_timeout +
++ bfqd->bfq_wr_min_idle_time);
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_update_io_add(bfqq_group(RQ_BFQQ(rq)), bfqq,
++ rq->cmd_flags);
++#endif
++ if (bfq_bfqq_sync(bfqq)) {
++ bool already_in_burst =
++ !hlist_unhashed(&bfqq->burst_list_node) ||
++ bfq_bfqq_in_large_burst(bfqq);
++ bfq_handle_burst(bfqd, bfqq, idle_for_long_time);
++ /*
++ * If bfqq was not already in the current burst,
++ * then, at this point, bfqq either has been
++ * added to the current burst or has caused the
++ * current burst to terminate. In particular, in
++ * the second case, bfqq has become the first
++ * queue in a possible new burst.
++ * In both cases last_ins_in_burst needs to be
++ * moved forward.
++ */
++ if (!already_in_burst)
++ bfqd->last_ins_in_burst = jiffies;
++ }
++
++ in_burst = bfq_bfqq_in_large_burst(bfqq);
++ soft_rt = bfqd->bfq_wr_max_softrt_rate > 0 &&
++ !in_burst &&
++ time_is_before_jiffies(bfqq->soft_rt_next_start);
++ interactive = !in_burst && idle_for_long_time;
++ entity->budget = max_t(unsigned long, bfqq->max_budget,
++ bfq_serv_to_charge(next_rq, bfqq));
++
++ if (!bfq_bfqq_IO_bound(bfqq)) {
++ if (time_before(jiffies,
++ RQ_BIC(rq)->ttime.last_end_request +
++ bfqd->bfq_slice_idle)) {
++ bfqq->requests_within_timer++;
++ if (bfqq->requests_within_timer >=
++ bfqd->bfq_requests_within_timer)
++ bfq_mark_bfqq_IO_bound(bfqq);
++ } else
++ bfqq->requests_within_timer = 0;
++ }
++
++ if (!bfqd->low_latency)
++ goto add_bfqq_busy;
++
++ /*
++ * If the queue:
++ * - is not being boosted,
++ * - has been idle for enough time,
++ * - is not a sync queue or is linked to a bfq_io_cq (it is
++ * shared "for its nature" or it is not shared and its
++ * requests have not been redirected to a shared queue)
++ * start a weight-raising period.
++ */
++ if (old_wr_coeff == 1 && (interactive || soft_rt) &&
++ (!bfq_bfqq_sync(bfqq) || bfqq->bic)) {
++ bfqq->wr_coeff = bfqd->bfq_wr_coeff;
++ if (interactive)
++ bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
++ else
++ bfqq->wr_cur_max_time =
++ bfqd->bfq_wr_rt_max_time;
++ bfq_log_bfqq(bfqd, bfqq,
++ "wrais starting at %lu, rais_max_time %u",
++ jiffies,
++ jiffies_to_msecs(bfqq->wr_cur_max_time));
++ } else if (old_wr_coeff > 1) {
++ if (interactive)
++ bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
++ else if (in_burst ||
++ (bfqq->wr_cur_max_time ==
++ bfqd->bfq_wr_rt_max_time &&
++ !soft_rt)) {
++ bfqq->wr_coeff = 1;
++ bfq_log_bfqq(bfqd, bfqq,
++ "wrais ending at %lu, rais_max_time %u",
++ jiffies,
++ jiffies_to_msecs(bfqq->
++ wr_cur_max_time));
++ } else if (time_before(
++ bfqq->last_wr_start_finish +
++ bfqq->wr_cur_max_time,
++ jiffies +
++ bfqd->bfq_wr_rt_max_time) &&
++ soft_rt) {
++ /*
++ *
++ * The remaining weight-raising time is lower
++ * than bfqd->bfq_wr_rt_max_time, which means
++ * that the application is enjoying weight
++ * raising either because deemed soft-rt in
++ * the near past, or because deemed interactive
++ * a long ago.
++ * In both cases, resetting now the current
++ * remaining weight-raising time for the
++ * application to the weight-raising duration
++ * for soft rt applications would not cause any
++ * latency increase for the application (as the
++ * new duration would be higher than the
++ * remaining time).
++ *
++ * In addition, the application is now meeting
++ * the requirements for being deemed soft rt.
++ * In the end we can correctly and safely
++ * (re)charge the weight-raising duration for
++ * the application with the weight-raising
++ * duration for soft rt applications.
++ *
++ * In particular, doing this recharge now, i.e.,
++ * before the weight-raising period for the
++ * application finishes, reduces the probability
++ * of the following negative scenario:
++ * 1) the weight of a soft rt application is
++ * raised at startup (as for any newly
++ * created application),
++ * 2) since the application is not interactive,
++ * at a certain time weight-raising is
++ * stopped for the application,
++ * 3) at that time the application happens to
++ * still have pending requests, and hence
++ * is destined to not have a chance to be
++ * deemed soft rt before these requests are
++ * completed (see the comments to the
++ * function bfq_bfqq_softrt_next_start()
++ * for details on soft rt detection),
++ * 4) these pending requests experience a high
++ * latency because the application is not
++ * weight-raised while they are pending.
++ */
++ bfqq->last_wr_start_finish = jiffies;
++ bfqq->wr_cur_max_time =
++ bfqd->bfq_wr_rt_max_time;
++ }
++ }
++ if (old_wr_coeff != bfqq->wr_coeff)
++ entity->prio_changed = 1;
++add_bfqq_busy:
++ bfqq->last_idle_bklogged = jiffies;
++ bfqq->service_from_backlogged = 0;
++ bfq_clear_bfqq_softrt_update(bfqq);
++ bfq_add_bfqq_busy(bfqd, bfqq);
++ } else {
++ if (bfqd->low_latency && old_wr_coeff == 1 && !rq_is_sync(rq) &&
++ time_is_before_jiffies(
++ bfqq->last_wr_start_finish +
++ bfqd->bfq_wr_min_inter_arr_async)) {
++ bfqq->wr_coeff = bfqd->bfq_wr_coeff;
++ bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
++
++ bfqd->wr_busy_queues++;
++ entity->prio_changed = 1;
++ bfq_log_bfqq(bfqd, bfqq,
++ "non-idle wrais starting at %lu, rais_max_time %u",
++ jiffies,
++ jiffies_to_msecs(bfqq->wr_cur_max_time));
++ }
++ if (prev != bfqq->next_rq)
++ bfq_updated_next_req(bfqd, bfqq);
++ }
++
++ if (bfqd->low_latency &&
++ (old_wr_coeff == 1 || bfqq->wr_coeff == 1 || interactive))
++ bfqq->last_wr_start_finish = jiffies;
++}
++
++static struct request *bfq_find_rq_fmerge(struct bfq_data *bfqd,
++ struct bio *bio)
++{
++ struct task_struct *tsk = current;
++ struct bfq_io_cq *bic;
++ struct bfq_queue *bfqq;
++
++ bic = bfq_bic_lookup(bfqd, tsk->io_context);
++ if (!bic)
++ return NULL;
++
++ bfqq = bic_to_bfqq(bic, bfq_bio_sync(bio));
++ if (bfqq)
++ return elv_rb_find(&bfqq->sort_list, bio_end_sector(bio));
++
++ return NULL;
++}
++
++static void bfq_activate_request(struct request_queue *q, struct request *rq)
++{
++ struct bfq_data *bfqd = q->elevator->elevator_data;
++
++ bfqd->rq_in_driver++;
++ bfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
++ bfq_log(bfqd, "activate_request: new bfqd->last_position %llu",
++ (long long unsigned)bfqd->last_position);
++}
++
++static void bfq_deactivate_request(struct request_queue *q, struct request *rq)
++{
++ struct bfq_data *bfqd = q->elevator->elevator_data;
++
++ BUG_ON(bfqd->rq_in_driver == 0);
++ bfqd->rq_in_driver--;
++}
++
++static void bfq_remove_request(struct request *rq)
++{
++ struct bfq_queue *bfqq = RQ_BFQQ(rq);
++ struct bfq_data *bfqd = bfqq->bfqd;
++ const int sync = rq_is_sync(rq);
++
++ if (bfqq->next_rq == rq) {
++ bfqq->next_rq = bfq_find_next_rq(bfqd, bfqq, rq);
++ bfq_updated_next_req(bfqd, bfqq);
++ }
++
++ if (rq->queuelist.prev != &rq->queuelist)
++ list_del_init(&rq->queuelist);
++ BUG_ON(bfqq->queued[sync] == 0);
++ bfqq->queued[sync]--;
++ bfqd->queued--;
++ elv_rb_del(&bfqq->sort_list, rq);
++
++ if (RB_EMPTY_ROOT(&bfqq->sort_list)) {
++ if (bfq_bfqq_busy(bfqq) && bfqq != bfqd->in_service_queue)
++ bfq_del_bfqq_busy(bfqd, bfqq, 1);
++ /*
++ * Remove queue from request-position tree as it is empty.
++ */
++ if (bfqq->pos_root) {
++ rb_erase(&bfqq->pos_node, bfqq->pos_root);
++ bfqq->pos_root = NULL;
++ }
++ }
++
++ if (rq->cmd_flags & REQ_META) {
++ BUG_ON(bfqq->meta_pending == 0);
++ bfqq->meta_pending--;
++ }
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_update_io_remove(bfqq_group(bfqq), rq->cmd_flags);
++#endif
++}
++
++static int bfq_merge(struct request_queue *q, struct request **req,
++ struct bio *bio)
++{
++ struct bfq_data *bfqd = q->elevator->elevator_data;
++ struct request *__rq;
++
++ __rq = bfq_find_rq_fmerge(bfqd, bio);
++ if (__rq && elv_rq_merge_ok(__rq, bio)) {
++ *req = __rq;
++ return ELEVATOR_FRONT_MERGE;
++ }
++
++ return ELEVATOR_NO_MERGE;
++}
++
++static void bfq_merged_request(struct request_queue *q, struct request *req,
++ int type)
++{
++ if (type == ELEVATOR_FRONT_MERGE &&
++ rb_prev(&req->rb_node) &&
++ blk_rq_pos(req) <
++ blk_rq_pos(container_of(rb_prev(&req->rb_node),
++ struct request, rb_node))) {
++ struct bfq_queue *bfqq = RQ_BFQQ(req);
++ struct bfq_data *bfqd = bfqq->bfqd;
++ struct request *prev, *next_rq;
++
++ /* Reposition request in its sort_list */
++ elv_rb_del(&bfqq->sort_list, req);
++ elv_rb_add(&bfqq->sort_list, req);
++ /* Choose next request to be served for bfqq */
++ prev = bfqq->next_rq;
++ next_rq = bfq_choose_req(bfqd, bfqq->next_rq, req,
++ bfqd->last_position);
++ BUG_ON(!next_rq);
++ bfqq->next_rq = next_rq;
++ }
++}
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++static void bfq_bio_merged(struct request_queue *q, struct request *req,
++ struct bio *bio)
++{
++ bfqg_stats_update_io_merged(bfqq_group(RQ_BFQQ(req)), bio->bi_rw);
++}
++#endif
++
++static void bfq_merged_requests(struct request_queue *q, struct request *rq,
++ struct request *next)
++{
++ struct bfq_queue *bfqq = RQ_BFQQ(rq), *next_bfqq = RQ_BFQQ(next);
++
++ /*
++ * If next and rq belong to the same bfq_queue and next is older
++ * than rq, then reposition rq in the fifo (by substituting next
++ * with rq). Otherwise, if next and rq belong to different
++ * bfq_queues, never reposition rq: in fact, we would have to
++ * reposition it with respect to next's position in its own fifo,
++ * which would most certainly be too expensive with respect to
++ * the benefits.
++ */
++ if (bfqq == next_bfqq &&
++ !list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
++ time_before(next->fifo_time, rq->fifo_time)) {
++ list_del_init(&rq->queuelist);
++ list_replace_init(&next->queuelist, &rq->queuelist);
++ rq->fifo_time = next->fifo_time;
++ }
++
++ if (bfqq->next_rq == next)
++ bfqq->next_rq = rq;
++
++ bfq_remove_request(next);
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_update_io_merged(bfqq_group(bfqq), next->cmd_flags);
++#endif
++}
++
++/* Must be called with bfqq != NULL */
++static void bfq_bfqq_end_wr(struct bfq_queue *bfqq)
++{
++ BUG_ON(!bfqq);
++ if (bfq_bfqq_busy(bfqq))
++ bfqq->bfqd->wr_busy_queues--;
++ bfqq->wr_coeff = 1;
++ bfqq->wr_cur_max_time = 0;
++ /* Trigger a weight change on the next activation of the queue */
++ bfqq->entity.prio_changed = 1;
++}
++
++static void bfq_end_wr_async_queues(struct bfq_data *bfqd,
++ struct bfq_group *bfqg)
++{
++ int i, j;
++
++ for (i = 0; i < 2; i++)
++ for (j = 0; j < IOPRIO_BE_NR; j++)
++ if (bfqg->async_bfqq[i][j])
++ bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]);
++ if (bfqg->async_idle_bfqq)
++ bfq_bfqq_end_wr(bfqg->async_idle_bfqq);
++}
++
++static void bfq_end_wr(struct bfq_data *bfqd)
++{
++ struct bfq_queue *bfqq;
++
++ spin_lock_irq(bfqd->queue->queue_lock);
++
++ list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list)
++ bfq_bfqq_end_wr(bfqq);
++ list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list)
++ bfq_bfqq_end_wr(bfqq);
++ bfq_end_wr_async(bfqd);
++
++ spin_unlock_irq(bfqd->queue->queue_lock);
++}
++
++static int bfq_allow_merge(struct request_queue *q, struct request *rq,
++ struct bio *bio)
++{
++ struct bfq_data *bfqd = q->elevator->elevator_data;
++ struct bfq_io_cq *bic;
++
++ /*
++ * Disallow merge of a sync bio into an async request.
++ */
++ if (bfq_bio_sync(bio) && !rq_is_sync(rq))
++ return 0;
++
++ /*
++ * Lookup the bfqq that this bio will be queued with. Allow
++ * merge only if rq is queued there.
++ * Queue lock is held here.
++ */
++ bic = bfq_bic_lookup(bfqd, current->io_context);
++ if (!bic)
++ return 0;
++
++ return bic_to_bfqq(bic, bfq_bio_sync(bio)) == RQ_BFQQ(rq);
++}
++
++static void __bfq_set_in_service_queue(struct bfq_data *bfqd,
++ struct bfq_queue *bfqq)
++{
++ if (bfqq) {
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_update_avg_queue_size(bfqq_group(bfqq));
++#endif
++ bfq_mark_bfqq_must_alloc(bfqq);
++ bfq_mark_bfqq_budget_new(bfqq);
++ bfq_clear_bfqq_fifo_expire(bfqq);
++
++ bfqd->budgets_assigned = (bfqd->budgets_assigned*7 + 256) / 8;
++
++ bfq_log_bfqq(bfqd, bfqq,
++ "set_in_service_queue, cur-budget = %d",
++ bfqq->entity.budget);
++ }
++
++ bfqd->in_service_queue = bfqq;
++}
++
++/*
++ * Get and set a new queue for service.
++ */
++static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd)
++{
++ struct bfq_queue *bfqq = bfq_get_next_queue(bfqd);
++
++ __bfq_set_in_service_queue(bfqd, bfqq);
++ return bfqq;
++}
++
++/*
++ * If enough samples have been computed, return the current max budget
++ * stored in bfqd, which is dynamically updated according to the
++ * estimated disk peak rate; otherwise return the default max budget
++ */
++static int bfq_max_budget(struct bfq_data *bfqd)
++{
++ if (bfqd->budgets_assigned < bfq_stats_min_budgets)
++ return bfq_default_max_budget;
++ else
++ return bfqd->bfq_max_budget;
++}
++
++/*
++ * Return min budget, which is a fraction of the current or default
++ * max budget (trying with 1/32)
++ */
++static int bfq_min_budget(struct bfq_data *bfqd)
++{
++ if (bfqd->budgets_assigned < bfq_stats_min_budgets)
++ return bfq_default_max_budget / 32;
++ else
++ return bfqd->bfq_max_budget / 32;
++}
++
++static void bfq_arm_slice_timer(struct bfq_data *bfqd)
++{
++ struct bfq_queue *bfqq = bfqd->in_service_queue;
++ struct bfq_io_cq *bic;
++ unsigned long sl;
++
++ BUG_ON(!RB_EMPTY_ROOT(&bfqq->sort_list));
++
++ /* Processes have exited, don't wait. */
++ bic = bfqd->in_service_bic;
++ if (!bic || atomic_read(&bic->icq.ioc->active_ref) == 0)
++ return;
++
++ bfq_mark_bfqq_wait_request(bfqq);
++
++ /*
++ * We don't want to idle for seeks, but we do want to allow
++ * fair distribution of slice time for a process doing back-to-back
++ * seeks. So allow a little bit of time for him to submit a new rq.
++ *
++ * To prevent processes with (partly) seeky workloads from
++ * being too ill-treated, grant them a small fraction of the
++ * assigned budget before reducing the waiting time to
++ * BFQ_MIN_TT. This happened to help reduce latency.
++ */
++ sl = bfqd->bfq_slice_idle;
++ /*
++ * Unless the queue is being weight-raised or the scenario is
++ * asymmetric, grant only minimum idle time if the queue either
++ * has been seeky for long enough or has already proved to be
++ * constantly seeky.
++ */
++ if (bfq_sample_valid(bfqq->seek_samples) &&
++ ((BFQQ_SEEKY(bfqq) && bfqq->entity.service >
++ bfq_max_budget(bfqq->bfqd) / 8) ||
++ bfq_bfqq_constantly_seeky(bfqq)) && bfqq->wr_coeff == 1 &&
++ bfq_symmetric_scenario(bfqd))
++ sl = min(sl, msecs_to_jiffies(BFQ_MIN_TT));
++ else if (bfqq->wr_coeff > 1)
++ sl = sl * 3;
++ bfqd->last_idling_start = ktime_get();
++ mod_timer(&bfqd->idle_slice_timer, jiffies + sl);
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_set_start_idle_time(bfqq_group(bfqq));
++#endif
++ bfq_log(bfqd, "arm idle: %u/%u ms",
++ jiffies_to_msecs(sl), jiffies_to_msecs(bfqd->bfq_slice_idle));
++}
++
++/*
++ * Set the maximum time for the in-service queue to consume its
++ * budget. This prevents seeky processes from lowering the disk
++ * throughput (always guaranteed with a time slice scheme as in CFQ).
++ */
++static void bfq_set_budget_timeout(struct bfq_data *bfqd)
++{
++ struct bfq_queue *bfqq = bfqd->in_service_queue;
++ unsigned int timeout_coeff;
++ if (bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time)
++ timeout_coeff = 1;
++ else
++ timeout_coeff = bfqq->entity.weight / bfqq->entity.orig_weight;
++
++ bfqd->last_budget_start = ktime_get();
++
++ bfq_clear_bfqq_budget_new(bfqq);
++ bfqq->budget_timeout = jiffies +
++ bfqd->bfq_timeout[bfq_bfqq_sync(bfqq)] * timeout_coeff;
++
++ bfq_log_bfqq(bfqd, bfqq, "set budget_timeout %u",
++ jiffies_to_msecs(bfqd->bfq_timeout[bfq_bfqq_sync(bfqq)] *
++ timeout_coeff));
++}
++
++/*
++ * Move request from internal lists to the request queue dispatch list.
++ */
++static void bfq_dispatch_insert(struct request_queue *q, struct request *rq)
++{
++ struct bfq_data *bfqd = q->elevator->elevator_data;
++ struct bfq_queue *bfqq = RQ_BFQQ(rq);
++
++ /*
++ * For consistency, the next instruction should have been executed
++ * after removing the request from the queue and dispatching it.
++ * We execute instead this instruction before bfq_remove_request()
++ * (and hence introduce a temporary inconsistency), for efficiency.
++ * In fact, in a forced_dispatch, this prevents two counters related
++ * to bfqq->dispatched to risk to be uselessly decremented if bfqq
++ * is not in service, and then to be incremented again after
++ * incrementing bfqq->dispatched.
++ */
++ bfqq->dispatched++;
++ bfq_remove_request(rq);
++ elv_dispatch_sort(q, rq);
++
++ if (bfq_bfqq_sync(bfqq))
++ bfqd->sync_flight++;
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_update_dispatch(bfqq_group(bfqq), blk_rq_bytes(rq),
++ rq->cmd_flags);
++#endif
++}
++
++/*
++ * Return expired entry, or NULL to just start from scratch in rbtree.
++ */
++static struct request *bfq_check_fifo(struct bfq_queue *bfqq)
++{
++ struct request *rq = NULL;
++
++ if (bfq_bfqq_fifo_expire(bfqq))
++ return NULL;
++
++ bfq_mark_bfqq_fifo_expire(bfqq);
++
++ if (list_empty(&bfqq->fifo))
++ return NULL;
++
++ rq = rq_entry_fifo(bfqq->fifo.next);
++
++ if (time_before(jiffies, rq->fifo_time))
++ return NULL;
++
++ return rq;
++}
++
++static int bfq_bfqq_budget_left(struct bfq_queue *bfqq)
++{
++ struct bfq_entity *entity = &bfqq->entity;
++ return entity->budget - entity->service;
++}
++
++static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq)
++{
++ BUG_ON(bfqq != bfqd->in_service_queue);
++
++ __bfq_bfqd_reset_in_service(bfqd);
++
++ if (RB_EMPTY_ROOT(&bfqq->sort_list)) {
++ /*
++ * Overloading budget_timeout field to store the time
++ * at which the queue remains with no backlog; used by
++ * the weight-raising mechanism.
++ */
++ bfqq->budget_timeout = jiffies;
++ bfq_del_bfqq_busy(bfqd, bfqq, 1);
++ } else
++ bfq_activate_bfqq(bfqd, bfqq);
++}
++
++/**
++ * __bfq_bfqq_recalc_budget - try to adapt the budget to the @bfqq behavior.
++ * @bfqd: device data.
++ * @bfqq: queue to update.
++ * @reason: reason for expiration.
++ *
++ * Handle the feedback on @bfqq budget at queue expiration.
++ * See the body for detailed comments.
++ */
++static void __bfq_bfqq_recalc_budget(struct bfq_data *bfqd,
++ struct bfq_queue *bfqq,
++ enum bfqq_expiration reason)
++{
++ struct request *next_rq;
++ int budget, min_budget;
++
++ budget = bfqq->max_budget;
++ min_budget = bfq_min_budget(bfqd);
++
++ BUG_ON(bfqq != bfqd->in_service_queue);
++
++ bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last budg %d, budg left %d",
++ bfqq->entity.budget, bfq_bfqq_budget_left(bfqq));
++ bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last max_budg %d, min budg %d",
++ budget, bfq_min_budget(bfqd));
++ bfq_log_bfqq(bfqd, bfqq, "recalc_budg: sync %d, seeky %d",
++ bfq_bfqq_sync(bfqq), BFQQ_SEEKY(bfqd->in_service_queue));
++
++ if (bfq_bfqq_sync(bfqq)) {
++ switch (reason) {
++ /*
++ * Caveat: in all the following cases we trade latency
++ * for throughput.
