Re: [libvirt] [PATCH] snapshot: fix rollback failure in transaction mode

On 09/12/2012 09:22 AM, Guannan Ren wrote: Can you give some exact steps to reproduce this, so that I know who is making the file have non-zero size? I'm worried that unlinking a non-empty file is discarding data, so the commit message needs a lot more details about how we are proving that the only way the file can be non-zero size is because qemu happened to put data into a previously empty file prior to the failed 'transaction' attempt. That is, after re-reading context code just now, I'm fairly confident that this code can only be reached when qemu supports the 'transaction' monitor command, and libvirt's --reuse-ext flag was not specified, and therefore libvirt must have just created the file. But I want that in the commit message rather than having to re-read the code every time I visit this commit in future reads of the git log. It may also be that qemu has a bug in that the 'transaction' command is modifying files even when it fails, so even while this works around the bug, I'm cc'ing Jeff to see if qemu also needs a bug fix. -- Eric Blake eblake(a)redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org