Commit c58c1f83 authored Dec 17, 2019 by Roman Penyaev Committed by Jens Axboe Dec 17, 2019

block: end bio with BLK_STS_AGAIN in case of non-mq devs and REQ_NOWAIT



Non-mq devs do not honor REQ_NOWAIT so give a chance to the caller to repeat
request gracefully on -EAGAIN error.

The problem is well reproduced using io_uring:

   mkfs.ext4 /dev/ram0
   mount /dev/ram0 /mnt

   # Preallocate a file
   dd if=/dev/zero of=/mnt/file bs=1M count=1

   # Start fio with io_uring and get -EIO
   fio --rw=write --ioengine=io_uring --size=1M --direct=1 --name=job --filename=/mnt/file

Signed-off-by: Roman Penyaev <rpenyaev@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

parent 1c05839a

block/blk-core.c

+7 −4

Original line number	Diff line number	Diff line
		@@ -885,11 +885,14 @@ generic_make_request_checks(struct bio *bio)
		}

		/*
		* For a REQ_NOWAIT based request, return -EOPNOTSUPP
		* if queue is not a request based queue.
		* Non-mq queues do not honor REQ_NOWAIT, so complete a bio
		* with BLK_STS_AGAIN status in order to catch -EAGAIN and
		* to give a chance to the caller to repeat request gracefully.
		*/
		if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_mq(q))
		goto not_supported;
		if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_mq(q)) {
		status = BLK_STS_AGAIN;
		goto end_io;
		}

		if (should_fail_bio(bio))
		goto end_io;

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