On Wed, Jun 30 2010 at 6:57am -0400, Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote: > On 06/30/2010 01:41 PM, Christoph Hellwig wrote: > > On Wed, Jun 30, 2010 at 01:25:01PM +0300, Boaz Harrosh wrote: > >> OK, Thanks, I see. Is it one of these operations, (like we have in OSD) where > >> the CDB information spills into the payload? like the scatter-gather and extent > >> lists and such. > > > > For UNMAP the payload is a list of block number / length pairs, while > > the CDB itself doesn't contain any information like that. It's a rather > > awkward command. > > > > How big can that be? could we, maybe, use the sense_buffer, properly allocated > already? > > >> Do we actually use a WRITE_SAME which is not zero? for what use? > > > > The kernel doesn't issue any WRITE SAME without the unmap bit set. > > So if the unmap bit is set then the page can just be zero, right? > > I still think a static zero-page is a worth while optimization. And > block-drivers can take care with special needs with a private mem_pool > or something. For the discard-type user and generic block layer the > page is just an implementation specific residue, No? Why should the block layer have any role in managing this page? Block layer doesn't care about it, SCSI does. Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
