Hello, On 05/16/2010 09:23 PM, James Bottomley wrote: >> request_queue is (or at least supposed to be) oblivious about genhd >> and its attributes including capacity. After all, request_queue can >> exist w/o genhd associated, so it would be quite odd to have capacity >> related method living in request_queue. > > Yes, I'll sort of buy this ... although it's not quite that clean: > barrier methods, which are only used for filesystem above block devices > also live in the queue. You mean prepare_flush_fn()? Hmmm... >> Another thing is that there is no generic way to reach the associated >> genhd from request_queue and I can't think of a clean way to map >> request_queue to the associated ata device w/o in-flight requests (can >> you even do that from SCSI?). > > No ... that's by design ... but you don't need it if all you're doing is > unlocking the native capacity (whether on behalf of block dev ops or > queue ops). libata defers all those managements stuff to EH and the ata device needs to be accessible to invoke EH. It can be worked around by issuing a pseudo command which is trapped and deferred to EH during command processing but it's much better to be able to access the device directly. >> Unfortunately, libata is still properly layered below SCSI, so I'm >> afraid threading through sd is clumsy yet the cleanest way to do it. > > s/properly/im\&/ Heh, yeah. :-) > but yes, > > Reluctantly-Acked-by: James Bottomley <James.Bottomley@xxxxxxx> Thanks. Much appreciated. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
