tests/generic/086

#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2015 Red Hat, Inc., Lukas Czerner <lczerner@redhat.com>
#
# FS QA Test 086
#
# This test excercises the problem with unwritten and delayed extents
# in ext4 extent status tree where we might in some cases lose a block
# worth of data. Even though this was a ext4 specific problem the
# reproducer can be easily tun on any file system so let's do that just
# in case.
#
# This tests excercises the problem fixed in kernel with commit
# "ext4: Fix data corruption caused by unwritten and delayed extents"
#
. ./common/preamble
_begin_fstest auto prealloc preallocrw quick

# Import common functions.
. ./common/filter

# real QA test starts here

# Modify as appropriate.
_supported_fs generic
_require_test
_require_xfs_io_command "falloc"

test_file=${TEST_DIR}/testfile-$seq

rm -f $test_file

# The first write creates a delayed extent, fallocate creates
# unwritten extent which will be marked as delayed in ext4
# extent status tree. Second write will convert unwritten/delayed
# block into written/delayed.
$XFS_IO_PROG -f -c "pwrite -S 0xaa 4096 2048" \
		-c "falloc 0 131072" \
		-c "pwrite -S 0xbb 65536 2048" \
		-c "fsync"  $test_file > $seqres.full 2>&1

# Drop the caches to evict dirty buffers from memory
echo 3 > /proc/sys/vm/drop_caches

# Write into the second part of the block with 0xbb write from before
# will create new empty! buffer because the block is still marked as
# delayed even though it's already written - resulting in
# overwriting previous data.
$XFS_IO_PROG -c "pwrite -S 0xdd 67584 2048" $test_file >> $seqres.full 2>&1

# On a faulty ext4 oxbb data will be missing, overwritten by zeroes.
_hexdump $test_file

# success, all done
status=0
exit