Re: [PATCH v4 3/4] tests/qemu-iotests: add case to write compressed data of multiple clusters

[Andrey Shinkevich]

>> +# Set compress=on. That will align the written data
>> +# by the cluster size and will write them compressed.
>> +QEMU_IO_OPTIONS=$QEMU_IO_OPTIONS_NO_FMT \
>> +$QEMU_IO -c "write -P 0xbb 0 $data_size" --image-opts \
>> +         driver=$IMGFMT,compress=on,file.filename=$TEST_IMG \
>> +         2>&1 | _filter_qemu_io | _filter_testdir
>> +
>> +let offset="4 * $cluster_size"
>> +QEMU_IO_OPTIONS=$QEMU_IO_OPTIONS_NO_FMT \
>> +$QEMU_IO -c "write -P 0xcc $offset $data_size" "json:{\
>> +    'driver': '$IMGFMT',
>> +    'file': {
>> +        'driver': 'file',
>> +        'filename': '$TEST_IMG'
>> +    },
>> +    'compress': true
>> +}" | _filter_qemu_io | _filter_testdir
>> +
> 
> It would be good to add case with unaligned offset as well. And, maybe,"
> check that we don't rewrite existing data in partial clusters when writing
> unaligned compressed data over it.
> 

The I/O error is raised in that case (see 
qcow2_alloc_compressed_cluster_offset()):
"Compression can't overwrite anything. Fail if the cluster was already 
allocated."

#0  qcow2_alloc_compressed_cluster_offset (bs=0x564669143390, 
offset=393216, compressed_size=79, host_offset=0x7f45289d9f00) at 
block/qcow2-cluster.c:767
#1  0x000056466703da7f in qcow2_co_pwritev_compressed_task 
(bs=0x564669143390, offset=393216, bytes=65536, qiov=0x7f4528dddec0, 
qiov_offset=196608) at block/qcow2.c:4198
#2  0x000056466703dc0c in qcow2_co_pwritev_compressed_task_entry 
(task=0x564669152ac0) at block/qcow2.c:4230
#3  0x00005646670a69d0 in aio_task_co (opaque=0x564669152ac0) at 
block/aio_task.c:45
#4  0x0000564667147a87 in coroutine_trampoline (i0=1762994976, i1=22086) 
at util/coroutine-ucontext.c:115

Andrey
-- 
With the best regards,
Andrey Shinkevich