diff options
| author | Ming Lei <ming.lei@redhat.com> | 2026-03-05 11:15:50 +0800 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2026-03-12 07:09:59 -0400 |
| commit | c3e8c75fcb2ef63c99727eadddd2bb577c386506 (patch) | |
| tree | 98a1a67069a455e5794a43be50b64e033e97c699 | |
| parent | 6b0e35123ba459d3f8688b18eba824e73071a3fd (diff) | |
block: use trylock to avoid lockdep circular dependency in sysfs
[ Upstream commit ce8ee8583ed83122405eabaa8fb351be4d9dc65c ]
Use trylock instead of blocking lock acquisition for update_nr_hwq_lock
in queue_requests_store() and elv_iosched_store() to avoid circular lock
dependency with kernfs active reference during concurrent disk deletion:
update_nr_hwq_lock -> kn->active (via del_gendisk -> kobject_del)
kn->active -> update_nr_hwq_lock (via sysfs write path)
Return -EBUSY when the lock is not immediately available.
Reported-and-tested-by: Yi Zhang <yi.zhang@redhat.com>
Closes: https://lore.kernel.org/linux-block/CAHj4cs-em-4acsHabMdT=jJhXkCzjnprD-aQH1OgrZo4nTnmMw@mail.gmail.com/
Fixes: 626ff4f8ebcb ("blk-mq: convert to serialize updating nr_requests with update_nr_hwq_lock")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | block/blk-sysfs.c | 8 | ||||
| -rw-r--r-- | block/elevator.c | 12 |
2 files changed, 18 insertions, 2 deletions
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index e0a70d26972b..af12526d866a 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -78,8 +78,14 @@ queue_requests_store(struct gendisk *disk, const char *page, size_t count) /* * Serialize updating nr_requests with concurrent queue_requests_store() * and switching elevator. + * + * Use trylock to avoid circular lock dependency with kernfs active + * reference during concurrent disk deletion: + * update_nr_hwq_lock -> kn->active (via del_gendisk -> kobject_del) + * kn->active -> update_nr_hwq_lock (via this sysfs write path) */ - down_write(&set->update_nr_hwq_lock); + if (!down_write_trylock(&set->update_nr_hwq_lock)) + return -EBUSY; if (nr == q->nr_requests) goto unlock; diff --git a/block/elevator.c b/block/elevator.c index a2f8b2251dc6..7a97998cd8bd 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -806,7 +806,16 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf, elv_iosched_load_module(ctx.name); ctx.type = elevator_find_get(ctx.name); - down_read(&set->update_nr_hwq_lock); + /* + * Use trylock to avoid circular lock dependency with kernfs active + * reference during concurrent disk deletion: + * update_nr_hwq_lock -> kn->active (via del_gendisk -> kobject_del) + * kn->active -> update_nr_hwq_lock (via this sysfs write path) + */ + if (!down_read_trylock(&set->update_nr_hwq_lock)) { + ret = -EBUSY; + goto out; + } if (!blk_queue_no_elv_switch(q)) { ret = elevator_change(q, &ctx); if (!ret) @@ -816,6 +825,7 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf, } up_read(&set->update_nr_hwq_lock); +out: if (ctx.type) elevator_put(ctx.type); return ret; |