From: Jens Axboe axboe@kernel.dk
commit 9cea62b2cbabff8ed46f2df17778b624ad9dd25a upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- block/blk-merge.c | 10 ++++++++++ 1 file changed, 10 insertions(+)
--- a/block/blk-merge.c +++ b/block/blk-merge.c @@ -279,6 +279,16 @@ static struct bio *blk_bio_segment_split *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;
/*