Re: [Qemu-block] [Qemu-devel] callout to *file in bdrv_co_get_block_status

[Paolo Bonzini]

On 31/03/2017 09:55, Peter Lieven wrote:
>>> Would it be an idea to introduce an inverse flag live BDRV_BLOCK_NOT_ZERO
>>> for cases where we know that there is really DATA and thus can avoid the
>>> second callout?
>> How would you know that a block is nonzero?
> I would trust the metadata. At least for VMDK and QCOW2v3.
> Bad idea?

The metadata only tells you that a block is zero, not that it's nonzero.
 What you are suggesting is really the same as removing the recursion.
However, I still haven't understood clearly if it's a QEMU or tmpfs bug;
if it's a tmpfs bug your suggestion would not fix tmpfs slowness on raw
images.

Paolo