On Mon, Jan 19, 2015 at 09:30:21AM -0500, Brian Foster wrote:

The secondary superblock verification in xfs_repair was subject to a bug
that unnecessarily leads to a brute force superblock scan if the last
superblock in the fs happens to be corrupt. Normally, xfs_repair handles
one-off superblock corruption gracefully using a heuristic that finds
the most consistent superblock content across the set of secondary
superblocks.

Create a regression test for xfs_repair that corrupts the last
superblock in the fs. Verify the superblock is updated from the
previously verified sb content and a brute force scan is not initiated.
In the event of failure, detect that a brute force scan has started and
abort the repair in order to fail the test quickly.

To support the test, extend the xfs_repair filter to handle corrupted
superblock repair output and provide generic test output for arbitrary
AG counts.

Signed-off-by: Brian Foster <redacted>
---

Hi all,

This is an xfs_repair regression test to trigger the problem fixed by
the following previously posted fix:

http://oss.sgi.com/archives/xfs/2015-01/msg00244.html

Thoughts appreciated, thanks.

...

+# Start and monitor an xfs_repair of the scratch device. This test can induce a
+# time consuming brute force superblock scan. Since a brute force scan means
+# test failure, detect it and end the repair.
+_xfs_repair_noscan()
+{
+	# invoke repair directly so we can kill the process if need be
+	$XFS_REPAIR_PROG $SCRATCH_DEV 2>&1 | tee -a $seqres.full > $tmp.repair &
+	repair_pid=$!
+
+	# monitor progress for as long as it is running
+	while [ `ps -q $repair_pid > /dev/null; echo $?` == 0 ]; do

	while [ `pgrep xfs_repair` -eq 0 ]; do

+		grep "couldn't verify primary superblock" $tmp.repair \
+			> /dev/null 2>&1
+		if [ $? == 0 ]; then
+			# we've started a brute force scan. kill repair and
+			# fail the test
+			kill -9 $repair_pid >> $seqres.full 2>&1
+			wait >> $seqres.full 2>&1
+
+			_fail "xfs_repair resorted to brute force scan"
+		fi
+
+		sleep 1
+	done
+
+	wait
+
+	cat $tmp.repair | _filter_repair
+}
+
+rm -f $seqres.full
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/repair
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs xfs
+_supported_os Linux
+_require_scratch_nocheck
+
+_scratch_mkfs >> $seqres.full 2>&1 || _fail "mkfs failed"
+
+# corrupt the last secondary sb in the fs
+agcount=`$XFS_DB_PROG -c "sb" -c "p agcount" $SCRATCH_DEV | awk '{ print $3 }'`

scratch_mkfs | _filter_mkfs 2> $tmp.mkfs
. $tmp.mkfs

And now you have the agcount variable already set up (and most other
fs geometry variables that mkfs outputs).

+last_secondary=$((agcount - 1))
+$XFS_DB_PROG -x -c "sb $last_secondary" -c "type data" \

you can just use  "sb $((agcount - 1))" directly. The comment above
tells us that it's the last secondary sb we are corrupting....

Otherwise look sok.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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