From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Elder Subject: [PATCH 1/3] libceph: reset BACKOFF if unable to re-queue Date: Tue, 09 Oct 2012 14:33:00 -0700 Message-ID: <5074980C.6090104@inktank.com> References: <507497AC.5030609@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-pb0-f46.google.com ([209.85.160.46]:53550 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754075Ab2JIVdD (ORCPT ); Tue, 9 Oct 2012 17:33:03 -0400 Received: by mail-pb0-f46.google.com with SMTP id rr4so5691963pbb.19 for ; Tue, 09 Oct 2012 14:33:03 -0700 (PDT) In-Reply-To: <507497AC.5030609@inktank.com> Sender: ceph-devel-owner@vger.kernel.org List-ID: To: ceph-devel@vger.kernel.org If ceph_fault() is unable to queue work after a delay, it sets the BACKOFF connection flag so con_work() will attempt to do so. In con_work(), when BACKOFF is set, if queue_delayed_work() doesn't result in newly-queued work, it simply ignores this condition and proceeds as if no backoff delay were desired. There are two problems with this--one of which is a bug. The first problem is simply that the intended behavior is to back off, and if we aren't able queue the work item to run after a delay we're not doing that. The only reason queue_delayed_work() won't queue work is if the provided work item is already queued. In the messenger, this means that con_work() is already scheduled to be run again. So if we simply set the BACKOFF flag again when this occurs, we know the next con_work() call will again attempt to hold off activity on the connection until after the delay. The second problem--the bug--is a leak of a reference count. If queue_delayed_work() returns 0 in con_work(), con->ops->put() drops the connection reference held on entry to con_work(). However, processing is (was) allowed to continue, and at the end of the function a second con->ops->put() is called. This patch fixes both problems. Signed-off-by: Alex Elder --- net/ceph/messenger.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c index f9f65fe..ece06bc 100644 --- a/net/ceph/messenger.c +++ b/net/ceph/messenger.c @@ -2300,10 +2300,11 @@ restart: mutex_unlock(&con->mutex); return; } else { - con->ops->put(con); dout("con_work %p FAILED to back off %lu\n", con, con->delay); + set_bit(CON_FLAG_BACKOFF, &con->flags); } + goto done; } if (con->state == CON_STATE_STANDBY) { -- 1.7.9.5