From mboxrd@z Thu Jan 1 00:00:00 1970 From: Josh Durgin Subject: Re: [PATCH] rbd: kill rbd_init_watch_dev() Date: Mon, 30 Jul 2012 14:46:25 -0700 Message-ID: <501700B1.8030002@inktank.com> References: <50119656.9080709@inktank.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-yw0-f46.google.com ([209.85.213.46]:61542 "EHLO mail-yw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754599Ab2G3Vq2 (ORCPT ); Mon, 30 Jul 2012 17:46:28 -0400 Received: by yhmm54 with SMTP id m54so5400173yhm.19 for ; Mon, 30 Jul 2012 14:46:27 -0700 (PDT) In-Reply-To: <50119656.9080709@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: Alex Elder Cc: ceph-devel@vger.kernel.org On 07/26/2012 12:11 PM, Alex Elder wrote: > When an rbd image is mapped, a watch request is issued so that the > client will get notified in the event the image header object > changes. This is done using rbd_init_watch_dev(), which calls > rbd_req_sync_watch(). > > rbd_init_watch_dev() is organized as a loop, arranging to re-issue > the request after refreshing the header if -ERANGE ever gets > returned. But the only way rbd_req_sync_watch() will return -ERANGE > is if the CEPH_OSD_OP_WATCH operation returns that, which it will > not. > > As a result, the whole looping structure and in fact the whole > function becomes excessive. So get rid of rbd_init_watch_dev(), > and call rbd_req_sync_watch() directly in the one place it's used. Instead of getting rid of this loop, we should make it send a compound operation consisting of (CEPH_OSD_OP_ASSERT_VER, CEPH_OSD_OP_WATCH). Then we will get -ERANGE if our version of the header is out of data, so we don't lose header updates before the watch is established. Josh > Signed-off-by: Alex Elder > --- > drivers/block/rbd.c | 18 +----------------- > 1 file changed, 1 insertion(+), 17 deletions(-) > > diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c > index 94d0745..71e3f3b 100644 > --- a/drivers/block/rbd.c > +++ b/drivers/block/rbd.c > @@ -2191,22 +2191,6 @@ static void rbd_bus_del_dev(struct rbd_device > *rbd_dev) > device_unregister(&rbd_dev->dev); > } > > -static int rbd_init_watch_dev(struct rbd_device *rbd_dev) > -{ > - int ret, rc; > - > - do { > - ret = rbd_req_sync_watch(rbd_dev); > - if (ret == -ERANGE) { > - rc = rbd_refresh_header(rbd_dev, NULL); > - if (rc < 0) > - return rc; > - } > - } while (ret == -ERANGE); > - > - return ret; > -} > - > static atomic64_t rbd_id_max = ATOMIC64_INIT(0); > > /* > @@ -2510,7 +2494,7 @@ static ssize_t rbd_add(struct bus_type *bus, > if (rc) > goto err_out_bus; > > - rc = rbd_init_watch_dev(rbd_dev); > + rc = rbd_req_sync_watch(rbd_dev); > if (rc) > goto err_out_bus; >