++ */
++ case BFQ_BFQQ_TOO_IDLE:
++ /*
++ * This is the only case where we may reduce
++ * the budget: if there is no request of the
++ * process still waiting for completion, then
++ * we assume (tentatively) that the timer has
++ * expired because the batch of requests of
++ * the process could have been served with a
++ * smaller budget. Hence, betting that
++ * process will behave in the same way when it
++ * becomes backlogged again, we reduce its
++ * next budget. As long as we guess right,
++ * this budget cut reduces the latency
++ * experienced by the process.
++ *
++ * However, if there are still outstanding
++ * requests, then the process may have not yet
++ * issued its next request just because it is
++ * still waiting for the completion of some of
++ * the still outstanding ones. So in this
++ * subcase we do not reduce its budget, on the
++ * contrary we increase it to possibly boost
++ * the throughput, as discussed in the
++ * comments to the BUDGET_TIMEOUT case.
++ */
++ if (bfqq->dispatched > 0) /* still outstanding reqs */
++ budget = min(budget * 2, bfqd->bfq_max_budget);
++ else {
++ if (budget > 5 * min_budget)
++ budget -= 4 * min_budget;
++ else
++ budget = min_budget;
++ }
++ break;
++ case BFQ_BFQQ_BUDGET_TIMEOUT:
++ /*
++ * We double the budget here because: 1) it
++ * gives the chance to boost the throughput if
++ * this is not a seeky process (which may have
++ * bumped into this timeout because of, e.g.,
++ * ZBR), 2) together with charge_full_budget
++ * it helps give seeky processes higher
++ * timestamps, and hence be served less
++ * frequently.
++ */
++ budget = min(budget * 2, bfqd->bfq_max_budget);
++ break;
++ case BFQ_BFQQ_BUDGET_EXHAUSTED:
++ /*
++ * The process still has backlog, and did not
++ * let either the budget timeout or the disk
++ * idling timeout expire. Hence it is not
++ * seeky, has a short thinktime and may be
++ * happy with a higher budget too. So
++ * definitely increase the budget of this good
++ * candidate to boost the disk throughput.
++ */
++ budget = min(budget * 4, bfqd->bfq_max_budget);
++ break;
++ case BFQ_BFQQ_NO_MORE_REQUESTS:
++ /*
++ * Leave the budget unchanged.
++ */
++ default:
++ return;
++ }
++ } else
++ /*
++ * Async queues get always the maximum possible budget
++ * (their ability to dispatch is limited by
++ * @bfqd->bfq_max_budget_async_rq).
++ */
++ budget = bfqd->bfq_max_budget;
++
++ bfqq->max_budget = budget;
++
++ if (bfqd->budgets_assigned >= bfq_stats_min_budgets &&
++ !bfqd->bfq_user_max_budget)
++ bfqq->max_budget = min(bfqq->max_budget, bfqd->bfq_max_budget);
++
++ /*
++ * Make sure that we have enough budget for the next request.
++ * Since the finish time of the bfqq must be kept in sync with
++ * the budget, be sure to call __bfq_bfqq_expire() after the
++ * update.
++ */
++ next_rq = bfqq->next_rq;
++ if (next_rq)
++ bfqq->entity.budget = max_t(unsigned long, bfqq->max_budget,
++ bfq_serv_to_charge(next_rq, bfqq));
++ else
++ bfqq->entity.budget = bfqq->max_budget;
++
++ bfq_log_bfqq(bfqd, bfqq, "head sect: %u, new budget %d",
++ next_rq ? blk_rq_sectors(next_rq) : 0,
++ bfqq->entity.budget);
++}
++
++static unsigned long bfq_calc_max_budget(u64 peak_rate, u64 timeout)
++{
++ unsigned long max_budget;
++
++ /*
++ * The max_budget calculated when autotuning is equal to the
++ * amount of sectors transfered in timeout_sync at the
++ * estimated peak rate.
++ */
++ max_budget = (unsigned long)(peak_rate * 1000 *
++ timeout >> BFQ_RATE_SHIFT);
++
++ return max_budget;
++}
++
++/*
++ * In addition to updating the peak rate, checks whether the process
++ * is "slow", and returns 1 if so. This slow flag is used, in addition
++ * to the budget timeout, to reduce the amount of service provided to
++ * seeky processes, and hence reduce their chances to lower the
++ * throughput. See the code for more details.
++ */
++static bool bfq_update_peak_rate(struct bfq_data *bfqd, struct bfq_queue *bfqq,
++ bool compensate, enum bfqq_expiration reason)
++{
++ u64 bw, usecs, expected, timeout;
++ ktime_t delta;
++ int update = 0;
++
++ if (!bfq_bfqq_sync(bfqq) || bfq_bfqq_budget_new(bfqq))
++ return false;
++
++ if (compensate)
++ delta = bfqd->last_idling_start;
++ else
++ delta = ktime_get();
++ delta = ktime_sub(delta, bfqd->last_budget_start);
++ usecs = ktime_to_us(delta);
++
++ /* Don't trust short/unrealistic values. */
++ if (usecs < 100 || usecs >= LONG_MAX)
++ return false;
++
++ /*
++ * Calculate the bandwidth for the last slice. We use a 64 bit
++ * value to store the peak rate, in sectors per usec in fixed
++ * point math. We do so to have enough precision in the estimate
++ * and to avoid overflows.
++ */
++ bw = (u64)bfqq->entity.service << BFQ_RATE_SHIFT;
++ do_div(bw, (unsigned long)usecs);
++
++ timeout = jiffies_to_msecs(bfqd->bfq_timeout[BLK_RW_SYNC]);
++
++ /*
++ * Use only long (> 20ms) intervals to filter out spikes for
++ * the peak rate estimation.
++ */
++ if (usecs > 20000) {
++ if (bw > bfqd->peak_rate ||
++ (!BFQQ_SEEKY(bfqq) &&
++ reason == BFQ_BFQQ_BUDGET_TIMEOUT)) {
++ bfq_log(bfqd, "measured bw =%llu", bw);
++ /*
++ * To smooth oscillations use a low-pass filter with
++ * alpha=7/8, i.e.,
++ * new_rate = (7/8) * old_rate + (1/8) * bw
++ */
++ do_div(bw, 8);
++ if (bw == 0)
++ return 0;
++ bfqd->peak_rate *= 7;
++ do_div(bfqd->peak_rate, 8);
++ bfqd->peak_rate += bw;
++ update = 1;
++ bfq_log(bfqd, "new peak_rate=%llu", bfqd->peak_rate);
++ }
++
++ update |= bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES - 1;
++
++ if (bfqd->peak_rate_samples < BFQ_PEAK_RATE_SAMPLES)
++ bfqd->peak_rate_samples++;
++
++ if (bfqd->peak_rate_samples == BFQ_PEAK_RATE_SAMPLES &&
++ update) {
++ int dev_type = blk_queue_nonrot(bfqd->queue);
++ if (bfqd->bfq_user_max_budget == 0) {
++ bfqd->bfq_max_budget =
++ bfq_calc_max_budget(bfqd->peak_rate,
++ timeout);
++ bfq_log(bfqd, "new max_budget=%d",
++ bfqd->bfq_max_budget);
++ }
++ if (bfqd->device_speed == BFQ_BFQD_FAST &&
++ bfqd->peak_rate < device_speed_thresh[dev_type]) {
++ bfqd->device_speed = BFQ_BFQD_SLOW;
++ bfqd->RT_prod = R_slow[dev_type] *
++ T_slow[dev_type];
++ } else if (bfqd->device_speed == BFQ_BFQD_SLOW &&
++ bfqd->peak_rate > device_speed_thresh[dev_type]) {
++ bfqd->device_speed = BFQ_BFQD_FAST;
++ bfqd->RT_prod = R_fast[dev_type] *
++ T_fast[dev_type];
++ }
++ }
++ }
++
++ /*
++ * If the process has been served for a too short time
++ * interval to let its possible sequential accesses prevail on
++ * the initial seek time needed to move the disk head on the
++ * first sector it requested, then give the process a chance
++ * and for the moment return false.
++ */
++ if (bfqq->entity.budget <= bfq_max_budget(bfqd) / 8)
++ return false;
++
++ /*
++ * A process is considered ``slow'' (i.e., seeky, so that we
++ * cannot treat it fairly in the service domain, as it would
++ * slow down too much the other processes) if, when a slice
++ * ends for whatever reason, it has received service at a
++ * rate that would not be high enough to complete the budget
++ * before the budget timeout expiration.
++ */
++ expected = bw * 1000 * timeout >> BFQ_RATE_SHIFT;
++
++ /*
++ * Caveat: processes doing IO in the slower disk zones will
++ * tend to be slow(er) even if not seeky. And the estimated
++ * peak rate will actually be an average over the disk
++ * surface. Hence, to not be too harsh with unlucky processes,
++ * we keep a budget/3 margin of safety before declaring a
++ * process slow.
++ */
++ return expected > (4 * bfqq->entity.budget) / 3;
++}
++
++/*
++ * To be deemed as soft real-time, an application must meet two
++ * requirements. First, the application must not require an average
++ * bandwidth higher than the approximate bandwidth required to playback or
++ * record a compressed high-definition video.
++ * The next function is invoked on the completion of the last request of a
++ * batch, to compute the next-start time instant, soft_rt_next_start, such
++ * that, if the next request of the application does not arrive before
++ * soft_rt_next_start, then the above requirement on the bandwidth is met.
++ *
++ * The second requirement is that the request pattern of the application is
++ * isochronous, i.e., that, after issuing a request or a batch of requests,
++ * the application stops issuing new requests until all its pending requests
++ * have been completed. After that, the application may issue a new batch,
++ * and so on.
++ * For this reason the next function is invoked to compute
++ * soft_rt_next_start only for applications that meet this requirement,
++ * whereas soft_rt_next_start is set to infinity for applications that do
++ * not.
++ *
++ * Unfortunately, even a greedy application may happen to behave in an
++ * isochronous way if the CPU load is high. In fact, the application may
++ * stop issuing requests while the CPUs are busy serving other processes,
++ * then restart, then stop again for a while, and so on. In addition, if
++ * the disk achieves a low enough throughput with the request pattern
++ * issued by the application (e.g., because the request pattern is random
++ * and/or the device is slow), then the application may meet the above
++ * bandwidth requirement too. To prevent such a greedy application to be
++ * deemed as soft real-time, a further rule is used in the computation of
++ * soft_rt_next_start: soft_rt_next_start must be higher than the current
++ * time plus the maximum time for which the arrival of a request is waited
++ * for when a sync queue becomes idle, namely bfqd->bfq_slice_idle.
++ * This filters out greedy applications, as the latter issue instead their
++ * next request as soon as possible after the last one has been completed
++ * (in contrast, when a batch of requests is completed, a soft real-time
++ * application spends some time processing data).
++ *
++ * Unfortunately, the last filter may easily generate false positives if
++ * only bfqd->bfq_slice_idle is used as a reference time interval and one
++ * or both the following cases occur:
++ * 1) HZ is so low that the duration of a jiffy is comparable to or higher
++ * than bfqd->bfq_slice_idle. This happens, e.g., on slow devices with
++ * HZ=100.
++ * 2) jiffies, instead of increasing at a constant rate, may stop increasing
++ * for a while, then suddenly 'jump' by several units to recover the lost
++ * increments. This seems to happen, e.g., inside virtual machines.
++ * To address this issue, we do not use as a reference time interval just
++ * bfqd->bfq_slice_idle, but bfqd->bfq_slice_idle plus a few jiffies. In
++ * particular we add the minimum number of jiffies for which the filter
++ * seems to be quite precise also in embedded systems and KVM/QEMU virtual
++ * machines.
++ */
++static unsigned long bfq_bfqq_softrt_next_start(struct bfq_data *bfqd,
++ struct bfq_queue *bfqq)
++{
++ return max(bfqq->last_idle_bklogged +
++ HZ * bfqq->service_from_backlogged /
++ bfqd->bfq_wr_max_softrt_rate,
++ jiffies + bfqq->bfqd->bfq_slice_idle + 4);
++}
++
++/*
++ * Return the largest-possible time instant such that, for as long as possible,
++ * the current time will be lower than this time instant according to the macro
++ * time_is_before_jiffies().
++ */
++static unsigned long bfq_infinity_from_now(unsigned long now)
++{
++ return now + ULONG_MAX / 2;
++}
++
++/**
++ * bfq_bfqq_expire - expire a queue.
++ * @bfqd: device owning the queue.
++ * @bfqq: the queue to expire.
++ * @compensate: if true, compensate for the time spent idling.
++ * @reason: the reason causing the expiration.
++ *
++ *
++ * If the process associated to the queue is slow (i.e., seeky), or in
++ * case of budget timeout, or, finally, if it is async, we
++ * artificially charge it an entire budget (independently of the
++ * actual service it received). As a consequence, the queue will get
++ * higher timestamps than the correct ones upon reactivation, and
++ * hence it will be rescheduled as if it had received more service
++ * than what it actually received. In the end, this class of processes
++ * will receive less service in proportion to how slowly they consume
++ * their budgets (and hence how seriously they tend to lower the
++ * throughput).
++ *
++ * In contrast, when a queue expires because it has been idling for
++ * too much or because it exhausted its budget, we do not touch the
++ * amount of service it has received. Hence when the queue will be
++ * reactivated and its timestamps updated, the latter will be in sync
++ * with the actual service received by the queue until expiration.
++ *
++ * Charging a full budget to the first type of queues and the exact
++ * service to the others has the effect of using the WF2Q+ policy to
++ * schedule the former on a timeslice basis, without violating the
++ * service domain guarantees of the latter.
++ */
++static void bfq_bfqq_expire(struct bfq_data *bfqd,
++ struct bfq_queue *bfqq,
++ bool compensate,
++ enum bfqq_expiration reason)
++{
++ bool slow;
++ BUG_ON(bfqq != bfqd->in_service_queue);
++
++ /*
++ * Update disk peak rate for autotuning and check whether the
++ * process is slow (see bfq_update_peak_rate).
++ */
++ slow = bfq_update_peak_rate(bfqd, bfqq, compensate, reason);
++
++ /*
++ * As above explained, 'punish' slow (i.e., seeky), timed-out
++ * and async queues, to favor sequential sync workloads.
++ *
++ * Processes doing I/O in the slower disk zones will tend to be
++ * slow(er) even if not seeky. Hence, since the estimated peak
++ * rate is actually an average over the disk surface, these
++ * processes may timeout just for bad luck. To avoid punishing
++ * them we do not charge a full budget to a process that
++ * succeeded in consuming at least 2/3 of its budget.
++ */
++ if (slow || (reason == BFQ_BFQQ_BUDGET_TIMEOUT &&
++ bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3))
++ bfq_bfqq_charge_full_budget(bfqq);
++
++ bfqq->service_from_backlogged += bfqq->entity.service;
++
++ if (BFQQ_SEEKY(bfqq) && reason == BFQ_BFQQ_BUDGET_TIMEOUT &&
++ !bfq_bfqq_constantly_seeky(bfqq)) {
++ bfq_mark_bfqq_constantly_seeky(bfqq);
++ if (!blk_queue_nonrot(bfqd->queue))
++ bfqd->const_seeky_busy_in_flight_queues++;
++ }
++
++ if (reason == BFQ_BFQQ_TOO_IDLE &&
++ bfqq->entity.service <= 2 * bfqq->entity.budget / 10 )
++ bfq_clear_bfqq_IO_bound(bfqq);
++
++ if (bfqd->low_latency && bfqq->wr_coeff == 1)
++ bfqq->last_wr_start_finish = jiffies;
++
++ if (bfqd->low_latency && bfqd->bfq_wr_max_softrt_rate > 0 &&
++ RB_EMPTY_ROOT(&bfqq->sort_list)) {
++ /*
++ * If we get here, and there are no outstanding requests,
++ * then the request pattern is isochronous (see the comments
++ * to the function bfq_bfqq_softrt_next_start()). Hence we
++ * can compute soft_rt_next_start. If, instead, the queue
++ * still has outstanding requests, then we have to wait
++ * for the completion of all the outstanding requests to
++ * discover whether the request pattern is actually
++ * isochronous.
++ */
++ if (bfqq->dispatched == 0)
++ bfqq->soft_rt_next_start =
++ bfq_bfqq_softrt_next_start(bfqd, bfqq);
++ else {
++ /*
++ * The application is still waiting for the
++ * completion of one or more requests:
++ * prevent it from possibly being incorrectly
++ * deemed as soft real-time by setting its
++ * soft_rt_next_start to infinity. In fact,
++ * without this assignment, the application
++ * would be incorrectly deemed as soft
++ * real-time if:
++ * 1) it issued a new request before the
++ * completion of all its in-flight
++ * requests, and
++ * 2) at that time, its soft_rt_next_start
++ * happened to be in the past.
++ */
++ bfqq->soft_rt_next_start =
++ bfq_infinity_from_now(jiffies);
++ /*
++ * Schedule an update of soft_rt_next_start to when
++ * the task may be discovered to be isochronous.
++ */
++ bfq_mark_bfqq_softrt_update(bfqq);
++ }
++ }
++
++ bfq_log_bfqq(bfqd, bfqq,
++ "expire (%d, slow %d, num_disp %d, idle_win %d)", reason,
++ slow, bfqq->dispatched, bfq_bfqq_idle_window(bfqq));
++
++ /*
++ * Increase, decrease or leave budget unchanged according to
++ * reason.
++ */
++ __bfq_bfqq_recalc_budget(bfqd, bfqq, reason);
++ __bfq_bfqq_expire(bfqd, bfqq);
++}
++
++/*
++ * Budget timeout is not implemented through a dedicated timer, but
++ * just checked on request arrivals and completions, as well as on
++ * idle timer expirations.
++ */
++static bool bfq_bfqq_budget_timeout(struct bfq_queue *bfqq)
++{
++ if (bfq_bfqq_budget_new(bfqq) ||
++ time_before(jiffies, bfqq->budget_timeout))
++ return false;
++ return true;
++}
++
++/*
++ * If we expire a queue that is waiting for the arrival of a new
++ * request, we may prevent the fictitious timestamp back-shifting that
++ * allows the guarantees of the queue to be preserved (see [1] for
++ * this tricky aspect). Hence we return true only if this condition
++ * does not hold, or if the queue is slow enough to deserve only to be
++ * kicked off for preserving a high throughput.
++*/
++static bool bfq_may_expire_for_budg_timeout(struct bfq_queue *bfqq)
++{
++ bfq_log_bfqq(bfqq->bfqd, bfqq,
++ "may_budget_timeout: wait_request %d left %d timeout %d",
++ bfq_bfqq_wait_request(bfqq),
++ bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3,
++ bfq_bfqq_budget_timeout(bfqq));
++
++ return (!bfq_bfqq_wait_request(bfqq) ||
++ bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3)
++ &&
++ bfq_bfqq_budget_timeout(bfqq);
++}
++
++/*
++ * For a queue that becomes empty, device idling is allowed only if
++ * this function returns true for that queue. As a consequence, since
++ * device idling plays a critical role for both throughput boosting
++ * and service guarantees, the return value of this function plays a
++ * critical role as well.
++ *
++ * In a nutshell, this function returns true only if idling is
++ * beneficial for throughput or, even if detrimental for throughput,
++ * idling is however necessary to preserve service guarantees (low
++ * latency, desired throughput distribution, ...). In particular, on
++ * NCQ-capable devices, this function tries to return false, so as to
++ * help keep the drives' internal queues full, whenever this helps the
++ * device boost the throughput without causing any service-guarantee
++ * issue.
++ *
++ * In more detail, the return value of this function is obtained by,
++ * first, computing a number of boolean variables that take into
++ * account throughput and service-guarantee issues, and, then,
++ * combining these variables in a logical expression. Most of the
++ * issues taken into account are not trivial. We discuss these issues
++ * while introducing the variables.
++ */
++static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq)
++{
++ struct bfq_data *bfqd = bfqq->bfqd;
++ bool idling_boosts_thr, idling_boosts_thr_without_issues,
++ all_queues_seeky, on_hdd_and_not_all_queues_seeky,
++ idling_needed_for_service_guarantees,
++ asymmetric_scenario;
++
++ /*
++ * The next variable takes into account the cases where idling
++ * boosts the throughput.
++ *
++ * The value of the variable is computed considering, first, that
++ * idling is virtually always beneficial for the throughput if:
++ * (a) the device is not NCQ-capable, or
++ * (b) regardless of the presence of NCQ, the device is rotational
++ * and the request pattern for bfqq is I/O-bound and sequential.
++ *
++ * Secondly, and in contrast to the above item (b), idling an
++ * NCQ-capable flash-based device would not boost the
++ * throughput even with sequential I/O; rather it would lower
++ * the throughput in proportion to how fast the device
++ * is. Accordingly, the next variable is true if any of the
++ * above conditions (a) and (b) is true, and, in particular,
++ * happens to be false if bfqd is an NCQ-capable flash-based
++ * device.
++ */
++ idling_boosts_thr = !bfqd->hw_tag ||
++ (!blk_queue_nonrot(bfqd->queue) && bfq_bfqq_IO_bound(bfqq) &&
++ bfq_bfqq_idle_window(bfqq)) ;
++
++ /*
++ * The value of the next variable,
++ * idling_boosts_thr_without_issues, is equal to that of
++ * idling_boosts_thr, unless a special case holds. In this
++ * special case, described below, idling may cause problems to
++ * weight-raised queues.
++ *
++ * When the request pool is saturated (e.g., in the presence
++ * of write hogs), if the processes associated with
++ * non-weight-raised queues ask for requests at a lower rate,
++ * then processes associated with weight-raised queues have a
++ * higher probability to get a request from the pool
++ * immediately (or at least soon) when they need one. Thus
++ * they have a higher probability to actually get a fraction
++ * of the device throughput proportional to their high
++ * weight. This is especially true with NCQ-capable drives,
++ * which enqueue several requests in advance, and further
++ * reorder internally-queued requests.
++ *
++ * For this reason, we force to false the value of
++ * idling_boosts_thr_without_issues if there are weight-raised
++ * busy queues. In this case, and if bfqq is not weight-raised,
++ * this guarantees that the device is not idled for bfqq (if,
++ * instead, bfqq is weight-raised, then idling will be
++ * guaranteed by another variable, see below). Combined with
++ * the timestamping rules of BFQ (see [1] for details), this
++ * behavior causes bfqq, and hence any sync non-weight-raised
++ * queue, to get a lower number of requests served, and thus
++ * to ask for a lower number of requests from the request
++ * pool, before the busy weight-raised queues get served
++ * again. This often mitigates starvation problems in the
++ * presence of heavy write workloads and NCQ, thereby
++ * guaranteeing a higher application and system responsiveness
++ * in these hostile scenarios.
