btrfs: ENOSPC test for a btrfs

Regression test for an ENOSPC issue when attempting to write to a file in
a filesystem without any data block groups allocated.

The btrfs issue is fixed by the linux kernel patch titled
"Btrfs: don't initialize a space info as full to prevent ENOSPC" and the
regression was introduced by the patch titled
"Btrfs: fix block group ->space_info null pointer dereference".

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

tests/btrfs/102

@@ -0,0 +1,82 @@
+#! /bin/bash
+# FSQA Test No. 102
+#
+# Regression test for an ENOSPC issue when attempting to write to a file in
+# a filesystem without any data block groups allocated.
+#
+#-----------------------------------------------------------------------
+#
+# 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"
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+_need_to_be_root
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch
+
+rm -f $seqres.full
+
+_scratch_mkfs >>$seqres.full 2>&1
+
+# Mount our filesystem without space caches enabled so that we do not get any
+# space used from the initial data block group that mkfs creates (space caches
+# used space from data block groups).
+_scratch_mount "-o nospace_cache"
+
+# Need an fs with at least 2Gb to make sure mkfs.btrfs does not create an fs
+# using mixed block groups (used both for data and metadata). We really need
+# to have dedicated block groups for data to reproduce the issue and mkfs.btrfs
+# defaults to mixed block groups only for small filesystems (up to 1Gb).
+_require_fs_space $SCRATCH_MNT $((2 * 1024 * 1024))
+
+# Run balance with the purpose of deleting the unused data block group that
+# mkfs created. We could also wait for the background kthread to automatically
+# delete the unused block group, but we do not have a way to make it run and
+# wait for it to complete, so just do a balance instead of some unreliable sleep
+_run_btrfs_util_prog balance start -dusage=0 $SCRATCH_MNT
+
+# Now unmount the filesystem, mount it again (either with or with space caches
+# enabled, it does not matter to trigger the problem) and attempt to create a
+# file with some data - this used to fail with ENOSPC because there were no
+# data block groups when the filesystem was mounted and the data space info
+# object was marked as full when initialized (because it had 0 total bytes),
+# which prevented the file write path from attempting to allocate a data block
+# group and fail immediately with ENOSPC.
+_scratch_remount
+echo "hello world" > $SCRATCH_MNT/foobar
+
+echo "Silence is golden"
+status=0
+exit

tests/btrfs/102.out

@@ -0,0 +1,2 @@
+QA output created by 102
+Silence is golden

tests/btrfs/group

@@ -104,3 +104,4 @@
 099 auto quick qgroup
 100 auto quick replace
 101 auto quick replace
+102 auto quick metadata enospc