[libvirt] [PATCH 3/3] Add volume zeroing

[Daniel P. Berrange]

On Tue, Feb 16, 2010 at 01:31:58PM +0100, Paolo Bonzini wrote:
> On 02/16/2010 12:33 PM, Daniel P. Berrange wrote:
> >The idea of zeroing upon delete, is that we want the currently allocated
> >extents to be overwritten with zeros. If we truncate to 0 size, then
> >extend to original size I imagine that would easily allow the filesystem
> >to give you a new set of extents filled with zeros, leaving the old
> >extents with data intact as unused space on the FS.
> 
> Yeah, as long as you use regular files as images you're safe, but you'd 
> expose the old data if you destroyed the partition on which the file 
> resided and used the partition as storage for a new guest.
> 
> But then in this scenario (delete file system partition and give it out 
> as raw) you could expose information not only about other/old guests, 
> but also about the host.  So for partitions it can be even more 
> important to provide an option to zero the partition _before_ giving it 
> out.  Currently you cannot do that with libvirt.

There is an unused 'flags' parameter in virStorageVolCreate(), where
we could/should add a VIR_STORAGE_VOL_CREATE_ZEROED  parameter too 
for that scenario

ANother option would be to add an explicit virStorageVolZero() API to
allow a volume to be wiped independently of create/delete operations.

Regards,
Daniel
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