On Mon, Feb 03, 2014 at 03:48:29PM +0100, Jan Kara wrote: > On Sat 01-02-14 17:48:27, Frederic Weisbecker wrote: > > On Mon, Dec 23, 2013 at 09:39:22PM +0100, Jan Kara wrote: > > > Block layer currently abuses rq->csd.list.next for storing fifo_time. > > > That is a terrible hack and completely unnecessary as well. Union > > > achieves the same space saving in a cleaner way. > > > > > > Signed-off-by: Jan Kara <j...@suse.cz> > > > > Hi Jan, > > > > Taken as is, the patch is fine and it builds. > > But later when I finally get rid of csd->list in a subsequent patch, > > rq_fifo_clear() callers break the build. > > > > This is because rq_fifo_clear() initialize the csd->list and I'm not > > sure how to fix that leftover because I am not clear about the purpose > > of that INIT_LIST_HEAD(): is it to reset fifo time or to prepare for > > an IPI to be queued? > I'm convinced it is there to prepare IPI to be queued. So just removing > the initialization as you did should be the right thing to do. You can > easily verify that it is correct - you boot the kernel, switch to 'deadline' > IO scheduler by doing > echo 'deadline' >/sys/block/sda/queue/scheduler > and then do some IO. If it doesn't blow up, it is correct.
Ok that seem to work :) > > > All in one it looks buggy because if this is to prepare for the IPI, > > it's useless as csd.list is not a list head but just a node. Otherwise if it > > is to reset fifo_time it's wrong because INIT_LIST_HEAD doesn't initialize > > to 0. > Yup, I think it is useless. Ok then I'll apply this change. I'm just moving it to a separate patch to lower the chance of it being missed. Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
