Patchwork [3.5.yuz,extended,stable] Patch "rbd: reset BACKOFF if unable to re-queue" has been added to staging queue

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Submitter Herton Ronaldo Krzesinski
Date Nov. 20, 2012, 5:19 p.m.
Message ID <1353431980-11274-1-git-send-email-herton.krzesinski@canonical.com>
Download mbox | patch
Permalink /patch/200481/
State New
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Herton Ronaldo Krzesinski - Nov. 20, 2012, 5:19 p.m.
This is a note to let you know that I have just added a patch titled

    rbd: reset BACKOFF if unable to re-queue

to the linux-3.5.y-queue branch of the 3.5.yuz extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.yuz tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Herton

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From 2f2bf413acd52e5a9bade876b9c7c726bf06b61f Mon Sep 17 00:00:00 2001
From: Alex Elder <elder@inktank.com>
Date: Mon, 8 Oct 2012 20:37:30 -0700
Subject: [PATCH 73/78] rbd: reset BACKOFF if unable to re-queue

commit 588377d6199034c36d335e7df5818b731fea072c upstream.

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 <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
---
 net/ceph/messenger.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--
1.7.9.5

Patch

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index 8ba0eee..0de041f 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -2296,10 +2296,11 @@  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) {