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block: blk_queue_enter() / __bio_queue_enter() must return -EAGAIN for nowait

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Today blk_queue_enter() and __bio_queue_enter() return -EBUSY for the
nowait code path. This is not correct: they should return -EAGAIN
instead.

This problem was detected by fio. The following command exposed the
above problem:

t/io_uring -p0 -d128 -b4096 -s32 -c32 -F1 -B0 -R0 -X1 -n24 -P1 -u1 -O0 /dev/ng0n1

By applying the patch, the retry case is handled correctly in the slow
path.

Signed-off-by: Stefan Roesch <shr@fb.com>
Fixes: bfd343aa17 ("blk-mq: don't wait in blk_mq_queue_enter() if __GFP_WAIT isn't set")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Stefan Roesch 2022-09-12 09:53:25 -07:00 committed by Jens Axboe
parent 745ed37277
commit 56f99b8d06
1 changed files with 2 additions and 2 deletions
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4
block/blk-core.c
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@ -295,7 +295,7 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
while (!blk_try_enter_queue(q, pm)) {
if (flags & BLK_MQ_REQ_NOWAIT)
return -EBUSY;
return -EAGAIN;
/*
* read pair of barrier in blk_freeze_queue_start(), we need to
@ -325,7 +325,7 @@ int __bio_queue_enter(struct request_queue *q, struct bio *bio)
if (test_bit(GD_DEAD, &disk->state))
goto dead;
bio_wouldblock_error(bio);
return -EBUSY;
return -EAGAIN;
}
/*