tests/btrfs/097

#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) 2015 SUSE Linux Products GmbH. All Rights Reserved.
#
# FS QA Test No. btrfs/097
#
# Test that an incremental send works after a file gets one of its extents
# cloned/deduplicated into lower file offsets.
#
. ./common/preamble
_begin_fstest auto quick send clone

# Override the default cleanup function.
_cleanup()
{
	rm -fr $send_files_dir
	rm -f $tmp.*
}

. ./common/filter

_require_scratch
_require_cloner

send_files_dir=$TEST_DIR/btrfs-test-$seq

rm -fr $send_files_dir
mkdir $send_files_dir

_scratch_mkfs >>$seqres.full 2>&1
_scratch_mount

BLOCK_SIZE=$(_get_block_size $SCRATCH_MNT)

# Create our test file with a single extent of 16 blocks starting at a file
# offset mapped by 32nd block.
$XFS_IO_PROG -f -c "pwrite -S 0xaa $((32 * $BLOCK_SIZE)) $((16 * $BLOCK_SIZE))" \
	     $SCRATCH_MNT/foo | _filter_xfs_io_blocks_modified

_btrfs subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/mysnap1

# Now clone parts of the original extent into lower offsets of the file.
#
# The first clone operation adds a file extent item to file offset 0 that points
# to our initial extent with a data offset of 4 blocks. The corresponding data back
# reference in the extent tree has a large value for the 'offset' field, which is
# the result of file_offset - data_offset = 0 - (file offset of 4th block).  For
# example in case of 4k block size, it will be 0 - 16k = 18446744073709535232.

# The second clone operation adds a file extent item to file offset mapped by
# 4th block that points to our initial extent with a data offset of 12
# blocks. The corresponding data back reference in the extent tree has a large
# value for the 'offset' field, which is the result of file_offset - data_offset
# = (file offset of 4th block) - (file offset of 12th block). For example in
# case of 4k block size, it will be 16K - 48K = 18446744073709518848.
#
# Those large back reference offsets (result of unsigned arithmetic underflow)
# confused the back reference walking code (used by an incremental send and
# the multiple inspect-internal ioctls) and made it miss the back references,
# which for the case of an incremental send it made it fail with -EIO and print
# a message like the following to dmesg:
#
# "BTRFS error (device sdc): did not find backref in send_root. inode=257, \
#  offset=0, disk_byte=12845056 found extent=12845056"
#
$CLONER_PROG -s $(((32 + 4) * $BLOCK_SIZE)) -d 0 -l $((4 * $BLOCK_SIZE)) \
	$SCRATCH_MNT/foo $SCRATCH_MNT/foo
$CLONER_PROG -s $(((32 + 12) * $BLOCK_SIZE)) -d $((4 * $BLOCK_SIZE)) \
	     -l $((4 * $BLOCK_SIZE)) $SCRATCH_MNT/foo $SCRATCH_MNT/foo

_btrfs subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/mysnap2

_btrfs send -f $send_files_dir/1.snap $SCRATCH_MNT/mysnap1
_btrfs send -p $SCRATCH_MNT/mysnap1 -f $send_files_dir/2.snap \
	$SCRATCH_MNT/mysnap2

echo "File contents in the original filesystem:"
od -t x1 $SCRATCH_MNT/mysnap2/foo | _filter_od

# Now recreate the filesystem by receiving both send streams and verify we get
# the same file contents that the original filesystem had.
_scratch_unmount
_scratch_mkfs >>$seqres.full 2>&1
_scratch_mount

_btrfs receive -f $send_files_dir/1.snap $SCRATCH_MNT
_btrfs receive -f $send_files_dir/2.snap $SCRATCH_MNT

echo "File contents in the new filesystem:"
od -t x1 $SCRATCH_MNT/mysnap2/foo | _filter_od

status=0
exit