generic: test hardlink to unlinked file

Kernel commit

aae8a97 fs: Don't allow to create hardlink for deleted file

disabled hardlink to unlinked file.

Test the race between link and unlink, which could end up adding link
count to an unlinked file and leading to fs corruption on xfs.

Test case was originally written by Eric Sandeen.

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

tests/generic/084

@@ -0,0 +1,104 @@
+#! /bin/bash
+# FS QA Test No. 084
+#
+# Test hardlink to unlinked file.
+#
+# Regression test for commit:
+# aae8a97 fs: Don't allow to create hardlink for deleted file
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2015 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!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+_supported_fs generic
+_supported_os Linux
+_require_scratch
+
+link_unlink_storm()
+{
+	local src=$1
+	local target=$2
+	local i=0
+
+	while true; do
+		ln -f $src $target.$i >/dev/null 2>&1
+		rm -f $target.$i >/dev/null 2>&1
+		let i=i+1
+	done
+}
+
+rm -f $seqres.full
+nr_cpu=`$here/src/feature -o`
+echo "Silence is golden"
+
+_scratch_mkfs >>$seqres.full 2>&1
+_scratch_mount
+
+# create, open & unlinked files so unlinked inode list is not empty
+for i in `seq 1 $nr_cpu`; do
+	testfile=$SCRATCH_MNT/$seq.unlinked.$i
+	touch $testfile
+	tail -f $testfile &
+	tail_pids="$tail_pids $!"
+done
+# give tail some time to open the file before the file is removed
+sleep 1
+rm -f $SCRATCH_MNT/$seq.unlinked.*
+
+# start link/unlink storm
+src=$SCRATCH_MNT/$seq.target
+touch $src
+for i in `seq 1 $nr_cpu`; do
+	target=$SCRATCH_MNT/$seq.target.link.$i
+	link_unlink_storm $src $target &
+	link_pids="$link_pids $!"
+done
+
+# remove & re-create target to race with link/unlink
+while true; do
+	rm -f $src
+	touch $src
+done &
+sleep 5
+kill $! >/dev/null 2>&1
+
+kill $tail_pids $link_pids >/dev/null 2>&1
+wait $tail_pids $link_pids
+
+# all done, no oops/hang expected, _check_filesystems checks SCRATCH_DEV after test
+status=0
+exit

tests/generic/084.out

@@ -0,0 +1,2 @@
+QA output created by 084
+Silence is golden

tests/generic/group

@@ -86,6 +86,7 @@
 081 auto quick
 082 auto quick
 083 rw auto enospc stress
+084 auto metadata quick
 088 perms auto quick
 089 metadata auto
 091 rw auto quick