tests/btrfs/095

#! /bin/bash
# FSQA Test No. 095
#
# Regression test for adding and dropping an equal number of references for
# file extents. Verify that if we drop N references for a file extent and we
# add too N new references for that same file extent in the same transaction,
# running the delayed references (always happens at transaction commit time)
# does not fail.
#
# The regression was introduced in the 4.2-rc1 Linux kernel.
#
#-----------------------------------------------------------------------
#
# Copyright (C) 2015 SUSE Linux Products GmbH. All Rights Reserved.
# Author: Filipe Manana <fdmanana@suse.com>
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it would be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write the Free Software Foundation,
# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
#-----------------------------------------------------------------------
#

seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"
tmp=/tmp/$$
status=1	# failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15

_cleanup()
{
	_cleanup_flakey
	rm -f $tmp.*
}

# get standard environment, filters and checks
. ./common/rc
. ./common/filter
. ./common/dmflakey

# real QA test starts here
_supported_fs btrfs
_supported_os Linux
_require_scratch
_require_dm_target flakey
_require_cloner
_require_xfs_io_command "falloc"

rm -f $seqres.full

_scratch_mkfs >>$seqres.full 2>&1
_require_metadata_journaling $SCRATCH_DEV
_init_flakey
_mount_flakey

BLOCK_SIZE=$(_get_block_size $SCRATCH_MNT)

# Create prealloc extent covering file block range [40, 155[
$XFS_IO_PROG -f -c "falloc $((40 * $BLOCK_SIZE)) $((115 * $BLOCK_SIZE))" \
	     $SCRATCH_MNT/foo

# Now write to the last 20 blocks of the prealloc extent plus 10 blocks to the
# unallocated space that immediately follows it. This creates a new extent of 10
# blocks that spans the block range [155, 165[.
$XFS_IO_PROG -c "pwrite -S 0xaa $((135 * $BLOCK_SIZE)) $((30 * $BLOCK_SIZE))" \
	     $SCRATCH_MNT/foo | _filter_xfs_io_blocks_modified

# At this point, there are now 2 back references to the prealloc extent in our
# extent tree. Both are for our file offset mapped by the 40th block of the file
# and one relates to a file extent item with a data offset of 0 and a length of
# 95 blocks, while the other relates to a file extent item with a data offset of
# 95 blocks and a length of 20 blocks.

# Make sure everything done so far is durably persisted (all back references are
# in the extent tree, etc).
sync

# Now clone all extents of our file that cover the file range spanned by 40th
# block up to its eof (165th block at this point) into itself at 512th
# block. This leaves a hole in the file covering the block range [165, 512[. The
# prealloc extent will now be referenced by the file twice, once for offset
# mapped by the 40th block and once for offset mapped by 512th block. The 10
# blocks extent that follows the prealloc extent will also be referenced twice
# by our file, once for offset mapped by the 155th block and once for offset
# (512 block + 115 blocks)
$CLONER_PROG -s $((40 * $BLOCK_SIZE)) -d $((512 * $BLOCK_SIZE)) -l 0 \
	     $SCRATCH_MNT/foo $SCRATCH_MNT/foo

# Now create one new extent in our file with a size of 25 blocks. It will span
# the block range [768, 768 + 25[. It also will cause creation of a hole
# spanning the block range [512 + 115, 768[. Our new file size is the file
# offset mapped by (768 + 25)th block.
$XFS_IO_PROG -c "pwrite -S 0xbb $((768 * $BLOCK_SIZE)) $((25 * $BLOCK_SIZE))" \
	     $SCRATCH_MNT/foo | _filter_xfs_io_blocks_modified

# At this point, there are now (in memory) 4 back references to the prealloc
# extent.
#
# Two of them are for file offset mapped by the 40th block, related to file
# extent items matching the file offsets mapped by 40th and 135th block
# respectively, with data offsets of 0 and 95 blocks respectively, and with
# lengths of 95 and 20 blocks respectively.
#
# The other two references are for file offset mapped by 512th block, related to
# file extent items matching the file offsets mapped by 512th and (512 + 95)th
# block respectively, with data offsets mapped by 0th and 95th block
# respectively, and with lengths of 95 and 20 blocks respectively.
#
# The 10 block extent has 2 back references, one for file offset mapped by 155th
# block and the other for file offset mapped by (512 + 115)th block.
#
# The 25 blocks extent has a single back reference and it relates to file offset
# mapped by 768th block.


# Now clone our 25 block extent into offset mapped by 150th block. That offset
# covers the last 5 blocks of the prealloc extent, the whole 10 block extent and
# 10 blocks of the hole starting at offset mapped by 165th block.
$CLONER_PROG -s $((768 * $BLOCK_SIZE)) -d $((150 * $BLOCK_SIZE)) -l $((25 * $BLOCK_SIZE)) \
	$SCRATCH_MNT/foo $SCRATCH_MNT/foo

# At this point there's only one reference to the 10 block extent, at file
# offset mapped by (512 + 115) block, we have 4 references for the prealloc
# extent (2 for file offset mapped by 40th block and 2 for file offset mapped by
# 512th block) and 2 references for the 25 block extent (1 for file offset
# mapped by 768th block and a new one for file offset mapped by 150th block).

# Now fsync our file to make all its new data and metadata updates are durably
# persisted and present if a power failure/crash happens after a successful
# fsync and before the next transaction commit.
$XFS_IO_PROG -c "fsync" $SCRATCH_MNT/foo

echo "File contents before power failure:"
od -t x1 $SCRATCH_MNT/foo | _filter_od

# During log replay, the btrfs delayed references implementation used to run the
# deletion of back references before the addition of new back references, which
# made the addition fail as it didn't find the key in the extent tree that it
# was looking for. The failure triggered by this test was related to the 10
# block extent, which got 1 reference dropped and 1 reference added during the
# fsync log replay - when running the delayed references at transaction commit
# time, btrfs was applying the deletion before the insertion, resulting in a
# failure of the insertion that ended up turning the fs into read-only mode.
_flakey_drop_and_remount

echo "File contents after log replay:"
od -t x1 $SCRATCH_MNT/foo | _filter_od

_unmount_flakey

status=0
exit