On 02/02/11 08:57, Stefan Hajnoczi wrote: > On Tue, Feb 1, 2011 at 10:58 AM, <jes.soren...@redhat.com> wrote: >> From: Jes Sorensen <jes.soren...@redhat.com> >> >> Implement freeze/thaw support in the guest, allowing the host to >> request the guest freezes all it's file systems before a live snapshot >> is performed. >> - fsfreeze(): Walk the list of mounted local real file systems, >> and freeze them. > > Does this add a requirement that guest agent code issues no disk I/O > in its main loop (e.g. logging)? Otherwise we might deadlock > ourselves waiting for I/O which is never issued.
Yes very much so[1] - one reason why it would be nice to have virtagent use threads to execute the actual commands. We should probably add a flag to agent commands indicating whether they issue disk I/O or not, so we can block attempts to execute commands that do so, while the guest is frozen. Cheers, Jes [1] speaking from experience ... a Linux desktop gets really upset if you freeze the file systems from a command in an xterm.... ho hum
