Re: [Qemu-devel] [PATCH v3 2/6] add basic backup support to block driver

[Paolo Bonzini]

Il 21/02/2013 07:33, Dietmar Maurer ha scritto:
>> This should call bdrv_is_allocated_above like the other block jobs do.
>> It would be needed later anyway to backup only the topmost image.
> 
> I do not need that information now, so why do you want that I add dead code?

I think you do.  You're wasting time reading unallocated clusters and
checking that they are zero.  bdrv_is_allocated_above gives you the same
information much more efficiently.  Do VMA files have to store all the
blocks of the source file?

Paolo