On 23.03.2020 11:00, Vladimir Sementsov-Ogievskiy wrote:
21.03.2020 17:34, Denis Plotnikov wrote:
The patch adds some preparation parts for incompatible compression type
feature to qcow2 allowing the use different compression methods for
image clusters (de)compressing.
It is implied that the compression type is set on the image creation and
can be changed only later by image conversion, thus compression type
defines the only compression algorithm used for the image, and thus,
for all image clusters.
The goal of the feature is to add support of other compression methods
to qcow2. For example, ZSTD which is more effective on compression
than ZLIB.
The default compression is ZLIB. Images created with ZLIB compression
type
are backward compatible with older qemu versions.
Adding of the compression type breaks a number of tests because now the
compression type is reported on image creation and there are some
changes
in the qcow2 header in size and offsets.
The tests are fixed in the following ways:
* filter out compression_type for many tests
* fix header size, feature table size and backing file offset
affected tests: 031, 036, 061, 080
header_size +=8: 1 byte compression type
7 bytes padding
feature_table += 48: incompatible feature compression type
backing_file_offset += 56 (8 + 48 -> header_change +
feature_table_change)
* add "compression type" for test output matching when it isn't
filtered
affected tests: 049, 060, 061, 065, 144, 182, 242, 255
Signed-off-by: Denis Plotnikov <dplotni...@virtuozzo.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsement...@virtuozzo.com>
---
[...]
@@ -4859,6 +4949,7 @@ static ImageInfoSpecific
*qcow2_get_specific_info(BlockDriverState *bs,
.data_file = g_strdup(s->image_data_file),
.has_data_file_raw = has_data_file(bs),
.data_file_raw = data_file_is_raw(bs),
+ .compression_type = s->compression_type,
};
} else {
/* if this assertion fails, this probably means a new
version was
@@ -5248,6 +5339,22 @@ static int
qcow2_amend_options(BlockDriverState *bs, QemuOpts *opts,
"images");
return -EINVAL;
}
+ } else if (!strcmp(desc->name, BLOCK_OPT_COMPRESSION_TYPE)) {
+ int compression_type =
+ qapi_enum_parse(&Qcow2CompressionType_lookup,
+ qemu_opt_get(opts,
BLOCK_OPT_COMPRESSION_TYPE),
+ -1, errp);
+
+ if (compression_type == -EINVAL) {
You should compare to -1, as qapi_enum_parse returns given default on
error.
ok
+ error_setg(errp, "Unknown compression type");
and errp is already set (ofcourse, if qemu_opt_get returned non NULL,
but I hope it is guaranteed by if (!strcmp(desc->name,
BLOCK_OPT_COMPRESSION_TYPE)) condition
I wouldn't propagate the error from qapi_enum_parse because it looks
like "invalid parameter value: foo". I think it's better to print
"Unknown compression type: foo"
+ return -ENOTSUP;
+ }
+
+ if (compression_type != s->compression_type) {
+ error_setg(errp, "Changing the compression type "
+ "is not supported");
+ return -ENOTSUP;
+ }
} else {
/* if this point is reached, this probably means a new
option was
* added without having it covered here */
@@ -5516,6 +5623,12 @@ static QemuOptsList qcow2_create_opts = {
.help = "Width of a reference count entry in bits",
.def_value_str = "16"
},
+ {
+ .name = BLOCK_OPT_COMPRESSION_TYPE,
+ .type = QEMU_OPT_STRING,
+ .help = "Compression method used for image cluster
compression",
+ .def_value_str = "zlib"
+ },
{ /* end of list */ }
}
};
[...]