Bug 734067

Summary:	Wiping volumes has side effect of changing the volume format for non-raw volumes
Product:	Red Hat Enterprise Linux 6	Reporter:	Nan Zhang <nzhang>
Component:	libvirt	Assignee:	Osier Yang <jyang>
Status:	CLOSED WONTFIX	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	medium	Docs Contact:
Priority:	medium
Version:	6.2	CC:	berrange, dallan, dyuan, eblake, juzhang, mzhan, rwu, whuang
Target Milestone:	rc	Keywords:	Reopened
Target Release:	---
Hardware:	Unspecified
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2011-11-10 21:31:32 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:

Description Nan Zhang 2011-08-29 11:14:10 UTC

Description of problem:
the volume data should be erased, but can not change its format.

Version-Release number of selected component (if applicable):
libvirt-0.9.4-6.el6.x86_64

How reproducible:
always

Steps to Reproduce:
# qemu-img info /var/lib/libvirt/images/rhel6.img 
image: /var/lib/libvirt/images/rhel6.img
file format: qcow2
virtual size: 512K (524288 bytes)
disk size: 392K
cluster_size: 65536

# virsh vol-wipe rhel6.img --pool default
Vol rhel6.img wiped

# qemu-img info /var/lib/libvirt/images/rhel6.img 
image: /var/lib/libvirt/images/rhel6.img
file format: raw
virtual size: 512K (524288 bytes)
disk size: 0
  
Actual results:
Be changed from qcow2 to raw format after volume wiped.

Expected results:
Should be kept qcow2 format after volume wiped.

Additional info:

Comment 2 Dave Allan 2011-09-06 18:49:18 UTC

Since wiping the volume destroys all the data in it, the volume is raw because the qcow metadata has been removed.  This is behavior by design, so I am closing as NOTABUG.

Comment 3 Eric Blake 2011-09-07 14:36:25 UTC

Should virsh vol-wipe add a new flag that wipes the contents, but then restores enough qcow2 metadata that the file is back to a blank qcow2 volume?

Comment 4 Dave Allan 2011-09-08 15:43:40 UTC

Not a bad RFE, but nobody's clamoring for it.

Comment 5 Nan Zhang 2011-09-08 19:24:26 UTC

Eric,
Thanks for your inputs!

QE requests this feature support, so re-open this BZ to ASSIGNED.

Comment 6 Daniel Berrangé 2011-09-12 08:34:47 UTC

IMHO this is a bug, not an RFE.

Wiping a volume should only be wiping the data, not the file format info. The problem is that the current code is not paying attention to the file format when wiping data, it just blindly truncates the file to zero bytes. For non-raw formats, we should run 'qemu-img create' again after truncation to ensure the original file format structure is preserved.