[PATCH V2] overlay: Test consistent st_ino numbers for non-samefs scenario

[Chandan Rajendra <chandan@linux.vnet.ibm.com>]

This commit adds a test to verify consistent st_ino feature when
the overlayfs instance is composed of two different underlying
filesystem instances.

For example,
$ mount -t xfs /dev/loop0 /mnt/test
$ mount -t xfs /dev/loop1 /mnt/scratch
$ mkdir /mnt/scratch/upper
$ mkdir /mnt/scratch/work
$ mount -t overlay overlay -o lowerdir=/mnt/test \
        -o upperdir=/mnt/scratch/upper \
        -o workdir=/mnt/scratch/work /mnt/merge

The goal of this test is to verify that overlayfs returns consistent
st_ino for the following scenarios,
- Copy-up of lowerdir files
- Rename files and drop dentry/inode cache
- Remount the overlayfs instance

Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
---
Changelog:
v1->v2:
Address review comments provided by Amir.
1. To succeed, the test now requires the underlying base filesystems to provide
   32-bit inode numbers or the user to provide "xino" mount option. The test
   also requires that either overlayfs 'index' config feature to be enabled by
   default or to be enabled by using the 'index=on' mount option.
2. Require $TEST_DEV for use as Overlayfs' lowerdir.
3. Pass $OVERLAY_MOUNT_OPTIONS as argument to _overlay_scratch_mount_dirs().
   
 tests/overlay/043     | 167 ++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/overlay/043.out |   2 +
 tests/overlay/group   |   1 +
 3 files changed, 170 insertions(+)
 create mode 100755 tests/overlay/043
 create mode 100644 tests/overlay/043.out

diff --git a/tests/overlay/043 b/tests/overlay/043
new file mode 100755
index 0000000..5778564
--- /dev/null
+++ b/tests/overlay/043
@@ -0,0 +1,167 @@
+#! /bin/bash
+# FSQA Test No. 043
+#
+# Test constant inode numbers on non-samefs setup
+# This is a variant of overlay/017 to test constant st_ino numbers for
+# non-samefs setup.
+#
+# This simple test demonstrates a known issue with overlayfs:
+# - stat file A shows inode number X
+# - modify A to trigger copy up
+# - stat file A shows inode number Y != X
+#
+# Also test if d_ino of readdir entries changes after copy up
+# and if inode numbers persist after rename, drop caches and
+# mount cycle.
+#
+# This test succeeds when either the underlying filesystems provide 32-bit
+# inode numbers or when the xino mount option is provided. This test
+# also requires that either overlayfs 'index' config feature to be enabled by
+# default or to be enabled by using the 'index=on' mount option.
+#
+#-----------------------------------------------------------------------
+#
+# Copyright (C) 2017 IBM Corporation. All Rights Reserved.
+# Author: Chandan Rajendra <chandan@linux.vnet.ibm.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"
+
+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 overlay
+_supported_os Linux
+_require_scratch
+_require_test
+_require_test_program "af_unix"
+_require_test_program "t_dir_type"
+
+rm -f $seqres.full
+
+lowerdir=$OVL_BASE_TEST_DIR/$seq-ovl-lower
+rm -rf $lowerdir
+mkdir $lowerdir
+
+# Create our test files.
+mkdir $lowerdir/dir
+touch $lowerdir/file
+ln -s $lowerdir/file $lowerdir/symlink
+mknod $lowerdir/chrdev c 1 1
+mknod $lowerdir/blkdev b 1 1
+mknod $lowerdir/fifo p
+$here/src/af_unix $lowerdir/socket
+touch $lowerdir/hardlink1
+ln $lowerdir/hardlink1 $lowerdir/hardlink2
+
+_scratch_mkfs >>$seqres.full 2>&1
+
+upperdir=$OVL_BASE_SCRATCH_MNT/$OVL_UPPER
+workdir=$OVL_BASE_SCRATCH_MNT/$OVL_WORK
+
+_overlay_scratch_mount_dirs $lowerdir $upperdir $workdir \
+			    $OVERLAY_MOUNT_OPTIONS
+
+FILES="dir file symlink chrdev blkdev fifo socket hardlink1 hardlink2"
+
+# Record inode numbers in format <ino> <basename>
+function record_inode_numbers()
+{
+	dir=$1
+	outfile=$2
+
+	for f in $FILES; do
+		ls -id $dir/$f
+	done | \
+	while read ino file; do
+		echo $ino `basename $file` >> $outfile
+	done
+}
+
+# Check inode numbers match recorder inode numbers
+function check_inode_numbers()
+{
+	dir=$1
+	before=$2
+	after=$3
+
+	record_inode_numbers $dir $after
+
+	# Test constant stat(2) st_ino -
+	# Compare before..after - expect silence
+	# We use diff -u so out.bad will tell us which stage failed
+	diff -u $before $after
+
+	# Test constant readdir(3)/getdents(2) d_ino -
+	# Expect to find file by inode number
+	cat $before | while read ino f; do
+		$here/src/t_dir_type $dir $ino | grep -q $f || \
+			echo "$f not found by ino $ino (from $before)"
+	done
+}
+
+rm -f $tmp.*
+testdir=$SCRATCH_MNT/test
+mkdir -p $testdir
+
+# Record inode numbers before copy up
+record_inode_numbers $SCRATCH_MNT $tmp.before
+
+for f in $FILES; do
+	# chown -h modifies all those file types
+	chown -h 100 $SCRATCH_MNT/$f
+done
+
+# Compare inode numbers before/after copy up
+check_inode_numbers $SCRATCH_MNT $tmp.before $tmp.after_copyup
+
+for f in $FILES; do
+	# move to another dir
+	mv $SCRATCH_MNT/$f $testdir/
+done
+
+echo 3 > /proc/sys/vm/drop_caches
+
+# Compare inode numbers before/after rename and drop caches
+check_inode_numbers $testdir $tmp.after_copyup $tmp.after_move
+
+# Verify that the inode numbers survive a mount cycle
+$UMOUNT_PROG $SCRATCH_MNT
+_overlay_scratch_mount_dirs $lowerdir $upperdir $workdir \
+			    $OVERLAY_MOUNT_OPTIONS
+
+# Compare inode numbers before/after mount cycle
+check_inode_numbers $testdir $tmp.after_move $tmp.after_cycle
+
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/overlay/043.out b/tests/overlay/043.out
new file mode 100644
index 0000000..f90f0a5
--- /dev/null
+++ b/tests/overlay/043.out
@@ -0,0 +1,2 @@
+QA output created by 043
+Silence is golden
diff --git a/tests/overlay/group b/tests/overlay/group
index 782c39f..a99ff07 100644
--- a/tests/overlay/group
+++ b/tests/overlay/group
@@ -45,3 +45,4 @@
 040 auto quick
 041 auto quick copyup nonsamefs
 042 auto quick copyup hardlink
+043 auto quick copyup nonsamefs
-- 
2.9.5