++ */
++ idling_boosts_thr_without_issues = idling_boosts_thr &&
++ bfqd->wr_busy_queues == 0;
++
++ /*
++ * There are then two cases where idling must be performed not
++ * for throughput concerns, but to preserve service
++ * guarantees. In the description of these cases, we say, for
++ * short, that a queue is sequential/random if the process
++ * associated to the queue issues sequential/random requests
++ * (in the second case the queue may be tagged as seeky or
++ * even constantly_seeky).
++ *
++ * To introduce the first case, we note that, since
++ * bfq_bfqq_idle_window(bfqq) is false if the device is
++ * NCQ-capable and bfqq is random (see
++ * bfq_update_idle_window()), then, from the above two
++ * assignments it follows that
++ * idling_boosts_thr_without_issues is false if the device is
++ * NCQ-capable and bfqq is random. Therefore, for this case,
++ * device idling would never be allowed if we used just
++ * idling_boosts_thr_without_issues to decide whether to allow
++ * it. And, beneficially, this would imply that throughput
++ * would always be boosted also with random I/O on NCQ-capable
++ * HDDs.
++ *
++ * But we must be careful on this point, to avoid an unfair
++ * treatment for bfqq. In fact, because of the same above
++ * assignments, idling_boosts_thr_without_issues is, on the
++ * other hand, true if 1) the device is an HDD and bfqq is
++ * sequential, and 2) there are no busy weight-raised
++ * queues. As a consequence, if we used just
++ * idling_boosts_thr_without_issues to decide whether to idle
++ * the device, then with an HDD we might easily bump into a
++ * scenario where queues that are sequential and I/O-bound
++ * would enjoy idling, whereas random queues would not. The
++ * latter might then get a low share of the device throughput,
++ * simply because the former would get many requests served
++ * after being set as in service, while the latter would not.
++ *
++ * To address this issue, we start by setting to true a
++ * sentinel variable, on_hdd_and_not_all_queues_seeky, if the
++ * device is rotational and not all queues with pending or
++ * in-flight requests are constantly seeky (i.e., there are
++ * active sequential queues, and bfqq might then be mistreated
++ * if it does not enjoy idling because it is random).
++ */
++ all_queues_seeky = bfq_bfqq_constantly_seeky(bfqq) &&
++ bfqd->busy_in_flight_queues ==
++ bfqd->const_seeky_busy_in_flight_queues;
++
++ on_hdd_and_not_all_queues_seeky =
++ !blk_queue_nonrot(bfqd->queue) && !all_queues_seeky;
++
++ /*
++ * To introduce the second case where idling needs to be
++ * performed to preserve service guarantees, we can note that
++ * allowing the drive to enqueue more than one request at a
++ * time, and hence delegating de facto final scheduling
++ * decisions to the drive's internal scheduler, causes loss of
++ * control on the actual request service order. In particular,
++ * the critical situation is when requests from different
++ * processes happens to be present, at the same time, in the
++ * internal queue(s) of the drive. In such a situation, the
++ * drive, by deciding the service order of the
++ * internally-queued requests, does determine also the actual
++ * throughput distribution among these processes. But the
++ * drive typically has no notion or concern about per-process
++ * throughput distribution, and makes its decisions only on a
++ * per-request basis. Therefore, the service distribution
++ * enforced by the drive's internal scheduler is likely to
++ * coincide with the desired device-throughput distribution
++ * only in a completely symmetric scenario where:
++ * (i) each of these processes must get the same throughput as
++ * the others;
++ * (ii) all these processes have the same I/O pattern
++ (either sequential or random).
++ * In fact, in such a scenario, the drive will tend to treat
++ * the requests of each of these processes in about the same
++ * way as the requests of the others, and thus to provide
++ * each of these processes with about the same throughput
++ * (which is exactly the desired throughput distribution). In
++ * contrast, in any asymmetric scenario, device idling is
++ * certainly needed to guarantee that bfqq receives its
++ * assigned fraction of the device throughput (see [1] for
++ * details).
++ *
++ * We address this issue by controlling, actually, only the
++ * symmetry sub-condition (i), i.e., provided that
++ * sub-condition (i) holds, idling is not performed,
++ * regardless of whether sub-condition (ii) holds. In other
++ * words, only if sub-condition (i) holds, then idling is
++ * allowed, and the device tends to be prevented from queueing
++ * many requests, possibly of several processes. The reason
++ * for not controlling also sub-condition (ii) is that, first,
++ * in the case of an HDD, the asymmetry in terms of types of
++ * I/O patterns is already taken in to account in the above
++ * sentinel variable
++ * on_hdd_and_not_all_queues_seeky. Secondly, in the case of a
++ * flash-based device, we prefer however to privilege
++ * throughput (and idling lowers throughput for this type of
++ * devices), for the following reasons:
++ * 1) differently from HDDs, the service time of random
++ * requests is not orders of magnitudes lower than the service
++ * time of sequential requests; thus, even if processes doing
++ * sequential I/O get a preferential treatment with respect to
++ * others doing random I/O, the consequences are not as
++ * dramatic as with HDDs;
++ * 2) if a process doing random I/O does need strong
++ * throughput guarantees, it is hopefully already being
++ * weight-raised, or the user is likely to have assigned it a
++ * higher weight than the other processes (and thus
++ * sub-condition (i) is likely to be false, which triggers
++ * idling).
++ *
++ * According to the above considerations, the next variable is
++ * true (only) if sub-condition (i) holds. To compute the
++ * value of this variable, we not only use the return value of
++ * the function bfq_symmetric_scenario(), but also check
++ * whether bfqq is being weight-raised, because
++ * bfq_symmetric_scenario() does not take into account also
++ * weight-raised queues (see comments to
++ * bfq_weights_tree_add()).
++ *
++ * As a side note, it is worth considering that the above
++ * device-idling countermeasures may however fail in the
++ * following unlucky scenario: if idling is (correctly)
++ * disabled in a time period during which all symmetry
++ * sub-conditions hold, and hence the device is allowed to
++ * enqueue many requests, but at some later point in time some
++ * sub-condition stops to hold, then it may become impossible
++ * to let requests be served in the desired order until all
++ * the requests already queued in the device have been served.
++ */
++ asymmetric_scenario = bfqq->wr_coeff > 1 ||
++ !bfq_symmetric_scenario(bfqd);
++
++ /*
++ * Finally, there is a case where maximizing throughput is the
++ * best choice even if it may cause unfairness toward
++ * bfqq. Such a case is when bfqq became active in a burst of
++ * queue activations. Queues that became active during a large
++ * burst benefit only from throughput, as discussed in the
++ * comments to bfq_handle_burst. Thus, if bfqq became active
++ * in a burst and not idling the device maximizes throughput,
++ * then the device must no be idled, because not idling the
++ * device provides bfqq and all other queues in the burst with
++ * maximum benefit. Combining this and the two cases above, we
++ * can now establish when idling is actually needed to
++ * preserve service guarantees.
++ */
++ idling_needed_for_service_guarantees =
++ (on_hdd_and_not_all_queues_seeky || asymmetric_scenario) &&
++ !bfq_bfqq_in_large_burst(bfqq);
++
++ /*
++ * We have now all the components we need to compute the return
++ * value of the function, which is true only if both the following
++ * conditions hold:
++ * 1) bfqq is sync, because idling make sense only for sync queues;
++ * 2) idling either boosts the throughput (without issues), or
++ * is necessary to preserve service guarantees.
++ */
++ return bfq_bfqq_sync(bfqq) &&
++ (idling_boosts_thr_without_issues ||
++ idling_needed_for_service_guarantees);
++}
++
++/*
++ * If the in-service queue is empty but the function bfq_bfqq_may_idle
++ * returns true, then:
++ * 1) the queue must remain in service and cannot be expired, and
++ * 2) the device must be idled to wait for the possible arrival of a new
++ * request for the queue.
++ * See the comments to the function bfq_bfqq_may_idle for the reasons
++ * why performing device idling is the best choice to boost the throughput
++ * and preserve service guarantees when bfq_bfqq_may_idle itself
++ * returns true.
++ */
++static bool bfq_bfqq_must_idle(struct bfq_queue *bfqq)
++{
++ struct bfq_data *bfqd = bfqq->bfqd;
++
++ return RB_EMPTY_ROOT(&bfqq->sort_list) && bfqd->bfq_slice_idle != 0 &&
++ bfq_bfqq_may_idle(bfqq);
++}
++
++/*
++ * Select a queue for service. If we have a current queue in service,
++ * check whether to continue servicing it, or retrieve and set a new one.
++ */
++static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
++{
++ struct bfq_queue *bfqq;
++ struct request *next_rq;
++ enum bfqq_expiration reason = BFQ_BFQQ_BUDGET_TIMEOUT;
++
++ bfqq = bfqd->in_service_queue;
++ if (!bfqq)
++ goto new_queue;
++
++ bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue");
++
++ if (bfq_may_expire_for_budg_timeout(bfqq) &&
++ !timer_pending(&bfqd->idle_slice_timer) &&
++ !bfq_bfqq_must_idle(bfqq))
++ goto expire;
++
++ next_rq = bfqq->next_rq;
++ /*
++ * If bfqq has requests queued and it has enough budget left to
++ * serve them, keep the queue, otherwise expire it.
++ */
++ if (next_rq) {
++ if (bfq_serv_to_charge(next_rq, bfqq) >
++ bfq_bfqq_budget_left(bfqq)) {
++ reason = BFQ_BFQQ_BUDGET_EXHAUSTED;
++ goto expire;
++ } else {
++ /*
++ * The idle timer may be pending because we may
++ * not disable disk idling even when a new request
++ * arrives.
++ */
++ if (timer_pending(&bfqd->idle_slice_timer)) {
++ /*
++ * If we get here: 1) at least a new request
++ * has arrived but we have not disabled the
++ * timer because the request was too small,
++ * 2) then the block layer has unplugged
++ * the device, causing the dispatch to be
++ * invoked.
++ *
++ * Since the device is unplugged, now the
++ * requests are probably large enough to
++ * provide a reasonable throughput.
++ * So we disable idling.
++ */
++ bfq_clear_bfqq_wait_request(bfqq);
++ del_timer(&bfqd->idle_slice_timer);
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_update_idle_time(bfqq_group(bfqq));
++#endif
++ }
++ goto keep_queue;
++ }
++ }
++
++ /*
++ * No requests pending. However, if the in-service queue is idling
++ * for a new request, or has requests waiting for a completion and
++ * may idle after their completion, then keep it anyway.
++ */
++ if (timer_pending(&bfqd->idle_slice_timer) ||
++ (bfqq->dispatched != 0 && bfq_bfqq_may_idle(bfqq))) {
++ bfqq = NULL;
++ goto keep_queue;
++ }
++
++ reason = BFQ_BFQQ_NO_MORE_REQUESTS;
++expire:
++ bfq_bfqq_expire(bfqd, bfqq, false, reason);
++new_queue:
++ bfqq = bfq_set_in_service_queue(bfqd);
++ bfq_log(bfqd, "select_queue: new queue %d returned",
++ bfqq ? bfqq->pid : 0);
++keep_queue:
++ return bfqq;
++}
++
++static void bfq_update_wr_data(struct bfq_data *bfqd, struct bfq_queue *bfqq)
++{
++ struct bfq_entity *entity = &bfqq->entity;
++ if (bfqq->wr_coeff > 1) { /* queue is being weight-raised */
++ bfq_log_bfqq(bfqd, bfqq,
++ "raising period dur %u/%u msec, old coeff %u, w %d(%d)",
++ jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish),
++ jiffies_to_msecs(bfqq->wr_cur_max_time),
++ bfqq->wr_coeff,
++ bfqq->entity.weight, bfqq->entity.orig_weight);
++
++ BUG_ON(bfqq != bfqd->in_service_queue && entity->weight !=
++ entity->orig_weight * bfqq->wr_coeff);
++ if (entity->prio_changed)
++ bfq_log_bfqq(bfqd, bfqq, "WARN: pending prio change");
++
++ /*
++ * If the queue was activated in a burst, or
++ * too much time has elapsed from the beginning
++ * of this weight-raising period, then end weight
++ * raising.
++ */
++ if (bfq_bfqq_in_large_burst(bfqq) ||
++ time_is_before_jiffies(bfqq->last_wr_start_finish +
++ bfqq->wr_cur_max_time)) {
++ bfqq->last_wr_start_finish = jiffies;
++ bfq_log_bfqq(bfqd, bfqq,
++ "wrais ending at %lu, rais_max_time %u",
++ bfqq->last_wr_start_finish,
++ jiffies_to_msecs(bfqq->wr_cur_max_time));
++ bfq_bfqq_end_wr(bfqq);
++ }
++ }
++ /* Update weight both if it must be raised and if it must be lowered */
++ if ((entity->weight > entity->orig_weight) != (bfqq->wr_coeff > 1))
++ __bfq_entity_update_weight_prio(
++ bfq_entity_service_tree(entity),
++ entity);
++}
++
++/*
++ * Dispatch one request from bfqq, moving it to the request queue
++ * dispatch list.
++ */
++static int bfq_dispatch_request(struct bfq_data *bfqd,
++ struct bfq_queue *bfqq)
++{
++ int dispatched = 0;
++ struct request *rq;
++ unsigned long service_to_charge;
++
++ BUG_ON(RB_EMPTY_ROOT(&bfqq->sort_list));
++
++ /* Follow expired path, else get first next available. */
++ rq = bfq_check_fifo(bfqq);
++ if (!rq)
++ rq = bfqq->next_rq;
++ service_to_charge = bfq_serv_to_charge(rq, bfqq);
++
++ if (service_to_charge > bfq_bfqq_budget_left(bfqq)) {
++ /*
++ * This may happen if the next rq is chosen in fifo order
++ * instead of sector order. The budget is properly
++ * dimensioned to be always sufficient to serve the next
++ * request only if it is chosen in sector order. The reason
++ * is that it would be quite inefficient and little useful
++ * to always make sure that the budget is large enough to
++ * serve even the possible next rq in fifo order.
++ * In fact, requests are seldom served in fifo order.
++ *
++ * Expire the queue for budget exhaustion, and make sure
++ * that the next act_budget is enough to serve the next
++ * request, even if it comes from the fifo expired path.
++ */
++ bfqq->next_rq = rq;
++ /*
++ * Since this dispatch is failed, make sure that
++ * a new one will be performed
++ */
++ if (!bfqd->rq_in_driver)
++ bfq_schedule_dispatch(bfqd);
++ goto expire;
++ }
++
++ /* Finally, insert request into driver dispatch list. */
++ bfq_bfqq_served(bfqq, service_to_charge);
++ bfq_dispatch_insert(bfqd->queue, rq);
++
++ bfq_update_wr_data(bfqd, bfqq);
++
++ bfq_log_bfqq(bfqd, bfqq,
++ "dispatched %u sec req (%llu), budg left %d",
++ blk_rq_sectors(rq),
++ (long long unsigned)blk_rq_pos(rq),
++ bfq_bfqq_budget_left(bfqq));
++
++ dispatched++;
++
++ if (!bfqd->in_service_bic) {
++ atomic_long_inc(&RQ_BIC(rq)->icq.ioc->refcount);
++ bfqd->in_service_bic = RQ_BIC(rq);
++ }
++
++ if (bfqd->busy_queues > 1 && ((!bfq_bfqq_sync(bfqq) &&
++ dispatched >= bfqd->bfq_max_budget_async_rq) ||
++ bfq_class_idle(bfqq)))
++ goto expire;
++
++ return dispatched;
++
++expire:
++ bfq_bfqq_expire(bfqd, bfqq, false, BFQ_BFQQ_BUDGET_EXHAUSTED);
++ return dispatched;
++}
++
++static int __bfq_forced_dispatch_bfqq(struct bfq_queue *bfqq)
++{
++ int dispatched = 0;
++
++ while (bfqq->next_rq) {
++ bfq_dispatch_insert(bfqq->bfqd->queue, bfqq->next_rq);
++ dispatched++;
++ }
++
++ BUG_ON(!list_empty(&bfqq->fifo));
++ return dispatched;
++}
++
++/*
++ * Drain our current requests.
++ * Used for barriers and when switching io schedulers on-the-fly.
++ */
++static int bfq_forced_dispatch(struct bfq_data *bfqd)
++{
++ struct bfq_queue *bfqq, *n;
++ struct bfq_service_tree *st;
++ int dispatched = 0;
++
++ bfqq = bfqd->in_service_queue;
++ if (bfqq)
++ __bfq_bfqq_expire(bfqd, bfqq);
++
++ /*
++ * Loop through classes, and be careful to leave the scheduler
++ * in a consistent state, as feedback mechanisms and vtime
++ * updates cannot be disabled during the process.
++ */
++ list_for_each_entry_safe(bfqq, n, &bfqd->active_list, bfqq_list) {
++ st = bfq_entity_service_tree(&bfqq->entity);
++
++ dispatched += __bfq_forced_dispatch_bfqq(bfqq);
++ bfqq->max_budget = bfq_max_budget(bfqd);
++
++ bfq_forget_idle(st);
++ }
++
++ BUG_ON(bfqd->busy_queues != 0);
++
++ return dispatched;
++}
++
++static int bfq_dispatch_requests(struct request_queue *q, int force)
++{
++ struct bfq_data *bfqd = q->elevator->elevator_data;
++ struct bfq_queue *bfqq;
++ int max_dispatch;
++
++ bfq_log(bfqd, "dispatch requests: %d busy queues", bfqd->busy_queues);
++ if (bfqd->busy_queues == 0)
++ return 0;
++
++ if (unlikely(force))
++ return bfq_forced_dispatch(bfqd);
++
++ bfqq = bfq_select_queue(bfqd);
++ if (!bfqq)
++ return 0;
++
++ if (bfq_class_idle(bfqq))
++ max_dispatch = 1;
++
++ if (!bfq_bfqq_sync(bfqq))
++ max_dispatch = bfqd->bfq_max_budget_async_rq;
++
++ if (!bfq_bfqq_sync(bfqq) && bfqq->dispatched >= max_dispatch) {
++ if (bfqd->busy_queues > 1)
++ return 0;
++ if (bfqq->dispatched >= 4 * max_dispatch)
++ return 0;
++ }
++
++ if (bfqd->sync_flight != 0 && !bfq_bfqq_sync(bfqq))
++ return 0;
++
++ bfq_clear_bfqq_wait_request(bfqq);
++ BUG_ON(timer_pending(&bfqd->idle_slice_timer));
++
++ if (!bfq_dispatch_request(bfqd, bfqq))
++ return 0;
++
++ bfq_log_bfqq(bfqd, bfqq, "dispatched %s request",
++ bfq_bfqq_sync(bfqq) ? "sync" : "async");
++
++ return 1;
++}
++
++/*
++ * Task holds one reference to the queue, dropped when task exits. Each rq
++ * in-flight on this queue also holds a reference, dropped when rq is freed.
++ *
++ * Queue lock must be held here.
++ */
++static void bfq_put_queue(struct bfq_queue *bfqq)
++{
++ struct bfq_data *bfqd = bfqq->bfqd;
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ struct bfq_group *bfqg = bfqq_group(bfqq);
++#endif
++
++ BUG_ON(atomic_read(&bfqq->ref) <= 0);
++
++ bfq_log_bfqq(bfqd, bfqq, "put_queue: %p %d", bfqq,
++ atomic_read(&bfqq->ref));
++ if (!atomic_dec_and_test(&bfqq->ref))
++ return;
++
++ BUG_ON(rb_first(&bfqq->sort_list));
++ BUG_ON(bfqq->allocated[READ] + bfqq->allocated[WRITE] != 0);
++ BUG_ON(bfqq->entity.tree);
++ BUG_ON(bfq_bfqq_busy(bfqq));
++ BUG_ON(bfqd->in_service_queue == bfqq);
++
++ if (bfq_bfqq_sync(bfqq))
++ /*
++ * The fact that this queue is being destroyed does not
++ * invalidate the fact that this queue may have been
++ * activated during the current burst. As a consequence,
++ * although the queue does not exist anymore, and hence
++ * needs to be removed from the burst list if there,
++ * the burst size has not to be decremented.
++ */
++ hlist_del_init(&bfqq->burst_list_node);
++
++ bfq_log_bfqq(bfqd, bfqq, "put_queue: %p freed", bfqq);
++
++ kmem_cache_free(bfq_pool, bfqq);
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_put(bfqg);
++#endif
++}
++
++static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
++{
++ if (bfqq == bfqd->in_service_queue) {
++ __bfq_bfqq_expire(bfqd, bfqq);
++ bfq_schedule_dispatch(bfqd);
++ }
++
++ bfq_log_bfqq(bfqd, bfqq, "exit_bfqq: %p, %d", bfqq,
++ atomic_read(&bfqq->ref));
++
++ bfq_put_queue(bfqq);
++}
++
++static void bfq_init_icq(struct io_cq *icq)
++{
++ struct bfq_io_cq *bic = icq_to_bic(icq);
++
++ bic->ttime.last_end_request = jiffies;
++}
++
++static void bfq_exit_icq(struct io_cq *icq)
++{
++ struct bfq_io_cq *bic = icq_to_bic(icq);
++ struct bfq_data *bfqd = bic_to_bfqd(bic);
++
++ if (bic->bfqq[BLK_RW_ASYNC]) {
++ bfq_exit_bfqq(bfqd, bic->bfqq[BLK_RW_ASYNC]);
++ bic->bfqq[BLK_RW_ASYNC] = NULL;
++ }
++
++ if (bic->bfqq[BLK_RW_SYNC]) {
++ bfq_exit_bfqq(bfqd, bic->bfqq[BLK_RW_SYNC]);
++ bic->bfqq[BLK_RW_SYNC] = NULL;
++ }
++}
++
++/*
++ * Update the entity prio values; note that the new values will not
++ * be used until the next (re)activation.
++ */
++static void bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
++{
++ struct task_struct *tsk = current;
++ int ioprio_class;
++
++ ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
++ switch (ioprio_class) {
++ default:
++ dev_err(bfqq->bfqd->queue->backing_dev_info.dev,
++ "bfq: bad prio class %d\n", ioprio_class);
++ case IOPRIO_CLASS_NONE:
++ /*
++ * No prio set, inherit CPU scheduling settings.
