On Thu, Jul 20 2006, Jeff Garzik wrote: > Jens Axboe wrote: > >On Thu, Jul 20 2006, Jeff Garzik wrote: > >>James Bottomley wrote: > >>>On Thu, 2006-07-20 at 17:27 -0400, Jeff Garzik wrote: > >>>>Since _no individual SCSI driver_ uses the block layer > >>>>tagging, it is likely that some instability and core kernel > >>>>development > >>>>will occur, in order to make that work. > >>>That's not quite true: 53c700 and tmscsim both use it ... I could with > >>>the usage were wider, but at least 53c700 has pretty regular and > >>>constant usage ... enough I think to validate the block tag code (it's > >>>been using it for the last three years). > >>Not for the case being discussed in this thread, adapter-wide tags. > > > >That just means the map is shared, otherwise there should be little if > >any difference. > > > >>AFAICS, no file in include/scsi/* or drivers/scsi/* ever calls > >>blk_queue_init_tags() with a non-NULL third arg. > > > >grpe again, it's in scsi_tcq.h. > > What tree are you looking at? > > There is only one user in the entire tree, and NULL is hardcoded as the > third arg. This is 2.6.18-rc2: Sorry, missed your non-NULL statement, I thought you meant in generel. As long as you get the locking right for the map access, there's really nothing that seperates shared vs non-shared tag mappings. So I don't think it's a big deal. If we don't encourage new drivers to use the block layer tagging, we might as well not bother with it. -- Jens Axboe - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
