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

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Feb 10, 2021 at 12:06:28PM -0500, 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>
> ---
> 
> 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

On my fstests (which sets unlimited core dumps) this test generates a
false negative because ./check trips on the core dump that the dying
xfs_io creates.  Assuming that we're /supposed/ to segfault here, I'll
send a patch to ulimit -c0.

--D

> +
> +# 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
> -- 
> 2.26.2
>