[PATCH v2] blk-mq: end the request if getting a keyslot fails

[PATCH v2] blk-mq: end the request if getting a keyslot fails

[Eric Biggers]

From: Josef Bacik <josef@toxicpanda.com>

When blk_crypto_rq_get_keyslot() fails, blk_mq_submit_bio() ends the bio
by hand and frees the request. By then blk_mq_bio_to_request() has done
the IO accounting, which blk_mq_free_request() doesn't undo, so the
in_flight counter never drops and iostat shows a device that is 100%
busy. If the bio went through zone write plugging the zone stays plugged
as well, and every later write to it waits forever.

Use blk_mq_end_request() like the dispatch path does for a request the
driver rejected, after marking it for zone write plugging.

Move the call to blk_zone_write_plug_init_request() before
blk_crypto_rq_get_keyslot() so that it doesn't need to be duplicated.
It doesn't depend on the keyslot.

Fixes: 99dc422335d8 ("block: support to account io_ticks precisely")
Fixes: dd291d77cc90 ("block: Introduce zone write plugging")
Cc: stable@vger.kernel.org
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---

v2:
  - Moved the call to blk_zone_write_plug_init_request()
  - Updated Fixes to list the commits that actually introduced the bugs
  - Added Cc stable
  - Sent as standalone patch

 block/blk-mq.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8d687b338d6d7..379c679b04138 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3199,16 +3199,15 @@ void blk_mq_submit_bio(struct bio *bio)
 
 	blk_mq_bio_to_request(rq, bio, nr_segs);
 
+	if (bio_zone_write_plugging(bio))
+		blk_zone_write_plug_init_request(rq);
+
 	ret = blk_crypto_rq_get_keyslot(rq);
 	if (ret != BLK_STS_OK) {
-		bio_endio_status(bio, ret);
-		blk_mq_free_request(rq);
+		blk_mq_end_request(rq, ret);
 		return;
 	}
 
-	if (bio_zone_write_plugging(bio))
-		blk_zone_write_plug_init_request(rq);
-
 	if (op_is_flush(bio->bi_opf) && blk_insert_flush(rq))
 		return;
 

base-commit: 4dd16e31135ea8437a720222df34e8745f385d6d
-- 
2.56.0.317.g454f8302e1-goog

Re: [PATCH v2] blk-mq: end the request if getting a keyslot fails

[Christoph Hellwig]

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v2] blk-mq: end the request if getting a keyslot fails

[Jens Axboe]

On Thu, 29 Oct 2026 20:01:10 +0000, Eric Biggers wrote:
> When blk_crypto_rq_get_keyslot() fails, blk_mq_submit_bio() ends the bio
> by hand and frees the request. By then blk_mq_bio_to_request() has done
> the IO accounting, which blk_mq_free_request() doesn't undo, so the
> in_flight counter never drops and iostat shows a device that is 100%
> busy. If the bio went through zone write plugging the zone stays plugged
> as well, and every later write to it waits forever.
> 
> [...]

Applied, thanks!

[1/1] blk-mq: end the request if getting a keyslot fails
      commit: e67cb6ed40e7f45912b63d7d575f18dfd2ebc98a

Best regards,
-- 
Jens Axboe