On Wed, Mar 05, 2014 at 09:40:34PM +0100, Guido Günther wrote:
> Hi Daniel,
> On Wed, Mar 05, 2014 at 05:53:53PM +0000, Daniel P. Berrange wrote:
> [..snip..]
> > + /* Discard if cache is older that QEMU binary */
> > + /* XXX must also compare to libvirtd timestamp */
> > + if (sb.st_mtime < qemuCaps->mtime) {
> I think looking at the mtime isn't sufficent here. Tools like dpkg set
> the mtime to the time the package was built at not the installation time
> so we might end up updating qemu but still having an mtime older than
> the time the xml was created (same holds for downgrades to older qemu
> versions) or are we simply requiring distributors to clean the cache
> upon package upgrades (which would mandate using a trigger)?
NB the existing code already has the flaw you speak of - we cache the
capabilities in memory currently and only invalidate when mtime is
outdated.
> Maybe we need to actually calculate the binaries checksum not only the
> pathname? We could then simply just wipe alle checksums upon libvirt
> upgrades to get rid of old entries.
Checksumming the binary content is reasonably heavyweight, but we could
just use ctime like Eric suggests
Regards,
Daniel
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