[PATCH] btrfs: Add simple stress test when qgroup limits are reached

[Nikolay Borisov <nborisov@suse.com>]

This test uncovered 2 deadlocks with qgroups when their limit was
reached.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 tests/btrfs/231     | 72 +++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/231.out |  2 ++
 tests/btrfs/group   |  1 +
 3 files changed, 75 insertions(+)
 create mode 100755 tests/btrfs/231
 create mode 100644 tests/btrfs/231.out

diff --git a/tests/btrfs/231 b/tests/btrfs/231
new file mode 100755
index 000000000000..d2026b55485f
--- /dev/null
+++ b/tests/btrfs/231
@@ -0,0 +1,72 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2021 SUSE Linux Products GmbH. All Rights Reserved.
+#
+# FS QA Test 231
+#
+# Test that performing io and exhausting qgroup limit won't deadlock. This
+# exercises issues fixed by the following kernel commits:
+#
+# btrfs: Unlock extents in btrfs_zero_range in case of errors
+# btrfs: Don't flush from btrfs_delayed_inode_reserve_metadata
+#
+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.*
+}
+
+writer() {
+	while [ 1 ]
+	do
+		args=`_scale_fsstress_args -p 20 -n 1000 $FSSTRESS_AVOID -d $SCRATCH_MNT/stressdir`
+		$FSSTRESS_PROG $args >/dev/null 2>&1
+	done
+}
+
+# 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 btrfs
+
+_require_scratch_size $((2 * 1024 * 1024))
+_scratch_mkfs > /dev/null 2>&1
+_scratch_mount
+
+_pwrite_byte 0xcd 0 900m $SCRATCH_MNT/file >> $seqres.full
+# Make sure the data reach disk so later qgroup scan can see it
+sync
+
+$BTRFS_UTIL_PROG quota enable $SCRATCH_MNT
+$BTRFS_UTIL_PROG quota rescan -w $SCRATCH_MNT >> $seqres.full
+# set the limit to 1 g, leaving us just 100mb of slack space
+$BTRFS_UTIL_PROG qgroup limit 1G 0/5 $SCRATCH_MNT
+
+writer &
+writer_pid=$!
+
+# Give time for the background thread to generate some load
+sleep 30
+
+kill $writer_pid
+wait
+
+# success, all done
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/btrfs/231.out b/tests/btrfs/231.out
new file mode 100644
index 000000000000..a31b87a289bf
--- /dev/null
+++ b/tests/btrfs/231.out
@@ -0,0 +1,2 @@
+QA output created by 231
+Silence is golden
diff --git a/tests/btrfs/group b/tests/btrfs/group
index a7c6598326c4..db3d20fb5bb8 100644
--- a/tests/btrfs/group
+++ b/tests/btrfs/group
@@ -233,3 +233,4 @@
 228 auto quick volume
 229 auto quick send clone
 230 auto quick qgroup limit
+231 auto quick qgroup limit
-- 
2.17.1