overlay: sgid inheritance over whiteout

Newly created files and dirs should inherit sgit bit from parent
dir, no matter the new files & dirs are created over whiteout or
not.

Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/overlay/015

@@ -0,0 +1,97 @@
+#! /bin/bash
+# FS QA Test 015
+#
+# SGID bit inheritance over whiteout.
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2016 Red Hat 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
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+_supported_fs overlay
+_supported_os Linux
+_require_scratch
+_require_user
+_require_group
+
+# Remove all files from previous tests
+_scratch_mkfs
+
+# set umask to make output deterministic
+umask 022
+
+# Create test dir in lower dir and set sgid bit
+lowerdir=$SCRATCH_DEV/$OVERLAY_LOWER_DIR
+mkdir -p $lowerdir/dir
+chown $qa_user:$qa_group $lowerdir/dir
+chmod 2775 $lowerdir/dir
+touch $lowerdir/dir/testdir
+touch $lowerdir/dir/testfile
+touch $lowerdir/dir/hardlink
+
+# mount overlayfs, create new file and dir in parent dir with sgid bit set, new
+# files and dirs all should inherit the sgid bit and the group
+_scratch_mount
+
+# new dir
+mkdir $SCRATCH_MNT/dir/newdir
+stat -c "%A %G" $SCRATCH_MNT/dir/newdir
+
+# new file
+touch $SCRATCH_MNT/dir/newfile
+stat -c "%A %G" $SCRATCH_MNT/dir/newfile
+
+# new dir over whiteout
+rm -f $SCRATCH_MNT/dir/testdir
+mkdir $SCRATCH_MNT/dir/testdir
+stat -c "%A %G" $SCRATCH_MNT/dir/testdir
+
+# new file over whiteout
+rm -f $SCRATCH_MNT/dir/testfile
+touch $SCRATCH_MNT/dir/testfile
+stat -c "%A %G" $SCRATCH_MNT/dir/testfile
+
+# new hardlink over whiteout
+rm -f $SCRATCH_MNT/dir/hardlink
+ln $SCRATCH_MNT/dir/testfile $SCRATCH_MNT/dir/hardlink
+stat -c "%A %G" $SCRATCH_MNT/dir/hardlink
+
+# success, all done
+status=0
+exit

tests/overlay/015.out

@@ -0,0 +1,6 @@
+QA output created by 015
+drwxr-sr-x fsgqa
+-rw-r--r-- fsgqa
+drwxr-sr-x fsgqa
+-rw-r--r-- fsgqa
+-rw-r--r-- fsgqa

tests/overlay/group

@@ -17,3 +17,4 @@
 012 auto quick
 013 auto quick
 014 auto quick copyup
+015 auto quick whiteout