++ */
++ bfqq->new_ioprio = task_nice_ioprio(tsk);
++ bfqq->new_ioprio_class = task_nice_ioclass(tsk);
++ break;
++ case IOPRIO_CLASS_RT:
++ bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
++ bfqq->new_ioprio_class = IOPRIO_CLASS_RT;
++ break;
++ case IOPRIO_CLASS_BE:
++ bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
++ bfqq->new_ioprio_class = IOPRIO_CLASS_BE;
++ break;
++ case IOPRIO_CLASS_IDLE:
++ bfqq->new_ioprio_class = IOPRIO_CLASS_IDLE;
++ bfqq->new_ioprio = 7;
++ bfq_clear_bfqq_idle_window(bfqq);
++ break;
++ }
++
++ if (bfqq->new_ioprio < 0 || bfqq->new_ioprio >= IOPRIO_BE_NR) {
++ printk(KERN_CRIT "bfq_set_next_ioprio_data: new_ioprio %d\n",
++ bfqq->new_ioprio);
++ BUG();
++ }
++
++ bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio);
++ bfqq->entity.prio_changed = 1;
++}
++
++static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio)
++{
++ struct bfq_data *bfqd;
++ struct bfq_queue *bfqq, *new_bfqq;
++ unsigned long uninitialized_var(flags);
++ int ioprio = bic->icq.ioc->ioprio;
++
++ bfqd = bfq_get_bfqd_locked(&(bic->icq.q->elevator->elevator_data),
++ &flags);
++ /*
++ * This condition may trigger on a newly created bic, be sure to
++ * drop the lock before returning.
++ */
++ if (unlikely(!bfqd) || likely(bic->ioprio == ioprio))
++ goto out;
++
++ bic->ioprio = ioprio;
++
++ bfqq = bic->bfqq[BLK_RW_ASYNC];
++ if (bfqq) {
++ new_bfqq = bfq_get_queue(bfqd, bio, BLK_RW_ASYNC, bic,
++ GFP_ATOMIC);
++ if (new_bfqq) {
++ bic->bfqq[BLK_RW_ASYNC] = new_bfqq;
++ bfq_log_bfqq(bfqd, bfqq,
++ "check_ioprio_change: bfqq %p %d",
++ bfqq, atomic_read(&bfqq->ref));
++ bfq_put_queue(bfqq);
++ }
++ }
++
++ bfqq = bic->bfqq[BLK_RW_SYNC];
++ if (bfqq)
++ bfq_set_next_ioprio_data(bfqq, bic);
++
++out:
++ bfq_put_bfqd_unlock(bfqd, &flags);
++}
++
++static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
++ struct bfq_io_cq *bic, pid_t pid, int is_sync)
++{
++ RB_CLEAR_NODE(&bfqq->entity.rb_node);
++ INIT_LIST_HEAD(&bfqq->fifo);
++ INIT_HLIST_NODE(&bfqq->burst_list_node);
++
++ atomic_set(&bfqq->ref, 0);
++ bfqq->bfqd = bfqd;
++
++ if (bic)
++ bfq_set_next_ioprio_data(bfqq, bic);
++
++ if (is_sync) {
++ if (!bfq_class_idle(bfqq))
++ bfq_mark_bfqq_idle_window(bfqq);
++ bfq_mark_bfqq_sync(bfqq);
++ } else
++ bfq_clear_bfqq_sync(bfqq);
++ bfq_mark_bfqq_IO_bound(bfqq);
++
++ /* Tentative initial value to trade off between thr and lat */
++ bfqq->max_budget = (2 * bfq_max_budget(bfqd)) / 3;
++ bfqq->pid = pid;
++
++ bfqq->wr_coeff = 1;
++ bfqq->last_wr_start_finish = 0;
++ /*
++ * Set to the value for which bfqq will not be deemed as
++ * soft rt when it becomes backlogged.
++ */
++ bfqq->soft_rt_next_start = bfq_infinity_from_now(jiffies);
++}
++
++static struct bfq_queue *bfq_find_alloc_queue(struct bfq_data *bfqd,
++ struct bio *bio, int is_sync,
++ struct bfq_io_cq *bic,
++ gfp_t gfp_mask)
++{
++ struct bfq_group *bfqg;
++ struct bfq_queue *bfqq, *new_bfqq = NULL;
++ struct blkcg *blkcg;
++
++retry:
++ rcu_read_lock();
++
++ blkcg = bio_blkcg(bio);
++ bfqg = bfq_find_alloc_group(bfqd, blkcg);
++ /* bic always exists here */
++ bfqq = bic_to_bfqq(bic, is_sync);
++
++ /*
++ * Always try a new alloc if we fall back to the OOM bfqq
++ * originally, since it should just be a temporary situation.
++ */
++ if (!bfqq || bfqq == &bfqd->oom_bfqq) {
++ bfqq = NULL;
++ if (new_bfqq) {
++ bfqq = new_bfqq;
++ new_bfqq = NULL;
++ } else if (gfpflags_allow_blocking(gfp_mask)) {
++ rcu_read_unlock();
++ spin_unlock_irq(bfqd->queue->queue_lock);
++ new_bfqq = kmem_cache_alloc_node(bfq_pool,
++ gfp_mask | __GFP_ZERO,
++ bfqd->queue->node);
++ spin_lock_irq(bfqd->queue->queue_lock);
++ if (new_bfqq)
++ goto retry;
++ } else {
++ bfqq = kmem_cache_alloc_node(bfq_pool,
++ gfp_mask | __GFP_ZERO,
++ bfqd->queue->node);
++ }
++
++ if (bfqq) {
++ bfq_init_bfqq(bfqd, bfqq, bic, current->pid,
++ is_sync);
++ bfq_init_entity(&bfqq->entity, bfqg);
++ bfq_log_bfqq(bfqd, bfqq, "allocated");
++ } else {
++ bfqq = &bfqd->oom_bfqq;
++ bfq_log_bfqq(bfqd, bfqq, "using oom bfqq");
++ }
++ }
++
++ if (new_bfqq)
++ kmem_cache_free(bfq_pool, new_bfqq);
++
++ rcu_read_unlock();
++
++ return bfqq;
++}
++
++static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd,
++ struct bfq_group *bfqg,
++ int ioprio_class, int ioprio)
++{
++ switch (ioprio_class) {
++ case IOPRIO_CLASS_RT:
++ return &bfqg->async_bfqq[0][ioprio];
++ case IOPRIO_CLASS_NONE:
++ ioprio = IOPRIO_NORM;
++ /* fall through */
++ case IOPRIO_CLASS_BE:
++ return &bfqg->async_bfqq[1][ioprio];
++ case IOPRIO_CLASS_IDLE:
++ return &bfqg->async_idle_bfqq;
++ default:
++ BUG();
++ }
++}
++
++static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
++ struct bio *bio, int is_sync,
++ struct bfq_io_cq *bic, gfp_t gfp_mask)
++{
++ const int ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
++ const int ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
++ struct bfq_queue **async_bfqq = NULL;
++ struct bfq_queue *bfqq = NULL;
++
++ if (!is_sync) {
++ struct blkcg *blkcg;
++ struct bfq_group *bfqg;
++
++ rcu_read_lock();
++ blkcg = bio_blkcg(bio);
++ rcu_read_unlock();
++ bfqg = bfq_find_alloc_group(bfqd, blkcg);
++ async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class,
++ ioprio);
++ bfqq = *async_bfqq;
++ }
++
++ if (!bfqq)
++ bfqq = bfq_find_alloc_queue(bfqd, bio, is_sync, bic, gfp_mask);
++
++ /*
++ * Pin the queue now that it's allocated, scheduler exit will
++ * prune it.
++ */
++ if (!is_sync && !(*async_bfqq)) {
++ atomic_inc(&bfqq->ref);
++ bfq_log_bfqq(bfqd, bfqq, "get_queue, bfqq not in async: %p, %d",
++ bfqq, atomic_read(&bfqq->ref));
++ *async_bfqq = bfqq;
++ }
++
++ atomic_inc(&bfqq->ref);
++ bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq,
++ atomic_read(&bfqq->ref));
++ return bfqq;
++}
++
++static void bfq_update_io_thinktime(struct bfq_data *bfqd,
++ struct bfq_io_cq *bic)
++{
++ unsigned long elapsed = jiffies - bic->ttime.last_end_request;
++ unsigned long ttime = min(elapsed, 2UL * bfqd->bfq_slice_idle);
++
++ bic->ttime.ttime_samples = (7*bic->ttime.ttime_samples + 256) / 8;
++ bic->ttime.ttime_total = (7*bic->ttime.ttime_total + 256*ttime) / 8;
++ bic->ttime.ttime_mean = (bic->ttime.ttime_total + 128) /
++ bic->ttime.ttime_samples;
++}
++
++static void bfq_update_io_seektime(struct bfq_data *bfqd,
++ struct bfq_queue *bfqq,
++ struct request *rq)
++{
++ sector_t sdist;
++ u64 total;
++
++ if (bfqq->last_request_pos < blk_rq_pos(rq))
++ sdist = blk_rq_pos(rq) - bfqq->last_request_pos;
++ else
++ sdist = bfqq->last_request_pos - blk_rq_pos(rq);
++
++ /*
++ * Don't allow the seek distance to get too large from the
++ * odd fragment, pagein, etc.
++ */
++ if (bfqq->seek_samples == 0) /* first request, not really a seek */
++ sdist = 0;
++ else if (bfqq->seek_samples <= 60) /* second & third seek */
++ sdist = min(sdist, (bfqq->seek_mean * 4) + 2*1024*1024);
++ else
++ sdist = min(sdist, (bfqq->seek_mean * 4) + 2*1024*64);
++
++ bfqq->seek_samples = (7*bfqq->seek_samples + 256) / 8;
++ bfqq->seek_total = (7*bfqq->seek_total + (u64)256*sdist) / 8;
++ total = bfqq->seek_total + (bfqq->seek_samples/2);
++ do_div(total, bfqq->seek_samples);
++ bfqq->seek_mean = (sector_t)total;
++
++ bfq_log_bfqq(bfqd, bfqq, "dist=%llu mean=%llu", (u64)sdist,
++ (u64)bfqq->seek_mean);
++}
++
++/*
++ * Disable idle window if the process thinks too long or seeks so much that
++ * it doesn't matter.
++ */
++static void bfq_update_idle_window(struct bfq_data *bfqd,
++ struct bfq_queue *bfqq,
++ struct bfq_io_cq *bic)
++{
++ int enable_idle;
++
++ /* Don't idle for async or idle io prio class. */
++ if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq))
++ return;
++
++ enable_idle = bfq_bfqq_idle_window(bfqq);
++
++ if (atomic_read(&bic->icq.ioc->active_ref) == 0 ||
++ bfqd->bfq_slice_idle == 0 ||
++ (bfqd->hw_tag && BFQQ_SEEKY(bfqq) &&
++ bfqq->wr_coeff == 1))
++ enable_idle = 0;
++ else if (bfq_sample_valid(bic->ttime.ttime_samples)) {
++ if (bic->ttime.ttime_mean > bfqd->bfq_slice_idle &&
++ bfqq->wr_coeff == 1)
++ enable_idle = 0;
++ else
++ enable_idle = 1;
++ }
++ bfq_log_bfqq(bfqd, bfqq, "update_idle_window: enable_idle %d",
++ enable_idle);
++
++ if (enable_idle)
++ bfq_mark_bfqq_idle_window(bfqq);
++ else
++ bfq_clear_bfqq_idle_window(bfqq);
++}
++
++/*
++ * Called when a new fs request (rq) is added to bfqq. Check if there's
++ * something we should do about it.
++ */
++static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq,
++ struct request *rq)
++{
++ struct bfq_io_cq *bic = RQ_BIC(rq);
++
++ if (rq->cmd_flags & REQ_META)
++ bfqq->meta_pending++;
++
++ bfq_update_io_thinktime(bfqd, bic);
++ bfq_update_io_seektime(bfqd, bfqq, rq);
++ if (!BFQQ_SEEKY(bfqq) && bfq_bfqq_constantly_seeky(bfqq)) {
++ bfq_clear_bfqq_constantly_seeky(bfqq);
++ if (!blk_queue_nonrot(bfqd->queue)) {
++ BUG_ON(!bfqd->const_seeky_busy_in_flight_queues);
++ bfqd->const_seeky_busy_in_flight_queues--;
++ }
++ }
++ if (bfqq->entity.service > bfq_max_budget(bfqd) / 8 ||
++ !BFQQ_SEEKY(bfqq))
++ bfq_update_idle_window(bfqd, bfqq, bic);
++
++ bfq_log_bfqq(bfqd, bfqq,
++ "rq_enqueued: idle_window=%d (seeky %d, mean %llu)",
++ bfq_bfqq_idle_window(bfqq), BFQQ_SEEKY(bfqq),
++ (long long unsigned)bfqq->seek_mean);
++
++ bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
++
++ if (bfqq == bfqd->in_service_queue && bfq_bfqq_wait_request(bfqq)) {
++ bool small_req = bfqq->queued[rq_is_sync(rq)] == 1 &&
++ blk_rq_sectors(rq) < 32;
++ bool budget_timeout = bfq_bfqq_budget_timeout(bfqq);
++
++ /*
++ * There is just this request queued: if the request
++ * is small and the queue is not to be expired, then
++ * just exit.
++ *
++ * In this way, if the disk is being idled to wait for
++ * a new request from the in-service queue, we avoid
++ * unplugging the device and committing the disk to serve
++ * just a small request. On the contrary, we wait for
++ * the block layer to decide when to unplug the device:
++ * hopefully, new requests will be merged to this one
++ * quickly, then the device will be unplugged and
++ * larger requests will be dispatched.
++ */
++ if (small_req && !budget_timeout)
++ return;
++
++ /*
++ * A large enough request arrived, or the queue is to
++ * be expired: in both cases disk idling is to be
++ * stopped, so clear wait_request flag and reset
++ * timer.
++ */
++ bfq_clear_bfqq_wait_request(bfqq);
++ del_timer(&bfqd->idle_slice_timer);
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_update_idle_time(bfqq_group(bfqq));
++#endif
++
++ /*
++ * The queue is not empty, because a new request just
++ * arrived. Hence we can safely expire the queue, in
++ * case of budget timeout, without risking that the
++ * timestamps of the queue are not updated correctly.
++ * See [1] for more details.
++ */
++ if (budget_timeout)
++ bfq_bfqq_expire(bfqd, bfqq, false,
++ BFQ_BFQQ_BUDGET_TIMEOUT);
++
++ /*
++ * Let the request rip immediately, or let a new queue be
++ * selected if bfqq has just been expired.
++ */
++ __blk_run_queue(bfqd->queue);
++ }
++}
++
++static void bfq_insert_request(struct request_queue *q, struct request *rq)
++{
++ struct bfq_data *bfqd = q->elevator->elevator_data;
++ struct bfq_queue *bfqq = RQ_BFQQ(rq);
++
++ assert_spin_locked(bfqd->queue->queue_lock);
++
++ bfq_add_request(rq);
++
++ rq->fifo_time = jiffies + bfqd->bfq_fifo_expire[rq_is_sync(rq)];
++ list_add_tail(&rq->queuelist, &bfqq->fifo);
++
++ bfq_rq_enqueued(bfqd, bfqq, rq);
++}
++
++static void bfq_update_hw_tag(struct bfq_data *bfqd)
++{
++ bfqd->max_rq_in_driver = max(bfqd->max_rq_in_driver,
++ bfqd->rq_in_driver);
++
++ if (bfqd->hw_tag == 1)
++ return;
++
++ /*
++ * This sample is valid if the number of outstanding requests
++ * is large enough to allow a queueing behavior. Note that the
++ * sum is not exact, as it's not taking into account deactivated
++ * requests.
++ */
++ if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD)
++ return;
++
++ if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES)
++ return;
++
++ bfqd->hw_tag = bfqd->max_rq_in_driver > BFQ_HW_QUEUE_THRESHOLD;
++ bfqd->max_rq_in_driver = 0;
++ bfqd->hw_tag_samples = 0;
++}
++
++static void bfq_completed_request(struct request_queue *q, struct request *rq)
++{
++ struct bfq_queue *bfqq = RQ_BFQQ(rq);
++ struct bfq_data *bfqd = bfqq->bfqd;
++ bool sync = bfq_bfqq_sync(bfqq);
++
++ bfq_log_bfqq(bfqd, bfqq, "completed one req with %u sects left (%d)",
++ blk_rq_sectors(rq), sync);
++
++ bfq_update_hw_tag(bfqd);
++
++ BUG_ON(!bfqd->rq_in_driver);
++ BUG_ON(!bfqq->dispatched);
++ bfqd->rq_in_driver--;
++ bfqq->dispatched--;
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_update_completion(bfqq_group(bfqq),
++ rq_start_time_ns(rq),
++ rq_io_start_time_ns(rq), rq->cmd_flags);
++#endif
++
++ if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) {
++ bfq_weights_tree_remove(bfqd, &bfqq->entity,
++ &bfqd->queue_weights_tree);
++ if (!blk_queue_nonrot(bfqd->queue)) {
++ BUG_ON(!bfqd->busy_in_flight_queues);
++ bfqd->busy_in_flight_queues--;
++ if (bfq_bfqq_constantly_seeky(bfqq)) {
++ BUG_ON(!bfqd->
++ const_seeky_busy_in_flight_queues);
++ bfqd->const_seeky_busy_in_flight_queues--;
++ }
++ }
++ }
++
++ if (sync) {
++ bfqd->sync_flight--;
++ RQ_BIC(rq)->ttime.last_end_request = jiffies;
++ }
++
++ /*
++ * If we are waiting to discover whether the request pattern of the
++ * task associated with the queue is actually isochronous, and
++ * both requisites for this condition to hold are satisfied, then
++ * compute soft_rt_next_start (see the comments to the function
++ * bfq_bfqq_softrt_next_start()).
++ */
++ if (bfq_bfqq_softrt_update(bfqq) && bfqq->dispatched == 0 &&
++ RB_EMPTY_ROOT(&bfqq->sort_list))
++ bfqq->soft_rt_next_start =
++ bfq_bfqq_softrt_next_start(bfqd, bfqq);
++
++ /*
++ * If this is the in-service queue, check if it needs to be expired,
++ * or if we want to idle in case it has no pending requests.
++ */
++ if (bfqd->in_service_queue == bfqq) {
++ if (bfq_bfqq_budget_new(bfqq))
++ bfq_set_budget_timeout(bfqd);
++
++ if (bfq_bfqq_must_idle(bfqq)) {
++ bfq_arm_slice_timer(bfqd);
++ goto out;
++ } else if (bfq_may_expire_for_budg_timeout(bfqq))
++ bfq_bfqq_expire(bfqd, bfqq, false,
++ BFQ_BFQQ_BUDGET_TIMEOUT);
++ else if (RB_EMPTY_ROOT(&bfqq->sort_list) &&
++ (bfqq->dispatched == 0 ||
++ !bfq_bfqq_may_idle(bfqq)))
++ bfq_bfqq_expire(bfqd, bfqq, false,
++ BFQ_BFQQ_NO_MORE_REQUESTS);
++ }
++
++ if (!bfqd->rq_in_driver)
++ bfq_schedule_dispatch(bfqd);
++
++out:
++ return;
++}
++
++static int __bfq_may_queue(struct bfq_queue *bfqq)
++{
++ if (bfq_bfqq_wait_request(bfqq) && bfq_bfqq_must_alloc(bfqq)) {
++ bfq_clear_bfqq_must_alloc(bfqq);
++ return ELV_MQUEUE_MUST;
++ }
++
++ return ELV_MQUEUE_MAY;
++}
++
++static int bfq_may_queue(struct request_queue *q, int rw)
++{
++ struct bfq_data *bfqd = q->elevator->elevator_data;
++ struct task_struct *tsk = current;
++ struct bfq_io_cq *bic;
++ struct bfq_queue *bfqq;
++
++ /*
++ * Don't force setup of a queue from here, as a call to may_queue
++ * does not necessarily imply that a request actually will be
++ * queued. So just lookup a possibly existing queue, or return
++ * 'may queue' if that fails.
++ */
++ bic = bfq_bic_lookup(bfqd, tsk->io_context);
++ if (!bic)
++ return ELV_MQUEUE_MAY;
++
++ bfqq = bic_to_bfqq(bic, rw_is_sync(rw));
++ if (bfqq)
++ return __bfq_may_queue(bfqq);
++
++ return ELV_MQUEUE_MAY;
++}
++
++/*
++ * Queue lock held here.
++ */
++static void bfq_put_request(struct request *rq)
++{
++ struct bfq_queue *bfqq = RQ_BFQQ(rq);
++
++ if (bfqq) {
++ const int rw = rq_data_dir(rq);
++
++ BUG_ON(!bfqq->allocated[rw]);
++ bfqq->allocated[rw]--;
++
++ rq->elv.priv[0] = NULL;
++ rq->elv.priv[1] = NULL;
++
++ bfq_log_bfqq(bfqq->bfqd, bfqq, "put_request %p, %d",
++ bfqq, atomic_read(&bfqq->ref));
++ bfq_put_queue(bfqq);
++ }
++}
++
++/*
++ * Allocate bfq data structures associated with this request.
++ */
++static int bfq_set_request(struct request_queue *q, struct request *rq,
++ struct bio *bio, gfp_t gfp_mask)
++{
++ struct bfq_data *bfqd = q->elevator->elevator_data;
++ struct bfq_io_cq *bic = icq_to_bic(rq->elv.icq);
++ const int rw = rq_data_dir(rq);
++ const int is_sync = rq_is_sync(rq);
++ struct bfq_queue *bfqq;
++ unsigned long flags;
++
++ might_sleep_if(gfpflags_allow_blocking(gfp_mask));
++
++ bfq_check_ioprio_change(bic, bio);
++
++ spin_lock_irqsave(q->queue_lock, flags);
++
++ if (!bic)
++ goto queue_fail;
++
++ bfq_bic_update_cgroup(bic, bio);
++
++ bfqq = bic_to_bfqq(bic, is_sync);
++ if (!bfqq || bfqq == &bfqd->oom_bfqq) {
++ bfqq = bfq_get_queue(bfqd, bio, is_sync, bic, gfp_mask);
++ bic_set_bfqq(bic, bfqq, is_sync);
++ if (is_sync) {
++ if (bfqd->large_burst)
++ bfq_mark_bfqq_in_large_burst(bfqq);
++ else
++ bfq_clear_bfqq_in_large_burst(bfqq);
++ }
++ }
++
++ bfqq->allocated[rw]++;
++ atomic_inc(&bfqq->ref);
++ bfq_log_bfqq(bfqd, bfqq, "set_request: bfqq %p, %d", bfqq,
++ atomic_read(&bfqq->ref));
++
++ rq->elv.priv[0] = bic;
++ rq->elv.priv[1] = bfqq;
++
++ spin_unlock_irqrestore(q->queue_lock, flags);
++
++ return 0;
++
++queue_fail:
++ bfq_schedule_dispatch(bfqd);
++ spin_unlock_irqrestore(q->queue_lock, flags);
++
++ return 1;
++}
++
++static void bfq_kick_queue(struct work_struct *work)
++{
++ struct bfq_data *bfqd =
++ container_of(work, struct bfq_data, unplug_work);
++ struct request_queue *q = bfqd->queue;
++
++ spin_lock_irq(q->queue_lock);
++ __blk_run_queue(q);
++ spin_unlock_irq(q->queue_lock);
++}
++
++/*
++ * Handler of the expiration of the timer running if the in-service queue
++ * is idling inside its time slice.
