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block: don't allow splitting of a REQ_NOWAIT bio

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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: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2023-01-04 08:52:06 -07:00
parent 613b14884b
commit 9cea62b2cb
1 changed files with 10 additions and 0 deletions
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10
block/blk-merge.c
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@ -309,6 +309,16 @@ static struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim,
*segs = nsegs; *segs = nsegs;
return NULL; return NULL;
split: 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; *segs = nsegs;
/* /*