Re: [Qemu-devel] [PATCH v3 14/38] block: Move BlockAcctStats into BlockBackend

[Alberto Garcia]

On Wed 03 Jun 2015 10:52:34 PM CEST, Eric Blake wrote:

>> As the comment above bdrv_get_stats() says, BlockAcctStats is
>> something which belongs to the device instead of each
>> BlockDriverState. This patch therefore moves it into the
>> BlockBackend.
>
> Again, Berto may want to eventually report stats for both BDS and BB,
> but that can come later.  For now, this is reasonable refactoring.

Yeah, this change makes sense and I was actually planning to do
something similar in my patch series.

The only problem that I see with this is that the data is stored in the
right place but the API is (still) wrong. query-blockstats queries BDSs,
but the information we'll get in return it's either the stats from the
BlockBackend (for root nodes) or all zeroes (for the rest), not the
stats from the BDSs themselves.

Ideally we would need one way to query information from the BlockBackend
(that we already have) and another way to query information from the BDS
(that we don't have yet). But I guess we have to look for a way to do
this without breaking the API compatibility.

And for the record, my priorities at the moment are the stats from the
BlockBackend, not the BDS.

Berto