++ */
++static void bfq_idle_slice_timer(unsigned long data)
++{
++ struct bfq_data *bfqd = (struct bfq_data *)data;
++ struct bfq_queue *bfqq;
++ unsigned long flags;
++ enum bfqq_expiration reason;
++
++ spin_lock_irqsave(bfqd->queue->queue_lock, flags);
++
++ bfqq = bfqd->in_service_queue;
++ /*
++ * Theoretical race here: the in-service queue can be NULL or
++ * different from the queue that was idling if the timer handler
++ * spins on the queue_lock and a new request arrives for the
++ * current queue and there is a full dispatch cycle that changes
++ * the in-service queue. This can hardly happen, but in the worst
++ * case we just expire a queue too early.
++ */
++ if (bfqq) {
++ bfq_log_bfqq(bfqd, bfqq, "slice_timer expired");
++ if (bfq_bfqq_budget_timeout(bfqq))
++ /*
++ * Also here the queue can be safely expired
++ * for budget timeout without wasting
++ * guarantees
++ */
++ reason = BFQ_BFQQ_BUDGET_TIMEOUT;
++ else if (bfqq->queued[0] == 0 && bfqq->queued[1] == 0)
++ /*
++ * The queue may not be empty upon timer expiration,
++ * because we may not disable the timer when the
++ * first request of the in-service queue arrives
++ * during disk idling.
++ */
++ reason = BFQ_BFQQ_TOO_IDLE;
++ else
++ goto schedule_dispatch;
++
++ bfq_bfqq_expire(bfqd, bfqq, true, reason);
++ }
++
++schedule_dispatch:
++ bfq_schedule_dispatch(bfqd);
++
++ spin_unlock_irqrestore(bfqd->queue->queue_lock, flags);
++}
++
++static void bfq_shutdown_timer_wq(struct bfq_data *bfqd)
++{
++ del_timer_sync(&bfqd->idle_slice_timer);
++ cancel_work_sync(&bfqd->unplug_work);
++}
++
++static void __bfq_put_async_bfqq(struct bfq_data *bfqd,
++ struct bfq_queue **bfqq_ptr)
++{
++ struct bfq_group *root_group = bfqd->root_group;
++ struct bfq_queue *bfqq = *bfqq_ptr;
++
++ bfq_log(bfqd, "put_async_bfqq: %p", bfqq);
++ if (bfqq) {
++ bfq_bfqq_move(bfqd, bfqq, &bfqq->entity, root_group);
++ bfq_log_bfqq(bfqd, bfqq, "put_async_bfqq: putting %p, %d",
++ bfqq, atomic_read(&bfqq->ref));
++ bfq_put_queue(bfqq);
++ *bfqq_ptr = NULL;
++ }
++}
++
++/*
++ * Release all the bfqg references to its async queues. If we are
++ * deallocating the group these queues may still contain requests, so
++ * we reparent them to the root cgroup (i.e., the only one that will
++ * exist for sure until all the requests on a device are gone).
++ */
++static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
++{
++ int i, j;
++
++ for (i = 0; i < 2; i++)
++ for (j = 0; j < IOPRIO_BE_NR; j++)
++ __bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]);
++
++ __bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);
++}
++
++static void bfq_exit_queue(struct elevator_queue *e)
++{
++ struct bfq_data *bfqd = e->elevator_data;
++ struct request_queue *q = bfqd->queue;
++ struct bfq_queue *bfqq, *n;
++
++ bfq_shutdown_timer_wq(bfqd);
++
++ spin_lock_irq(q->queue_lock);
++
++ BUG_ON(bfqd->in_service_queue);
++ list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list)
++ bfq_deactivate_bfqq(bfqd, bfqq, 0);
++
++ spin_unlock_irq(q->queue_lock);
++
++ bfq_shutdown_timer_wq(bfqd);
++
++ synchronize_rcu();
++
++ BUG_ON(timer_pending(&bfqd->idle_slice_timer));
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ blkcg_deactivate_policy(q, &blkcg_policy_bfq);
++#else
++ kfree(bfqd->root_group);
++#endif
++
++ kfree(bfqd);
++}
++
++static void bfq_init_root_group(struct bfq_group *root_group,
++ struct bfq_data *bfqd)
++{
++ int i;
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ root_group->entity.parent = NULL;
++ root_group->my_entity = NULL;
++ root_group->bfqd = bfqd;
++#endif
++ for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
++ root_group->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
++}
++
++static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
++{
++ struct bfq_data *bfqd;
++ struct elevator_queue *eq;
++
++ eq = elevator_alloc(q, e);
++ if (!eq)
++ return -ENOMEM;
++
++ bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node);
++ if (!bfqd) {
++ kobject_put(&eq->kobj);
++ return -ENOMEM;
++ }
++ eq->elevator_data = bfqd;
++
++ /*
++ * Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues.
++ * Grab a permanent reference to it, so that the normal code flow
++ * will not attempt to free it.
++ */
++ bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, NULL, 1, 0);
++ atomic_inc(&bfqd->oom_bfqq.ref);
++ bfqd->oom_bfqq.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO;
++ bfqd->oom_bfqq.new_ioprio_class = IOPRIO_CLASS_BE;
++ bfqd->oom_bfqq.entity.new_weight =
++ bfq_ioprio_to_weight(bfqd->oom_bfqq.new_ioprio);
++ /*
++ * Trigger weight initialization, according to ioprio, at the
++ * oom_bfqq's first activation. The oom_bfqq's ioprio and ioprio
++ * class won't be changed any more.
++ */
++ bfqd->oom_bfqq.entity.prio_changed = 1;
++
++ bfqd->queue = q;
++
++ spin_lock_irq(q->queue_lock);
++ q->elevator = eq;
++ spin_unlock_irq(q->queue_lock);
++
++ bfqd->root_group = bfq_create_group_hierarchy(bfqd, q->node);
++ if (!bfqd->root_group)
++ goto out_free;
++ bfq_init_root_group(bfqd->root_group, bfqd);
++ bfq_init_entity(&bfqd->oom_bfqq.entity, bfqd->root_group);
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqd->active_numerous_groups = 0;
++#endif
++
++ init_timer(&bfqd->idle_slice_timer);
++ bfqd->idle_slice_timer.function = bfq_idle_slice_timer;
++ bfqd->idle_slice_timer.data = (unsigned long)bfqd;
++
++ bfqd->queue_weights_tree = RB_ROOT;
++ bfqd->group_weights_tree = RB_ROOT;
++
++ INIT_WORK(&bfqd->unplug_work, bfq_kick_queue);
++
++ INIT_LIST_HEAD(&bfqd->active_list);
++ INIT_LIST_HEAD(&bfqd->idle_list);
++ INIT_HLIST_HEAD(&bfqd->burst_list);
++
++ bfqd->hw_tag = -1;
++
++ bfqd->bfq_max_budget = bfq_default_max_budget;
++
++ bfqd->bfq_fifo_expire[0] = bfq_fifo_expire[0];
++ bfqd->bfq_fifo_expire[1] = bfq_fifo_expire[1];
++ bfqd->bfq_back_max = bfq_back_max;
++ bfqd->bfq_back_penalty = bfq_back_penalty;
++ bfqd->bfq_slice_idle = bfq_slice_idle;
++ bfqd->bfq_class_idle_last_service = 0;
++ bfqd->bfq_max_budget_async_rq = bfq_max_budget_async_rq;
++ bfqd->bfq_timeout[BLK_RW_ASYNC] = bfq_timeout_async;
++ bfqd->bfq_timeout[BLK_RW_SYNC] = bfq_timeout_sync;
++
++ bfqd->bfq_requests_within_timer = 120;
++
++ bfqd->bfq_large_burst_thresh = 11;
++ bfqd->bfq_burst_interval = msecs_to_jiffies(500);
++
++ bfqd->low_latency = true;
++
++ bfqd->bfq_wr_coeff = 20;
++ bfqd->bfq_wr_rt_max_time = msecs_to_jiffies(300);
++ bfqd->bfq_wr_max_time = 0;
++ bfqd->bfq_wr_min_idle_time = msecs_to_jiffies(2000);
++ bfqd->bfq_wr_min_inter_arr_async = msecs_to_jiffies(500);
++ bfqd->bfq_wr_max_softrt_rate = 7000; /*
++ * Approximate rate required
++ * to playback or record a
++ * high-definition compressed
++ * video.
++ */
++ bfqd->wr_busy_queues = 0;
++ bfqd->busy_in_flight_queues = 0;
++ bfqd->const_seeky_busy_in_flight_queues = 0;
++
++ /*
++ * Begin by assuming, optimistically, that the device peak rate is
++ * equal to the highest reference rate.
++ */
++ bfqd->RT_prod = R_fast[blk_queue_nonrot(bfqd->queue)] *
++ T_fast[blk_queue_nonrot(bfqd->queue)];
++ bfqd->peak_rate = R_fast[blk_queue_nonrot(bfqd->queue)];
++ bfqd->device_speed = BFQ_BFQD_FAST;
++
++ return 0;
++
++out_free:
++ kfree(bfqd);
++ kobject_put(&eq->kobj);
++ return -ENOMEM;
++}
++
++static void bfq_slab_kill(void)
++{
++ if (bfq_pool)
++ kmem_cache_destroy(bfq_pool);
++}
++
++static int __init bfq_slab_setup(void)
++{
++ bfq_pool = KMEM_CACHE(bfq_queue, 0);
++ if (!bfq_pool)
++ return -ENOMEM;
++ return 0;
++}
++
++static ssize_t bfq_var_show(unsigned int var, char *page)
++{
++ return sprintf(page, "%d\n", var);
++}
++
++static ssize_t bfq_var_store(unsigned long *var, const char *page,
++ size_t count)
++{
++ unsigned long new_val;
++ int ret = kstrtoul(page, 10, &new_val);
++
++ if (ret == 0)
++ *var = new_val;
++
++ return count;
++}
++
++static ssize_t bfq_wr_max_time_show(struct elevator_queue *e, char *page)
++{
++ struct bfq_data *bfqd = e->elevator_data;
++ return sprintf(page, "%d\n", bfqd->bfq_wr_max_time > 0 ?
++ jiffies_to_msecs(bfqd->bfq_wr_max_time) :
++ jiffies_to_msecs(bfq_wr_duration(bfqd)));
++}
++
++static ssize_t bfq_weights_show(struct elevator_queue *e, char *page)
++{
++ struct bfq_queue *bfqq;
++ struct bfq_data *bfqd = e->elevator_data;
++ ssize_t num_char = 0;
++
++ num_char += sprintf(page + num_char, "Tot reqs queued %d\n\n",
++ bfqd->queued);
++
++ spin_lock_irq(bfqd->queue->queue_lock);
++
++ num_char += sprintf(page + num_char, "Active:\n");
++ list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list) {
++ num_char += sprintf(page + num_char,
++ "pid%d: weight %hu, nr_queued %d %d, dur %d/%u\n",
++ bfqq->pid,
++ bfqq->entity.weight,
++ bfqq->queued[0],
++ bfqq->queued[1],
++ jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish),
++ jiffies_to_msecs(bfqq->wr_cur_max_time));
++ }
++
++ num_char += sprintf(page + num_char, "Idle:\n");
++ list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list) {
++ num_char += sprintf(page + num_char,
++ "pid%d: weight %hu, dur %d/%u\n",
++ bfqq->pid,
++ bfqq->entity.weight,
++ jiffies_to_msecs(jiffies -
++ bfqq->last_wr_start_finish),
++ jiffies_to_msecs(bfqq->wr_cur_max_time));
++ }
++
++ spin_unlock_irq(bfqd->queue->queue_lock);
++
++ return num_char;
++}
++
++#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
++static ssize_t __FUNC(struct elevator_queue *e, char *page) \
++{ \
++ struct bfq_data *bfqd = e->elevator_data; \
++ unsigned int __data = __VAR; \
++ if (__CONV) \
++ __data = jiffies_to_msecs(__data); \
++ return bfq_var_show(__data, (page)); \
++}
++SHOW_FUNCTION(bfq_fifo_expire_sync_show, bfqd->bfq_fifo_expire[1], 1);
++SHOW_FUNCTION(bfq_fifo_expire_async_show, bfqd->bfq_fifo_expire[0], 1);
++SHOW_FUNCTION(bfq_back_seek_max_show, bfqd->bfq_back_max, 0);
++SHOW_FUNCTION(bfq_back_seek_penalty_show, bfqd->bfq_back_penalty, 0);
++SHOW_FUNCTION(bfq_slice_idle_show, bfqd->bfq_slice_idle, 1);
++SHOW_FUNCTION(bfq_max_budget_show, bfqd->bfq_user_max_budget, 0);
++SHOW_FUNCTION(bfq_max_budget_async_rq_show,
++ bfqd->bfq_max_budget_async_rq, 0);
++SHOW_FUNCTION(bfq_timeout_sync_show, bfqd->bfq_timeout[BLK_RW_SYNC], 1);
++SHOW_FUNCTION(bfq_timeout_async_show, bfqd->bfq_timeout[BLK_RW_ASYNC], 1);
++SHOW_FUNCTION(bfq_low_latency_show, bfqd->low_latency, 0);
++SHOW_FUNCTION(bfq_wr_coeff_show, bfqd->bfq_wr_coeff, 0);
++SHOW_FUNCTION(bfq_wr_rt_max_time_show, bfqd->bfq_wr_rt_max_time, 1);
++SHOW_FUNCTION(bfq_wr_min_idle_time_show, bfqd->bfq_wr_min_idle_time, 1);
++SHOW_FUNCTION(bfq_wr_min_inter_arr_async_show, bfqd->bfq_wr_min_inter_arr_async,
++ 1);
++SHOW_FUNCTION(bfq_wr_max_softrt_rate_show, bfqd->bfq_wr_max_softrt_rate, 0);
++#undef SHOW_FUNCTION
++
++#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
++static ssize_t \
++__FUNC(struct elevator_queue *e, const char *page, size_t count) \
++{ \
++ struct bfq_data *bfqd = e->elevator_data; \
++ unsigned long uninitialized_var(__data); \
++ int ret = bfq_var_store(&__data, (page), count); \
++ if (__data < (MIN)) \
++ __data = (MIN); \
++ else if (__data > (MAX)) \
++ __data = (MAX); \
++ if (__CONV) \
++ *(__PTR) = msecs_to_jiffies(__data); \
++ else \
++ *(__PTR) = __data; \
++ return ret; \
++}
++STORE_FUNCTION(bfq_fifo_expire_sync_store, &bfqd->bfq_fifo_expire[1], 1,
++ INT_MAX, 1);
++STORE_FUNCTION(bfq_fifo_expire_async_store, &bfqd->bfq_fifo_expire[0], 1,
++ INT_MAX, 1);
++STORE_FUNCTION(bfq_back_seek_max_store, &bfqd->bfq_back_max, 0, INT_MAX, 0);
++STORE_FUNCTION(bfq_back_seek_penalty_store, &bfqd->bfq_back_penalty, 1,
++ INT_MAX, 0);
++STORE_FUNCTION(bfq_slice_idle_store, &bfqd->bfq_slice_idle, 0, INT_MAX, 1);
++STORE_FUNCTION(bfq_max_budget_async_rq_store, &bfqd->bfq_max_budget_async_rq,
++ 1, INT_MAX, 0);
++STORE_FUNCTION(bfq_timeout_async_store, &bfqd->bfq_timeout[BLK_RW_ASYNC], 0,
++ INT_MAX, 1);
++STORE_FUNCTION(bfq_wr_coeff_store, &bfqd->bfq_wr_coeff, 1, INT_MAX, 0);
++STORE_FUNCTION(bfq_wr_max_time_store, &bfqd->bfq_wr_max_time, 0, INT_MAX, 1);
++STORE_FUNCTION(bfq_wr_rt_max_time_store, &bfqd->bfq_wr_rt_max_time, 0, INT_MAX,
++ 1);
++STORE_FUNCTION(bfq_wr_min_idle_time_store, &bfqd->bfq_wr_min_idle_time, 0,
++ INT_MAX, 1);
++STORE_FUNCTION(bfq_wr_min_inter_arr_async_store,
++ &bfqd->bfq_wr_min_inter_arr_async, 0, INT_MAX, 1);
++STORE_FUNCTION(bfq_wr_max_softrt_rate_store, &bfqd->bfq_wr_max_softrt_rate, 0,
++ INT_MAX, 0);
++#undef STORE_FUNCTION
++
++/* do nothing for the moment */
++static ssize_t bfq_weights_store(struct elevator_queue *e,
++ const char *page, size_t count)
++{
++ return count;
++}
++
++static unsigned long bfq_estimated_max_budget(struct bfq_data *bfqd)
++{
++ u64 timeout = jiffies_to_msecs(bfqd->bfq_timeout[BLK_RW_SYNC]);
++
++ if (bfqd->peak_rate_samples >= BFQ_PEAK_RATE_SAMPLES)
++ return bfq_calc_max_budget(bfqd->peak_rate, timeout);
++ else
++ return bfq_default_max_budget;
++}
++
++static ssize_t bfq_max_budget_store(struct elevator_queue *e,
++ const char *page, size_t count)
++{
++ struct bfq_data *bfqd = e->elevator_data;
++ unsigned long uninitialized_var(__data);
++ int ret = bfq_var_store(&__data, (page), count);
++
++ if (__data == 0)
++ bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd);
++ else {
++ if (__data > INT_MAX)
++ __data = INT_MAX;
++ bfqd->bfq_max_budget = __data;
++ }
++
++ bfqd->bfq_user_max_budget = __data;
++
++ return ret;
++}
++
++static ssize_t bfq_timeout_sync_store(struct elevator_queue *e,
++ const char *page, size_t count)
++{
++ struct bfq_data *bfqd = e->elevator_data;
++ unsigned long uninitialized_var(__data);
++ int ret = bfq_var_store(&__data, (page), count);
++
++ if (__data < 1)
++ __data = 1;
++ else if (__data > INT_MAX)
++ __data = INT_MAX;
++
++ bfqd->bfq_timeout[BLK_RW_SYNC] = msecs_to_jiffies(__data);
++ if (bfqd->bfq_user_max_budget == 0)
++ bfqd->bfq_max_budget = bfq_estimated_max_budget(bfqd);
++
++ return ret;
++}
++
++static ssize_t bfq_low_latency_store(struct elevator_queue *e,
++ const char *page, size_t count)
++{
++ struct bfq_data *bfqd = e->elevator_data;
++ unsigned long uninitialized_var(__data);
++ int ret = bfq_var_store(&__data, (page), count);
++
++ if (__data > 1)
++ __data = 1;
++ if (__data == 0 && bfqd->low_latency != 0)
++ bfq_end_wr(bfqd);
++ bfqd->low_latency = __data;
++
++ return ret;
++}
++
++#define BFQ_ATTR(name) \
++ __ATTR(name, S_IRUGO|S_IWUSR, bfq_##name##_show, bfq_##name##_store)
++
++static struct elv_fs_entry bfq_attrs[] = {
++ BFQ_ATTR(fifo_expire_sync),
++ BFQ_ATTR(fifo_expire_async),
++ BFQ_ATTR(back_seek_max),
++ BFQ_ATTR(back_seek_penalty),
++ BFQ_ATTR(slice_idle),
++ BFQ_ATTR(max_budget),
++ BFQ_ATTR(max_budget_async_rq),
++ BFQ_ATTR(timeout_sync),
++ BFQ_ATTR(timeout_async),
++ BFQ_ATTR(low_latency),
++ BFQ_ATTR(wr_coeff),
++ BFQ_ATTR(wr_max_time),
++ BFQ_ATTR(wr_rt_max_time),
++ BFQ_ATTR(wr_min_idle_time),
++ BFQ_ATTR(wr_min_inter_arr_async),
++ BFQ_ATTR(wr_max_softrt_rate),
++ BFQ_ATTR(weights),
++ __ATTR_NULL
++};
++
++static struct elevator_type iosched_bfq = {
++ .ops = {
++ .elevator_merge_fn = bfq_merge,
++ .elevator_merged_fn = bfq_merged_request,
++ .elevator_merge_req_fn = bfq_merged_requests,
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ .elevator_bio_merged_fn = bfq_bio_merged,
++#endif
++ .elevator_allow_merge_fn = bfq_allow_merge,
++ .elevator_dispatch_fn = bfq_dispatch_requests,
++ .elevator_add_req_fn = bfq_insert_request,
++ .elevator_activate_req_fn = bfq_activate_request,
++ .elevator_deactivate_req_fn = bfq_deactivate_request,
++ .elevator_completed_req_fn = bfq_completed_request,
++ .elevator_former_req_fn = elv_rb_former_request,
++ .elevator_latter_req_fn = elv_rb_latter_request,
++ .elevator_init_icq_fn = bfq_init_icq,
++ .elevator_exit_icq_fn = bfq_exit_icq,
++ .elevator_set_req_fn = bfq_set_request,
++ .elevator_put_req_fn = bfq_put_request,
++ .elevator_may_queue_fn = bfq_may_queue,
++ .elevator_init_fn = bfq_init_queue,
++ .elevator_exit_fn = bfq_exit_queue,
++ },
++ .icq_size = sizeof(struct bfq_io_cq),
++ .icq_align = __alignof__(struct bfq_io_cq),
++ .elevator_attrs = bfq_attrs,
++ .elevator_name = "bfq",
++ .elevator_owner = THIS_MODULE,
++};
++
++static int __init bfq_init(void)
++{
++ int ret;
++
++ /*
++ * Can be 0 on HZ < 1000 setups.
++ */
++ if (bfq_slice_idle == 0)
++ bfq_slice_idle = 1;
++
++ if (bfq_timeout_async == 0)
++ bfq_timeout_async = 1;
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ ret = blkcg_policy_register(&blkcg_policy_bfq);
++ if (ret)
++ return ret;
++#endif
++
++ ret = -ENOMEM;
++ if (bfq_slab_setup())
++ goto err_pol_unreg;
++
++ /*
++ * Times to load large popular applications for the typical systems
++ * installed on the reference devices (see the comments before the
++ * definitions of the two arrays).
++ */
++ T_slow[0] = msecs_to_jiffies(2600);
++ T_slow[1] = msecs_to_jiffies(1000);
++ T_fast[0] = msecs_to_jiffies(5500);
++ T_fast[1] = msecs_to_jiffies(2000);
++
++ /*
++ * Thresholds that determine the switch between speed classes (see
++ * the comments before the definition of the array).
++ */
++ device_speed_thresh[0] = (R_fast[0] + R_slow[0]) / 2;
++ device_speed_thresh[1] = (R_fast[1] + R_slow[1]) / 2;
++
++ ret = elv_register(&iosched_bfq);
++ if (ret)
++ goto err_pol_unreg;
++
++ pr_info("BFQ I/O-scheduler: v7r11");
++
++ return 0;
++
++err_pol_unreg:
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ blkcg_policy_unregister(&blkcg_policy_bfq);
++#endif
++ return ret;
++}
++
++static void __exit bfq_exit(void)
++{
++ elv_unregister(&iosched_bfq);
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ blkcg_policy_unregister(&blkcg_policy_bfq);
++#endif
++ bfq_slab_kill();
++}
++
++module_init(bfq_init);
++module_exit(bfq_exit);
++
++MODULE_AUTHOR("Arianna Avanzini, Fabio Checconi, Paolo Valente");
++MODULE_LICENSE("GPL");
+diff --git a/block/bfq-sched.c b/block/bfq-sched.c
+new file mode 100644
+index 000000000000..a64fec1197f7
+--- /dev/null
++++ b/block/bfq-sched.c
+@@ -0,0 +1,1200 @@
++/*
++ * BFQ: Hierarchical B-WF2Q+ scheduler.
