overlay: test file handle decode with multi lower layers on same fs

This test is for a regression that was introduced in kernel v4.17 by
commit 8b58924ad55c ("ovl: lookup in inode cache first when decoding
lower file handle").

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

tests/overlay/062

@@ -0,0 +1,86 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2018 CTERA Networks. All Rights Reserved.
+#
+# FS QA Test No. 062
+#
+# Test file handle decode with multi lower layers on same fs
+#
+# This test is for a regression that was introduced in kernel v4.17 by
+# commit 8b58924ad55c ("ovl: lookup in inode cache first when decoding
+# lower file handle").
+#
+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.*
+	$UMOUNT_PROG $lowertestdir
+}
+
+# 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_program "open_by_handle"
+# We need to require all features together, because nfs_export cannot
+# be enabled when index is disabled
+_require_scratch_overlay_features index nfs_export
+
+NUMFILES=1
+
+# Create test dir and empty test files
+create_test_files()
+{
+	local dir=$1
+
+	mkdir -p $dir
+	$here/src/open_by_handle -cwp $dir $NUMFILES
+}
+
+# Test encode/decode file handles on overlay mount
+test_file_handles()
+{
+	local dir=$1
+
+	$here/src/open_by_handle -rp $dir $NUMFILES
+}
+
+_scratch_mkfs
+
+# All lower layers are on scratch partition
+lower=$OVL_BASE_SCRATCH_MNT/$OVL_LOWER
+lower2=$OVL_BASE_SCRATCH_MNT/$OVL_LOWER.2
+lowertestdir=$lower2/testdir
+
+create_test_files $lowertestdir
+
+# bind mount to pin lower test dir dentry to dcache
+$MOUNT_PROG --bind $lowertestdir $lowertestdir
+
+# For non-upper overlay mount, nfs_export requires disabling redirect_dir.
+$MOUNT_PROG -t overlay $OVL_BASE_SCRATCH_MNT $SCRATCH_MNT \
+	-o ro,redirect_dir=nofollow,nfs_export=on,lowerdir=$lower:$lower2
+
+# Decode an overlay directory file handle, whose underlying lower dir dentry
+# is in dcache and connected and does not belong to the upper most lower layer.
+# The test program drops caches, but $lowertestdir dcache in pinned, so only
+# the overlay dentry is dropped.
+test_file_handles $SCRATCH_MNT/testdir -rp
+
+echo "Silence is golden"
+status=0
+exit

tests/overlay/062.out

@@ -0,0 +1,2 @@
+QA output created by 062
+Silence is golden

tests/overlay/group

@@ -64,3 +64,4 @@
 059 auto quick copyup
 060 auto quick metacopy
 061 auto quick copyup
+062 auto quick exportfs