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storage: add support for QCOW2 cluster_size option

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The default value hard-coded in QEMU (64KiB) is not always the ideal.
Having a possibility to set the cluster_size by user may in specific
use-cases improve performance for QCOW2 images.

QEMU internally has some limits, the value has to be between 512B and
2048KiB and must by power of two, except when the image has Extended L2
Entries the minimal value has to be 16KiB.

Since qemu-img ensures the value is correct and the limit is not always
the same libvirt will not duplicate any of these checks as the error
message from qemu-img is good enough:

    Cluster size must be a power of two between 512 and 2048k

Resolves: https://gitlab.com/libvirt/libvirt/-/issues/154

Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
This commit is contained in:
Pavel Hrdina 2021-05-12 17:43:36 +02:00
parent 19967f64f4
commit 3e1d2c93a3
10 changed files with 78 additions and 0 deletions
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6
docs/formatstorage.html.in
View File

@ -791,6 +791,7 @@
&lt;/encryption&gt;
&lt;compat&gt;1.1&lt;/compat&gt;
&lt;nocow/&gt;
&lt;clusterSize unit='KiB'&gt;64&lt;/clusterSize&gt;
&lt;features&gt;
&lt;lazy_refcounts/&gt;
&lt;/features&gt;
@ -867,6 +868,11 @@
the file image is used in VM. To create non-raw file images, it
requires QEMU version since 2.1. <span class="since">Since 1.2.7</span>
</dd>
<dt><code>clusterSize</code></dt>
<dd>Changes the qcow2 cluster size which can affect image file size
and performance.
<span class="since">Since 7.4.0</span>
</dd>
<dt><code>features</code></dt>
<dd>Format-specific features. Only used for <code>qcow2</code> now.
Valid sub-elements are:

7
docs/schemas/storagecommon.rng
View File

@ -110,6 +110,13 @@
</data>
</element>
</define>
<define name="clusterSize">
<element name="clusterSize">
<ref name="scaledInteger"/>
</element>
</define>
<define name="fileFormatFeatures">
<element name="features">
<interleave>

3
docs/schemas/storagevol.rng
View File

@ -124,6 +124,9 @@
<empty/>
</element>
</optional>
<optional>
<ref name="clusterSize"/>
</optional>
<optional>
<ref name="fileFormatFeatures"/>
</optional>

12
src/conf/storage_conf.c
View File

@ -1416,6 +1416,13 @@ virStorageVolDefParseXML(virStoragePoolDef *pool,
if (virXPathNode("./target/nocow", ctxt))
def->target.nocow = true;
if (virParseScaledValue("./target/clusterSize",
"./target/clusterSize/@unit",
ctxt, &def->target.clusterSize,
1, ULLONG_MAX, false) < 0) {
return NULL;
}
if (virXPathNode("./target/features", ctxt)) {
if ((n = virXPathNodeSet("./target/features/*", ctxt, &nodes)) < 0)
return NULL;
@ -1580,6 +1587,11 @@ virStorageVolTargetDefFormat(virStorageVolOptions *options,
virBufferEscapeString(buf, "<compat>%s</compat>\n", def->compat);
if (def->clusterSize > 0) {
virBufferAsprintf(buf, "<clusterSize unit='B'>%llu</clusterSize>\n",
def->clusterSize);
}
if (def->features) {
size_t i;
bool empty = virBitmapIsAllClear(def->features);

5
src/storage/storage_util.c
View File

@ -664,6 +664,7 @@ struct _virStorageBackendQemuImgInfo {
const char *path;
unsigned long long size_arg;
unsigned long long allocation;
unsigned long long clusterSize;
bool encryption;
bool preallocate;
const char *compat;
@ -780,6 +781,9 @@ storageBackendCreateQemuImgOpts(virStorageEncryptionInfoDef *encinfo,
else if (info->format == VIR_STORAGE_FILE_QCOW2)
virBufferAddLit(&buf, "compat=0.10,");
if (info->clusterSize > 0)
virBufferAsprintf(&buf, "cluster_size=%llu,", info->clusterSize);
if (info->features && info->format == VIR_STORAGE_FILE_QCOW2) {
if (virBitmapIsBitSet(info->features,
VIR_STORAGE_FILE_FEATURE_LAZY_REFCOUNTS)) {
@ -1130,6 +1134,7 @@ virStorageBackendCreateQemuImgCmdFromVol(virStoragePoolObj *pool,
.compat = vol->target.compat,
.features = vol->target.features,
.nocow = vol->target.nocow,
.clusterSize = vol->target.clusterSize,
.secretAlias = NULL,
};
virStorageEncryption *enc = vol->target.encryption;

6
tests/storagevolxml2argvdata/qcow2-clusterSize.argv Normal file
View File

@ -0,0 +1,6 @@
qemu-img \
create \
-f qcow2 \
-o compat=0.10,cluster_size=131072 \
/var/lib/libvirt/images/OtherDemo.img \
5242880K

4
tests/storagevolxml2argvtest.c
View File

@ -238,6 +238,10 @@ mymain(void)
"pool-dir", "vol-qcow2-nocapacity-backing", NULL, NULL,
"qcow2-nocapacity", 0);
DO_TEST("pool-dir", "vol-qcow2-clusterSize",
NULL, NULL,
"qcow2-clusterSize", 0);
DO_TEST("pool-dir", "vol-file-iso",
NULL, NULL,
"iso", 0);

17
tests/storagevolxml2xmlin/vol-qcow2-clusterSize.xml Normal file
View File

@ -0,0 +1,17 @@
<volume>
<name>OtherDemo.img</name>
<key>/var/lib/libvirt/images/OtherDemo.img</key>
<capacity unit="G">5</capacity>
<allocation>294912</allocation>
<target>
<path>/var/lib/libvirt/images/OtherDemo.img</path>
<format type='qcow2'/>
<permissions>
<mode>0644</mode>
<owner>0</owner>
<group>0</group>
<label>unconfined_u:object_r:virt_image_t:s0</label>
</permissions>
<clusterSize unit='KiB'>128</clusterSize>
</target>
</volume>

17
tests/storagevolxml2xmlout/vol-qcow2-clusterSize.xml Normal file
View File

@ -0,0 +1,17 @@
<volume type='file'>
<name>OtherDemo.img</name>
<key>/var/lib/libvirt/images/OtherDemo.img</key>
<capacity unit='bytes'>5368709120</capacity>
<allocation unit='bytes'>294912</allocation>
<target>
<path>/var/lib/libvirt/images/OtherDemo.img</path>
<format type='qcow2'/>
<permissions>
<mode>0644</mode>
<owner>0</owner>
<group>0</group>
<label>unconfined_u:object_r:virt_image_t:s0</label>
</permissions>
<clusterSize unit='B'>131072</clusterSize>
</target>
</volume>

1
tests/storagevolxml2xmltest.c
View File

@ -88,6 +88,7 @@ mymain(void)
DO_TEST("pool-dir", "vol-qcow2-nobacking");
DO_TEST("pool-dir", "vol-qcow2-encryption");
DO_TEST("pool-dir", "vol-qcow2-luks");
DO_TEST("pool-dir", "vol-qcow2-clusterSize");
DO_TEST("pool-dir", "vol-luks");
DO_TEST("pool-dir", "vol-luks-cipher");
DO_TEST("pool-disk", "vol-partition");