[PATCH] btrfs: test unaligned punch hole at ENOSPC

[Anand Jain <anand.jain@oracle.com>]

Try to punch hole with unaligned size and offset when the FS is
full. Mainly holes are punched at locations which are unaligned
with the file extent boundaries when the FS is full by data.
As the punching holes at unaligned location will involve
truncating blocks instead of just dropping the extents, it shall
involve reserving data and metadata space for delalloc and so data
alloc fails as the FS is full.

btrfs_punch_hole()
 btrfs_truncate_block()
   btrfs_check_data_free_space() <-- ENOSPC

We don't fail punch hole if the holes are aligned with the file
extent boundaries as it shall involve just dropping the related
extents, without truncating data extent blocks.

Link: https://patchwork.kernel.org/patch/11357415/
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
(cherry picked from commit 4c2c678cd56a81a210cb16f9f9347073e91e2fb0)
Signed-off-by: Anand Jain <anand.jain@oracle.com>

Conflicts:
	tests/btrfs/group
---
Its decided to bring back this test case, now the problem is better understood
and the fix is available in the ML as in [Link].

 tests/btrfs/172     | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/172.out |  2 ++
 tests/btrfs/group   |  1 +
 3 files changed, 76 insertions(+)
 create mode 100755 tests/btrfs/172
 create mode 100644 tests/btrfs/172.out

diff --git a/tests/btrfs/172 b/tests/btrfs/172
new file mode 100755
index 000000000000..0dffb2dff40b
--- /dev/null
+++ b/tests/btrfs/172
@@ -0,0 +1,73 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2018 Oracle. All Rights Reserved.
+#
+# FS QA Test 172
+#
+# Test if the unaligned (by size and offset) punch hole is successful when FS
+# is at ENOSPC.
+#
+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 "fpunch"
+
+_scratch_mkfs_sized $((256 * 1024 *1024)) >> $seqres.full
+
+# max_inline ensures data is not inlined within metadata extents
+_scratch_mount "-o max_inline=0,nodatacow"
+
+cat /proc/self/mounts | grep $SCRATCH_DEV >> $seqres.full
+$BTRFS_UTIL_PROG filesystem df $SCRATCH_MNT >> $seqres.full
+
+extent_size=$(_scratch_btrfs_sectorsize)
+unalign_by=512
+echo extent_size=$extent_size unalign_by=$unalign_by >> $seqres.full
+
+$XFS_IO_PROG -f -c "pwrite -S 0xab 0 $((extent_size * 10))" \
+					$SCRATCH_MNT/testfile >> $seqres.full
+
+echo "Fill all space available for data and all unallocated space." >> $seqres.full
+dd status=none if=/dev/zero of=$SCRATCH_MNT/filler bs=512 >> $seqres.full 2>&1
+
+hole_offset=0
+hole_len=$unalign_by
+$XFS_IO_PROG -c "fpunch $hole_offset $hole_len" $SCRATCH_MNT/testfile
+
+hole_offset=$(($extent_size + $unalign_by))
+hole_len=$(($extent_size - $unalign_by))
+$XFS_IO_PROG -c "fpunch $hole_offset $hole_len" $SCRATCH_MNT/testfile
+
+hole_offset=$(($extent_size * 2 + $unalign_by))
+hole_len=$(($extent_size * 5))
+$XFS_IO_PROG -c "fpunch $hole_offset $hole_len" $SCRATCH_MNT/testfile
+
+# success, all done
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/btrfs/172.out b/tests/btrfs/172.out
new file mode 100644
index 000000000000..ce2de3f0d107
--- /dev/null
+++ b/tests/btrfs/172.out
@@ -0,0 +1,2 @@
+QA output created by 172
+Silence is golden
diff --git a/tests/btrfs/group b/tests/btrfs/group
index 4b64bf8b6d2f..697b6a38ea00 100644
--- a/tests/btrfs/group
+++ b/tests/btrfs/group
@@ -174,6 +174,7 @@
 169 auto quick send
 170 auto quick snapshot
 171 auto quick qgroup
+172 auto quick punch
 173 auto quick swap
 174 auto quick swap
 175 auto quick swap volume
-- 
1.8.3.1