997977 – Always specify the compat level for qcow2 if qemu-img allows it

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Bug 997977 - Always specify the compat level for qcow2 if qemu-img allows it

Summary: Always specify the compat level for qcow2 if qemu-img allows it

Keywords:
Status:	CLOSED CURRENTRELEASE
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:	2013-08-16 16:25 UTC by Ján Tomko
Modified:	2014-06-18 00:53 UTC (History)
CC List:	6 users (show)
Fixed In Version:	libvirt-1.1.1-4.el7
Doc Type:	Bug Fix
Doc Text:
Clone Of:
Environment:
Last Closed:	2014-06-13 10:57:27 UTC
Target Upstream Version:
Embargoed:

Attachments	(Terms of Use)

Description Ján Tomko 2013-08-16 16:25:53 UTC

There are plans to switch the QEMU default for the QCOW2 format from v2 (compat=0.10) to v3 (compat=1.1).

Let libvirt users decide which format they want by always specifying the compat level (if understood by qemu-img) and providing an option in qemu.conf to adjust the default.

Comment 2 Ján Tomko 2013-08-23 11:32:12 UTC

Upstream discussion:
https://www.redhat.com/archives/libvir-list/2013-August/msg00921.html

Upstream patch always specifying the compat level (default is hard-coded to 0.10):
https://www.redhat.com/archives/libvir-list/2013-August/msg01253.html

Comment 3 Ján Tomko 2013-08-28 09:00:18 UTC

Now pushed upstream:
commit bab2eda6ada1bf832decdc64cc5062e54eb105df
Author:     Ján Tomko <jtomko>
AuthorDate: 2013-08-20 17:37:08 +0200
Commit:     Ján Tomko <jtomko>
CommitDate: 2013-08-27 12:45:58 +0200

    Always specify qcow2 compat level on qemu-img command line
    
    qemu-img is going to switch the default for QCOW2
    to QCOW2v3 (compat=1.1)
    
    Extend the probing for qemu-img command line options to check
    if -o compat is supported. If the volume definition specifies
    the qcow2 format but no compat level and -o compat is supported,
    specify -o compat=0.10 to create a QCOW2v2 image.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=997977

git describe: v1.1.1-233-gbab2eda

Comment 6 Ján Tomko 2013-09-04 10:47:05 UTC

Now posted downstream:
http://post-office.corp.redhat.com/archives/rhvirt-patches/2013-September/msg00079.html

Comment 7 Hao Liu 2013-09-10 10:02:38 UTC

Using packages:
libvirt-1.1.1-3.el7.x86_64
libvirt-1.1.1-4.el7.x86_64
qemu-img-1.5.3-2.el7.x86_64
qemu-img-1.6.50-1.el7.x86_64 (self builf from git repo)

Since the patch on qemu to triger this bug has not been release.
I used a self built qemu package to test. so pls ignore the version
which I made up.

1. Confirm change on qemu.
# qemu-img create test.img 0 -f qcow2

# hexdump test.img | head -n1
**Output**
0000000 4651 fb49 0000 0200 0000 0000 0000 0000 
                        ^    <= for qemu-img-1.5.3-2.el7.x86_64
0000000 4651 fb49 0000 0300 0000 0000 0000 0000 
                        ^    <= for qemu-img-1.6.50-1.el7.x86_64
    
2. Create a storage XML file.
# cat > vol.xml << EOF
<volume>
  <name>test.qcow2</name>
  <key>/var/lib/libvirt/images/test.qcow2</key>
  <source>
  </source>
  <capacity unit='bytes'>0</capacity>
  <allocation unit='bytes'>1000</allocation>
  <target>
    <path>/var/lib/libvirt/images/test.qcow2</path>
    <format type='qcow2'/>
    <permissions>
      <mode>0644</mode>
      <owner>107</owner>
      <group>107</group>
    </permissions>
  </target>
</volume>
EOF

3. Create a volume using virsh and check its compatibility.
# virsh vol-create default vol.xml
Vol test.qcow2 created from vol.xml

# hexdump /var/lib/libvirt/images/test.qcow2 | head -n1
**Output** 
for libvirt-1.1.1-3:
0000000 4651 fb49 0000 0200 0000 0000 0000 0000
                        ^    <= with qemu-img-1.5.3-2.el7.x86_64
0000000 4651 fb49 0000 0300 0000 0000 0000 0000
                        ^    <= with qemu-img-1.6.50-1.el7.x86_64

for libvirt-1.1.1-4 with either version of qemu-img.
0000000 4651 fb49 0000 0200 0000 0000 0000 0000
                        ^    
This patch prevent the difference when using with future
qemu-img creates new image without specifying compatibility.
It is considered VERIFIED.

Comment 8 Ludek Smid 2014-06-13 10:57:27 UTC

This request was resolved in Red Hat Enterprise Linux 7.0.

Contact your manager or support representative in case you have further questions about the request.

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