qemu/tests/qemu-iotests/121

#!/usr/bin/env bash
#
# Test cases for qcow2 refcount table growth
#
# Copyright (C) 2015 Red Hat, Inc.
#
# 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; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will 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, see <http://www.gnu.org/licenses/>.
#

# creator
owner=mreitz@redhat.com

seq="$(basename $0)"
echo "QA output created by $seq"

status=1	# failure is the default!

_cleanup()
{
	_cleanup_test_img
}
trap "_cleanup; exit \$status" 0 1 2 3 15

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

_supported_fmt qcow2
_supported_proto file
_supported_os Linux

echo
echo '=== New refcount structures may not conflict with existing structures ==='

echo
echo '--- Test 1 ---'
echo

# Preallocation speeds up the write operation, but preallocating everything will
# destroy the purpose of the write; so preallocate one KB less than what would
# cause a reftable growth...
_make_test_img -o 'preallocation=metadata,cluster_size=1k' 64512K
# ...and make the image the desired size afterwards.
$QEMU_IMG resize "$TEST_IMG" 65M

# The first write results in a growth of the refcount table during an allocation
# which has precisely the required size so that the new refcount block allocated
# in alloc_refcount_block() is right after cluster_index; this did lead to a
# different refcount block being written to disk (a zeroed cluster) than what is
# cached (a refblock with one entry having a refcount of 1), and the second
# write would then result in that cached cluster being marked dirty and then
# in it being written to disk.
# This should not happen, the new refcount structures may not conflict with
# new_block.
# (Note that for some reason, 'write 63M 1K' does not trigger the problem)
$QEMU_IO -c 'write 62M 1025K' -c 'write 64M 1M' "$TEST_IMG" | _filter_qemu_io

_check_test_img


echo
echo '--- Test 2 ---'
echo

_make_test_img -o 'preallocation=metadata,cluster_size=1k' 64513K
# This results in an L1 table growth which in turn results in some clusters at
# the start of the image becoming free
$QEMU_IMG resize "$TEST_IMG" 65M

# This write results in a refcount table growth; but the refblock allocated
# immediately before that (new_block) takes cluster index 4 (which is now free)
# and is thus not self-describing (in contrast to test 1, where new_block was
# self-describing). The refcount table growth algorithm then used to place the
# new refcount structures at cluster index 65536 (which is the same as the
# cluster_index parameter in this case), allocating a new refcount block for
# that cluster while new_block already existed, leaking new_block.
# Therefore, the new refcount structures may not be put at cluster_index
# (because new_block already describes that cluster, and the new structures try
# to be self-describing).
$QEMU_IO -c 'write 63M 130K' "$TEST_IMG" | _filter_qemu_io

_check_test_img

echo
echo '=== Allocating a new refcount block must not leave holes in the image ==='
echo

_make_test_img -o 'cluster_size=512,refcount_bits=16' 1M

# This results in an image with 256 used clusters: the qcow2 header,
# the refcount table, one refcount block, the L1 table, four L2 tables
# and 248 data clusters
$QEMU_IO -c 'write 0 124k' "$TEST_IMG" | _filter_qemu_io

# 256 clusters of 512 bytes each give us a 128K image
stat -c "size=%s (expected 131072)" $TEST_IMG

# All 256 entries of the refcount block are used, so writing a new
# data cluster also allocates a new refcount block
$QEMU_IO -c 'write 124k 512' "$TEST_IMG" | _filter_qemu_io

# Two more clusters, the image size should be 129K now
stat -c "size=%s (expected 132096)" $TEST_IMG

# success, all done
echo
echo '*** done'
rm -f $seq.full
status=0