ext4: test file/dir/symlink metadata corruption checking and repair

Targeted fuzzing tests which destroy various pieces of file,
directory, and symlink metadata; the tests look for (a) kernel
detection of corruption, (b) e2fsck repair of said corruption, and (c)
post-repair fs usability.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/ext4/019

@@ -0,0 +1,95 @@
+#! /bin/bash
+# FS QA Test No. 019
+#
+# Create and populate an ext4 filesystem, corrupt a big symlink, then
+# see how the kernel and e2fsck deal with it.  (They won't)
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2015 Oracle, 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 $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/attr
+
+# real QA test starts here
+_supported_fs ext4
+_supported_os Linux
+
+_require_scratch
+test -n "${FORCE_FUZZ}" || _require_scratch_ext4_crc
+_require_attrs
+
+rm -f $seqres.full
+TESTDIR="${SCRATCH_MNT}/scratchdir"
+TESTFILE="${TESTDIR}/testfile"
+
+echo "+ create scratch fs"
+_scratch_mkfs_ext4 -O journal > /dev/null 2>&1
+
+echo "+ mount fs image"
+_scratch_mount
+blksz="$(stat -f -c '%s' "${SCRATCH_MNT}")"
+test "${blksz}" -gt 4096 && blksz=4096
+
+echo "+ make some files"
+echo "file contents: moo" > "${SCRATCH_MNT}/x"
+str="$(perl -e "print './' x $(( (blksz / 2) - 16));")x"
+(cd $SCRATCH_MNT; ln -s "${str}" "long_symlink")
+cat "${SCRATCH_MNT}/long_symlink"
+umount "${SCRATCH_MNT}"
+
+echo "+ check fs"
+e2fsck -fn "${SCRATCH_DEV}" >> $seqres.full 2>&1 || _fail "fsck should not fail"
+
+echo "+ corrupt image"
+debugfs -w -R 'zap -f /long_symlink -p 0x62 0' "${SCRATCH_DEV}" 2> /dev/null
+
+echo "+ mount image"
+_scratch_mount 2> /dev/null
+cat "${SCRATCH_MNT}/long_symlink" 2>/dev/null && _fail "symlink should be broken"
+umount "${SCRATCH_MNT}"
+
+echo "+ repair fs"
+e2fsck -fy "${SCRATCH_DEV}" >> $seqres.full 2>&1
+
+echo "+ mount image (2)"
+_scratch_mount
+cat "${SCRATCH_MNT}/long_symlink" 2>/dev/null && _fail "symlink should be broken"
+umount "${SCRATCH_MNT}"
+
+echo "+ check fs (2)"
+e2fsck -fn "${SCRATCH_DEV}" >> $seqres.full 2>&1 || _fail "fsck should not fail"
+
+status=0
+exit