[PATCH] overlay: test creating lower hardlinks for copied up files

[Amir Goldstein <amir73il@gmail.com>]

kernel v4.13 introduced the index=on feature for not breaking hardlinks
on copy-up.  With the index feature enabled a regression was introduced -
lower files that are hardlined while overlay is offline can result in
lookup error after overlay in mounted.

The regression was fixed by upstream commit
  6eaf011144af ovl: fix EIO from lookup of non-indexed upper
that was merged to v4.14-rc7.

This test verifies that behavior is sane after creating lower hardlinks
for copied up files while overlayfs is offline.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---

Eryu,

This is a regression test for a fix that was just merged to v4.14-rc7.

The test requires and enables index=on, so it would fail on kernels
prior to v4.14-rc7 regardless if they are complied with
CONFIG_OVERLAY_FS_INDEX=y or not.

Amir.

 tests/overlay/042     | 137 ++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/overlay/042.out |   2 +
 tests/overlay/group   |   1 +
 3 files changed, 140 insertions(+)
 create mode 100755 tests/overlay/042
 create mode 100644 tests/overlay/042.out

diff --git a/tests/overlay/042 b/tests/overlay/042
new file mode 100755
index 0000000..29858d6
--- /dev/null
+++ b/tests/overlay/042
@@ -0,0 +1,137 @@
+#! /bin/bash
+# FS QA Test 042
+#
+# Test creating lower hardlinks for copied up files.
+#
+# kernel v4.13 introduced the index=on feature for not breaking
+# hardlinks on copy-up. With the index feature enabled a regression was
+# introduced - lower files that are hardlined while overlay is offline
+# can result in lookup error after overlay in mounted.
+# The regression was fixed by upstream commit
+#   6eaf011144af ovl: fix EIO from lookup of non-indexed upper
+# that was merged to v4.14-rc7.
+#
+# This test verifies that behavior is sane after creating lower hardlinks
+# for copied up files while overlayfs is offline.
+#
+#-----------------------------------------------------------------------
+# Copyright (C) 2017 CTERA Networks. All Rights Reserved.
+# Author: Amir Goldstein <amir73il@gmail.com>
+#
+# 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"
+
+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
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+_supported_fs overlay
+_supported_os Linux
+_require_scratch
+# Without overlay index feature hardlinks are broken on copy up
+_require_scratch_feature index
+
+# Remove all files from previous tests
+_scratch_mkfs
+
+# Create lower file
+lowerdir=$OVL_BASE_SCRATCH_MNT/$OVL_LOWER
+mkdir -p $lowerdir
+touch $lowerdir/0
+
+# Disable overlay index feature to copy up with no index
+_scratch_mount -o index=off
+
+# Copy up lower and create upper hardlink with no index
+ln $SCRATCH_MNT/0 $SCRATCH_MNT/1
+
+$UMOUNT_PROG $SCRATCH_MNT
+
+# Add lower hardlinks while overlay is offline
+ln $lowerdir/0 $lowerdir/2
+ln $lowerdir/0 $lowerdir/3
+
+# Enable overlay index feature to lookup copied up upper aliases
+_scratch_mount -o index=on
+
+# Stat upper hardlink that were created with no index and whose copy up
+# origin is now an hardlink - expect same st_ino
+ino0=$(stat -c '%i' $SCRATCH_MNT/0)
+ino1=$(stat -c '%i' $SCRATCH_MNT/1)
+[[ $ino0 == $ino1 ]] || \
+	echo "Mismatch inode number for non-indexed upper hardlinks"
+
+# Copy up lower and create new upper hardlink with index, because
+# lower is a hardlink and index is enabled. The new hardlinks are not
+# associated with the hardlinks that were created when lower was not
+# a hardlink.
+ln $SCRATCH_MNT/2 $SCRATCH_MNT/4
+
+# Mount cycle to reset inode/dentry cache
+_scratch_cycle_mount index=on
+
+# Stat files that were copied up with index and whose copy up origin
+# is now an hardlink - expect same st_ino as lower aliases and different
+# st_ino from non-indexed upper aliases.
+ino0=$(stat -c '%i' $SCRATCH_MNT/0)
+ino1=$(stat -c '%i' $SCRATCH_MNT/1)
+ino2=$(stat -c '%i' $SCRATCH_MNT/2)
+ino3=$(stat -c '%i' $SCRATCH_MNT/3)
+ino4=$(stat -c '%i' $SCRATCH_MNT/4)
+[[ $ino0 == $ino1 ]] || \
+	echo "Mismatch inode number for non-indexed upper hardlinks"
+[[ $ino2 == $ino4 ]] || \
+	echo "Mismatch inode number for indexed upper hardlinks"
+[[ $ino2 == $ino3 ]] || \
+	echo "Mismatch inode number for indexed upper and lower hardlinks"
+[[ $ino2 != $ino0 ]] || \
+	echo "Unexpected matching inode number for indexed and non-indexed upper hardlinks"
+
+# Mount cycle to reset inode/dentry cache
+_scratch_cycle_mount index=on
+
+# Unlink all hardlinks - if overlay inode nlink is 0, this will trigger
+# WARN_ON() in drop_nlink()
+rm $SCRATCH_MNT/0
+rm $SCRATCH_MNT/1
+rm $SCRATCH_MNT/2
+rm $SCRATCH_MNT/3
+rm $SCRATCH_MNT/4
+
+# Verify that orphan index is cleaned on mount
+_scratch_cycle_mount index=on
+ls $OVL_BASE_SCRATCH_MNT/$OVL_WORK/index
+
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/overlay/042.out b/tests/overlay/042.out
new file mode 100644
index 0000000..85eac7a
--- /dev/null
+++ b/tests/overlay/042.out
@@ -0,0 +1,2 @@
+QA output created by 042
+Silence is golden
diff --git a/tests/overlay/group b/tests/overlay/group
index 8629325..782c39f 100644
--- a/tests/overlay/group
+++ b/tests/overlay/group
@@ -44,3 +44,4 @@
 039 auto quick atime
 040 auto quick
 041 auto quick copyup nonsamefs
+042 auto quick copyup hardlink
-- 
2.7.4