btrfs: Verify falloc on multiple holes won't leak qgroup reserved data space

Add a test case where falloc is called on multiple holes with qgroup
enabled.

This can cause qgroup reserved data space leak and false EDQUOT
error even we're not reaching the limit.

The fix is titled:
"btrfs: qgroup: Fix the wrong target io_tree when freeing
 reserved data space"

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

tests/btrfs/193

@@ -0,0 +1,69 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2019 SUSE Linux Products GmbH. All Rights Reserved.
+#
+# FS QA Test btrfs/193
+#
+# Test if btrfs is going to leak qgroup reserved data space when
+# falloc on multiple holes fails.
+# The fix is titled:
+# "btrfs: qgroup: Fix the wrong target io_tree when freeing reserved data space"
+#
+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 $seqres.full
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch
+_require_xfs_io_command falloc
+
+_scratch_mkfs > /dev/null
+_scratch_mount
+
+$BTRFS_UTIL_PROG quota enable "$SCRATCH_MNT" > /dev/null
+$BTRFS_UTIL_PROG quota rescan -w "$SCRATCH_MNT" > /dev/null
+$BTRFS_UTIL_PROG qgroup limit -e 256M "$SCRATCH_MNT"
+
+# Create a file with the following layout:
+# 0         128M      256M      384M
+# |  Hole   |4K| Hole |4K| Hole |
+# The total hole size will be 384M - 8k
+truncate -s 384m "$SCRATCH_MNT/file"
+$XFS_IO_PROG -c "pwrite 128m 4k" -c "pwrite 256m 4k" \
+	"$SCRATCH_MNT/file" | _filter_xfs_io
+
+# Falloc 0~384M range, it's going to fail due to the qgroup limit
+$XFS_IO_PROG -c "falloc 0 384m" "$SCRATCH_MNT/file" | _filter_xfs_io_error
+rm -f "$SCRATCH_MNT/file"
+
+# Ensure above delete reaches disk and free some space
+sync
+
+# We should be able to write at least 3/4 of the limit
+$XFS_IO_PROG -f -c "pwrite 0 192m" "$SCRATCH_MNT/file" | _filter_xfs_io
+
+# success, all done
+status=0
+exit

tests/btrfs/193.out

@@ -0,0 +1,8 @@
+QA output created by 193
+wrote 4096/4096 bytes at offset 134217728
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 4096/4096 bytes at offset 268435456
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+fallocate: Disk quota exceeded
+wrote 201326592/201326592 bytes at offset 0
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)

tests/btrfs/group

@@ -195,3 +195,4 @@
 190 auto quick replay balance qgroup
 191 auto quick send dedupe
 192 auto replay snapshot stress
+193 auto quick qgroup enospc limit