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Re: [PATCH v8 1/4] qcow2: introduce compression type feature
From: |
Vladimir Sementsov-Ogievskiy |
Subject: |
Re: [PATCH v8 1/4] qcow2: introduce compression type feature |
Date: |
Mon, 23 Mar 2020 11:00:42 +0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 |
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 <address@hidden>
Reviewed-by: Vladimir Sementsov-Ogievskiy <address@hidden>
---
[...]
@@ -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.
+ 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
+ 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 */ }
}
};
[...]
--
Best regards,
Vladimir
[PATCH v8 1/4] qcow2: introduce compression type feature, Denis Plotnikov, 2020/03/21
- Re: [PATCH v8 1/4] qcow2: introduce compression type feature,
Vladimir Sementsov-Ogievskiy <=