[PATCH v4] overlay/072: test for whiteout inode sharing

[Chengguang Xu <cgxu519@mykernel.net>]

This is a test for whiteout inode sharing feature.

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
---
v1->v2:
- Address Amir's comments in v1

v2->v3:
- Address Amir's comments in v2 

v3->v4:
- Fix test case based on latest kernel patch(removed module param)
https://git.kernel.org/pub/scm/linux/kernel/git/mszeredi/vfs.git/commit/?h=overlayfs-next&id=4e49695244661568130bfefcb6143dd1eaa3d8e7

 tests/overlay/072     | 106 ++++++++++++++++++++++++++++++++++++++++++
 tests/overlay/072.out |   2 +
 tests/overlay/group   |   1 +
 3 files changed, 109 insertions(+)
 create mode 100755 tests/overlay/072
 create mode 100644 tests/overlay/072.out

diff --git a/tests/overlay/072 b/tests/overlay/072
new file mode 100755
index 00000000..fc847092
--- /dev/null
+++ b/tests/overlay/072
@@ -0,0 +1,106 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2020 Chengguang Xu <cgxu519@mykernel.net>.
+# All Rights Reserved.
+#
+# FS QA Test 072
+#
+# Test whiteout inode sharing functionality.
+#
+# A "whiteout" is an object that has special meaning in overlayfs.
+# A whiteout on an upper layer will effectively hide a matching file
+# in the lower layer, making it appear as if the file didn't exist.
+#
+# Whiteout inode sharing means multiple whiteout objects will share
+# one inode in upper layer, without this feature every whiteout object
+# will consume one inode in upper layer.
+
+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
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+_supported_fs overlay
+_supported_os Linux
+_require_scratch
+
+lowerdir=$OVL_BASE_SCRATCH_MNT/$OVL_LOWER
+upperdir=$OVL_BASE_SCRATCH_MNT/$OVL_UPPER
+workdir=$OVL_BASE_SCRATCH_MNT/$OVL_WORK
+
+# Make some testing files in lowerdir.
+# Argument:
+# $1: Testing file number
+make_lower_files()
+{
+	for name in `seq ${1}`; do
+		touch $lowerdir/file${name} &>/dev/null
+	done
+}
+
+# Delete all copy-uped files in upperdir.
+make_whiteout_files()
+{
+	rm -f $SCRATCH_MNT/* &>/dev/null
+}
+
+# Check link count of whiteout files.
+# Arguments:
+# $1: Testing file number
+# $2: Expected link count
+check_whiteout_files()
+{
+	for name in `seq ${1}`; do
+		local real_count=`stat -c %h $upperdir/file${name} 2>/dev/null`
+		if [[ ${2} != $real_count ]]; then
+			echo "Expected link count is ${2} but real count is $real_count, file name is file${name}"
+		fi
+	done
+	local tmpfile_count=`ls $workdir/work/\#* $workdir/index/\#* 2>/dev/null |wc -l 2>/dev/null`
+	if [[ -n "$tmpfile_count" && $tmpfile_count > 1 ]]; then
+		echo "There are more than one whiteout tmpfile in work/index dir!"
+		ls -l $workdir/work/\#* $workdir/index/\#* 2>/dev/null
+	fi
+}
+
+# Run test case with specific arguments.
+# Arguments:
+# $1: Testing file number
+# $2: Expected link count
+run_test_case()
+{
+	_scratch_mkfs
+	make_lower_files ${1}
+	_scratch_mount
+	make_whiteout_files
+	check_whiteout_files ${1} ${2}
+	_scratch_unmount
+}
+
+#Test case
+file_count=10
+link_count=11
+run_test_case $file_count $link_count
+
+# success, all done
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/overlay/072.out b/tests/overlay/072.out
new file mode 100644
index 00000000..590bbc6c
--- /dev/null
+++ b/tests/overlay/072.out
@@ -0,0 +1,2 @@
+QA output created by 072
+Silence is golden
diff --git a/tests/overlay/group b/tests/overlay/group
index 43ad8a52..8b2276f1 100644
--- a/tests/overlay/group
+++ b/tests/overlay/group
@@ -74,3 +74,4 @@
 069 auto quick copyup hardlink exportfs nested nonsamefs
 070 auto quick copyup redirect nested
 071 auto quick copyup redirect nested nonsamefs
+072 auto quick whiteout
-- 
2.20.1