On Sun, 2009-05-03 at 14:40 -0400, Jeff Garzik wrote: > Jeff Garzik wrote: > > (2) determine at init if queue (a) supports explicit DISCARD and/or (b) > > supports DISCARD flag passed with READ or WRITE > > > As an aside -- does any existing command set support case #b, above? Not to my knowledge. I think discard was modelled on barrier (which can be associated with data or stand on its own). > AFAICT, ATA, SCSI and NVMHCI all have a single, explicit hardware > command to discard/deallocate unused sectors. > > Therefore, creating REQ_TYPE_DISCARD seems to eliminate any need for new > hook ->prepare_discard(). Well, yes and no ... in the SCSI implementation of either UNMAP or WRITE SAME, we still need a data buffer to store either the extents or the actual same data. > This provides a 1:1 correspondence between hardware and struct request, > most closely matching the setup of known hardware. Agreed ... but we still have to allocate the adjunct buffer somewhere .... James -- 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
