linux/block/bfq-cgroup.c

1233 lines
34 KiB
C
Raw Normal View History

/*
* cgroups support for the BFQ I/O scheduler.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*/
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
#include <linux/cgroup.h>
#include <linux/elevator.h>
#include <linux/ktime.h>
#include <linux/rbtree.h>
#include <linux/ioprio.h>
#include <linux/sbitmap.h>
#include <linux/delay.h>
#include "bfq-iosched.h"
2017-11-13 14:34:10 +08:00
#if defined(CONFIG_BFQ_GROUP_IOSCHED) && defined(CONFIG_DEBUG_BLK_CGROUP)
/* 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
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
/* This should be called with the scheduler lock held. */
static void bfqg_stats_update_group_wait_time(struct bfqg_stats *stats)
{
u64 now;
if (!bfqg_stats_waiting(stats))
return;
now = ktime_get_ns();
if (now > stats->start_group_wait_time)
blkg_stat_add(&stats->group_wait_time,
now - stats->start_group_wait_time);
bfqg_stats_clear_waiting(stats);
}
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
/* This should be called with the scheduler 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 = ktime_get_ns();
bfqg_stats_mark_waiting(stats);
}
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
/* This should be called with the scheduler lock held. */
static void bfqg_stats_end_empty_time(struct bfqg_stats *stats)
{
u64 now;
if (!bfqg_stats_empty(stats))
return;
now = ktime_get_ns();
if (now > stats->start_empty_time)
blkg_stat_add(&stats->empty_time,
now - stats->start_empty_time);
bfqg_stats_clear_empty(stats);
}
void bfqg_stats_update_dequeue(struct bfq_group *bfqg)
{
blkg_stat_add(&bfqg->stats.dequeue, 1);
}
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 = ktime_get_ns();
bfqg_stats_mark_empty(stats);
}
void bfqg_stats_update_idle_time(struct bfq_group *bfqg)
{
struct bfqg_stats *stats = &bfqg->stats;
if (bfqg_stats_idling(stats)) {
u64 now = ktime_get_ns();
if (now > stats->start_idle_time)
blkg_stat_add(&stats->idle_time,
now - stats->start_idle_time);
bfqg_stats_clear_idling(stats);
}
}
void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg)
{
struct bfqg_stats *stats = &bfqg->stats;
stats->start_idle_time = ktime_get_ns();
bfqg_stats_mark_idling(stats);
}
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);
}
2017-11-13 14:34:10 +08:00
void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.queued, op, 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));
}
void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.queued, op, -1);
}
void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op)
{
blkg_rwstat_add(&bfqg->stats.merged, op, 1);
}
void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
u64 io_start_time_ns, unsigned int op)
2017-11-13 14:34:10 +08:00
{
struct bfqg_stats *stats = &bfqg->stats;
u64 now = ktime_get_ns();
2017-11-13 14:34:10 +08:00
if (now > io_start_time_ns)
2017-11-13 14:34:10 +08:00
blkg_rwstat_add(&stats->service_time, op,
now - io_start_time_ns);
if (io_start_time_ns > start_time_ns)
2017-11-13 14:34:10 +08:00
blkg_rwstat_add(&stats->wait_time, op,
io_start_time_ns - start_time_ns);
2017-11-13 14:34:10 +08:00
}
#else /* CONFIG_BFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
void bfqg_stats_update_io_add(struct bfq_group *bfqg, struct bfq_queue *bfqq,
unsigned int op) { }
void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { }
void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { }
void bfqg_stats_update_completion(struct bfq_group *bfqg, u64 start_time_ns,
u64 io_start_time_ns, unsigned int op) { }
2017-11-13 14:34:10 +08:00
void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { }
void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { }
void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { }
void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { }
void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { }
#endif /* CONFIG_BFQ_GROUP_IOSCHED && CONFIG_DEBUG_BLK_CGROUP */
#ifdef CONFIG_BFQ_GROUP_IOSCHED
/*
* 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;
}
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)
{
return pd_to_bfqg(blkg_to_pd(blkg, &blkcg_policy_bfq));
}
/*
* 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;
}
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)
{
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
bfqg->ref++;
}
static void bfqg_put(struct bfq_group *bfqg)
{
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
bfqg->ref--;
if (bfqg->ref == 0)
kfree(bfqg);
}
static void bfqg_and_blkg_get(struct bfq_group *bfqg)
{
/* see comments in bfq_bic_update_cgroup for why refcounting bfqg */
bfqg_get(bfqg);
blkg_get(bfqg_to_blkg(bfqg));
}
void bfqg_and_blkg_put(struct bfq_group *bfqg)
{
bfqg_put(bfqg);
blkg_put(bfqg_to_blkg(bfqg));
}
/* @stats = 0 */
static void bfqg_stats_reset(struct bfqg_stats *stats)
{
2017-11-13 14:34:10 +08:00
#ifdef CONFIG_DEBUG_BLK_CGROUP
/* queued stats shouldn't be cleared */
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->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);
2017-11-13 14:34:10 +08:00
#endif
}
/* @to += @from */
static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from)
{
if (!to || !from)
return;
2017-11-13 14:34:10 +08:00
#ifdef CONFIG_DEBUG_BLK_CGROUP
/* queued stats shouldn't be cleared */
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->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);
2017-11-13 14:34:10 +08:00
#endif
}
/*
* Transfer @bfqg's stats to its parent's aux counts 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_add_aux(&parent->stats, &bfqg->stats);
bfqg_stats_reset(&bfqg->stats);
}
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;
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
/*
* Make sure that bfqg and its associated blkg do not
* disappear before entity.
