diff options
| author | Yu Kuai <yukuai@fnnas.com> | 2026-02-14 13:43:50 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2026-02-16 10:47:25 -0700 |
| commit | dfe48ea179733be948c432f6af2fc3913cf5dd28 (patch) | |
| tree | 5b931d881352843e79ab7d7509f4750dfe6d0284 /block/blk-wbt.c | |
| parent | 3678a334a55e869b413e2fb4824e92200b149d73 (diff) | |
blk-mq: use NOIO context to prevent deadlock during debugfs creation
Creating debugfs entries can trigger fs reclaim, which can enter back
into the block layer request_queue. This can cause deadlock if the
queue is frozen.
Previously, a WARN_ON_ONCE check was used in debugfs_create_files()
to detect this condition, but it was racy since the queue can be frozen
from another context at any time.
Introduce blk_debugfs_lock()/blk_debugfs_unlock() helpers that combine
the debugfs_mutex with memalloc_noio_save()/restore() to prevent fs
reclaim from triggering block I/O. Also add blk_debugfs_lock_nomemsave()
and blk_debugfs_unlock_nomemrestore() variants for callers that don't
need NOIO protection (e.g., debugfs removal or read-only operations).
Replace all raw debugfs_mutex lock/unlock pairs with these helpers,
using the _nomemsave/_nomemrestore variants where appropriate.
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Closes: https://lore.kernel.org/all/CAHj4cs9gNKEYAPagD9JADfO5UH+OiCr4P7OO2wjpfOYeM-RV=A@mail.gmail.com/
Reported-by: Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Closes: https://lore.kernel.org/all/aYWQR7CtYdk3K39g@shinmob/
Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-wbt.c')
| -rw-r--r-- | block/blk-wbt.c | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/block/blk-wbt.c b/block/blk-wbt.c index 1415f2bf8611..6dba71e87387 100644 --- a/block/blk-wbt.c +++ b/block/blk-wbt.c @@ -776,6 +776,7 @@ void wbt_init_enable_default(struct gendisk *disk) { struct request_queue *q = disk->queue; struct rq_wb *rwb; + unsigned int memflags; if (!__wbt_enable_default(disk)) return; @@ -789,9 +790,9 @@ void wbt_init_enable_default(struct gendisk *disk) return; } - mutex_lock(&q->debugfs_mutex); + memflags = blk_debugfs_lock(q); blk_mq_debugfs_register_rq_qos(q); - mutex_unlock(&q->debugfs_mutex); + blk_debugfs_unlock(q, memflags); } static u64 wbt_default_latency_nsec(struct request_queue *q) @@ -1015,9 +1016,10 @@ int wbt_set_lat(struct gendisk *disk, s64 val) blk_mq_unquiesce_queue(q); out: blk_mq_unfreeze_queue(q, memflags); - mutex_lock(&q->debugfs_mutex); + + memflags = blk_debugfs_lock(q); blk_mq_debugfs_register_rq_qos(q); - mutex_unlock(&q->debugfs_mutex); + blk_debugfs_unlock(q, memflags); return ret; } |