Re: [libvirt] RFC: API additions for enhanced snapshot support

[Stefan Hajnoczi <stefanha gmail com>]

On Thu, Jul 7, 2011 at 8:34 PM, Eric Blake <eblake redhat com> wrote:
> On 07/07/2011 03:13 AM, Stefan Hajnoczi wrote:
>> On Wed, Jul 6, 2011 at 3:03 PM, Eric Blake <eblake redhat com> wrote:
>>> In other words, it looks like we are stuck with updating XML to track
>>> new file names any time we take a snapshot.
>>
>> Yes, but QEMU's snapshot_blkdev command takes a filename argument so
>> at least you get to specify that new filename.
>
> Well, the best thing (from libvirt's point of view) would be if
> snapshot_blkdev took a single string argument, which is either a
> /path/to/filename (and qemu does open()) or fd:name notation (to refer
> to a previously-named fd passed via the getfd monitor command, so that
> libvirt does open()).  This would make SELinux integration easier, as
> one of the sVirt goals is to get to the point where we can use SELinux
> to forbid qemu from open()ing files on NFS shares, while still
> permitting all other operations on already-open fds passed in from libvirt.

Today QEMU supports /path/to/filename.  An fd argument to
snapshot_blkdev requires a little bit of work since the QEMU block
layer .bdrv_create() interface takes a filename and tries to create
it.

Jes: Is the fd argument to snapshot_blkdev in your plans?

Stefan