*/
bfqg_and_blkg_get(bfqg);
}
entity->parent = bfqg->my_entity; /* NULL for root group */
entity->sched_data = &bfqg->sched_data;
}
static void bfqg_stats_exit(struct bfqg_stats *stats)
{
2017-11-13 14:34:10 +08:00
#ifdef CONFIG_DEBUG_BLK_CGROUP
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->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);
2017-11-13 14:34:10 +08:00
#endif
}
static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
{
2017-11-13 14:34:10 +08:00
#ifdef CONFIG_DEBUG_BLK_CGROUP
if (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->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;
}
2017-11-13 14:34:10 +08:00
#endif
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 struct blkcg_policy_data *bfq_cpd_alloc(gfp_t gfp)
{
struct bfq_group_data *bgd;
bgd = kzalloc(sizeof(*bgd), gfp);
if (!bgd)
return NULL;
return &bgd->pd;
}
static void bfq_cpd_init(struct blkcg_policy_data *cpd)
{
struct bfq_group_data *d = cpd_to_bfqgd(cpd);
d->weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ?
CGROUP_WEIGHT_DFL : BFQ_WEIGHT_LEGACY_DFL;
}
static void bfq_cpd_free(struct blkcg_policy_data *cpd)
{
kfree(cpd_to_bfqgd(cpd));
}
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)) {
kfree(bfqg);
return NULL;
}
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
/* see comments in bfq_bic_update_cgroup for why refcounting */
bfqg_get(bfqg);
return &bfqg->pd;
}
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;
bfqg->rq_pos_tree = RB_ROOT;
}
static void bfq_pd_free(struct blkg_policy_data *pd)
{
struct bfq_group *bfqg = pd_to_bfqg(pd);
bfqg_stats_exit(&bfqg->stats);
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
bfqg_put(bfqg);
}
static void bfq_pd_reset_stats(struct blkg_policy_data *pd)
{
struct bfq_group *bfqg = pd_to_bfqg(pd);
bfqg_stats_reset(&bfqg->stats);
}
static void bfq_group_set_parent(struct bfq_group *bfqg,
struct bfq_group *parent)
{
struct bfq_entity *entity;
entity = &bfqg->entity;
entity->parent = parent->my_entity;
entity->sched_data = &parent->sched_data;
}
static struct bfq_group *bfq_lookup_bfqg(struct bfq_data *bfqd,
struct blkcg *blkcg)
{
struct blkcg_gq *blkg;
blkg = blkg_lookup(blkcg, bfqd->queue);
if (likely(blkg))
return blkg_to_bfqg(blkg);
return NULL;
}
struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
struct blkcg *blkcg)
{
struct bfq_group *bfqg, *parent;
struct bfq_entity *entity;
bfqg = bfq_lookup_bfqg(bfqd, blkcg);
if (unlikely(!bfqg))
return NULL;
/*
* 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);
if (bfqg != bfqd->root_group) {
parent = bfqg_parent(bfqg);
if (!parent)
parent = bfqd->root_group;
bfq_group_set_parent(bfqg, parent);
}
}
return bfqg;
}
/**
* bfq_bfqq_move - migrate @bfqq to @bfqg.
* @bfqd: queue descriptor.
* @bfqq: the queue to move.
* @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.
