Commit 9cea62b2 authored by Jens Axboe's avatar Jens Axboe
Browse files

block: don't allow splitting of a REQ_NOWAIT bio 

If we split a bio marked with REQ_NOWAIT, then we can trigger spurious
EAGAIN if constituent parts of that split bio end up failing request
allocations. Parts will complete just fine, but just a single failure
in one of the chained bios will yield an EAGAIN final result for the
parent bio.

Return EAGAIN early if we end up needing to split such a bio, which
allows for saner recovery handling.

Cc: stable@vger.kernel.org # 5.15+
Link: https://github.com/axboe/liburing/issues/766


Reported-by: default avatarMichael Kelley <mikelley@microsoft.com>
Reviewed-by: default avatarKeith Busch <kbusch@kernel.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 613b1488

block/blk-merge.c

+10 −0
Original line number Diff line number Diff line
@@ -309,6 +309,16 @@ static struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim, 
	*segs = nsegs;

	return NULL;

split:

	/*

	 * We can't sanely support splitting for a REQ_NOWAIT bio. End it

	 * with EAGAIN if splitting is required and return an error pointer.

	 */

	if (bio->bi_opf & REQ_NOWAIT) {

		bio->bi_status = BLK_STS_AGAIN;

		bio_endio(bio);

		return ERR_PTR(-EAGAIN);

	}



	*segs = nsegs;



	/*