On Thu, Jun 27, 2013 at 08:30:04PM +0800, Wenchao Xia wrote:
> 于 2013-6-27 17:01, Stefan Hajnoczi 写道:
> >On Tue, Jun 25, 2013 at 07:14:19PM +0800, Wenchao Xia wrote:
> >>于 2013-6-25 17:13, Stefan Hajnoczi 写道:
> >>>On Thu, Jun 20, 2013 at 04:59:17PM +0800, Wenchao Xia wrote:
> >BTW we already have qemu-io -c map which prints out allocation
> >information for an image file. If that command is extended to support
> >-s then you can get your info easily.
> Do you mean use it like:
> 1 call qemu-io file -c map -s sn0
> 2 call qemu-io file -c map -s sn1
> 3 for (offset = 0; offset < len; offset +=512) {
> if (allocated on sn0) {
> call qemu-io file read -s sn0, into buf0
> }
> if (allocated on sn1) {
> call qemu-io file read -s sn1, into buf1
> }
> if strcmp(buf0, buf1) {
> write down the delta
> }
> }
> ?
> I think it is workable and flex, the bottle neck is the string
> parsing of qemu-io. For delta data info retrieving purpose, qemu-img
> approach would faster.
It's also possible to put Step 3 into qemu-img so that this feature is
fast and easy to use with a single command.
Stefan
