Re: [PATCH] generic: test mapped write after shutdown and failed writeback

Brian Foster
2021-02-10T19:14:34Z

On Wed, Feb 10, 2021 at 12:56:28PM -0600, Eric Sandeen wrote:
> On 2/10/21 11:06 AM, Brian Foster wrote:
> > XFS has a regression where it failed to check shutdown status in the
> > write fault path. This produced an iomap warning if the page
> > happened to recently fail a writeback attempt because writeback
> > failure can clear Uptodate status on the page. Add a test for this
> > scenario to help ensure mapped write failures are handled as
> > expected in the event of filesystem shutdown.
> >
> > Signed-off-by: Brian Foster <bfoster@redhat.com>
>
> This looks reasonable to me, I have run the same xfs_io tests when
> looking at this behavior and they do provoke it.
>
> This could maybe run on $TEST? But I don't really care much either
> way.
>

I suppose that would be possible, but I'd prefer not to shut down the
test device intentionally. I don't _think_ we currently do that
anywhere. AFAICT, there's only a handful of open-coded shutdowns and
most others use _scratch_shutdown...

> I spot-checked this on ext4 and it passes.
>
> Reviewed-by: Eric Sandeen <sandeen@redhat.com>
>

Thanks.

Brian

>
> > ---
> >
> > Note that this test currently fails on XFS. The fix is posted for review
> > on linux-xfs:
> >
> > https://lore.kernel.org/linux-xfs/20210210170112.172734-1-bfoster@redhat.com/
> >
> > Brian
> >
> > tests/generic/999 | 45 +++++++++++++++++++++++++++++++++++++++++++
> > tests/generic/999.out | 4 ++++
> > tests/generic/group | 1 +
> > 3 files changed, 50 insertions(+)
> > create mode 100755 tests/generic/999
> > create mode 100644 tests/generic/999.out
> >
> > diff --git a/tests/generic/999 b/tests/generic/999
> > new file mode 100755
> > index 00000000..5e5408e7
> > --- /dev/null
> > +++ b/tests/generic/999
> > @@ -0,0 +1,45 @@
> > +#! /bin/bash
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +# Copyright 2021 Red Hat, Inc.
> > +#
> > +# FS QA Test No. 999
> > +#
> > +# Test a write fault scenario on a shutdown fs.
> > +#
> > +seq=`basename $0`
> > +seqres=$RESULT_DIR/$seq
> > +echo "QA output created by $seq"
> > +
> > +here=`pwd`
> > +tmp=/tmp/$$
> > +status=1 # failure is the default!
> > +trap "_cleanup; exit \$status" 0 1 2 3 15
> > +
> > +_cleanup()
> > +{
> > + rm -f $tmp.*
> > +}
> > +
> > +. ./common/rc
> > +. ./common/filter
> > +
> > +rm -f $seqres.full
> > +
> > +_supported_fs generic
> > +_require_scratch_nocheck
> > +_require_scratch_shutdown
> > +
> > +_scratch_mkfs &>> $seqres.full
> > +_scratch_mount
> > +
> > +# XFS had a regression where it failed to check shutdown status in the fault
> > +# path. This produced an iomap warning because writeback failure clears Uptodate
> > +# status on the page.
> > +file=$SCRATCH_MNT/file
> > +$XFS_IO_PROG -fc "pwrite 0 4k" -c fsync $file | _filter_xfs_io
> > +$XFS_IO_PROG -x -c "mmap 0 4k" -c "mwrite 0 4k" -c shutdown -c fsync \
> > + -c "mwrite 0 4k" $file | _filter_xfs_io
> > +
> > +# success, all done
> > +status=0
> > +exit
> > diff --git a/tests/generic/999.out b/tests/generic/999.out
> > new file mode 100644
> > index 00000000..f55569ff
> > --- /dev/null
> > +++ b/tests/generic/999.out
> > @@ -0,0 +1,4 @@
> > +QA output created by 999
> > +wrote 4096/4096 bytes at offset 0
> > +XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
> > +fsync: Input/output error
> > diff --git a/tests/generic/group b/tests/generic/group
> > index b10fdea4..edd54ce5 100644
> > --- a/tests/generic/group
> > +++ b/tests/generic/group
> > @@ -625,3 +625,4 @@
> > 620 auto mount quick
> > 621 auto quick encrypt
> > 622 auto shutdown metadata atime
> > +999 auto quick shutdown
> >
>