Am 23.02.2018 um 17:43 hat Eric Blake geschrieben: > > OFFSET_VALID | DATA might be excusable because I can see that it's > > convenient that a protocol driver refers to itself as *file instead of > > returning NULL there and then the offset is valid (though it would be > > pointless to actually follow the file pointer), but OFFSET_VALID without > > DATA probably isn't. > > So OFFSET_VALID | DATA for a protocol BDS is not just convenient, but > necessary to avoid breaking qemu-img map output. But you are also right > that OFFSET_VALID without data makes little sense at a protocol layer. So > with that in mind, I'm auditing all of the protocol layers to make sure > OFFSET_VALID ends up as something sane.
That's one way to look at it. The other way is that qemu-img map shouldn't ask the protocol layer for its offset because it already knows the offset (it is what it passes as a parameter to bdrv_co_block_status). Anyway, it's probably not worth changing the interface, we should just make sure that the return values of the individual drivers are consistent. Kevin