*
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
* Must be called under the scheduler lock, to make sure that the blkg
* owning @bfqg does not disappear (see comments in
* bfq_bic_update_cgroup on guaranteeing the consistency of blkg
* objects).
*/
void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct bfq_group *bfqg)
{
struct bfq_entity *entity = &bfqq->entity;
/* If bfqq is empty, then bfq_bfqq_expire also invokes
* bfq_del_bfqq_busy, thereby removing bfqq and its entity
* from data structures related to current group. Otherwise we
* need to remove bfqq explicitly with bfq_deactivate_bfqq, as
* we do below.
*/
if (bfqq == bfqd->in_service_queue)
bfq_bfqq_expire(bfqd, bfqd->in_service_queue,
false, BFQQE_PREEMPTED);
if (bfq_bfqq_busy(bfqq))
bfq_deactivate_bfqq(bfqd, bfqq, false, false);
else if (entity->on_st)
bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
bfqg_and_blkg_put(bfqq_group(bfqq));
entity->parent = bfqg->my_entity;
entity->sched_data = &bfqg->sched_data;
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
/* pin down bfqg and its associated blkg */
bfqg_and_blkg_get(bfqg);
if (bfq_bfqq_busy(bfqq)) {
bfq_pos_tree_add_move(bfqd, bfqq);
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.
*
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
* Move bic to blkcg, assuming that bfqd->lock is held; which makes
* sure that the reference to cgroup is valid across the call (see
* comments in bfq_bic_update_cgroup on this issue)
*
* 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;
bfqg = bfq_find_set_group(bfqd, blkcg);
if (unlikely(!bfqg))
bfqg = bfqd->root_group;
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, 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, bfqg);
}
return bfqg;
}
void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
{
struct bfq_data *bfqd = bic_to_bfqd(bic);
struct bfq_group *bfqg = NULL;
uint64_t serial_nr;
rcu_read_lock();
serial_nr = bio_blkcg(bio)->css.serial_nr;
/*
* 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_serial_nr == serial_nr))
goto out;
bfqg = __bfq_bic_change_cgroup(bfqd, bic, bio_blkcg(bio));
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
/*
* Update blkg_path for bfq_log_* functions. We cache this
* path, and update it here, for the following
* reasons. Operations on blkg objects in blk-cgroup are
* protected with the request_queue lock, and not with the
* lock that protects the instances of this scheduler
* (bfqd->lock). This exposes BFQ to the following sort of
* race.
*
* The blkg_lookup performed in bfq_get_queue, protected
* through rcu, may happen to return the address of a copy of
* the original blkg. If this is the case, then the
* bfqg_and_blkg_get performed in bfq_get_queue, to pin down
* the blkg, is useless: it does not prevent blk-cgroup code
* from destroying both the original blkg and all objects
* directly or indirectly referred by the copy of the
* blkg.
*
* On the bright side, destroy operations on a blkg invoke, as
* a first step, hooks of the scheduler associated with the
* blkg. And these hooks are executed with bfqd->lock held for
* BFQ. As a consequence, for any blkg associated with the
* request queue this instance of the scheduler is attached
* to, we are guaranteed that such a blkg is not destroyed, and
* that all the pointers it contains are consistent, while we
* are holding bfqd->lock. A blkg_lookup performed with
* bfqd->lock held then returns a fully consistent blkg, which
* remains consistent until this lock is held.
*
* Thanks to the last fact, and to the fact that: (1) bfqg has
* been obtained through a blkg_lookup in the above
* assignment, and (2) bfqd->lock is being held, here we can
* safely use the policy data for the involved blkg (i.e., the
* field bfqg->pd) to get to the blkg associated with bfqg,
* and then we can safely use any field of blkg. After we
* release bfqd->lock, even just getting blkg through this
* bfqg may cause dangling references to be traversed, as
* bfqg->pd may not exist any more.
*
* In view of the above facts, here we cache, in the bfqg, any
* blkg data we may need for this bic, and for its associated
* bfq_queue. As of now, we need to cache only the path of the
* blkg, which is used in the bfq_log_* functions.
*
* Finally, note that bfqg itself needs to be protected from
* destruction on the blkg_free of the original blkg (which
* invokes bfq_pd_free). We use an additional private
* refcounter for bfqg, to let it disappear only after no
* bfq_queue refers to it any longer.
*/
blkg_path(bfqg_to_blkg(bfqg), bfqg->blkg_path, sizeof(bfqg->blkg_path));
bic->blkcg_serial_nr = serial_nr;
out:
rcu_read_unlock();
}
/**
* 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, false);
}
/**
* 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);
bfq_bfqq_move(bfqd, bfqq, bfqd->root_group);
}
/**
* 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.
