generic: test dir fsync after deleting dentry post eviction of its inode

Test that if we fsync a file, evict its inode, unlink it and then fsync
its parent directory, after a power failure the file does not exists.

This is motivated by a bug found in btrfs, which is fixed by the following
patch for the linux kernel:

 "Btrfs: fix fsync not persisting dentry deletions due to inode evictions"

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

tests/generic/557

@@ -0,0 +1,79 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2019 SUSE Linux Products GmbH. All Rights Reserved.
+#
+# FSQA Test No. 557
+#
+# Test that if we fsync a file, evict its inode, unlink it and then fsync its
+# parent directory, after a power failure the file does not exists.
+#
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	_cleanup_flakey
+	cd /
+	rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/dmflakey
+
+# real QA test starts here
+_supported_fs generic
+_supported_os Linux
+_require_scratch
+_require_dm_target flakey
+
+rm -f $seqres.full
+
+_scratch_mkfs >>$seqres.full 2>&1
+_require_metadata_journaling $SCRATCH_DEV
+_init_flakey
+_mount_flakey
+
+# Create our test directory with one file in it and fsync the file.
+mkdir $SCRATCH_MNT/dir
+touch $SCRATCH_MNT/dir/foo
+$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/dir/foo
+
+# Keep an open file descriptor on our directory while we evict inodes. We just
+# want to evict the file's inode, the directory's inode must not be evicted.
+(
+	cd $SCRATCH_MNT/dir
+	while true; do
+		:
+	done
+) &
+pid=$!
+# Wait a bit to give time to background process to chdir to our test directory.
+sleep 0.1
+
+# Trigger eviction of the file's inode.
+echo 2 > /proc/sys/vm/drop_caches
+
+# Unlink our file and fsync the parent directory. After a power failure we don't
+# expect to see the file anymore, since we fsync'ed the parent directory.
+unlink $SCRATCH_MNT/dir/foo
+$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/dir
+
+# Kill the background process using our test directory.
+kill $pid
+wait $pid
+
+# Simulate a power failure and then check file foo does not exists anymore.
+_flakey_drop_and_remount
+
+[ -f $SCRATCH_MNT/dir/foo ] && echo "File foo still exists"
+
+_unmount_flakey
+echo "Silence is golden"
+status=0
+exit

tests/generic/557.out

@@ -0,0 +1,2 @@
+QA output created by 557
+Silence is golden

tests/generic/group

@@ -559,3 +559,4 @@
 554 auto quick copy_range swap
 555 auto quick cap
 556 auto quick casefold
+557 auto quick log