btrfs: test unaligned punch hole at ENOSPC

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.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>

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

tests/btrfs/172.out

@@ -0,0 +1,2 @@
+QA output created by 172
+Silence is golden

tests/btrfs/group

@@ -174,3 +174,4 @@
 169 auto quick send
 170 auto quick snapshot
 171 auto quick qgroup
+172 auto quick punch