From: Yu Kuai <yukuai@kernel.org>
To: axboe@kernel.dk, tj@kernel.org, linux-block@vger.kernel.org,
cgroups@vger.kernel.org, nilay@linux.ibm.com, bvanassche@acm.org,
ming.lei@redhat.com, hch@lst.de
Cc: linux-kernel@vger.kernel.org, Yu Kuai <yukuai3@huawei.com>
Subject: [PATCH v2 02/19] blk-cgroup: delay freeing policy data after rcu grace period
Date: Fri, 10 Oct 2025 17:14:27 +0800 [thread overview]
Message-ID: <20251010091446.3048529-3-yukuai@kernel.org> (raw)
In-Reply-To: <20251010091446.3048529-1-yukuai@kernel.org>
From: Yu Kuai <yukuai3@huawei.com>
Currently blkcg_print_blkgs() must be protected by rcu to iterate blkgs
from blkcg, and then prfill() must be protected by queue_lock to prevent
policy_data to be freed by deactivating policy. For consequence,
queue_lock have to be nested under rcu from blkcg_print_blkgs().
This patch delay freeing policy_data after rcu grace period, so that it's
possible to protect prfill() just with rcu lock held.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
block/bfq-cgroup.c | 10 ++++++++--
block/blk-cgroup.h | 2 ++
block/blk-iocost.c | 14 ++++++++++++--
block/blk-iolatency.c | 10 +++++++++-
block/blk-throttle.c | 13 +++++++++++--
5 files changed, 42 insertions(+), 7 deletions(-)
diff --git a/block/bfq-cgroup.c b/block/bfq-cgroup.c
index 9fb9f3533150..a7e705d98751 100644
--- a/block/bfq-cgroup.c
+++ b/block/bfq-cgroup.c
@@ -548,14 +548,20 @@ 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_stats_exit(&bfqg->stats);
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);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 1cce3294634d..fd206d1fa3c9 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -140,6 +140,8 @@ struct blkg_policy_data {
struct blkcg_gq *blkg;
int plid;
bool online;
+
+ struct rcu_head rcu_head;
};
/*
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 5bfd70311359..3593547930cc 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -3017,6 +3017,16 @@ 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);
@@ -3041,8 +3051,8 @@ 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)
diff --git a/block/blk-iolatency.c b/block/blk-iolatency.c
index 45bd18f68541..ce25fbb8aaf6 100644
--- a/block/blk-iolatency.c
+++ b/block/blk-iolatency.c
@@ -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",
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 2c5b64b1a724..cb3bfdb4684a 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -360,16 +360,25 @@ static void throtl_pd_online(struct blkg_policy_data *pd)
tg_update_has_rules(tg);
}
-static void throtl_pd_free(struct blkg_policy_data *pd)
+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);
- timer_delete_sync(&tg->service_queue.pending_timer);
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);
+ call_rcu(&pd->rcu_head, tg_release);
+}
+
static struct throtl_grp *
throtl_rb_first(struct throtl_service_queue *parent_sq)
{
--
2.51.0
next prev parent reply other threads:[~2025-10-10 9:14 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-10 9:14 [PATCH v2 00/19] blk-cgroup: convert to use blkcg_mutex for protection Yu Kuai
2025-10-10 9:14 ` [PATCH v2 01/19] blk-cgroup: protect iterating blkgs with blkcg->lock in blkcg_print_stat() Yu Kuai
2025-10-10 9:14 ` Yu Kuai [this message]
2025-10-10 9:14 ` [PATCH v2 03/19] blk-cgroup: don't nest queue_lock under rcu in blkcg_print_blkgs() Yu Kuai
2025-10-10 9:14 ` [PATCH v2 04/19] blk-cgroup: don't nest queue_lock under rcu in blkg_lookup_create() Yu Kuai
2025-10-10 9:14 ` [PATCH v2 05/19] blk-cgroup: don't nest queu_lock under rcu in bio_associate_blkg() Yu Kuai
2025-10-10 9:14 ` [PATCH v2 06/19] blk-cgroup: don't nest queue_lock under blkcg->lock in blkcg_destroy_blkgs() Yu Kuai
2025-10-10 9:14 ` [PATCH v2 07/19] mm/page_io: don't nest queue_lock under rcu in bio_associate_blkg_from_page() Yu Kuai
2025-10-10 9:14 ` [PATCH v2 08/19] block, bfq: don't grab queue_lock to initialize bfq Yu Kuai
2025-10-10 9:14 ` [PATCH v2 09/19] blk-cgroup: convert to protect blkgs with blkcg_mutex Yu Kuai
2025-10-10 9:14 ` [PATCH v2 10/19] blk-cgroup: remove radix_tree_preload() Yu Kuai
2025-10-10 9:14 ` [PATCH v2 11/19] blk-cgroup: remove preallocate blkg for blkg_create() Yu Kuai
2025-10-10 9:14 ` [PATCH v2 12/19] blk-throttle: fix possible deadlock due to queue_lock in timer Yu Kuai
2025-10-10 9:14 ` [PATCH v2 13/19] blk-cgroup: add new blkg configuration helpers Yu Kuai
2025-10-10 9:14 ` [PATCH v2 14/19] blk-cgroup: factor out a helper __blkg_activate_policy() Yu Kuai
2025-10-10 9:14 ` [PATCH v2 15/19] blk-throttle: convert to use blkg_conf_{start, end} Yu Kuai
2025-10-10 9:14 ` [PATCH v2 16/19] block, bfq: " Yu Kuai
2025-10-10 9:14 ` [PATCH v2 17/19] blk-iolatency: " Yu Kuai
2025-10-10 9:14 ` [PATCH v2 18/19] blk-iocost: " Yu Kuai
2025-10-10 9:14 ` [PATCH v2 19/19] blk-cgroup: remove unsed blkg configuration helpers Yu Kuai
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