overlay: test concurrent copy up of lower hardlinks

Two tasks make a modification concurrently on two hardlinks of a
large lower inode.  The copy up should be triggered by one of the
tasks and the other should be waiting for copy up to complete.  Both
copy up targets should end up being upper hardlinks and both
metadata changes should be visible in both hardlinks.

With kernel <= v4.12, hardlinks are broken on copy up, meaning that
copy up is performed independetly and the resulting upper copy up
targets each have only one of the the metadata changes visible.

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

tests/overlay/032

@@ -0,0 +1,109 @@
+#! /bin/bash
+# FS QA Test 032
+#
+# Test concurrent copy up of lower hardlinks.
+#
+# Two tasks make a metadata change concurrently on two hardlinks of a large
+# lower inode.  The copy up should be triggers by one of the tasks and the
+# other should be waiting for copy up to complete.  Both copy up targets
+# should end up being upper hardlinks and both metadata changes should be
+# applied.
+#
+#-----------------------------------------------------------------------
+# Copyright (C) 2017 CTERA Networks. All Rights Reserved.
+# Author: Amir Goldstein <amir73il@gmail.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"
+
+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
+
+# Remove all files from previous tests
+_scratch_mkfs
+
+# overlay copy_up doesn't deal with sparse file well, holes will be filled by
+# zeros, so if both hardlinks are broken on copy up, we need (2*1G) free space
+# on $OVL_BASE_SCRATCH_MNT.
+_require_fs_space $OVL_BASE_SCRATCH_MNT $((1024*1024*2))
+
+# Create a large file in lower with 2 hardlinks.
+# Make the file have non zero blocks, so copy up won't be able to do
+# a naive sparse file copy up optimization.
+lowerdir=$OVL_BASE_SCRATCH_MNT/$OVL_LOWER
+mkdir -p $lowerdir
+$XFS_IO_PROG -fc "pwrite 1g 4k" $lowerdir/zero >> $seqres.full
+ln $lowerdir/zero $lowerdir/one
+ln $lowerdir/zero $lowerdir/two
+
+_scratch_mount
+
+do_cmd()
+{
+	echo "`date +%T` $1..." >> $seqres.full
+	eval "$1"
+	echo "`date +%T` ...$1" >> $seqres.full
+}
+
+# Perform one modification on each hardlink (size and owner)
+do_cmd "echo >> $SCRATCH_MNT/one" &
+#
+# When hardlinks are broken and overlayfs supports concurrent copy up,
+# $seqres.full will show that file two copy up started ~2s after file one
+# copy up started and ended ~2s after file one copy up ended.
+# With synchronized copy up of lower inodes, $seqres.full will show that
+# file two copy up ended at the same time as file one copy up.
+# Without sparse file copy up optimizations, copy of 1g on a standard disk
+# is expected to take more than 2s.
+# If underlying filesystem supports clone, overlay clone up with take less
+# than 1s and this test will not be doing concurrent copy up of hardlinks,
+# but rather consequent copy up of hardlinks.
+#
+sleep 2
+do_cmd "chown 100 $SCRATCH_MNT/two" &
+
+wait
+
+# Expect all hardlinks to show both metadata modifications (owner and size).
+# List <nlink> <owner> <size> <name>:
+for f in zero one two; do
+	_ls_l -n $SCRATCH_MNT/$f | awk '{ print $2, $3, $5, $9 }' | _filter_scratch
+done
+
+status=0
+exit

tests/overlay/032.out

@@ -0,0 +1,4 @@
+QA output created by 032
+3 100 1073745921 SCRATCH_MNT/zero
+3 100 1073745921 SCRATCH_MNT/one
+3 100 1073745921 SCRATCH_MNT/two

tests/overlay/group

@@ -34,3 +34,4 @@
 029 auto quick
 030 auto quick perms
 031 auto quick whiteout
+032 auto quick copyup hardlink