*/
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);
}
/**
* bfq_pd_offline - deactivate the entity associated with @pd,
* and reparent its children entities.
* @pd: descriptor of the policy going offline.
*
* 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 = pd_to_bfqg(pd);
struct bfq_data *bfqd = bfqg->bfqd;
struct bfq_entity *entity = bfqg->my_entity;
unsigned long flags;
int i;
spin_lock_irqsave(&bfqd->lock, flags);
if (!entity) /* root group */
goto put_async_queues;
/*
* Empty all service_trees belonging to this group before
* deactivating the group itself.
*/
for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) {
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
block, bfq: access and cache blkg data only when safe In blk-cgroup, operations on blkg objects are protected with the request_queue lock. This is no more the lock that protects I/O-scheduler operations in blk-mq. In fact, the latter are now protected with a finer-grained per-scheduler-instance lock. As a consequence, although blkg lookups are also rcu-protected, blk-mq I/O schedulers may see inconsistent data when they access blkg and blkg-related objects. BFQ does access these objects, and does incur this problem, in the following case. The blkg_lookup performed in bfq_get_queue, being protected (only) through rcu, may happen to return the address of a copy of the original blkg. If this is the case, then the blkg_get performed in bfq_get_queue, to pin down the blkg, is useless: it does not prevent blk-cgroup code from destroying both the original blkg and all objects directly or indirectly referred by the copy of the blkg. BFQ accesses these objects, which typically causes a crash for NULL-pointer dereference of memory-protection violation. Some additional protection mechanism should be added to blk-cgroup to address this issue. In the meantime, this commit provides a quick temporary fix for BFQ: cache (when safe) blkg data that might disappear right after a blkg_lookup. In particular, this commit exploits the following facts to achieve its goal without introducing further locks. Destroy operations on a blkg invoke, as a first step, hooks of the scheduler associated with the blkg. And these hooks are executed with bfqd->lock held for BFQ. As a consequence, for any blkg associated with the request queue an instance of BFQ is attached to, we are guaranteed that such a blkg is not destroyed, and that all the pointers it contains are consistent, while that instance is holding its bfqd->lock. A blkg_lookup performed with bfqd->lock held then returns a fully consistent blkg, which remains consistent until this lock is held. In more detail, this holds even if the returned blkg is a copy of the original one. Finally, also the object describing a group inside BFQ needs to be protected from destruction on the blkg_free of the original blkg (which invokes bfq_pd_free). This commit adds private refcounting for this object, to let it disappear only after no bfq_queue refers to it any longer. This commit also removes or updates some stale comments on locking issues related to blk-cgroup operations. Reported-by: Tomas Konir <tomas.konir@gmail.com> Reported-by: Lee Tibbert <lee.tibbert@gmail.com> Reported-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Tested-by: Tomas Konir <tomas.konir@gmail.com> Tested-by: Lee Tibbert <lee.tibbert@gmail.com> Tested-by: Marco Piazza <mpiazza@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2017-06-05 16:11:15 +08:00
* cgroup from the one being destroyed now.
*/
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);
}
__bfq_deactivate_entity(entity, false);
put_async_queues:
bfq_put_async_queues(bfqd, bfqg);
spin_unlock_irqrestore(&bfqd->lock, flags);
/*
* @blkg is going offline and will be ignored by
* blkg_[rw]stat_recursive_sum(). Transfer stats to the parent so
* that they don't get lost. If IOs complete after this point, the
* stats for them will be lost. Oh well...
