Re: [Qemu-devel] [PATCH 1/4] block: Fix dirty bitmap in bdrv_co_discard

[Paolo Bonzini]

On 06/05/2015 03:45, Fam Zheng wrote:
>> > This is not enough, you also have to do the discard in block/mirror.c,
>> > otherwise the destination image could even become fully provisioned!
> I wasn't sure what if src and dest have different can_write_zeroes_with_unmap
> value, but your argument is stronger.
> 
> I will add discard in mirror.  Besides that, do we need to compare the
> can_write_zeroes_with_unmap?

Hmm, if can_write_zeroes_with_unmap is set, it's probably better to
write zeroes instead of discarding, in case the guest is relying on it.

Paolo