overlay: Test consistent st_ino numbers for non-samefs scenario

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>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/overlay/043

@@ -0,0 +1,160 @@
+#! /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.
+#
+#-----------------------------------------------------------------------
+#
+# 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 $lowerdir/socket
+
+_scratch_mkfs >>$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"
+
+# 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

tests/overlay/043.out

@@ -0,0 +1,2 @@
+QA output created by 043
+Silence is golden

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