*/
bfqg_stats_xfer_dead(bfqg);
}
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 int bfq_io_show_weight(struct seq_file *sf, void *v)
{
struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
unsigned int val = 0;
if (bfqgd)
val = bfqgd->weight;
seq_printf(sf, "%u\n", val);
return 0;
}
static int bfq_io_set_weight_legacy(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 = -ERANGE;
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 bfq_io_set_weight(struct kernfs_open_file *of,
char *buf, size_t nbytes,
loff_t off)
{
u64 weight;
/* First unsigned long found in the file is used */
int ret = kstrtoull(strim(buf), 0, &weight);
if (ret)
return ret;
return bfq_io_set_weight_legacy(of_css(of), NULL, weight);
}
2017-11-13 14:34:10 +08:00
#ifdef CONFIG_DEBUG_BLK_CGROUP
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 = blkg_stat_recursive_sum(pd_to_blkg(pd),
&blkcg_policy_bfq, 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 = blkg_rwstat_recursive_sum(pd_to_blkg(pd),
&blkcg_policy_bfq,
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_sectors(struct seq_file *sf, struct blkg_policy_data *pd,
int off)
{
u64 sum = blkg_rwstat_total(&pd->blkg->stat_bytes);
return __blkg_prfill_u64(sf, pd, sum >> 9);
}
static int bfqg_print_stat_sectors(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
bfqg_prfill_sectors, &blkcg_policy_bfq, 0, false);
return 0;
}
static u64 bfqg_prfill_sectors_recursive(struct seq_file *sf,
struct blkg_policy_data *pd, int off)
{
struct blkg_rwstat tmp = blkg_rwstat_recursive_sum(pd->blkg, NULL,
offsetof(struct blkcg_gq, stat_bytes));
u64 sum = atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]);
return __blkg_prfill_u64(sf, pd, sum >> 9);
}
static int bfqg_print_stat_sectors_recursive(struct seq_file *sf, void *v)
{
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
bfqg_prfill_sectors_recursive, &blkcg_policy_bfq, 0,
false);
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;
}
2017-11-13 14:34:10 +08:00
#endif /* CONFIG_DEBUG_BLK_CGROUP */
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);
}
struct blkcg_policy blkcg_policy_bfq = {
.dfl_cftypes = bfq_blkg_files,
.legacy_cftypes = bfq_blkcg_legacy_files,
.cpd_alloc_fn = bfq_cpd_alloc,
.cpd_init_fn = bfq_cpd_init,
.cpd_bind_fn = bfq_cpd_init,
.cpd_free_fn = bfq_cpd_free,
.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,
};
struct cftype bfq_blkcg_legacy_files[] = {
{
.name = "bfq.weight",
.flags = CFTYPE_NOT_ON_ROOT,
.seq_show = bfq_io_show_weight,
.write_u64 = bfq_io_set_weight_legacy,
},
/* statistics, covers only the tasks in the bfqg */
{
.name = "bfq.io_service_bytes",
.private = (unsigned long)&blkcg_policy_bfq,
.seq_show = blkg_print_stat_bytes,
},
{
.name = "bfq.io_serviced",
.private = (unsigned long)&blkcg_policy_bfq,
.seq_show = blkg_print_stat_ios,
},
2017-11-13 14:34:10 +08:00
#ifdef CONFIG_DEBUG_BLK_CGROUP
{
.name = "bfq.time",
.private = offsetof(struct bfq_group, stats.time),
.seq_show = bfqg_print_stat,
},
{
.name = "bfq.sectors",
.seq_show = bfqg_print_stat_sectors,
},
{
.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,
},
2017-11-13 14:34:10 +08:00
#endif /* CONFIG_DEBUG_BLK_CGROUP */
/* the same statictics which cover the bfqg and its descendants */
{
.name = "bfq.io_service_bytes_recursive",
.private = (unsigned long)&blkcg_policy_bfq,
.seq_show = blkg_print_stat_bytes_recursive,
},
{
.name = "bfq.io_serviced_recursive",
.private = (unsigned long)&blkcg_policy_bfq,
.seq_show = blkg_print_stat_ios_recursive,
},
2017-11-13 14:34:10 +08:00
#ifdef CONFIG_DEBUG_BLK_CGROUP
{
.name = "bfq.time_recursive",
.private = offsetof(struct bfq_group, stats.time),
.seq_show = bfqg_print_stat_recursive,
},
{
.name = "bfq.sectors_recursive",
.seq_show = bfqg_print_stat_sectors_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,
},
2017-11-13 14:34:10 +08:00
#endif /* CONFIG_DEBUG_BLK_CGROUP */
{ } /* terminate */
};
struct cftype bfq_blkg_files[] = {
{
.name = "bfq.weight",
.flags = CFTYPE_NOT_ON_ROOT,
.seq_show = bfq_io_show_weight,
.write = bfq_io_set_weight,
},
{} /* terminate */
};
#else /* CONFIG_BFQ_GROUP_IOSCHED */
void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
struct bfq_group *bfqg) {}
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;
}
void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio) {}
void bfq_end_wr_async(struct bfq_data *bfqd)
{
bfq_end_wr_async_queues(bfqd, bfqd->root_group);
}
struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd, struct blkcg *blkcg)
{
return bfqd->root_group;
}
struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
{
return bfqq->bfqd->root_group;
}
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 /* CONFIG_BFQ_GROUP_IOSCHED */