On Tue, Aug 17 2010 at 12:51pm -0400, Tejun Heo <tj@xxxxxxxxxx> wrote: > Hello, > > On 08/17/2010 04:07 PM, Mike Snitzer wrote: > >> With the patch applied, there's no second flush. Those requests would > >> now be REQ_FLUSH + REQ_DISCARD. The first can't be avoided anyway and > >> there won't be the second flush to begin with, so I don't think this > >> worsens anything. > > > > Makes sense, but your patches still need to be refreshed against the > > latest (2.6.36-rc1) upstream code. Numerous changes went in to DM > > recently. > > Sure thing. The block part isn't fixed yet and so the RFC tag. Once > the block layer part is settled, it probably should be pulled into > dm/md and other trees and conversions should happen there. Why base your work on a partial 2.6.36 tree? Why not rebase to linus' 2.6.36-rc1? Once we get the changes in a more suitable state (across the entire tree) we can split the individual changes out to their respective trees. Without a comprehensive tree I fear this code isn't going to get tested or reviewed properly. For example: any review of DM changes, against stale DM code, is wasted effort. > >> * For request based dm: > >> > >> * The sequencing is done by the block layer for the top level > >> request_queue, so the only things request based dm needs to make > >> sure is 1. handling empty REQ_FLUSH correctly (block layer will > >> only send down empty REQ_FLUSHes) and 2. propagate REQ_FUA bit to > >> member devices. > > > > OK, so seems 1 is done, 2 is still TODO. Looking at your tree it seems > > 2 would be as simple as using the following in > > Oh, I was talking about the other way around. Passing REQ_FUA in > bio->bi_rw down to member request_queues. Sometimes while > constructing clone / split bios, the bit is lost (e.g. md raid5). Seems we need to change __blk_rq_prep_clone to propagate REQ_FUA just like REQ_DISCARD: http://git.kernel.org/linus/3383977 Doesn't seem like we need to do the same for REQ_FLUSH (at least not for rq-based DM's benefit) because dm.c:setup_clone already special cases flush requests and sets REQ_FLUSH in cmd_flags. Mike -- To unsubscribe from this list: 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
