xfstests: create a test for xfs log grant head leak detection

Changes in the XFS logging code have lead to small leaks in the log
grant heads that consume log space slowly over time. Such problems have
gone undetected for an unnecessarily long time due to code complexity
and potential for very subtle problems. Losing only a few bytes per
logged item on a reasonably large enough fs (10s of GB) means only the
most continuously stressful workloads will cause a severe enough failure
(deadlock due to log reservation exhaustion) quickly enough to indicate
something is seriously wrong.

Recent changes in XFS export the state of the various log heads through
sysfs to aid in userspace/runtime analysis of the log. This test runs a
workload against an XFS filesystem, quiesces the fs and verifies that
the log reserve and write grant heads have not leaked any space with
respect to the current head of the physical log.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

common/rc

@@ -1131,6 +1131,23 @@ _require_xfs_finobt()
 	umount $SCRATCH_MNT
 }
 
+# this test requires xfs sysfs attribute support
+#
+_require_xfs_sysfs()
+{
+	attr=$1
+	sysfsdir=/sys/fs/xfs
+	testdev=`_short_dev $TEST_DEV`
+
+	if [ ! -e $sysfsdir ]; then
+		_notrun "no kernel support for XFS sysfs attributes"
+	fi
+
+	if [ ! -z $1 ] && [ ! -e $sysfsdir/$testdev/$attr ]; then
+		_notrun "sysfs attribute '$attr' is not supported"
+	fi
+}
+
 # this test requires that external log/realtime devices are not in use
 #
 _require_nonexternal()

tests/xfs/011

@@ -0,0 +1,116 @@
+#!/bin/bash
+# FS QA Test No. xfs/011
+#
+# Test the xfs log reservation mechanism for leaks. Run an fsstress workload to
+# include a variety of fs operations, freeze the filesystem and verify that
+# there are no oustanding reservations against the log.
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2014 Red Hat, Inc.  All Rights Reserved.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it would be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write the Free Software Foundation,
+# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+#
+#-----------------------------------------------------------------------
+#
+
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+# get standard environment, filters and checks
+. ./common/rc
+
+_cleanup()
+{
+	killall -9 fsstress 2>/dev/null
+	wait
+	cd /
+	umount $SCRATCH_MNT 2>/dev/null
+	rm -f $tmp.*
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# Use the information exported by XFS to sysfs to determine whether the log has
+# active reservations after a filesystem freeze.
+_check_scratch_log_state()
+{
+	devname=`_short_dev $SCRATCH_DEV`
+	attrpath="/sys/fs/xfs/$devname/log"
+
+	# freeze the fs to ensure data is synced and the log is flushed. this
+	# means no outstanding transactions, and thus no outstanding log
+	# reservations, should exist
+	xfs_freeze -f $SCRATCH_MNT
+
+	# the log head is exported in basic blocks and the log grant heads in
+	# bytes. convert the log head to bytes for precise comparison
+	log_head_cycle=`awk -F : '{ print $1 }' $attrpath/log_head_lsn`
+	log_head_bytes=`awk -F : '{ print $2 }' $attrpath/log_head_lsn`
+	log_head_bytes=$((log_head_bytes * 512))
+
+	for attr in "reserve_grant_head" "write_grant_head"; do
+		cycle=`cat $attrpath/$attr | awk -F : '{ print $1 }'`
+		bytes=`cat $attrpath/$attr | awk -F : '{ print $2 }'`
+
+		if [ $cycle != $log_head_cycle ] ||
+		   [ $bytes != $log_head_bytes ]
+		then
+			echo "$attr ($cycle:$bytes) does not match" \
+				"log_head_lsn ($log_head_cycle:$log_head_bytes)," \
+				"possible leak detected."
+		fi
+	done
+
+	xfs_freeze -u $SCRATCH_MNT
+}
+
+# real QA test starts here
+_supported_fs xfs
+_supported_os Linux
+
+_require_scratch
+_require_freeze
+_require_xfs_sysfs log
+
+rm -f $seqres.full
+
+echo "Silence is golden."
+
+_scratch_mkfs_xfs >> $seqres.full 2>&1
+_scratch_mount
+
+_check_scratch_log_state
+
+$FSSTRESS_PROG -d $SCRATCH_MNT/fsstress -n 9999999 -p 2 -S t \
+	>> $seqres.full 2>&1 &
+
+iters=5
+while [ $iters -gt 0 ]; do
+	sleep 3
+	_check_scratch_log_state
+	iters=$((iters - 1))
+done
+
+killall $FSSTRESS_PROG
+wait
+
+umount $SCRATCH_MNT
+_check_scratch_fs
+
+status=0
+exit

tests/xfs/011.out

@@ -0,0 +1,2 @@
+QA output created by 011
+Silence is golden.

tests/xfs/group

@@ -8,6 +8,7 @@
 008 rw ioctl auto quick
 009 rw ioctl auto prealloc quick
 010 auto quick repair
+011 auto freeze log metadata quick
 012 rw auto quick
 013 auto metadata stress
 014 auto enospc quick quota