958510 – virStorageVolCreateXML requires <capacity> even when <backingStore> is specified

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Bug 958510 - virStorageVolCreateXML requires <capacity> even when <backingStore> is specified

Summary: virStorageVolCreateXML requires <capacity> even when <backingStore> is specified

Keywords:
Status:	CLOSED ERRATA
Alias:	None
Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	libvirt
Sub Component:
Version:	7.0
Hardware:	Unspecified
OS:	Unspecified
Priority:	unspecified
Severity:	unspecified
Target Milestone:	rc
Target Release:	---
Assignee:	Ján Tomko
QA Contact:	Virtualization Bugs
Docs Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+	depends on / blocked

Reported:	2013-05-01 17:21 UTC by Ian McLeod
Modified:	2016-04-26 14:08 UTC (History)
CC List:	10 users (show)
Fixed In Version:	libvirt-1.2.14-1.el7
Doc Type:	Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed:	2015-11-19 05:43:10 UTC
Target Upstream Version:
Embargoed:

Attachments	(Terms of Use)

Links
System	ID	Private	Priority	Status	Summary	Last Updated
Red Hat Bugzilla	1104862	0	unspecified	CLOSED	[RFE] Volume creation as external snapshot shouldn't require capacity	2021-02-22 00:41:40 UTC
Red Hat Product Errata	RHBA-2015:2202	0	normal	SHIPPED_LIVE	libvirt bug fix and enhancement update	2015-11-19 08:17:58 UTC

Internal Links: 1104862

Description Ian McLeod 2013-05-01 17:21:42 UTC

Description of problem:

virStorageVolCreateXML() fails without a <capacity> element in the presence
of a <backingStorage> section that points to a file.

libvirt throws the following error:

"libvirt.libvirtError: XML error: missing capacity element"


This is on RHEL 6.4 with:

libvirt-0.10.2-18.el6.x86_64
libvirt-python-0.10.2-18.el6.x86_64

Per a brief chat with eblake, it would be nice to allow the capacity element to be omitted in situations where the volume is being created with backingStorage of known size (as with an existing raw or qcow2 image file), since qemu-img does not require a size when doing this type of create.

At present, I have to derive the capacity of the backing file (which may be either raw or qcow2 in this particular case) and then specify that as the capacity in the XML.

Comment 5 Jiri Denemark 2014-04-04 21:37:44 UTC

This bug was not selected to be addressed in Red Hat Enterprise Linux 6. We will look at it again within the Red Hat Enterprise Linux 7 product.

Comment 7 Ján Tomko 2015-02-19 15:23:33 UTC

Upstream patches:
https://www.redhat.com/archives/libvir-list/2015-February/msg00697.html

Comment 8 Ján Tomko 2015-03-02 07:45:34 UTC

Fixed upstream as of
commit 155ca616eb231181f6978efc9e3a1eb0eb60af8a
Author:     Ján Tomko <jtomko>
CommitDate: 2015-03-02 08:07:11 +0100

    Allow creating volumes with a backing store but no capacity
    
    The tool creating the image can get the capacity from the backing
    storage. Just refresh the volume afterwards.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=958510

git describe: v1.2.13-17-g155ca61

Comment 11 Yang Yang 2015-05-29 09:57:14 UTC

Verified on libvirt-1.2.15-2.el7.x86_64

Steps
1. test vol-create
# cat BZ958510 
<volume>
  <name>demo</name>
  <source>
  </source>
  <target>
    <format type='qcow2'/>
  </target>
  <backingStore>
    <path>/var/lib/libvirt/images/vm1.raw</path>
  </backingStore>
</volume>

# virsh vol-create default BZ958510 
Vol demo created from BZ958510

# virsh vol-info demo default
Name:           demo
Type:           file
Capacity:       5.00 GiB
Allocation:     196.00 KiB

