btrfs: Test if btrfs hits EDQUOT without trying to reclaim some space

Commit a514d63882c3 ("btrfs: qgroup: Commit transaction in advance
to reduce early EDQUOT") is no longer forcing transaction commit to
reclaim space, and only commits transaction asynchronously in
advance to address it.

However the criteria used in async transaction commit is not
comprehensive, thus it doesn't reclaim space automatically.

This test case will check the behavior by:
1) Falloc a large padding file
   This file will take 90% of the qgroup limit

2) Sync the fs
   To reflect the qgroup changes

3) Delete the file
   Qgroup won't reclaim the space until transaction committed.

4) Try to write a file
   If kernel not fixed, qgroup will not automatically commit transaction
   to reclaim the freed space and hit EDQUOT.

This bug is going to be fixed by a patch for kernel titled:
"btrfs: qgroup: Make qgroup async transaction commit more aggressive".

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

tests/btrfs/180

@@ -0,0 +1,62 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2019 SUSE Linux Products GmbH. All Rights Reserved.
+#
+# FS QA Test 180
+#
+# Test if btrfs hits EDQUOT without reclaiming already freed extents when quota
+# is enabled.
+#
+# This bug is going to be fxied by a patch for kernel titled
+# "btrfs: qgroup: Make qgroup async transaction commit more aggressive"
+#
+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 1G "$SCRATCH_MNT"
+
+$XFS_IO_PROG -f -c "falloc 0 900M" "$SCRATCH_MNT/padding"
+
+# Commit transaction to reflect the quota usage
+sync
+
+rm -f "$SCRATCH_MNT/padding"
+
+# Without the kernel fix, this will trigger EDQUOT.
+_pwrite_byte 0xcd 0 512M "$SCRATCH_MNT/real_file" | _filter_xfs_io
+
+# success, all done
+status=0
+exit

tests/btrfs/180.out

@@ -0,0 +1,3 @@
+QA output created by 180
+wrote 536870912/536870912 bytes at offset 0
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)

tests/btrfs/group

@@ -182,3 +182,4 @@
 177 auto quick swap balance
 178 auto quick send
 179 auto qgroup dangerous
+180 auto quick qgroup limit