From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: [PATCH] rbd: barriers are hard Date: Fri, 22 Feb 2013 11:17:20 -0600 Message-ID: <5127A820.6070505@inktank.com> References: <5127A7C1.3070609@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ia0-f179.google.com ([209.85.210.179]:64258 "EHLO mail-ia0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758313Ab3BVRRX (ORCPT ); Fri, 22 Feb 2013 12:17:23 -0500 Received: by mail-ia0-f179.google.com with SMTP id x24so737631iak.10 for ; Fri, 22 Feb 2013 09:17:22 -0800 (PST) In-Reply-To: <5127A7C1.3070609@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: ceph-devel Let's go shopping! I'm afraid this may not have gotten it right: 07741308 rbd: add barriers near done flag operations The smp_wmb() should have been done *before* setting the done flag, to ensure all other data was valid before marking the object request done. Switch to use atomic_inc_return() here to set the done flag, which allows us to verify we don't mark something done more than once. Doing this also implies general barriers before and after the call. And although a read memory barrier might have been sufficient before reading the done flag, convert this to a full memory barrier just to put this issue to bed. This resolves: http://tracker.ceph.com/issues/4238 Signed-off-by: Alex Elder --- drivers/block/rbd.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 3cc003b..bd6078b 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -1226,13 +1226,22 @@ static void obj_request_done_init(struct rbd_obj_request *obj_request) static void obj_request_done_set(struct rbd_obj_request *obj_request) { - atomic_set(&obj_request->done, 1); - smp_wmb(); + int done; + + done = atomic_inc_return(&obj_request->done); + if (done > 1) { + struct rbd_img_request *img_request = obj_request->img_request; + struct rbd_device *rbd_dev; + + rbd_dev = img_request ? img_request->rbd_dev : NULL; + rbd_warn(rbd_dev, "obj_request %p was already done\n", + obj_request); + } } static bool obj_request_done_test(struct rbd_obj_request *obj_request) { - smp_rmb(); + smp_mb(); return atomic_read(&obj_request->done) != 0; } -- 1.7.9.5