generic: test for fsync after adding hard link to a file

This test is motivated by an issue found in btrfs.

It tests that after syncing the filesystem, adding a hard link to a file,
syncing the filesystem again, doing a write to the file that increases
its size and then doing a fsync against that file, durably persists the
data written to the file. That is, after log/journal replay, the data
is available.

The btrfs issue is fixed by the commit titled:

  "Btrfs: fix fsync data loss after append write"

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/generic/090

@@ -0,0 +1,108 @@
+#! /bin/bash
+# FS QA Test No. 090
+#
+# Test that after syncing the filesystem, adding a hard link to a file,
+# syncing the filesystem again, doing a write to the file that increases
+# its size and then doing a fsync against that file, durably persists the
+# data written to the file. That is, after log/journal replay, the data
+# is available.
+#
+# This test is motivated by a bug found in btrfs.
+#
+#-----------------------------------------------------------------------
+# Copyright (C) 2015 SUSE Linux Products GmbH. All Rights Reserved.
+# Author: Filipe Manana <fdmanana@suse.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!
+
+_cleanup()
+{
+	_cleanup_flakey
+	rm -f $tmp.*
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/dmflakey
+
+# real QA test starts here
+_supported_fs generic
+_supported_os Linux
+_need_to_be_root
+_require_scratch
+_require_dm_flakey
+_require_metadata_journaling $SCRATCH_DEV
+
+rm -f $seqres.full
+
+_scratch_mkfs >> $seqres.full 2>&1
+_init_flakey
+_mount_flakey
+
+# Create the test file with some initial data and then fsync it.
+# The fsync here is only needed to trigger the issue in btrfs, as it causes the
+# the flag BTRFS_INODE_NEEDS_FULL_SYNC to be removed from the btrfs inode.
+$XFS_IO_PROG -f -c "pwrite -S 0xaa 0 32k" \
+		-c "fsync" \
+		$SCRATCH_MNT/foo | _filter_xfs_io
+sync
+
+# Add a hard link to our file.
+# On btrfs this sets the flag BTRFS_INODE_COPY_EVERYTHING on the btrfs inode,
+# which is a necessary condition to trigger the issue.
+ln $SCRATCH_MNT/foo $SCRATCH_MNT/bar
+
+# Sync the filesystem to force a commit of the current btrfs transaction, this
+# is a necessary condition to trigger the bug on btrfs.
+sync
+
+# Now append more data to our file, increasing its size, and fsync the file.
+# In btrfs because the inode flag BTRFS_INODE_COPY_EVERYTHING was set and the
+# write path did not update the inode item in the btree nor the delayed inode
+# item (in memory structure) in the current transaction (created by the fsync
+# handler), the fsync did not record the inode's new i_size in the fsync
+# log/journal. This made the data unavailable after the fsync log/journal is
+# replayed.
+$XFS_IO_PROG -c "pwrite -S 0xbb 32K 32K" \
+		-c "fsync" \
+		$SCRATCH_MNT/foo | _filter_xfs_io
+
+echo "File content after fsync and before crash:"
+od -t x1 $SCRATCH_MNT/foo
+
+# Simulate a crash/power loss.
+_load_flakey_table $FLAKEY_DROP_WRITES
+_unmount_flakey
+
+# Allow writes again and mount. This makes the fs replay its fsync log.
+_load_flakey_table $FLAKEY_ALLOW_WRITES
+_mount_flakey
+
+echo "File content after crash and log replay:"
+od -t x1 $SCRATCH_MNT/foo
+
+status=0
+exit

tests/generic/090.out

@@ -0,0 +1,17 @@
+QA output created by 090
+wrote 32768/32768 bytes at offset 0
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 32768/32768 bytes at offset 32768
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+File content after fsync and before crash:
+0000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa
+*
+0100000 bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
+*
+0200000
+File content after crash and log replay:
+0000000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa
+*
+0100000 bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb bb
+*
+0200000

tests/generic/group

@@ -92,6 +92,7 @@
 087 perms auto quick
 088 perms auto quick
 089 metadata auto
+090 metadata auto quick
 091 rw auto quick
 092 auto quick prealloc
 093 attr cap udf auto