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blk-cgroup: delay freeing policy data after rcu grace period

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Currently blkcg_print_blkgs() must hold RCU to iterate blkgs from a
blkcg, and prfill() must hold queue_lock to prevent policy data from
being freed by policy deactivation. As a consequence, queue_lock has to
be nested under RCU from blkcg_print_blkgs().

Delay freeing policy data until after an RCU grace period so prfill() can
be protected by RCU alone.

Signed-off-by: Yu Kuai <yukuai@fygo.io>
Link: https://patch.msgid.link/e20e5d984b41a026d61851966bed35eb094c4bff.1780621988.git.yukuai@fygo.io
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Yu Kuai
2026-06-08 11:42:43 +08:00
committed by Jens Axboe
parent 25656304da
commit 0af3fedb8c
5 changed files with 43 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
block/bfq-cgroup.c
View File

@@ -550,13 +550,20 @@ static void bfq_pd_init(struct blkg_policy_data *pd)
bfqg->rq_pos_tree = RB_ROOT;
}
static void bfq_pd_free(struct blkg_policy_data *pd)
static void bfqg_release(struct rcu_head *rcu)
{
struct blkg_policy_data *pd =
container_of(rcu, struct blkg_policy_data, rcu_head);
struct bfq_group *bfqg = pd_to_bfqg(pd);
bfqg_put(bfqg);
}
static void bfq_pd_free(struct blkg_policy_data *pd)
{
call_rcu(&pd->rcu_head, bfqg_release);
}
static void bfq_pd_reset_stats(struct blkg_policy_data *pd)
{
struct bfq_group *bfqg = pd_to_bfqg(pd);

2
block/blk-cgroup.h
View File

@@ -140,6 +140,8 @@ struct blkg_policy_data {
struct blkcg_gq *blkg;
int plid;
bool online;
struct rcu_head rcu_head;
};
/*

14
block/blk-iocost.c
View File

@@ -3050,6 +3050,16 @@ static void ioc_pd_init(struct blkg_policy_data *pd)
spin_unlock_irqrestore(&ioc->lock, flags);
}
static void iocg_release(struct rcu_head *rcu)
{
struct blkg_policy_data *pd =
container_of(rcu, struct blkg_policy_data, rcu_head);
struct ioc_gq *iocg = pd_to_iocg(pd);
free_percpu(iocg->pcpu_stat);
kfree(iocg);
}
static void ioc_pd_free(struct blkg_policy_data *pd)
{
struct ioc_gq *iocg = pd_to_iocg(pd);
@@ -3074,8 +3084,8 @@ static void ioc_pd_free(struct blkg_policy_data *pd)
hrtimer_cancel(&iocg->waitq_timer);
}
free_percpu(iocg->pcpu_stat);
kfree(iocg);
call_rcu(&pd->rcu_head, iocg_release);
}
static void ioc_pd_stat(struct blkg_policy_data *pd, struct seq_file *s)

10
block/blk-iolatency.c
View File

@@ -1031,13 +1031,21 @@ static void iolatency_pd_offline(struct blkg_policy_data *pd)
iolatency_clear_scaling(blkg);
}
static void iolatency_pd_free(struct blkg_policy_data *pd)
static void iolat_release(struct rcu_head *rcu)
{
struct blkg_policy_data *pd =
container_of(rcu, struct blkg_policy_data, rcu_head);
struct iolatency_grp *iolat = pd_to_lat(pd);
free_percpu(iolat->stats);
kfree(iolat);
}
static void iolatency_pd_free(struct blkg_policy_data *pd)
{
call_rcu(&pd->rcu_head, iolat_release);
}
static struct cftype iolatency_files[] = {
{
.name = "latency",

15
block/blk-throttle.c
View File

@@ -353,14 +353,23 @@ static void throtl_pd_online(struct blkg_policy_data *pd)
tg_update_has_rules(tg);
}
static void tg_release(struct rcu_head *rcu)
{
struct blkg_policy_data *pd =
container_of(rcu, struct blkg_policy_data, rcu_head);
struct throtl_grp *tg = pd_to_tg(pd);
blkg_rwstat_exit(&tg->stat_bytes);
blkg_rwstat_exit(&tg->stat_ios);
kfree(tg);
}
static void throtl_pd_free(struct blkg_policy_data *pd)
{
struct throtl_grp *tg = pd_to_tg(pd);
timer_delete_sync(&tg->service_queue.pending_timer);
blkg_rwstat_exit(&tg->stat_bytes);
blkg_rwstat_exit(&tg->stat_ios);
kfree(tg);
call_rcu(&pd->rcu_head, tg_release);
}
static struct throtl_grp *