On 10/16/2012 02:51 PM, Laine Stump wrote:
On 10/13/2012 06:00 PM, Eric Blake wrote:
We used to walk the backing file chain at least twice per disk, once to set up cgroup device whitelisting, and once to set up security labeling. Rather than walk the chain every iteration, which possibly includes calls to fork() in order to open root-squashed NFS files, we can exploit the cache of the previous patch.
Obviously creating the rule that you can't mess with the backing chain outside the libvirt API, but I think you've already said that :-)
Thankfully, since the cache is only kept for running qemu, and you can't change the backing chain behind a running qemu's back except through snapshot-create, block-pull, block-copy, or block-commit, all of which are libvirt APIs that correctly update/invalidate the cache, we're set (for now) :)
Whew! Can't see the code for all the deletions! :-)
Yep, this is one of those nice cleanups enabled by doing things right in the first place.
+ if (disk->format > 0) + format = disk->format; + else if (ctl->allowDiskFormatProbing) + format = VIR_STORAGE_FILE_AUTO; + else + format = VIR_STORAGE_FILE_RAW;
It seems like I've seen this same bit of code a few times now...
+ + /* XXX - if we knew the qemu user:group here we could send it in + * so that the open could be re-tried as that user:group. + */ + disk->chain = virStorageFileGetMetadata(disk->src, format, -1, -1, + ctl->allowDiskFormatProbing, + NULL); +
True - I'll experiment with a followup patch that moves the format selection of the initial layer into virStorageFileGetMetadata; if it works, expect another patch to be added in v3 (and if not, we'll just live with the duplication). -- Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org