Re: [PATCH v2] common/xfs: wipe the XFS superblock of each AGs

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Sep 20, 2019 at 02:23:27PM +0800, Zorro Lang wrote:
> xfs/030 always fails after d0e484ac699f ("check: wipe scratch devices
> between tests") get merged.
> 
> Due to xfs/030 does a sized(100m) mkfs. Before we merge above commit,
> mkfs.xfs detects an old primary superblock, it will write zeroes to
> all superblocks before formatting the new filesystem. But this won't
> be done if we wipe the first superblock(by merging above commit).
> 
> That means if we make a (smaller) sized xfs after wipefs, those *old*
> superblocks which created by last time mkfs.xfs will be left on disk.
> Then when we do xfs_repair, if xfs_repair can't find the first SB, it
> will go to find those *old* SB at first. When it finds them,
> everyting goes wrong.
> 
> So I try to get XFS AG geometry(by default) and then try to erase all
> superblocks. Thanks Darrick J. Wong helped to analyze this issue.
> 
> Reported-by: Yang Xu <xuyang2018.jy@cn.fujitsu.com>
> Signed-off-by: Zorro Lang <zlang@redhat.com>
> ---
> 
> Hi,
> 
> V2 did below changes:
> 1) Use xfs_db to detect the real xfs geometry
> 2) Do a $FSTYP specified wipe before trying to wipefs all scratch devices
> 
> Thanks,
> Zorro
> 
>  common/rc  |  8 ++++++++
>  common/xfs | 20 ++++++++++++++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/common/rc b/common/rc
> index 66c7fd4d..56329747 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -4045,6 +4045,14 @@ _try_wipe_scratch_devs()
>  {
>  	test -x "$WIPEFS_PROG" || return 0
>  
> +	# Do specified filesystem wipe at first
> +	case "$FSTYP" in
> +	"xfs")
> +		_try_wipe_scratch_xfs
> +		;;
> +	esac
> +
> +	# Then do wipefs on all scratch devices
>  	for dev in $SCRATCH_DEV_POOL $SCRATCH_DEV $SCRATCH_LOGDEV $SCRATCH_RTDEV; do
>  		test -b $dev && $WIPEFS_PROG -a $dev
>  	done
> diff --git a/common/xfs b/common/xfs
> index 1bce3c18..082a1744 100644
> --- a/common/xfs
> +++ b/common/xfs
> @@ -884,3 +884,23 @@ _xfs_mount_agcount()
>  {
>  	$XFS_INFO_PROG "$1" | grep agcount= | sed -e 's/^.*agcount=\([0-9]*\),.*$/\1/g'
>  }
> +
> +# Wipe the superblock of each XFS AGs
> +_try_wipe_scratch_xfs()
> +{
> +	local num='^[0-9]+$'
> +	local agcount
> +	local agsize
> +	local dbsize
> +
> +	agcount=`_scratch_xfs_get_sb_field agcount 2>/dev/null`
> +	agsize=`_scratch_xfs_get_sb_field agblocks 2>/dev/null`
> +	dbsize=`_scratch_xfs_get_sb_field blocksize 2>/dev/null`
> +
> +	if [[ $agcount =~ $num && $agsize =~ $num && $dbsize =~ $num ]];then
> +		for ((i = 0; i < agcount; i++)); do
> +			$XFS_IO_PROG -c "pwrite $((i * dbsize * agsize)) $dbsize" \
> +				$SCRATCH_DEV >/dev/null;
> +		done
> +	fi

What happened to the loop that simulates a _scratch_mkfs_xfs run (to get
the AG geometry) and then zaps that too?  You need both zeroing loops to
make sure xfs/030 doesn't trip over old superblocks, right?

--D

> +}
> -- 
> 2.20.1
>