Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756593AbZCXONX (ORCPT ); Tue, 24 Mar 2009 10:13:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756760AbZCXOFe (ORCPT ); Tue, 24 Mar 2009 10:05:34 -0400 Received: from brick.kernel.dk ([93.163.65.50]:47789 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759264AbZCXOF1 (ORCPT ); Tue, 24 Mar 2009 10:05:27 -0400 Date: Tue, 24 Mar 2009 15:05:24 +0100 From: Jens Axboe To: Mikulas Patocka Cc: device-mapper development , Linux Kernel Mailing List , Andi Kleen , "MASON, CHRISTOPHER" Subject: Re: [dm-devel] Barriers still not passing on simple dm devices... Message-ID: <20090324140524.GV27476@kernel.dk> References: <49C7DD3C.2020401@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3594 Lines: 113 On Tue, Mar 24 2009, Mikulas Patocka wrote: > > > On Mon, 23 Mar 2009, Eric Sandeen wrote: > > > I've noticed that on 2.6.29-rcX, with Andi's patch > > (ab4c1424882be9cd70b89abf2b484add355712fa, dm: support barriers on > > simple devices) barriers are still getting rejected on these simple devices. > > > > The problem is in __generic_make_request(): > > > > if (bio_barrier(bio) && bio_has_data(bio) && > > (q->next_ordered == QUEUE_ORDERED_NONE)) { > > err = -EOPNOTSUPP; > > goto end_io; > > } > > > > and dm isn't flagging its queue as supporting ordered writes, so it's > > rejected here. > > > > Doing something like this: > > > > + if (t->barriers_supported) > > + blk_queue_ordered(q, QUEUE_ORDERED_DRAIN, NULL); > > > > somewhere in dm (I stuck it in dm_table_set_restrictions() - almost > > certainly the wrong thing to do) did get my dm-linear device to mount > > with xfs, w/o xfs complaining that its mount-time barrier tests failed. > > > > So what's the right way around this? What should dm (or md for that > > matter) advertise on their queues about ordered-ness? Should there be > > some sort of "QUEUE_ORDERED_PASSTHROUGH" or something to say "this level > > doesn't care, ask the next level" or somesuch? Or should it inherit the > > flag from the next level down? Ideas? > > > > Thanks, > > -Eric > > > > -- > > dm-devel mailing list > > dm-devel@redhat.com > > https://www.redhat.com/mailman/listinfo/dm-devel > > Hi > > This is misdesign in generic bio layer and it should be fixed there. I > think it is blocking barrier support in md-raid1 too. Jens, pls apply the > attached patch. > > Mikulas > > ---- > > Move test for not-supported barriers to __make_request. > > This test prevents barriers from being dispatched to device mapper > and md. > > This test is sensible only for drivers that use requests (such as disk > drivers), not for drivers that use bios. > > It is better to fix it in generic code than to make workaround for it > in device mapper and md. So you audited any ->make_request_fn style driver and made sure they rejected barriers? > > Signed-off-by: Mikulas Patocka > > --- > block/blk-core.c | 11 ++++++----- > 1 file changed, 6 insertions(+), 5 deletions(-) > > Index: linux-2.6.29-rc6-devel/block/blk-core.c > =================================================================== > --- linux-2.6.29-rc6-devel.orig/block/blk-core.c 2009-02-23 18:43:37.000000000 +0100 > +++ linux-2.6.29-rc6-devel/block/blk-core.c 2009-02-23 18:44:27.000000000 +0100 > @@ -1145,6 +1145,12 @@ static int __make_request(struct request > const int unplug = bio_unplug(bio); > int rw_flags; > > + if (bio_barrier(bio) && bio_has_data(bio) && > + (q->next_ordered == QUEUE_ORDERED_NONE)) { > + bio_endio(bio, -EOPNOTSUPP); > + return 0; > + } > + > nr_sectors = bio_sectors(bio); > > /* > @@ -1450,11 +1456,6 @@ static inline void __generic_make_reques > err = -EOPNOTSUPP; > goto end_io; > } > - if (bio_barrier(bio) && bio_has_data(bio) && > - (q->next_ordered == QUEUE_ORDERED_NONE)) { > - err = -EOPNOTSUPP; > - goto end_io; > - } > > ret = q->make_request_fn(q, bio); > } while (ret); > > -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/