++ *
++ * Based on ideas and code from CFQ:
++ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
++ *
++ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
++ * Paolo Valente <paolo.valente@unimore.it>
++ *
++ * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
++ */
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++#define for_each_entity(entity) \
++ for (; entity ; entity = entity->parent)
++
++#define for_each_entity_safe(entity, parent) \
++ for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
++
++
++static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd,
++ int extract,
++ struct bfq_data *bfqd);
++
++static struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
++
++static void bfq_update_budget(struct bfq_entity *next_in_service)
++{
++ struct bfq_entity *bfqg_entity;
++ struct bfq_group *bfqg;
++ struct bfq_sched_data *group_sd;
++
++ BUG_ON(!next_in_service);
++
++ group_sd = next_in_service->sched_data;
++
++ bfqg = container_of(group_sd, struct bfq_group, sched_data);
++ /*
++ * bfq_group's my_entity field is not NULL only if the group
++ * is not the root group. We must not touch the root entity
++ * as it must never become an in-service entity.
++ */
++ bfqg_entity = bfqg->my_entity;
++ if (bfqg_entity)
++ bfqg_entity->budget = next_in_service->budget;
++}
++
++static int bfq_update_next_in_service(struct bfq_sched_data *sd)
++{
++ struct bfq_entity *next_in_service;
++
++ if (sd->in_service_entity)
++ /* will update/requeue at the end of service */
++ return 0;
++
++ /*
++ * NOTE: this can be improved in many ways, such as returning
++ * 1 (and thus propagating upwards the update) only when the
++ * budget changes, or caching the bfqq that will be scheduled
++ * next from this subtree. By now we worry more about
++ * correctness than about performance...
++ */
++ next_in_service = bfq_lookup_next_entity(sd, 0, NULL);
++ sd->next_in_service = next_in_service;
++
++ if (next_in_service)
++ bfq_update_budget(next_in_service);
++
++ return 1;
++}
++
++static void bfq_check_next_in_service(struct bfq_sched_data *sd,
++ struct bfq_entity *entity)
++{
++ BUG_ON(sd->next_in_service != entity);
++}
++#else
++#define for_each_entity(entity) \
++ for (; entity ; entity = NULL)
++
++#define for_each_entity_safe(entity, parent) \
++ for (parent = NULL; entity ; entity = parent)
++
++static int bfq_update_next_in_service(struct bfq_sched_data *sd)
++{
++ return 0;
++}
++
++static void bfq_check_next_in_service(struct bfq_sched_data *sd,
++ struct bfq_entity *entity)
++{
++}
++
++static void bfq_update_budget(struct bfq_entity *next_in_service)
++{
++}
++#endif
++
++/*
++ * Shift for timestamp calculations. This actually limits the maximum
++ * service allowed in one timestamp delta (small shift values increase it),
++ * the maximum total weight that can be used for the queues in the system
++ * (big shift values increase it), and the period of virtual time
++ * wraparounds.
++ */
++#define WFQ_SERVICE_SHIFT 22
++
++/**
++ * bfq_gt - compare two timestamps.
++ * @a: first ts.
++ * @b: second ts.
++ *
++ * Return @a > @b, dealing with wrapping correctly.
++ */
++static int bfq_gt(u64 a, u64 b)
++{
++ return (s64)(a - b) > 0;
++}
++
++static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity)
++{
++ struct bfq_queue *bfqq = NULL;
++
++ BUG_ON(!entity);
++
++ if (!entity->my_sched_data)
++ bfqq = container_of(entity, struct bfq_queue, entity);
++
++ return bfqq;
++}
++
++
++/**
++ * bfq_delta - map service into the virtual time domain.
++ * @service: amount of service.
++ * @weight: scale factor (weight of an entity or weight sum).
++ */
++static u64 bfq_delta(unsigned long service, unsigned long weight)
++{
++ u64 d = (u64)service << WFQ_SERVICE_SHIFT;
++
++ do_div(d, weight);
++ return d;
++}
++
++/**
++ * bfq_calc_finish - assign the finish time to an entity.
++ * @entity: the entity to act upon.
++ * @service: the service to be charged to the entity.
++ */
++static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service)
++{
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++
++ BUG_ON(entity->weight == 0);
++
++ entity->finish = entity->start +
++ bfq_delta(service, entity->weight);
++
++ if (bfqq) {
++ bfq_log_bfqq(bfqq->bfqd, bfqq,
++ "calc_finish: serv %lu, w %d",
++ service, entity->weight);
++ bfq_log_bfqq(bfqq->bfqd, bfqq,
++ "calc_finish: start %llu, finish %llu, delta %llu",
++ entity->start, entity->finish,
++ bfq_delta(service, entity->weight));
++ }
++}
++
++/**
++ * bfq_entity_of - get an entity from a node.
++ * @node: the node field of the entity.
++ *
++ * Convert a node pointer to the relative entity. This is used only
++ * to simplify the logic of some functions and not as the generic
++ * conversion mechanism because, e.g., in the tree walking functions,
++ * the check for a %NULL value would be redundant.
++ */
++static struct bfq_entity *bfq_entity_of(struct rb_node *node)
++{
++ struct bfq_entity *entity = NULL;
++
++ if (node)
++ entity = rb_entry(node, struct bfq_entity, rb_node);
++
++ return entity;
++}
++
++/**
++ * bfq_extract - remove an entity from a tree.
++ * @root: the tree root.
++ * @entity: the entity to remove.
++ */
++static void bfq_extract(struct rb_root *root, struct bfq_entity *entity)
++{
++ BUG_ON(entity->tree != root);
++
++ entity->tree = NULL;
++ rb_erase(&entity->rb_node, root);
++}
++
++/**
++ * bfq_idle_extract - extract an entity from the idle tree.
++ * @st: the service tree of the owning @entity.
++ * @entity: the entity being removed.
++ */
++static void bfq_idle_extract(struct bfq_service_tree *st,
++ struct bfq_entity *entity)
++{
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++ struct rb_node *next;
++
++ BUG_ON(entity->tree != &st->idle);
++
++ if (entity == st->first_idle) {
++ next = rb_next(&entity->rb_node);
++ st->first_idle = bfq_entity_of(next);
++ }
++
++ if (entity == st->last_idle) {
++ next = rb_prev(&entity->rb_node);
++ st->last_idle = bfq_entity_of(next);
++ }
++
++ bfq_extract(&st->idle, entity);
++
++ if (bfqq)
++ list_del(&bfqq->bfqq_list);
++}
++
++/**
++ * bfq_insert - generic tree insertion.
++ * @root: tree root.
++ * @entity: entity to insert.
++ *
++ * This is used for the idle and the active tree, since they are both
++ * ordered by finish time.
++ */
++static void bfq_insert(struct rb_root *root, struct bfq_entity *entity)
++{
++ struct bfq_entity *entry;
++ struct rb_node **node = &root->rb_node;
++ struct rb_node *parent = NULL;
++
++ BUG_ON(entity->tree);
++
++ while (*node) {
++ parent = *node;
++ entry = rb_entry(parent, struct bfq_entity, rb_node);
++
++ if (bfq_gt(entry->finish, entity->finish))
++ node = &parent->rb_left;
++ else
++ node = &parent->rb_right;
++ }
++
++ rb_link_node(&entity->rb_node, parent, node);
++ rb_insert_color(&entity->rb_node, root);
++
++ entity->tree = root;
++}
++
++/**
++ * bfq_update_min - update the min_start field of a entity.
++ * @entity: the entity to update.
++ * @node: one of its children.
++ *
++ * This function is called when @entity may store an invalid value for
++ * min_start due to updates to the active tree. The function assumes
++ * that the subtree rooted at @node (which may be its left or its right
++ * child) has a valid min_start value.
++ */
++static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node)
++{
++ struct bfq_entity *child;
++
++ if (node) {
++ child = rb_entry(node, struct bfq_entity, rb_node);
++ if (bfq_gt(entity->min_start, child->min_start))
++ entity->min_start = child->min_start;
++ }
++}
++
++/**
++ * bfq_update_active_node - recalculate min_start.
++ * @node: the node to update.
++ *
++ * @node may have changed position or one of its children may have moved,
++ * this function updates its min_start value. The left and right subtrees
++ * are assumed to hold a correct min_start value.
++ */
++static void bfq_update_active_node(struct rb_node *node)
++{
++ struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node);
++
++ entity->min_start = entity->start;
++ bfq_update_min(entity, node->rb_right);
++ bfq_update_min(entity, node->rb_left);
++}
++
++/**
++ * bfq_update_active_tree - update min_start for the whole active tree.
++ * @node: the starting node.
++ *
++ * @node must be the deepest modified node after an update. This function
++ * updates its min_start using the values held by its children, assuming
++ * that they did not change, and then updates all the nodes that may have
++ * changed in the path to the root. The only nodes that may have changed
++ * are the ones in the path or their siblings.
++ */
++static void bfq_update_active_tree(struct rb_node *node)
++{
++ struct rb_node *parent;
++
++up:
++ bfq_update_active_node(node);
++
++ parent = rb_parent(node);
++ if (!parent)
++ return;
++
++ if (node == parent->rb_left && parent->rb_right)
++ bfq_update_active_node(parent->rb_right);
++ else if (parent->rb_left)
++ bfq_update_active_node(parent->rb_left);
++
++ node = parent;
++ goto up;
++}
++
++static void bfq_weights_tree_add(struct bfq_data *bfqd,
++ struct bfq_entity *entity,
++ struct rb_root *root);
++
++static void bfq_weights_tree_remove(struct bfq_data *bfqd,
++ struct bfq_entity *entity,
++ struct rb_root *root);
++
++
++/**
++ * bfq_active_insert - insert an entity in the active tree of its
++ * group/device.
++ * @st: the service tree of the entity.
++ * @entity: the entity being inserted.
++ *
++ * The active tree is ordered by finish time, but an extra key is kept
++ * per each node, containing the minimum value for the start times of
++ * its children (and the node itself), so it's possible to search for
++ * the eligible node with the lowest finish time in logarithmic time.
++ */
++static void bfq_active_insert(struct bfq_service_tree *st,
++ struct bfq_entity *entity)
++{
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++ struct rb_node *node = &entity->rb_node;
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ struct bfq_sched_data *sd = NULL;
++ struct bfq_group *bfqg = NULL;
++ struct bfq_data *bfqd = NULL;
++#endif
++
++ bfq_insert(&st->active, entity);
++
++ if (node->rb_left)
++ node = node->rb_left;
++ else if (node->rb_right)
++ node = node->rb_right;
++
++ bfq_update_active_tree(node);
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ sd = entity->sched_data;
++ bfqg = container_of(sd, struct bfq_group, sched_data);
++ BUG_ON(!bfqg);
++ bfqd = (struct bfq_data *)bfqg->bfqd;
++#endif
++ if (bfqq)
++ list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list);
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ else { /* bfq_group */
++ BUG_ON(!bfqd);
++ bfq_weights_tree_add(bfqd, entity, &bfqd->group_weights_tree);
++ }
++ if (bfqg != bfqd->root_group) {
++ BUG_ON(!bfqg);
++ BUG_ON(!bfqd);
++ bfqg->active_entities++;
++ if (bfqg->active_entities == 2)
++ bfqd->active_numerous_groups++;
++ }
++#endif
++}
++
++/**
++ * bfq_ioprio_to_weight - calc a weight from an ioprio.
++ * @ioprio: the ioprio value to convert.
++ */
++static unsigned short bfq_ioprio_to_weight(int ioprio)
++{
++ BUG_ON(ioprio < 0 || ioprio >= IOPRIO_BE_NR);
++ return IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - ioprio;
++}
++
++/**
++ * bfq_weight_to_ioprio - calc an ioprio from a weight.
++ * @weight: the weight value to convert.
++ *
++ * To preserve as much as possible the old only-ioprio user interface,
++ * 0 is used as an escape ioprio value for weights (numerically) equal or
++ * larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF.
++ */
++static unsigned short bfq_weight_to_ioprio(int weight)
++{
++ BUG_ON(weight < BFQ_MIN_WEIGHT || weight > BFQ_MAX_WEIGHT);
++ return IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight < 0 ?
++ 0 : IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight;
++}
++
++static void bfq_get_entity(struct bfq_entity *entity)
++{
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++
++ if (bfqq) {
++ atomic_inc(&bfqq->ref);
++ bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d",
++ bfqq, atomic_read(&bfqq->ref));
++ }
++}
++
++/**
++ * bfq_find_deepest - find the deepest node that an extraction can modify.
++ * @node: the node being removed.
++ *
++ * Do the first step of an extraction in an rb tree, looking for the
++ * node that will replace @node, and returning the deepest node that
++ * the following modifications to the tree can touch. If @node is the
++ * last node in the tree return %NULL.
++ */
++static struct rb_node *bfq_find_deepest(struct rb_node *node)
++{
++ struct rb_node *deepest;
++
++ if (!node->rb_right && !node->rb_left)
++ deepest = rb_parent(node);
++ else if (!node->rb_right)
++ deepest = node->rb_left;
++ else if (!node->rb_left)
++ deepest = node->rb_right;
++ else {
++ deepest = rb_next(node);
++ if (deepest->rb_right)
++ deepest = deepest->rb_right;
++ else if (rb_parent(deepest) != node)
++ deepest = rb_parent(deepest);
++ }
++
++ return deepest;
++}
++
++/**
++ * bfq_active_extract - remove an entity from the active tree.
++ * @st: the service_tree containing the tree.
++ * @entity: the entity being removed.
++ */
++static void bfq_active_extract(struct bfq_service_tree *st,
++ struct bfq_entity *entity)
++{
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++ struct rb_node *node;
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ struct bfq_sched_data *sd = NULL;
++ struct bfq_group *bfqg = NULL;
++ struct bfq_data *bfqd = NULL;
++#endif
++
++ node = bfq_find_deepest(&entity->rb_node);
++ bfq_extract(&st->active, entity);
++
++ if (node)
++ bfq_update_active_tree(node);
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ sd = entity->sched_data;
++ bfqg = container_of(sd, struct bfq_group, sched_data);
++ BUG_ON(!bfqg);
++ bfqd = (struct bfq_data *)bfqg->bfqd;
++#endif
++ if (bfqq)
++ list_del(&bfqq->bfqq_list);
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ else { /* bfq_group */
++ BUG_ON(!bfqd);
++ bfq_weights_tree_remove(bfqd, entity,
++ &bfqd->group_weights_tree);
++ }
++ if (bfqg != bfqd->root_group) {
++ BUG_ON(!bfqg);
++ BUG_ON(!bfqd);
++ BUG_ON(!bfqg->active_entities);
++ bfqg->active_entities--;
++ if (bfqg->active_entities == 1) {
++ BUG_ON(!bfqd->active_numerous_groups);
++ bfqd->active_numerous_groups--;
++ }
++ }
++#endif
++}
++
++/**
++ * bfq_idle_insert - insert an entity into the idle tree.
++ * @st: the service tree containing the tree.
++ * @entity: the entity to insert.
++ */
++static void bfq_idle_insert(struct bfq_service_tree *st,
++ struct bfq_entity *entity)
++{
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++ struct bfq_entity *first_idle = st->first_idle;
++ struct bfq_entity *last_idle = st->last_idle;
++
++ if (!first_idle || bfq_gt(first_idle->finish, entity->finish))
++ st->first_idle = entity;
++ if (!last_idle || bfq_gt(entity->finish, last_idle->finish))
++ st->last_idle = entity;
++
++ bfq_insert(&st->idle, entity);
++
++ if (bfqq)
++ list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list);
++}
++
++/**
++ * bfq_forget_entity - remove an entity from the wfq trees.
++ * @st: the service tree.
++ * @entity: the entity being removed.
++ *
++ * Update the device status and forget everything about @entity, putting
++ * the device reference to it, if it is a queue. Entities belonging to
++ * groups are not refcounted.
++ */
++static void bfq_forget_entity(struct bfq_service_tree *st,
++ struct bfq_entity *entity)
++{
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++ struct bfq_sched_data *sd;
++
++ BUG_ON(!entity->on_st);
++
++ entity->on_st = 0;
++ st->wsum -= entity->weight;
++ if (bfqq) {
++ sd = entity->sched_data;
++ bfq_log_bfqq(bfqq->bfqd, bfqq, "forget_entity: %p %d",
++ bfqq, atomic_read(&bfqq->ref));
++ bfq_put_queue(bfqq);
++ }
++}
++
++/**
++ * bfq_put_idle_entity - release the idle tree ref of an entity.
++ * @st: service tree for the entity.
++ * @entity: the entity being released.
++ */
++static void bfq_put_idle_entity(struct bfq_service_tree *st,
++ struct bfq_entity *entity)
++{
++ bfq_idle_extract(st, entity);
++ bfq_forget_entity(st, entity);
++}
++
++/**
++ * bfq_forget_idle - update the idle tree if necessary.
++ * @st: the service tree to act upon.
++ *
++ * To preserve the global O(log N) complexity we only remove one entry here;
++ * as the idle tree will not grow indefinitely this can be done safely.
++ */
++static void bfq_forget_idle(struct bfq_service_tree *st)
++{
++ struct bfq_entity *first_idle = st->first_idle;
++ struct bfq_entity *last_idle = st->last_idle;
++
++ if (RB_EMPTY_ROOT(&st->active) && last_idle &&
++ !bfq_gt(last_idle->finish, st->vtime)) {
++ /*
++ * Forget the whole idle tree, increasing the vtime past
++ * the last finish time of idle entities.
++ */
++ st->vtime = last_idle->finish;
++ }
++
++ if (first_idle && !bfq_gt(first_idle->finish, st->vtime))
++ bfq_put_idle_entity(st, first_idle);
++}
++
++static struct bfq_service_tree *
++__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
++ struct bfq_entity *entity)
++{
++ struct bfq_service_tree *new_st = old_st;
++
++ if (entity->prio_changed) {
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++ unsigned short prev_weight, new_weight;
++ struct bfq_data *bfqd = NULL;
++ struct rb_root *root;
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ struct bfq_sched_data *sd;
++ struct bfq_group *bfqg;
++#endif
++
++ if (bfqq)
++ bfqd = bfqq->bfqd;
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ else {
++ sd = entity->my_sched_data;
++ bfqg = container_of(sd, struct bfq_group, sched_data);
++ BUG_ON(!bfqg);
++ bfqd = (struct bfq_data *)bfqg->bfqd;
++ BUG_ON(!bfqd);
++ }
++#endif
++
++ BUG_ON(old_st->wsum < entity->weight);
++ old_st->wsum -= entity->weight;
++
++ if (entity->new_weight != entity->orig_weight) {
++ if (entity->new_weight < BFQ_MIN_WEIGHT ||
++ entity->new_weight > BFQ_MAX_WEIGHT) {
++ printk(KERN_CRIT "update_weight_prio: "
++ "new_weight %d\n",
++ entity->new_weight);
++ BUG();
++ }
++ entity->orig_weight = entity->new_weight;
++ if (bfqq)
++ bfqq->ioprio =
++ bfq_weight_to_ioprio(entity->orig_weight);
++ }
++
++ if (bfqq)
++ bfqq->ioprio_class = bfqq->new_ioprio_class;
++ entity->prio_changed = 0;
++
++ /*
++ * NOTE: here we may be changing the weight too early,
++ * this will cause unfairness. The correct approach
++ * would have required additional complexity to defer
++ * weight changes to the proper time instants (i.e.,
++ * when entity->finish <= old_st->vtime).
++ */
++ new_st = bfq_entity_service_tree(entity);
++
++ prev_weight = entity->weight;
++ new_weight = entity->orig_weight *
++ (bfqq ? bfqq->wr_coeff : 1);
++ /*
++ * If the weight of the entity changes, remove the entity
++ * from its old weight counter (if there is a counter
++ * associated with the entity), and add it to the counter
++ * associated with its new weight.
++ */
++ if (prev_weight != new_weight) {
++ root = bfqq ? &bfqd->queue_weights_tree :
++ &bfqd->group_weights_tree;
++ bfq_weights_tree_remove(bfqd, entity, root);
++ }
++ entity->weight = new_weight;
++ /*
++ * Add the entity to its weights tree only if it is
++ * not associated with a weight-raised queue.
++ */
++ if (prev_weight != new_weight &&
++ (bfqq ? bfqq->wr_coeff == 1 : 1))
++ /* If we get here, root has been initialized. */
++ bfq_weights_tree_add(bfqd, entity, root);
++
++ new_st->wsum += entity->weight;
++
++ if (new_st != old_st)
++ entity->start = new_st->vtime;
++ }
++
++ return new_st;
++}
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++static void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg);
++#endif
++
++/**
++ * bfq_bfqq_served - update the scheduler status after selection for
++ * service.
++ * @bfqq: the queue being served.
++ * @served: bytes to transfer.
++ *
++ * NOTE: this can be optimized, as the timestamps of upper level entities
++ * are synchronized every time a new bfqq is selected for service. By now,
++ * we keep it to better check consistency.
++ */
++static void bfq_bfqq_served(struct bfq_queue *bfqq, int served)
++{
++ struct bfq_entity *entity = &bfqq->entity;
++ struct bfq_service_tree *st;
++
++ for_each_entity(entity) {
++ st = bfq_entity_service_tree(entity);
++
++ entity->service += served;
++ BUG_ON(entity->service > entity->budget);
++ BUG_ON(st->wsum == 0);
++
++ st->vtime += bfq_delta(served, st->wsum);
++ bfq_forget_idle(st);
++ }
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_set_start_empty_time(bfqq_group(bfqq));
++#endif
++ bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served);
++}
++
++/**
++ * bfq_bfqq_charge_full_budget - set the service to the entity budget.
++ * @bfqq: the queue that needs a service update.
++ *
++ * When it's not possible to be fair in the service domain, because
++ * a queue is not consuming its budget fast enough (the meaning of
++ * fast depends on the timeout parameter), we charge it a full
++ * budget. In this way we should obtain a sort of time-domain
++ * fairness among all the seeky/slow queues.
++ */
++static void bfq_bfqq_charge_full_budget(struct bfq_queue *bfqq)
++{
++ struct bfq_entity *entity = &bfqq->entity;
++
++ bfq_log_bfqq(bfqq->bfqd, bfqq, "charge_full_budget");
++
++ bfq_bfqq_served(bfqq, entity->budget - entity->service);
++}
++
++/**
++ * __bfq_activate_entity - activate an entity.
