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

[Zorro Lang <zlang@redhat.com>]

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.

Signed-off-by: Zorro Lang <zlang@redhat.com>
---
 common/rc  |  4 ++++
 common/xfs | 23 +++++++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/common/rc b/common/rc
index 66c7fd4d..fe13f659 100644
--- a/common/rc
+++ b/common/rc
@@ -4048,6 +4048,10 @@ _try_wipe_scratch_devs()
 	for dev in $SCRATCH_DEV_POOL $SCRATCH_DEV $SCRATCH_LOGDEV $SCRATCH_RTDEV; do
 		test -b $dev && $WIPEFS_PROG -a $dev
 	done
+
+	if [ "$FSTYP" = "xfs" ];then
+		try_wipe_scratch_xfs
+	fi
 }
 
 # Only run this on xfs if xfs_scrub is available and has the unicode checker
diff --git a/common/xfs b/common/xfs
index 1bce3c18..34516f82 100644
--- a/common/xfs
+++ b/common/xfs
@@ -884,3 +884,26 @@ _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 tmp=`mktemp -u`
+
+	_scratch_mkfs_xfs -N 2>/dev/null | perl -ne '
+		if (/^meta-data=.*\s+agcount=(\d+), agsize=(\d+) blks/) {
+			print STDOUT "agcount=$1\nagsize=$2\n";
+		}
+		if (/^data\s+=\s+bsize=(\d+)\s/) {
+			print STDOUT "dbsize=$1\n";
+		}' > $tmp.mkfs
+
+	. $tmp.mkfs
+	if [ -n "$agcount" -a -n "$agsize" -a -n "$dbsize" ];then
+		for ((i = 0; i < agcount; i++)); do
+			$XFS_IO_PROG -c "pwrite $((i * dbsize * agsize)) $dbsize" \
+				$SCRATCH_DEV >/dev/null;
+		done
+       fi
+       rm -f $tmp.mkfs
+}
-- 
2.20.1