[PATCH] fstests: generic: Test space allocation when there is only fragmented space

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

This test case will test if file system works well when handling large
write while available space are all fragmented.

This can expose a bug in a btrfs unmerged patch, which wrongly modified
the delayed allocation code, to exit before allocating all space, and
cause hang when unmounting.

The wrong patch is:
[PATCH v6 1/2] btrfs: Fix metadata underflow caused by btrfs_reloc_clone_csum error

The test case will:
1) Fill small filesystem with page sized small files
   All these files has a sequential number as file name
2) Remove files with odd number as file name
   This will free almost half of the space
3) Try to write a file which takes 1/8 of the file system

The method to create fragmented fs may not be generic enough, but should
work for most extent based fs.
Unless one file system will allocate extents from both end of its free
space.

Cc: Filipe Manana <fdmanana@kernel.org>
Cc: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
 tests/generic/416     | 99 +++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/generic/416.out |  3 ++
 tests/generic/group   |  1 +
 3 files changed, 103 insertions(+)
 create mode 100755 tests/generic/416
 create mode 100644 tests/generic/416.out

diff --git a/tests/generic/416 b/tests/generic/416
new file mode 100755
index 0000000..925524b
--- /dev/null
+++ b/tests/generic/416
@@ -0,0 +1,99 @@
+#! /bin/bash
+# FS QA Test 416
+#
+# Test fs behavior when large write request can't be met by one single extent
+#
+# Inspired by a bug in a btrfs fix, which doesn't get exposed by current test
+# cases
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2017 Fujitsu.  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 $seqres.full
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs generic
+_supported_os IRIX Linux
+_require_scratch
+
+fs_size=$((128 * 1024 * 1024))
+page_size=$(get_page_size)
+
+# We will never reach this number though
+nr_files=$(($fs_size / $page_size))
+
+# Use small fs to make the fill more faster
+_scratch_mkfs_sized $fs_size >> $seqres.full 2>&1
+
+_scratch_mount
+
+fill_fs()
+{
+	dir=$1
+	for i in $(seq -w $nr_files); do
+		# xfs_io can't return correct value when it hit ENOSPC, use
+		# dd here to detect ENOSPC
+		dd if=/dev/zero of=$SCRATCH_MNT/$i bs=$page_size count=1 \
+			&> /dev/null
+		if [ $? -ne 0 ]; then
+			break
+		fi
+	done
+}
+
+fill_fs $SCRATCH_MNT
+
+# remount to sync every thing into fs, and drop all cache
+_scratch_remount
+
+# remove all files with odd file names, which should free near half
+# of the space
+rm $SCRATCH_MNT/*[13579]
+sync
+
+# We should be able to write at least 1/8 of the whole fs size
+# The number 1/8 is for btrfs, which only has about 47M for data.
+# And half of the 47M is already taken up, so only 1/8 is safe here
+$XFS_IO_PROG -f -c "pwrite 0 $(($fs_size / 8))" $SCRATCH_MNT/large_file | \
+	_filter_xfs_io
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/416.out b/tests/generic/416.out
new file mode 100644
index 0000000..8d2ffac
--- /dev/null
+++ b/tests/generic/416.out
@@ -0,0 +1,3 @@
+QA output created by 416
+wrote 16777216/16777216 bytes at offset 0
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
diff --git a/tests/generic/group b/tests/generic/group
index b510d41..59f94f9 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -418,3 +418,4 @@
 413 auto quick
 414 auto quick clone
 415 auto clone
+416 auto enospc
-- 
2.9.3