++ * @entity: the entity being activated.
++ *
++ * Called whenever an entity is activated, i.e., it is not active and one
++ * of its children receives a new request, or has to be reactivated due to
++ * budget exhaustion. It uses the current budget of the entity (and the
++ * service received if @entity is active) of the queue to calculate its
++ * timestamps.
++ */
++static void __bfq_activate_entity(struct bfq_entity *entity)
++{
++ struct bfq_sched_data *sd = entity->sched_data;
++ struct bfq_service_tree *st = bfq_entity_service_tree(entity);
++
++ if (entity == sd->in_service_entity) {
++ BUG_ON(entity->tree);
++ /*
++ * If we are requeueing the current entity we have
++ * to take care of not charging to it service it has
++ * not received.
++ */
++ bfq_calc_finish(entity, entity->service);
++ entity->start = entity->finish;
++ sd->in_service_entity = NULL;
++ } else if (entity->tree == &st->active) {
++ /*
++ * Requeueing an entity due to a change of some
++ * next_in_service entity below it. We reuse the
++ * old start time.
++ */
++ bfq_active_extract(st, entity);
++ } else if (entity->tree == &st->idle) {
++ /*
++ * Must be on the idle tree, bfq_idle_extract() will
++ * check for that.
++ */
++ bfq_idle_extract(st, entity);
++ entity->start = bfq_gt(st->vtime, entity->finish) ?
++ st->vtime : entity->finish;
++ } else {
++ /*
++ * The finish time of the entity may be invalid, and
++ * it is in the past for sure, otherwise the queue
++ * would have been on the idle tree.
++ */
++ entity->start = st->vtime;
++ st->wsum += entity->weight;
++ bfq_get_entity(entity);
++
++ BUG_ON(entity->on_st);
++ entity->on_st = 1;
++ }
++
++ st = __bfq_entity_update_weight_prio(st, entity);
++ bfq_calc_finish(entity, entity->budget);
++ bfq_active_insert(st, entity);
++}
++
++/**
++ * bfq_activate_entity - activate an entity and its ancestors if necessary.
++ * @entity: the entity to activate.
++ *
++ * Activate @entity and all the entities on the path from it to the root.
++ */
++static void bfq_activate_entity(struct bfq_entity *entity)
++{
++ struct bfq_sched_data *sd;
++
++ for_each_entity(entity) {
++ __bfq_activate_entity(entity);
++
++ sd = entity->sched_data;
++ if (!bfq_update_next_in_service(sd))
++ /*
++ * No need to propagate the activation to the
++ * upper entities, as they will be updated when
++ * the in-service entity is rescheduled.
++ */
++ break;
++ }
++}
++
++/**
++ * __bfq_deactivate_entity - deactivate an entity from its service tree.
++ * @entity: the entity to deactivate.
++ * @requeue: if false, the entity will not be put into the idle tree.
++ *
++ * Deactivate an entity, independently from its previous state. If the
++ * entity was not on a service tree just return, otherwise if it is on
++ * any scheduler tree, extract it from that tree, and if necessary
++ * and if the caller did not specify @requeue, put it on the idle tree.
++ *
++ * Return %1 if the caller should update the entity hierarchy, i.e.,
++ * if the entity was in service or if it was the next_in_service for
++ * its sched_data; return %0 otherwise.
++ */
++static int __bfq_deactivate_entity(struct bfq_entity *entity, int requeue)
++{
++ struct bfq_sched_data *sd = entity->sched_data;
++ struct bfq_service_tree *st;
++ int was_in_service;
++ int ret = 0;
++
++ if (sd == NULL || !entity->on_st) /* never activated, or inactive */
++ return 0;
++
++ st = bfq_entity_service_tree(entity);
++ was_in_service = entity == sd->in_service_entity;
++
++ BUG_ON(was_in_service && entity->tree);
++
++ if (was_in_service) {
++ bfq_calc_finish(entity, entity->service);
++ sd->in_service_entity = NULL;
++ } else if (entity->tree == &st->active)
++ bfq_active_extract(st, entity);
++ else if (entity->tree == &st->idle)
++ bfq_idle_extract(st, entity);
++ else if (entity->tree)
++ BUG();
++
++ if (was_in_service || sd->next_in_service == entity)
++ ret = bfq_update_next_in_service(sd);
++
++ if (!requeue || !bfq_gt(entity->finish, st->vtime))
++ bfq_forget_entity(st, entity);
++ else
++ bfq_idle_insert(st, entity);
++
++ BUG_ON(sd->in_service_entity == entity);
++ BUG_ON(sd->next_in_service == entity);
++
++ return ret;
++}
++
++/**
++ * bfq_deactivate_entity - deactivate an entity.
++ * @entity: the entity to deactivate.
++ * @requeue: true if the entity can be put on the idle tree
++ */
++static void bfq_deactivate_entity(struct bfq_entity *entity, int requeue)
++{
++ struct bfq_sched_data *sd;
++ struct bfq_entity *parent;
++
++ for_each_entity_safe(entity, parent) {
++ sd = entity->sched_data;
++
++ if (!__bfq_deactivate_entity(entity, requeue))
++ /*
++ * The parent entity is still backlogged, and
++ * we don't need to update it as it is still
++ * in service.
++ */
++ break;
++
++ if (sd->next_in_service)
++ /*
++ * The parent entity is still backlogged and
++ * the budgets on the path towards the root
++ * need to be updated.
++ */
++ goto update;
++
++ /*
++ * If we reach there the parent is no more backlogged and
++ * we want to propagate the dequeue upwards.
++ */
++ requeue = 1;
++ }
++
++ return;
++
++update:
++ entity = parent;
++ for_each_entity(entity) {
++ __bfq_activate_entity(entity);
++
++ sd = entity->sched_data;
++ if (!bfq_update_next_in_service(sd))
++ break;
++ }
++}
++
++/**
++ * bfq_update_vtime - update vtime if necessary.
++ * @st: the service tree to act upon.
++ *
++ * If necessary update the service tree vtime to have at least one
++ * eligible entity, skipping to its start time. Assumes that the
++ * active tree of the device is not empty.
++ *
++ * NOTE: this hierarchical implementation updates vtimes quite often,
++ * we may end up with reactivated processes getting timestamps after a
++ * vtime skip done because we needed a ->first_active entity on some
++ * intermediate node.
++ */
++static void bfq_update_vtime(struct bfq_service_tree *st)
++{
++ struct bfq_entity *entry;
++ struct rb_node *node = st->active.rb_node;
++
++ entry = rb_entry(node, struct bfq_entity, rb_node);
++ if (bfq_gt(entry->min_start, st->vtime)) {
++ st->vtime = entry->min_start;
++ bfq_forget_idle(st);
++ }
++}
++
++/**
++ * bfq_first_active_entity - find the eligible entity with
++ * the smallest finish time
++ * @st: the service tree to select from.
++ *
++ * This function searches the first schedulable entity, starting from the
++ * root of the tree and going on the left every time on this side there is
++ * a subtree with at least one eligible (start >= vtime) entity. The path on
++ * the right is followed only if a) the left subtree contains no eligible
++ * entities and b) no eligible entity has been found yet.
++ */
++static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st)
++{
++ struct bfq_entity *entry, *first = NULL;
++ struct rb_node *node = st->active.rb_node;
++
++ while (node) {
++ entry = rb_entry(node, struct bfq_entity, rb_node);
++left:
++ if (!bfq_gt(entry->start, st->vtime))
++ first = entry;
++
++ BUG_ON(bfq_gt(entry->min_start, st->vtime));
++
++ if (node->rb_left) {
++ entry = rb_entry(node->rb_left,
++ struct bfq_entity, rb_node);
++ if (!bfq_gt(entry->min_start, st->vtime)) {
++ node = node->rb_left;
++ goto left;
++ }
++ }
++ if (first)
++ break;
++ node = node->rb_right;
++ }
++
++ BUG_ON(!first && !RB_EMPTY_ROOT(&st->active));
++ return first;
++}
++
++/**
++ * __bfq_lookup_next_entity - return the first eligible entity in @st.
++ * @st: the service tree.
++ *
++ * Update the virtual time in @st and return the first eligible entity
++ * it contains.
++ */
++static struct bfq_entity *__bfq_lookup_next_entity(struct bfq_service_tree *st,
++ bool force)
++{
++ struct bfq_entity *entity, *new_next_in_service = NULL;
++
++ if (RB_EMPTY_ROOT(&st->active))
++ return NULL;
++
++ bfq_update_vtime(st);
++ entity = bfq_first_active_entity(st);
++ BUG_ON(bfq_gt(entity->start, st->vtime));
++
++ /*
++ * If the chosen entity does not match with the sched_data's
++ * next_in_service and we are forcedly serving the IDLE priority
++ * class tree, bubble up budget update.
++ */
++ if (unlikely(force && entity != entity->sched_data->next_in_service)) {
++ new_next_in_service = entity;
++ for_each_entity(new_next_in_service)
++ bfq_update_budget(new_next_in_service);
++ }
++
++ return entity;
++}
++
++/**
++ * bfq_lookup_next_entity - return the first eligible entity in @sd.
++ * @sd: the sched_data.
++ * @extract: if true the returned entity will be also extracted from @sd.
++ *
++ * NOTE: since we cache the next_in_service entity at each level of the
++ * hierarchy, the complexity of the lookup can be decreased with
++ * absolutely no effort just returning the cached next_in_service value;
++ * we prefer to do full lookups to test the consistency of * the data
++ * structures.
++ */
++static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd,
++ int extract,
++ struct bfq_data *bfqd)
++{
++ struct bfq_service_tree *st = sd->service_tree;
++ struct bfq_entity *entity;
++ int i = 0;
++
++ BUG_ON(sd->in_service_entity);
++
++ if (bfqd &&
++ jiffies - bfqd->bfq_class_idle_last_service > BFQ_CL_IDLE_TIMEOUT) {
++ entity = __bfq_lookup_next_entity(st + BFQ_IOPRIO_CLASSES - 1,
++ true);
++ if (entity) {
++ i = BFQ_IOPRIO_CLASSES - 1;
++ bfqd->bfq_class_idle_last_service = jiffies;
++ sd->next_in_service = entity;
++ }
++ }
++ for (; i < BFQ_IOPRIO_CLASSES; i++) {
++ entity = __bfq_lookup_next_entity(st + i, false);
++ if (entity) {
++ if (extract) {
++ bfq_check_next_in_service(sd, entity);
++ bfq_active_extract(st + i, entity);
++ sd->in_service_entity = entity;
++ sd->next_in_service = NULL;
++ }
++ break;
++ }
++ }
++
++ return entity;
++}
++
++/*
++ * Get next queue for service.
++ */
++static struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd)
++{
++ struct bfq_entity *entity = NULL;
++ struct bfq_sched_data *sd;
++ struct bfq_queue *bfqq;
++
++ BUG_ON(bfqd->in_service_queue);
++
++ if (bfqd->busy_queues == 0)
++ return NULL;
++
++ sd = &bfqd->root_group->sched_data;
++ for (; sd ; sd = entity->my_sched_data) {
++ entity = bfq_lookup_next_entity(sd, 1, bfqd);
++ BUG_ON(!entity);
++ entity->service = 0;
++ }
++
++ bfqq = bfq_entity_to_bfqq(entity);
++ BUG_ON(!bfqq);
++
++ return bfqq;
++}
++
++static void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd)
++{
++ if (bfqd->in_service_bic) {
++ put_io_context(bfqd->in_service_bic->icq.ioc);
++ bfqd->in_service_bic = NULL;
++ }
++
++ bfqd->in_service_queue = NULL;
++ del_timer(&bfqd->idle_slice_timer);
++}
++
++static void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
++ int requeue)
++{
++ struct bfq_entity *entity = &bfqq->entity;
++
++ if (bfqq == bfqd->in_service_queue)
++ __bfq_bfqd_reset_in_service(bfqd);
++
++ bfq_deactivate_entity(entity, requeue);
++}
++
++static void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
++{
++ struct bfq_entity *entity = &bfqq->entity;
++
++ bfq_activate_entity(entity);
++}
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++static void bfqg_stats_update_dequeue(struct bfq_group *bfqg);
++#endif
++
++/*
++ * Called when the bfqq no longer has requests pending, remove it from
++ * the service tree.
++ */
++static void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
++ int requeue)
++{
++ BUG_ON(!bfq_bfqq_busy(bfqq));
++ BUG_ON(!RB_EMPTY_ROOT(&bfqq->sort_list));
++
++ bfq_log_bfqq(bfqd, bfqq, "del from busy");
++
++ bfq_clear_bfqq_busy(bfqq);
++
++ BUG_ON(bfqd->busy_queues == 0);
++ bfqd->busy_queues--;
++
++ if (!bfqq->dispatched) {
++ bfq_weights_tree_remove(bfqd, &bfqq->entity,
++ &bfqd->queue_weights_tree);
++ if (!blk_queue_nonrot(bfqd->queue)) {
++ BUG_ON(!bfqd->busy_in_flight_queues);
++ bfqd->busy_in_flight_queues--;
++ if (bfq_bfqq_constantly_seeky(bfqq)) {
++ BUG_ON(!bfqd->
++ const_seeky_busy_in_flight_queues);
++ bfqd->const_seeky_busy_in_flight_queues--;
++ }
++ }
++ }
++ if (bfqq->wr_coeff > 1)
++ bfqd->wr_busy_queues--;
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ bfqg_stats_update_dequeue(bfqq_group(bfqq));
++#endif
++
++ bfq_deactivate_bfqq(bfqd, bfqq, requeue);
++}
++
++/*
++ * Called when an inactive queue receives a new request.
++ */
++static void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq)
++{
++ BUG_ON(bfq_bfqq_busy(bfqq));
++ BUG_ON(bfqq == bfqd->in_service_queue);
++
++ bfq_log_bfqq(bfqd, bfqq, "add to busy");
++
++ bfq_activate_bfqq(bfqd, bfqq);
++
++ bfq_mark_bfqq_busy(bfqq);
++ bfqd->busy_queues++;
++
++ if (!bfqq->dispatched) {
++ if (bfqq->wr_coeff == 1)
++ bfq_weights_tree_add(bfqd, &bfqq->entity,
++ &bfqd->queue_weights_tree);
++ if (!blk_queue_nonrot(bfqd->queue)) {
++ bfqd->busy_in_flight_queues++;
++ if (bfq_bfqq_constantly_seeky(bfqq))
++ bfqd->const_seeky_busy_in_flight_queues++;
++ }
++ }
++ if (bfqq->wr_coeff > 1)
++ bfqd->wr_busy_queues++;
++}
+diff --git a/block/bfq.h b/block/bfq.h
+new file mode 100644
+index 000000000000..485d0c9e33e9
+--- /dev/null
++++ b/block/bfq.h
+@@ -0,0 +1,801 @@
++/*
++ * BFQ-v7r11 for 4.5.0: data structures and common functions prototypes.
++ *
++ * Based on ideas and code from CFQ:
++ * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
++ *
++ * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
++ * Paolo Valente <paolo.valente@unimore.it>
++ *
++ * Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
++ */
++
++#ifndef _BFQ_H
++#define _BFQ_H
++
++#include <linux/blktrace_api.h>
++#include <linux/hrtimer.h>
++#include <linux/ioprio.h>
++#include <linux/rbtree.h>
++#include <linux/blk-cgroup.h>
++
++#define BFQ_IOPRIO_CLASSES 3
++#define BFQ_CL_IDLE_TIMEOUT (HZ/5)
++
++#define BFQ_MIN_WEIGHT 1
++#define BFQ_MAX_WEIGHT 1000
++#define BFQ_WEIGHT_CONVERSION_COEFF 10
++
++#define BFQ_DEFAULT_QUEUE_IOPRIO 4
++
++#define BFQ_DEFAULT_GRP_WEIGHT 10
++#define BFQ_DEFAULT_GRP_IOPRIO 0
++#define BFQ_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE
++
++struct bfq_entity;
++
++/**
++ * struct bfq_service_tree - per ioprio_class service tree.
++ * @active: tree for active entities (i.e., those backlogged).
++ * @idle: tree for idle entities (i.e., those not backlogged, with V <= F_i).
++ * @first_idle: idle entity with minimum F_i.
++ * @last_idle: idle entity with maximum F_i.
++ * @vtime: scheduler virtual time.
++ * @wsum: scheduler weight sum; active and idle entities contribute to it.
++ *
++ * Each service tree represents a B-WF2Q+ scheduler on its own. Each
++ * ioprio_class has its own independent scheduler, and so its own
++ * bfq_service_tree. All the fields are protected by the queue lock
++ * of the containing bfqd.
++ */
++struct bfq_service_tree {
++ struct rb_root active;
++ struct rb_root idle;
++
++ struct bfq_entity *first_idle;
++ struct bfq_entity *last_idle;
++
++ u64 vtime;
++ unsigned long wsum;
++};
++
++/**
++ * struct bfq_sched_data - multi-class scheduler.
++ * @in_service_entity: entity in service.
++ * @next_in_service: head-of-the-line entity in the scheduler.
++ * @service_tree: array of service trees, one per ioprio_class.
++ *
++ * bfq_sched_data is the basic scheduler queue. It supports three
++ * ioprio_classes, and can be used either as a toplevel queue or as
++ * an intermediate queue on a hierarchical setup.
++ * @next_in_service points to the active entity of the sched_data
++ * service trees that will be scheduled next.
++ *
++ * The supported ioprio_classes are the same as in CFQ, in descending
++ * priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
++ * Requests from higher priority queues are served before all the
++ * requests from lower priority queues; among requests of the same
++ * queue requests are served according to B-WF2Q+.
++ * All the fields are protected by the queue lock of the containing bfqd.
++ */
++struct bfq_sched_data {
++ struct bfq_entity *in_service_entity;
++ struct bfq_entity *next_in_service;
++ struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES];
++};
++
++/**
++ * struct bfq_weight_counter - counter of the number of all active entities
++ * with a given weight.
++ * @weight: weight of the entities that this counter refers to.
++ * @num_active: number of active entities with this weight.
++ * @weights_node: weights tree member (see bfq_data's @queue_weights_tree
++ * and @group_weights_tree).
++ */
++struct bfq_weight_counter {
++ short int weight;
++ unsigned int num_active;
++ struct rb_node weights_node;
++};
++
++/**
++ * struct bfq_entity - schedulable entity.
++ * @rb_node: service_tree member.
++ * @weight_counter: pointer to the weight counter associated with this entity.
++ * @on_st: flag, true if the entity is on a tree (either the active or
++ * the idle one of its service_tree).
++ * @finish: B-WF2Q+ finish timestamp (aka F_i).
++ * @start: B-WF2Q+ start timestamp (aka S_i).
++ * @tree: tree the entity is enqueued into; %NULL if not on a tree.
++ * @min_start: minimum start time of the (active) subtree rooted at
++ * this entity; used for O(log N) lookups into active trees.
++ * @service: service received during the last round of service.
++ * @budget: budget used to calculate F_i; F_i = S_i + @budget / @weight.
++ * @weight: weight of the queue
++ * @parent: parent entity, for hierarchical scheduling.
++ * @my_sched_data: for non-leaf nodes in the cgroup hierarchy, the
++ * associated scheduler queue, %NULL on leaf nodes.
++ * @sched_data: the scheduler queue this entity belongs to.
++ * @ioprio: the ioprio in use.
++ * @new_weight: when a weight change is requested, the new weight value.
++ * @orig_weight: original weight, used to implement weight boosting
++ * @prio_changed: flag, true when the user requested a weight, ioprio or
++ * ioprio_class change.
++ *
++ * A bfq_entity is used to represent either a bfq_queue (leaf node in the
++ * cgroup hierarchy) or a bfq_group into the upper level scheduler. Each
++ * entity belongs to the sched_data of the parent group in the cgroup
++ * hierarchy. Non-leaf entities have also their own sched_data, stored
++ * in @my_sched_data.
++ *
++ * Each entity stores independently its priority values; this would
++ * allow different weights on different devices, but this
++ * functionality is not exported to userspace by now. Priorities and
++ * weights are updated lazily, first storing the new values into the
++ * new_* fields, then setting the @prio_changed flag. As soon as
++ * there is a transition in the entity state that allows the priority
++ * update to take place the effective and the requested priority
++ * values are synchronized.
++ *
++ * Unless cgroups are used, the weight value is calculated from the
++ * ioprio to export the same interface as CFQ. When dealing with
++ * ``well-behaved'' queues (i.e., queues that do not spend too much
++ * time to consume their budget and have true sequential behavior, and
++ * when there are no external factors breaking anticipation) the
++ * relative weights at each level of the cgroups hierarchy should be
++ * guaranteed. All the fields are protected by the queue lock of the
++ * containing bfqd.
++ */
++struct bfq_entity {
++ struct rb_node rb_node;
++ struct bfq_weight_counter *weight_counter;
++
++ int on_st;
++
++ u64 finish;
++ u64 start;
++
++ struct rb_root *tree;
++
++ u64 min_start;
++
++ int service, budget;
++ unsigned short weight, new_weight;
++ unsigned short orig_weight;
++
++ struct bfq_entity *parent;
++
++ struct bfq_sched_data *my_sched_data;
++ struct bfq_sched_data *sched_data;
++
++ int prio_changed;
++};
++
++struct bfq_group;
++
++/**
++ * struct bfq_queue - leaf schedulable entity.
++ * @ref: reference counter.
++ * @bfqd: parent bfq_data.
++ * @new_ioprio: when an ioprio change is requested, the new ioprio value.
++ * @ioprio_class: the ioprio_class in use.
++ * @new_ioprio_class: when an ioprio_class change is requested, the new
++ * ioprio_class value.
++ * @new_bfqq: shared bfq_queue if queue is cooperating with
++ * one or more other queues.
++ * @sort_list: sorted list of pending requests.
++ * @next_rq: if fifo isn't expired, next request to serve.
++ * @queued: nr of requests queued in @sort_list.
++ * @allocated: currently allocated requests.
++ * @meta_pending: pending metadata requests.
++ * @fifo: fifo list of requests in sort_list.
++ * @entity: entity representing this queue in the scheduler.
++ * @max_budget: maximum budget allowed from the feedback mechanism.
++ * @budget_timeout: budget expiration (in jiffies).
++ * @dispatched: number of requests on the dispatch list or inside driver.
++ * @flags: status flags.
++ * @bfqq_list: node for active/idle bfqq list inside our bfqd.
++ * @burst_list_node: node for the device's burst list.
++ * @seek_samples: number of seeks sampled
++ * @seek_total: sum of the distances of the seeks sampled
++ * @seek_mean: mean seek distance
++ * @last_request_pos: position of the last request enqueued
++ * @requests_within_timer: number of consecutive pairs of request completion
++ * and arrival, such that the queue becomes idle
++ * after the completion, but the next request arrives
++ * within an idle time slice; used only if the queue's
++ * IO_bound has been cleared.
++ * @pid: pid of the process owning the queue, used for logging purposes.
