linux/block/bfq-cgroup.c
Paolo Valente 52257ffbfc block, bfq: put async queues for root bfq groups too
For each pair [device for which bfq is selected as I/O scheduler,
group in blkio/io], bfq maintains a corresponding bfq group. Each such
bfq group contains a set of async queues, with each async queue
created on demand, i.e., when some I/O request arrives for it.  On
creation, an async queue gets an extra reference, to make sure that
the queue is not freed as long as its bfq group exists.  Accordingly,
to allow the queue to be freed after the group exited, this extra
reference must released on group exit.

The above holds also for a bfq root group, i.e., for the bfq group
corresponding to the root blkio/io root for a given device. Yet, by
mistake, the references to the existing async queues of a root group
are not released when the latter exits. This causes a memory leak when
the instance of bfq for a given device exits. In a similar vein,
bfqg_stats_xfer_dead is not executed for a root group.

This commit fixes bfq_pd_offline so that the latter executes the above
missing operations for a root group too.

Reported-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Reported-by: Guoqing Jiang <gqjiang@suse.com>
Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Davide Ferrari <davideferrari8@gmail.com>
Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2018-01-09 08:45:25 -07:00

1233 lines
34 KiB
C

/*
* 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"
#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
/* This should be called with the scheduler 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 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 = sched_clock();
bfqg_stats_mark_waiting(stats);
}
/* This should be called with the scheduler 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);
}
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 = sched_clock();
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)) {
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);
}
}
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);
}
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);
}
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, uint64_t start_time,
uint64_t io_start_time, unsigned int op)
{
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, op,
now - io_start_time);
if (time_after64(io_start_time, start_time))
blkg_rwstat_add(&stats->wait_time, op,
io_start_time - start_time);
}
#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, uint64_t start_time,
uint64_t io_start_time, unsigned int op) { }
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)
{
bfqg->ref++;
}
static void bfqg_put(struct bfq_group *bfqg)
{
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)
{
#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);
#endif
}
/* @to += @from */
static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from)
{
if (!to || !from)
return;
#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);
#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;
/*
* 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)
{
#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);
#endif
}
static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
{
#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;
}
#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;
}
/* 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);
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.
*
* 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);
bfqg_and_blkg_put(bfqq_group(bfqq));
entity->parent = bfqg->my_entity;
entity->sched_data = &bfqg->sched_data;
/* 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.
*
* 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));
/*
* 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
* 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);
}
#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;
}
#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,
},
#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,
},
#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,
},
#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,
},
#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 */