On Wed, Feb 03, 2021 at 01:28:26PM -0800, Andres Freund wrote:

Hi,

On 2021-02-03 14:03:09 +0100, Greg Kroah-Hartman wrote:

quoted

quoted

On v5.4.43-101-gbba91cdba612 this fails with
fio: io_u error on file /mnt/t2/test.0.0: Input/output error: write offset=0, buflen=4096
fio: pid=734, err=5/file:io_u.c:1834, func=io_u error, error=Input/output error

whereas previously it worked. libaio still works...

I haven't checked which major kernel version fixed this again, but I did
verify that it's still broken in 5.4.94 and that 5.10.9 works.

I would suspect it's

commit 4503b7676a2e0abe69c2f2c0d8b03aec53f2f048
Author: Jens Axboe [off-list ref]
Date:   2020-06-01 10:00:27 -0600

    io_uring: catch -EIO from buffered issue request failure

    -EIO bubbles up like -EAGAIN if we fail to allocate a request at the
    lower level. Play it safe and treat it like -EAGAIN in terms of sync
    retry, to avoid passing back an errant -EIO.

    Catch some of these early for block based file, as non-mq devices
    generally do not support NOWAIT. That saves us some overhead by
    not first trying, then retrying from async context. We can go straight
    to async punt instead.

    Signed-off-by: Jens Axboe [off-list ref]


which isn't in stable/linux-5.4.y

Can you test that if the above commit is added, all works well again?

It doesn't apply cleanly, I'll try to resolve the conflict. However, I
assume that the revert was for a concrete reason - but I can't quite
figure out what b0beb28097fa04177b3769f4bb7a0d0d9c4ae76e was concretely
solving, and whether reverting the revert in 5.4 would re-introduce a
different problem.

commit b0beb28097fa04177b3769f4bb7a0d0d9c4ae76e (tag: block-5.7-2020-05-29, linux-block/block-5.7)
Author: Jens Axboe [off-list ref]
Date:   2020-05-28 13:19:29 -0600

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

    This reverts commit c58c1f83436b501d45d4050fd1296d71a9760bcb.

    io_uring does do the right thing for this case, and we're still returning
    -EAGAIN to userspace for the cases we don't support. Revert this change
    to avoid doing endless spins of resubmits.

    Cc: stable@vger.kernel.org # v5.6
    Reported-by: Bijan Mottahedeh [off-list ref]
    Signed-off-by: Jens Axboe [off-list ref]

I suspect it just wasn't aimed at 5.4, and that's that, but I'm not
sure. In which case presumably reverting
bba91cdba612fbce4f8575c5d94d2b146fb83ea3 would be the right fix, not
backporting 4503b7676a2e0abe69c2f2c0d8b03aec53f2f048 et al.

Ok, can you send a revert patch for this?

But it would be good to get Jens to weigh in on this...

thanks,

greg k-h