Re: [PATCH 2/6] common: capture metadump output if xfs filesystem check fails

Brian Foster
2021-02-11T14:03:50Z

On Tue, Feb 09, 2021 at 06:56:30PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@djwong.org>
>
> Capture metadump output when various userspace repair and checker tools
> fail or indicate corruption, to aid in debugging. We don't bother to
> annotate xfs_check because it's bitrotting.
>
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
> README | 2 ++
> common/xfs | 26 ++++++++++++++++++++++++++
> 2 files changed, 28 insertions(+)
>
>
> diff --git a/README b/README
> index 43bb0cee..36f72088 100644
> --- a/README
> +++ b/README
> @@ -109,6 +109,8 @@ Preparing system for tests:
> - Set TEST_FS_MODULE_RELOAD=1 to unload the module and reload
> it between test invocations. This assumes that the name of
> the module is the same as FSTYP.
> + - Set SNAPSHOT_CORRUPT_XFS=1 to record compressed metadumps of XFS
> + filesystems if the various stages of _check_xfs_filesystem fail.
>
> - or add a case to the switch in common/config assigning
> these variables based on the hostname of your test
> diff --git a/common/xfs b/common/xfs
> index 2156749d..ad1eb6ee 100644
> --- a/common/xfs
> +++ b/common/xfs
> @@ -432,6 +432,21 @@ _supports_xfs_scrub()
> return 0
> }
>
> +# Save a compressed snapshot of a corrupt xfs filesystem for later debugging.
> +_snapshot_xfs() {

The term snapshot has a well known meaning. Can we just call this
_metadump_xfs()?

> + local metadump="$1"
> + local device="$2"
> + local logdev="$3"
> + local options="-a -o"
> +
> + if [ "$logdev" != "none" ]; then
> + options="$options -l $logdev"
> + fi
> +
> + $XFS_METADUMP_PROG $options "$device" "$metadump" >> "$seqres.full" 2>&1
> + gzip -f "$metadump" >> "$seqres.full" 2>&1 &

Why compress in the background? I wonder if we should just skip the
compression step since this requires an option to enable in the first
place..

> +}
> +
> # run xfs_check and friends on a FS.
> _check_xfs_filesystem()
> {
...
> @@ -540,6 +564,8 @@ _check_xfs_filesystem()
> cat $tmp.repair >>$seqres.full
> echo "*** end xfs_repair output" >>$seqres.full
>
> + test "$SNAPSHOT_CORRUPT_XFS" = "1" && \
> + _snapshot_xfs "$seqres.rebuildrepair.md" "$device" "$2"

Why do we collect so many metadump images? Shouldn't all but the last
TEST_XFS_REPAIR_REBUILD thing not modify the fs? If so, it seems like we
should be able to collect one image (and perhaps just call it
"$seqres.$device.md") if any of the first several checks flag a problem.

Brian

> ok=0
> fi
> rm -f $tmp.repair
>