Re: [PATCH] generic: shutdown might leave NULL files with nonzero di_size

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

On Sat, Nov 05, 2022 at 12:20:02AM +0800, Zorro Lang wrote:
> An old issue might cause on-disk inode sizes are logged prematurely
> via the free eofblocks path on file close. Then fs shutdown might
> leave NULL files but their di_size > 0.
> 
> Signed-off-by: Zorro Lang <zlang@kernel.org>
> ---
> 
> Hi,
> 
> There was an very old xfs bug on rhel-6.5, I'd like to share its reproducer to
> fstests. I've tried generic/044~049, no one can reproduce this bug, so I
> have to write this new one. It fails on rhel-6.5 [1], and test passed on
> later kernel.
> 
> I hard to say which patch fix this issue exactly, it's fixed by a patchset
> which does code improvement/cleanup.
> 
> Thanks,
> Zorro
> 
> [1]
> # ./check generic/999
> FSTYP         -- xfs (non-debug)
> PLATFORM      -- Linux/x86_64
> MKFS_OPTIONS  -- -f -bsize=4096 /dev/loop1
> MOUNT_OPTIONS -- -o context=system_u:object_r:nfs_t:s0 /dev/loop1 /mnt/scratch
> 
> generic/999 2s ... - output mismatch (see /root/xfstests-dev/results//generic/999.out.bad)
>     --- tests/generic/999.out   2022-11-04 00:54:11.123353054 -0400
>     +++ /root/xfstests-dev/results//generic/999.out.bad 2022-11-04 04:24:57.861673433 -0400
>     @@ -1 +1,3 @@
>      QA output created by 999
>     + - /mnt/scratch/1 get no extents, but its di_size > 0
>     +/mnt/scratch/1:
>     ...
>     (Run 'diff -u tests/generic/045.out /root/xfstests-dev/results//generic/999.out.bad'  to see the entire diff)
> Ran: generic/999
> Failures: generic/999
> Failed 1 of 1 tests
> 
>  tests/generic/999     | 46 +++++++++++++++++++++++++++++++++++++++++++
>  tests/generic/999.out |  5 +++++
>  2 files changed, 51 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..a2e662fc
> --- /dev/null
> +++ b/tests/generic/999
> @@ -0,0 +1,46 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0
> +# Copyright (c) 2022 Red Hat, Inc.  All Rights Reserved.
> +#
> +# FS QA Test No. 999
> +#
> +# Test an issue in the truncate codepath where on-disk inode sizes are logged
> +# prematurely via the free eofblocks path on file close.
> +#
> +. ./common/preamble
> +_begin_fstest auto quick shutdown
> +
> +# real QA test starts here
> +_supported_fs xfs
> +_require_scratch
> +_require_xfs_io_command fiemap

/me would've thought you'd use the xfs_io stat/bmap commands to detect
either nextents > 0 (stat) or actual mappings returned (bmap), but I
guess if RHEL 6.5 xfsprogs has a fiemap command then this is fine with
me.

If the answer to the above is "um, RHEL 6.5 xfsprogs *does* have FIEMAP",
then there's little point in rewriting a stable regression test, so:

Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> +_require_scratch_shutdown
> +_scratch_mkfs > $seqres.full 2>&1
> +_scratch_mount
> +
> +echo "Create many small files with one extent at least"
> +for ((i=0; i<10000; i++));do
> +	$XFS_IO_PROG -f -c "pwrite 0 4k" $SCRATCH_MNT/file.$i >/dev/null 2>&1
> +done
> +
> +echo "Shutdown the fs suddently"
> +_scratch_shutdown
> +
> +echo "Cycle mount"
> +_scratch_cycle_mount
> +
> +echo "Check file's (di_size > 0) extents"
> +for f in $(find $SCRATCH_MNT -type f -size +0);do
> +	$XFS_IO_PROG -c "fiemap" $f > $tmp.fiemap
> +	# Check if the file has any extent
> +	grep -Eq '^[[:space:]]+[0-9]+:' $tmp.fiemap
> +	if [ $? -ne 0 ];then
> +		echo " - $f get no extents, but its di_size > 0"
> +		cat $tmp.fiemap
> +		break
> +	fi
> +done
> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/generic/999.out b/tests/generic/999.out
> new file mode 100644
> index 00000000..50008783
> --- /dev/null
> +++ b/tests/generic/999.out
> @@ -0,0 +1,5 @@
> +QA output created by 999
> +Create many small files with one extent at least
> +Shutdown the fs suddently
> +Cycle mount
> +Check file's (di_size > 0) extents
> -- 
> 2.31.1
>