# virsh vol-dumpxml demo default
<volume type='file'>
  <name>demo</name>
  <key>/var/lib/libvirt/images/demo</key>
  <source>
  </source>
  <capacity unit='bytes'>5368709120</capacity>
  <allocation unit='bytes'>200704</allocation>
  <target>
    <path>/var/lib/libvirt/images/demo</path>
    <format type='qcow2'/>
    <permissions>
      <mode>0600</mode>
      <owner>0</owner>
      <group>0</group>
      <label>system_u:object_r:virt_image_t:s0</label>
    </permissions>
    <timestamps>
      <atime>1432804118.667607029</atime>
      <mtime>1432804118.616607010</mtime>
      <ctime>1432804118.666607029</ctime>
    </timestamps>
  </target>
  <backingStore>
    <path>/var/lib/libvirt/images/vm1.raw</path>
    <format type='raw'/>
    <permissions>
      <mode>0644</mode>
      <owner>107</owner>
      <group>107</group>
      <label>system_u:object_r:svirt_image_t:s0:c469,c778</label>
    </permissions>
    <timestamps>
      <atime>1432804118.667607029</atime>
      <mtime>1432520901.532815217</mtime>
      <ctime>1432520901.532815217</ctime>
    </timestamps>
  </backingStore>
</volume>

start a vm with demo, it works well
 <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/var/lib/libvirt/images/demo'/>
      <backingStore type='file' index='1'>
        <format type='raw'/>
        <source file='/var/lib/libvirt/images/vm1.raw'/>
        <backingStore/>
      </backingStore>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </disk>

# virsh vol-delete demo default
Vol demo deleted

2. test vol-create-from
# cat BZ958510 
<volume>
  <name>demo</name>
  <source>
  </source>
  <target>
    <format type='qcow2'/>
  </target>
</volume>

# qemu-img info /var/lib/libvirt/images/vm1.raw 
image: /var/lib/libvirt/images/vm1.raw
file format: raw
virtual size: 5.0G (5368709120 bytes)
disk size: 1.3G

# virsh vol-create-from default BZ958510 --inputpool default vm1.raw
Vol demo created from input vol vm1.raw

# virsh vol-info demo default
Name:           demo
Type:           file
Capacity:       5.00 GiB
Allocation:     2.00 GiB

# qemu-img info /var/lib/libvirt/images/demo 
image: /var/lib/libvirt/images/demo
file format: qcow2
virtual size: 5.0G (5368709120 bytes)
disk size: 2.0G
cluster_size: 65536
Format specific information:
    compat: 0.10

start a vm with demo, it works well
<disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/var/lib/libvirt/images/demo'/>
      <backingStore/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </disk>

3. negative test: dir type vol with backing file
# cat BZ958510 
<volume type='dir'>
  <name>demo</name>
  <source>
  </source>
  <target>
    <format type='dir'/>
  </target>
<backingStore>
    <path>/var/lib/libvirt/images/vm1.raw</path>
  </backingStore>
</volume>

# virsh vol-create default BZ958510 
error: Failed to create vol from BZ958510
error: this function is not supported by the connection driver: backing storage not supported for directories volumes

4. negative test: raw type vol with backing file
# cat BZ958510 
<volume type='file'>
  <name>demo</name>
  <source>
  </source>
  <target>
    <format type='raw'/>
  </target>
<backingStore>
    <path>/var/lib/libvirt/images/vm1.raw</path>
  </backingStore>
</volume>

# virsh vol-create default BZ958510 
error: Failed to create vol from BZ958510
error: this function is not supported by the connection driver: backing storage not supported for raw volumes

5. negative test: lack of capacity in rbd pool
# cat BZ958510-RBD 
<volume type='network'>
  <name>demo</name>
  <source>
  </source>
</volume>

# virsh vol-create rbd BZ958510-RBD 
error: Failed to create vol from BZ958510-RBD
error: XML error: missing capacity element

6. negative test: vol with backing file in rbd pool. The issue is tracked in bz1223177

# cat BZ958510-RBD 
<volume type='network'>
  <name>demo</name>
  <source>
  </source>
<backingStore>
    <path>/var/lib/libvirt/images/vm1.raw</path>
  </backingStore>
</volume>

# virsh vol-create rbd BZ958510-RBD 
error: Failed to create vol from BZ958510-RBD
error: failed to remove volume 'libvirt-pool/demo': No such file or directory

# virsh vol-list rbd | grep demo
 demo                 libvirt-pool/demo 

# virsh vol-delete demo rbd
error: Failed to delete vol demo
error: failed to remove volume 'libvirt-pool/demo': No such file or directory

Comment 13 errata-xmlrpc 2015-11-19 05:43:10 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHBA-2015-2202.html

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