btrfs: test unaligned punch hole at ENOSPC

Try to punch hole with unaligned size and offset when the FS is full
and mounted with nodatacow option.

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.

This test was orignally merged as btrfs/172 (commit 4c2c678cd), then
Iremoved by commit 538d8a4bcc. But it's decided to bring back this
test case, now the problem is better understood and the fix is
available in the ML as below.

Link: https://patchwork.kernel.org/patch/11357415/

Reviewed-by: Filipe Manana <fdmanana@suse.com>
(cherry picked from commit 4c2c678cd5)
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

tests/btrfs/204

@@ -0,0 +1,73 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2018 Oracle. All Rights Reserved.
+#
+# FS QA Test 204
+#
+# 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

tests/btrfs/204.out

@@ -0,0 +1,2 @@
+QA output created by 204
+Silence is golden

tests/btrfs/group

@@ -206,3 +206,4 @@
 201 auto quick punch log
 202 auto quick subvol snapshot
 203 auto quick send clone
+204 auto quick punch