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-mq-debugfs.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-mq-debugfs.c')
| -rw-r--r-- | block/blk-mq-debugfs.c | 10 |
1 files changed, 3 insertions, 7 deletions
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index faeaa1fc86a7..28167c9baa55 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -614,11 +614,6 @@ static void debugfs_create_files(struct request_queue *q, struct dentry *parent, { lockdep_assert_held(&q->debugfs_mutex); /* - * Creating new debugfs entries with queue freezed has the risk of - * deadlock. - */ - WARN_ON_ONCE(q->mq_freeze_depth != 0); - /* * debugfs_mutex should not be nested under other locks that can be * grabbed while queue is frozen. */ @@ -693,12 +688,13 @@ void blk_mq_debugfs_unregister_hctx(struct blk_mq_hw_ctx *hctx) void blk_mq_debugfs_register_hctxs(struct request_queue *q) { struct blk_mq_hw_ctx *hctx; + unsigned int memflags; unsigned long i; - mutex_lock(&q->debugfs_mutex); + memflags = blk_debugfs_lock(q); queue_for_each_hw_ctx(q, hctx, i) blk_mq_debugfs_register_hctx(q, hctx); - mutex_unlock(&q->debugfs_mutex); + blk_debugfs_unlock(q, memflags); } void blk_mq_debugfs_unregister_hctxs(struct request_queue *q) |