On Wed, Sep 01 2010 at 9:50am -0400, Tejun Heo <tj@xxxxxxxxxx> wrote: > Hello, > > On 09/01/2010 03:43 PM, Mike Snitzer wrote: > > On Mon, Aug 30 2010 at 5:58am -0400, > > Tejun Heo <tj@xxxxxxxxxx> wrote: > > > >> This patch converts bio-based dm to support REQ_FLUSH/FUA instead of > >> now deprecated REQ_HARDBARRIER. > >> > >> * -EOPNOTSUPP handling logic dropped. > > > > Can you expand on _why_ -EOPNOTSUPP handling is no longer needed? And > > please at it to the final patch header. > > It just doesn't happen anymore. If the underlying device doesn't > support FLUSH/FUA, the block layer simply make those parts noop. IOW, > it no longer distinguishes between writeback cache which doesn't > support cache flush at all and writethrough cache. Devices which have > WB cache w/o flush very difficult to come by these days and there's > nothing much we can do anyway, so it doesn't make sense to require > everyone to implement -EOPNOTSUPP. > > One scheduled feature is to implement falling back to REQ_FLUSH when > the device advertises REQ_FUA but fails to process it, but one way or > the other, the goal is encapsulating REQ_FLUSH/FUA support in block > layer proper. If FLUSH/FUA can be retried using a different strategy, > it should be done inside request_queue proper instead of pushing retry > logic to all its users. OK, so maybe add this info to the patch header one of the primary FLUSH+FUA conversion patches? Thanks for the detailed explanation! Mike -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
