On 07/27/11 20:36, Christoph Hellwig wrote: > Initiating the freeze from kernelspace doesn't make much sense. With > virtio we could add in-band freeze request to the protocol, and although > that would be a major change in that way virtio-blk works right now it's > at least doable. But all other "real" storage targets only communicate > with their initators over out of band procotols that are entirely handled > in userspace, and given their high-level nature better are - that is if > we know them at all given how vendors like to keep this secrete IP > closed and just offer userspace management tools in binary form. > > building new infrastructure in the kernel just for virtio, while needing > to duplicate the same thing in userspace for all real storage seems like > a really bad idea. That is in addition to the userspace freeze notifier > similar to what e.g. Windows has - if the freeze process is driven from > userspace it's much easier to handle those properly compared to requiring > kernel upcalls. >
The freeze operation would really just be a case of walking the list of mounted file systems and calling the FIFREEZE ioctl operation on them. I wouldn't anticipate doing anything else in a virtio-fsfreeze.ko module. Cheers, Jes