++ * @last_wr_start_finish: start time of the current weight-raising period if
++ * the @bfq-queue is being weight-raised, otherwise
++ * finish time of the last weight-raising period
++ * @wr_cur_max_time: current max raising time for this queue
++ * @soft_rt_next_start: minimum time instant such that, only if a new
++ * request is enqueued after this time instant in an
++ * idle @bfq_queue with no outstanding requests, then
++ * the task associated with the queue it is deemed as
++ * soft real-time (see the comments to the function
++ * bfq_bfqq_softrt_next_start())
++ * @last_idle_bklogged: time of the last transition of the @bfq_queue from
++ * idle to backlogged
++ * @service_from_backlogged: cumulative service received from the @bfq_queue
++ * since the last transition from idle to
++ * backlogged
++ * @bic: pointer to the bfq_io_cq owning the bfq_queue, set to %NULL if the
++ * queue is shared
++ *
++ * A bfq_queue is a leaf request queue; it can be associated with an
++ * io_context or more, if it is async or shared between cooperating
++ * processes. @cgroup holds a reference to the cgroup, to be sure that it
++ * does not disappear while a bfqq still references it (mostly to avoid
++ * races between request issuing and task migration followed by cgroup
++ * destruction).
++ * All the fields are protected by the queue lock of the containing bfqd.
++ */
++struct bfq_queue {
++ atomic_t ref;
++ struct bfq_data *bfqd;
++
++ unsigned short ioprio, new_ioprio;
++ unsigned short ioprio_class, new_ioprio_class;
++
++ /* fields for cooperating queues handling */
++ struct bfq_queue *new_bfqq;
++ struct rb_node pos_node;
++ struct rb_root *pos_root;
++
++ struct rb_root sort_list;
++ struct request *next_rq;
++ int queued[2];
++ int allocated[2];
++ int meta_pending;
++ struct list_head fifo;
++
++ struct bfq_entity entity;
++
++ int max_budget;
++ unsigned long budget_timeout;
++
++ int dispatched;
++
++ unsigned int flags;
++
++ struct list_head bfqq_list;
++
++ struct hlist_node burst_list_node;
++
++ unsigned int seek_samples;
++ u64 seek_total;
++ sector_t seek_mean;
++ sector_t last_request_pos;
++
++ unsigned int requests_within_timer;
++
++ pid_t pid;
++ struct bfq_io_cq *bic;
++
++ /* weight-raising fields */
++ unsigned long wr_cur_max_time;
++ unsigned long soft_rt_next_start;
++ unsigned long last_wr_start_finish;
++ unsigned int wr_coeff;
++ unsigned long last_idle_bklogged;
++ unsigned long service_from_backlogged;
++};
++
++/**
++ * struct bfq_ttime - per process thinktime stats.
++ * @ttime_total: total process thinktime
++ * @ttime_samples: number of thinktime samples
++ * @ttime_mean: average process thinktime
++ */
++struct bfq_ttime {
++ unsigned long last_end_request;
++
++ unsigned long ttime_total;
++ unsigned long ttime_samples;
++ unsigned long ttime_mean;
++};
++
++/**
++ * struct bfq_io_cq - per (request_queue, io_context) structure.
++ * @icq: associated io_cq structure
++ * @bfqq: array of two process queues, the sync and the async
++ * @ttime: associated @bfq_ttime struct
++ * @ioprio: per (request_queue, blkcg) ioprio.
++ * @blkcg_id: id of the blkcg the related io_cq belongs to.
++ */
++struct bfq_io_cq {
++ struct io_cq icq; /* must be the first member */
++ struct bfq_queue *bfqq[2];
++ struct bfq_ttime ttime;
++ int ioprio;
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ uint64_t blkcg_id; /* the current blkcg ID */
++#endif
++};
++
++enum bfq_device_speed {
++ BFQ_BFQD_FAST,
++ BFQ_BFQD_SLOW,
++};
++
++/**
++ * struct bfq_data - per device data structure.
++ * @queue: request queue for the managed device.
++ * @root_group: root bfq_group for the device.
++ * @active_numerous_groups: number of bfq_groups containing more than one
++ * active @bfq_entity.
++ * @queue_weights_tree: rbtree of weight counters of @bfq_queues, sorted by
++ * weight. Used to keep track of whether all @bfq_queues
++ * have the same weight. The tree contains one counter
++ * for each distinct weight associated to some active
++ * and not weight-raised @bfq_queue (see the comments to
++ * the functions bfq_weights_tree_[add|remove] for
++ * further details).
++ * @group_weights_tree: rbtree of non-queue @bfq_entity weight counters, sorted
++ * by weight. Used to keep track of whether all
++ * @bfq_groups have the same weight. The tree contains
++ * one counter for each distinct weight associated to
++ * some active @bfq_group (see the comments to the
++ * functions bfq_weights_tree_[add|remove] for further
++ * details).
++ * @busy_queues: number of bfq_queues containing requests (including the
++ * queue in service, even if it is idling).
++ * @busy_in_flight_queues: number of @bfq_queues containing pending or
++ * in-flight requests, plus the @bfq_queue in
++ * service, even if idle but waiting for the
++ * possible arrival of its next sync request. This
++ * field is updated only if the device is rotational,
++ * but used only if the device is also NCQ-capable.
++ * The reason why the field is updated also for non-
++ * NCQ-capable rotational devices is related to the
++ * fact that the value of @hw_tag may be set also
++ * later than when busy_in_flight_queues may need to
++ * be incremented for the first time(s). Taking also
++ * this possibility into account, to avoid unbalanced
++ * increments/decrements, would imply more overhead
++ * than just updating busy_in_flight_queues
++ * regardless of the value of @hw_tag.
++ * @const_seeky_busy_in_flight_queues: number of constantly-seeky @bfq_queues
++ * (that is, seeky queues that expired
++ * for budget timeout at least once)
++ * containing pending or in-flight
++ * requests, including the in-service
++ * @bfq_queue if constantly seeky. This
++ * field is updated only if the device
++ * is rotational, but used only if the
++ * device is also NCQ-capable (see the
++ * comments to @busy_in_flight_queues).
++ * @wr_busy_queues: number of weight-raised busy @bfq_queues.
++ * @queued: number of queued requests.
++ * @rq_in_driver: number of requests dispatched and waiting for completion.
++ * @sync_flight: number of sync requests in the driver.
++ * @max_rq_in_driver: max number of reqs in driver in the last
++ * @hw_tag_samples completed requests.
++ * @hw_tag_samples: nr of samples used to calculate hw_tag.
++ * @hw_tag: flag set to one if the driver is showing a queueing behavior.
++ * @budgets_assigned: number of budgets assigned.
++ * @idle_slice_timer: timer set when idling for the next sequential request
++ * from the queue in service.
++ * @unplug_work: delayed work to restart dispatching on the request queue.
++ * @in_service_queue: bfq_queue in service.
++ * @in_service_bic: bfq_io_cq (bic) associated with the @in_service_queue.
++ * @last_position: on-disk position of the last served request.
++ * @last_budget_start: beginning of the last budget.
++ * @last_idling_start: beginning of the last idle slice.
++ * @peak_rate: peak transfer rate observed for a budget.
++ * @peak_rate_samples: number of samples used to calculate @peak_rate.
++ * @bfq_max_budget: maximum budget allotted to a bfq_queue before
++ * rescheduling.
++ * @active_list: list of all the bfq_queues active on the device.
++ * @idle_list: list of all the bfq_queues idle on the device.
++ * @bfq_fifo_expire: timeout for async/sync requests; when it expires
++ * requests are served in fifo order.
++ * @bfq_back_penalty: weight of backward seeks wrt forward ones.
++ * @bfq_back_max: maximum allowed backward seek.
++ * @bfq_slice_idle: maximum idling time.
++ * @bfq_user_max_budget: user-configured max budget value
++ * (0 for auto-tuning).
++ * @bfq_max_budget_async_rq: maximum budget (in nr of requests) allotted to
++ * async queues.
++ * @bfq_timeout: timeout for bfq_queues to consume their budget; used to
++ * to prevent seeky queues to impose long latencies to well
++ * behaved ones (this also implies that seeky queues cannot
++ * receive guarantees in the service domain; after a timeout
++ * they are charged for the whole allocated budget, to try
++ * to preserve a behavior reasonably fair among them, but
++ * without service-domain guarantees).
++ * @bfq_coop_thresh: number of queue merges after which a @bfq_queue is
++ * no more granted any weight-raising.
++ * @bfq_failed_cooperations: number of consecutive failed cooperation
++ * chances after which weight-raising is restored
++ * to a queue subject to more than bfq_coop_thresh
++ * queue merges.
++ * @bfq_requests_within_timer: number of consecutive requests that must be
++ * issued within the idle time slice to set
++ * again idling to a queue which was marked as
++ * non-I/O-bound (see the definition of the
++ * IO_bound flag for further details).
++ * @last_ins_in_burst: last time at which a queue entered the current
++ * burst of queues being activated shortly after
++ * each other; for more details about this and the
++ * following parameters related to a burst of
++ * activations, see the comments to the function
++ * @bfq_handle_burst.
++ * @bfq_burst_interval: reference time interval used to decide whether a
++ * queue has been activated shortly after
++ * @last_ins_in_burst.
++ * @burst_size: number of queues in the current burst of queue activations.
++ * @bfq_large_burst_thresh: maximum burst size above which the current
++ * queue-activation burst is deemed as 'large'.
++ * @large_burst: true if a large queue-activation burst is in progress.
++ * @burst_list: head of the burst list (as for the above fields, more details
++ * in the comments to the function bfq_handle_burst).
++ * @low_latency: if set to true, low-latency heuristics are enabled.
++ * @bfq_wr_coeff: maximum factor by which the weight of a weight-raised
++ * queue is multiplied.
++ * @bfq_wr_max_time: maximum duration of a weight-raising period (jiffies).
++ * @bfq_wr_rt_max_time: maximum duration for soft real-time processes.
++ * @bfq_wr_min_idle_time: minimum idle period after which weight-raising
++ * may be reactivated for a queue (in jiffies).
++ * @bfq_wr_min_inter_arr_async: minimum period between request arrivals
++ * after which weight-raising may be
++ * reactivated for an already busy queue
++ * (in jiffies).
++ * @bfq_wr_max_softrt_rate: max service-rate for a soft real-time queue,
++ * sectors per seconds.
++ * @RT_prod: cached value of the product R*T used for computing the maximum
++ * duration of the weight raising automatically.
++ * @device_speed: device-speed class for the low-latency heuristic.
++ * @oom_bfqq: fallback dummy bfqq for extreme OOM conditions.
++ *
++ * All the fields are protected by the @queue lock.
++ */
++struct bfq_data {
++ struct request_queue *queue;
++
++ struct bfq_group *root_group;
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++ int active_numerous_groups;
++#endif
++
++ struct rb_root queue_weights_tree;
++ struct rb_root group_weights_tree;
++
++ int busy_queues;
++ int busy_in_flight_queues;
++ int const_seeky_busy_in_flight_queues;
++ int wr_busy_queues;
++ int queued;
++ int rq_in_driver;
++ int sync_flight;
++
++ int max_rq_in_driver;
++ int hw_tag_samples;
++ int hw_tag;
++
++ int budgets_assigned;
++
++ struct timer_list idle_slice_timer;
++ struct work_struct unplug_work;
++
++ struct bfq_queue *in_service_queue;
++ struct bfq_io_cq *in_service_bic;
++
++ sector_t last_position;
++
++ ktime_t last_budget_start;
++ ktime_t last_idling_start;
++ int peak_rate_samples;
++ u64 peak_rate;
++ int bfq_max_budget;
++
++ struct list_head active_list;
++ struct list_head idle_list;
++
++ unsigned int bfq_fifo_expire[2];
++ unsigned int bfq_back_penalty;
++ unsigned int bfq_back_max;
++ unsigned int bfq_slice_idle;
++ u64 bfq_class_idle_last_service;
++
++ int bfq_user_max_budget;
++ int bfq_max_budget_async_rq;
++ unsigned int bfq_timeout[2];
++
++ unsigned int bfq_coop_thresh;
++ unsigned int bfq_failed_cooperations;
++ unsigned int bfq_requests_within_timer;
++
++ unsigned long last_ins_in_burst;
++ unsigned long bfq_burst_interval;
++ int burst_size;
++ unsigned long bfq_large_burst_thresh;
++ bool large_burst;
++ struct hlist_head burst_list;
++
++ bool low_latency;
++
++ /* parameters of the low_latency heuristics */
++ unsigned int bfq_wr_coeff;
++ unsigned int bfq_wr_max_time;
++ unsigned int bfq_wr_rt_max_time;
++ unsigned int bfq_wr_min_idle_time;
++ unsigned long bfq_wr_min_inter_arr_async;
++ unsigned int bfq_wr_max_softrt_rate;
++ u64 RT_prod;
++ enum bfq_device_speed device_speed;
++
++ struct bfq_queue oom_bfqq;
++};
++
++enum bfqq_state_flags {
++ BFQ_BFQQ_FLAG_busy = 0, /* has requests or is in service */
++ BFQ_BFQQ_FLAG_wait_request, /* waiting for a request */
++ BFQ_BFQQ_FLAG_must_alloc, /* must be allowed rq alloc */
++ BFQ_BFQQ_FLAG_fifo_expire, /* FIFO checked in this slice */
++ BFQ_BFQQ_FLAG_idle_window, /* slice idling enabled */
++ BFQ_BFQQ_FLAG_sync, /* synchronous queue */
++ BFQ_BFQQ_FLAG_budget_new, /* no completion with this budget */
++ BFQ_BFQQ_FLAG_IO_bound, /*
++ * bfqq has timed-out at least once
++ * having consumed at most 2/10 of
++ * its budget
++ */
++ BFQ_BFQQ_FLAG_in_large_burst, /*
++ * bfqq activated in a large burst,
++ * see comments to bfq_handle_burst.
++ */
++ BFQ_BFQQ_FLAG_constantly_seeky, /*
++ * bfqq has proved to be slow and
++ * seeky until budget timeout
++ */
++ BFQ_BFQQ_FLAG_softrt_update, /*
++ * may need softrt-next-start
++ * update
++ */
++};
++
++#define BFQ_BFQQ_FNS(name) \
++static void bfq_mark_bfqq_##name(struct bfq_queue *bfqq) \
++{ \
++ (bfqq)->flags |= (1 << BFQ_BFQQ_FLAG_##name); \
++} \
++static void bfq_clear_bfqq_##name(struct bfq_queue *bfqq) \
++{ \
++ (bfqq)->flags &= ~(1 << BFQ_BFQQ_FLAG_##name); \
++} \
++static int bfq_bfqq_##name(const struct bfq_queue *bfqq) \
++{ \
++ return ((bfqq)->flags & (1 << BFQ_BFQQ_FLAG_##name)) != 0; \
++}
++
++BFQ_BFQQ_FNS(busy);
++BFQ_BFQQ_FNS(wait_request);
++BFQ_BFQQ_FNS(must_alloc);
++BFQ_BFQQ_FNS(fifo_expire);
++BFQ_BFQQ_FNS(idle_window);
++BFQ_BFQQ_FNS(sync);
++BFQ_BFQQ_FNS(budget_new);
++BFQ_BFQQ_FNS(IO_bound);
++BFQ_BFQQ_FNS(in_large_burst);
++BFQ_BFQQ_FNS(constantly_seeky);
++BFQ_BFQQ_FNS(softrt_update);
++#undef BFQ_BFQQ_FNS
++
++/* Logging facilities. */
++#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) \
++ blk_add_trace_msg((bfqd)->queue, "bfq%d " fmt, (bfqq)->pid, ##args)
++
++#define bfq_log(bfqd, fmt, args...) \
++ blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args)
++
++/* Expiration reasons. */
++enum bfqq_expiration {
++ BFQ_BFQQ_TOO_IDLE = 0, /*
++ * queue has been idling for
++ * too long
++ */
++ BFQ_BFQQ_BUDGET_TIMEOUT, /* budget took too long to be used */
++ BFQ_BFQQ_BUDGET_EXHAUSTED, /* budget consumed */
++ BFQ_BFQQ_NO_MORE_REQUESTS, /* the queue has no more requests */
++};
++
++#ifdef CONFIG_BFQ_GROUP_IOSCHED
++
++struct bfqg_stats {
++ /* total bytes transferred */
++ struct blkg_rwstat service_bytes;
++ /* total IOs serviced, post merge */
++ struct blkg_rwstat serviced;
++ /* number of ios merged */
++ struct blkg_rwstat merged;
++ /* total time spent on device in ns, may not be accurate w/ queueing */
++ struct blkg_rwstat service_time;
++ /* total time spent waiting in scheduler queue in ns */
++ struct blkg_rwstat wait_time;
++ /* number of IOs queued up */
++ struct blkg_rwstat queued;
++ /* total sectors transferred */
++ struct blkg_stat sectors;
++ /* total disk time and nr sectors dispatched by this group */
++ struct blkg_stat time;
++ /* time not charged to this cgroup */
++ struct blkg_stat unaccounted_time;
++ /* sum of number of ios queued across all samples */
++ struct blkg_stat avg_queue_size_sum;
++ /* count of samples taken for average */
++ struct blkg_stat avg_queue_size_samples;
++ /* how many times this group has been removed from service tree */
++ struct blkg_stat dequeue;
++ /* total time spent waiting for it to be assigned a timeslice. */
++ struct blkg_stat group_wait_time;
++ /* time spent idling for this blkcg_gq */
++ struct blkg_stat idle_time;
++ /* total time with empty current active q with other requests queued */
++ struct blkg_stat empty_time;
++ /* fields after this shouldn't be cleared on stat reset */
++ uint64_t start_group_wait_time;
++ uint64_t start_idle_time;
++ uint64_t start_empty_time;
++ uint16_t flags;
++};
++
++/*
++ * struct bfq_group_data - per-blkcg storage for the blkio subsystem.
++ *
++ * @ps: @blkcg_policy_storage that this structure inherits
++ * @weight: weight of the bfq_group
++ */
++struct bfq_group_data {
++ /* must be the first member */
++ struct blkcg_policy_data pd;
++
++ unsigned short weight;
++};
++
++/**
++ * struct bfq_group - per (device, cgroup) data structure.
++ * @entity: schedulable entity to insert into the parent group sched_data.
++ * @sched_data: own sched_data, to contain child entities (they may be
++ * both bfq_queues and bfq_groups).
++ * @bfqd: the bfq_data for the device this group acts upon.
++ * @async_bfqq: array of async queues for all the tasks belonging to
++ * the group, one queue per ioprio value per ioprio_class,
++ * except for the idle class that has only one queue.
++ * @async_idle_bfqq: async queue for the idle class (ioprio is ignored).
++ * @my_entity: pointer to @entity, %NULL for the toplevel group; used
++ * to avoid too many special cases during group creation/
++ * migration.
++ * @active_entities: number of active entities belonging to the group;
++ * unused for the root group. Used to know whether there
++ * are groups with more than one active @bfq_entity
++ * (see the comments to the function
++ * bfq_bfqq_must_not_expire()).
++ *
++ * Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup
++ * there is a set of bfq_groups, each one collecting the lower-level
++ * entities belonging to the group that are acting on the same device.
++ *
++ * Locking works as follows:
++ * o @bfqd is protected by the queue lock, RCU is used to access it
++ * from the readers.
++ * o All the other fields are protected by the @bfqd queue lock.
++ */
++struct bfq_group {
++ /* must be the first member */
++ struct blkg_policy_data pd;
++
++ struct bfq_entity entity;
++ struct bfq_sched_data sched_data;
++
++ void *bfqd;
++
++ struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
++ struct bfq_queue *async_idle_bfqq;
++
++ struct bfq_entity *my_entity;
++
++ int active_entities;
++
++ struct bfqg_stats stats;
++ struct bfqg_stats dead_stats; /* stats pushed from dead children */
++};
++
++#else
++struct bfq_group {
++ struct bfq_sched_data sched_data;
++
++ struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
++ struct bfq_queue *async_idle_bfqq;
++};
++#endif
++
++static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
++
++static struct bfq_service_tree *
++bfq_entity_service_tree(struct bfq_entity *entity)
++{
++ struct bfq_sched_data *sched_data = entity->sched_data;
++ struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
++ unsigned int idx = bfqq ? bfqq->ioprio_class - 1 :
++ BFQ_DEFAULT_GRP_CLASS;
++
++ BUG_ON(idx >= BFQ_IOPRIO_CLASSES);
++ BUG_ON(sched_data == NULL);
++
++ return sched_data->service_tree + idx;
++}
++
++static struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync)
++{
++ return bic->bfqq[is_sync];
++}
++
++static void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq,
++ bool is_sync)
++{
++ bic->bfqq[is_sync] = bfqq;
++}
++
++static struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic)
++{
++ return bic->icq.q->elevator->elevator_data;
++}
++
++/**
++ * bfq_get_bfqd_locked - get a lock to a bfqd using a RCU protected pointer.
++ * @ptr: a pointer to a bfqd.
++ * @flags: storage for the flags to be saved.
++ *
++ * This function allows bfqg->bfqd to be protected by the
++ * queue lock of the bfqd they reference; the pointer is dereferenced
++ * under RCU, so the storage for bfqd is assured to be safe as long
++ * as the RCU read side critical section does not end. After the
++ * bfqd->queue->queue_lock is taken the pointer is rechecked, to be
++ * sure that no other writer accessed it. If we raced with a writer,
++ * the function returns NULL, with the queue unlocked, otherwise it
++ * returns the dereferenced pointer, with the queue locked.
++ */
++static struct bfq_data *bfq_get_bfqd_locked(void **ptr, unsigned long *flags)
++{
++ struct bfq_data *bfqd;
++
++ rcu_read_lock();
++ bfqd = rcu_dereference(*(struct bfq_data **)ptr);
++
++ if (bfqd != NULL) {
++ spin_lock_irqsave(bfqd->queue->queue_lock, *flags);
++ if (ptr == NULL)
++ printk(KERN_CRIT "get_bfqd_locked pointer NULL\n");
++ else if (*ptr == bfqd)
++ goto out;
++ spin_unlock_irqrestore(bfqd->queue->queue_lock, *flags);
++ }
++
++ bfqd = NULL;
++out:
++ rcu_read_unlock();
++ return bfqd;
++}
++
++static void bfq_put_bfqd_unlock(struct bfq_data *bfqd, unsigned long *flags)
++{
++ spin_unlock_irqrestore(bfqd->queue->queue_lock, *flags);
++}
++
++static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio);
++static void bfq_put_queue(struct bfq_queue *bfqq);
++static void bfq_dispatch_insert(struct request_queue *q, struct request *rq);
++static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
++ struct bio *bio, int is_sync,
++ struct bfq_io_cq *bic, gfp_t gfp_mask);
++static void bfq_end_wr_async_queues(struct bfq_data *bfqd,
++ struct bfq_group *bfqg);
++static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
++static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq);
++
++#endif /* _BFQ_H */