On Wed, Aug 14, 2013 at 01:03:48PM +0100, Alex Bligh wrote: > > On 14 Aug 2013, at 12:52, Fam Zheng wrote: > > > Yes, this one sounds good to have. VMDK and VHDX have this kind of > > backing file status validation. > > ... though I'd prefer something safer than looking at mtime, for > instance a sequence number that is incremented prior to any > bdrv_close if a write has been done since bdrv_open.
Yes, please not mtime. User-mode Linux COW files use mtime to check this, and it causes no end of problems (eg. if the backing file is copied from one place to another without using the magic incantations to preserve file times). Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Fedora Windows cross-compiler. Compile Windows programs, test, and build Windows installers. Over 100 libraries supported. http://fedoraproject.org/wiki/MinGW
