[ 3.8.y.z extended stable ] Patch "libceph: must hold mutex for reset_changed_osds()" has been added to staging queue

Kamal Mostafa kamal at canonical.com
Fri Jun 14 18:33:43 UTC 2013


This is a note to let you know that I have just added a patch titled

    libceph: must hold mutex for reset_changed_osds()

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.3.

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

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 1579343b25d154140632bbc3b5cafb543c62f3ea Mon Sep 17 00:00:00 2001
From: Alex Elder <elder at inktank.com>
Date: Wed, 15 May 2013 16:28:33 -0500
Subject: libceph: must hold mutex for reset_changed_osds()

commit 14d2f38df67fadee34625fcbd282ee22514c4846 upstream.

An osd client has a red-black tree describing its osds, and
occasionally we would get crashes due to one of these trees tree
becoming corrupt somehow.

The problem turned out to be that reset_changed_osds() was being
called without protection of the osd client request mutex.  That
function would call __reset_osd() for any osd that had changed, and
__reset_osd() would call __remove_osd() for any osd with no
outstanding requests, and finally __remove_osd() would remove the
corresponding entry from the red-black tree.  Thus, the tree was
getting modified without having any lock protection, and was
vulnerable to problems due to concurrent updates.

This appears to be the only osd tree updating path that has this
problem.  It can be fairly easily fixed by moving the call up
a few lines, to just before the request mutex gets dropped
in kick_requests().

This resolves:
    http://tracker.ceph.com/issues/5043

Signed-off-by: Alex Elder <elder at inktank.com>
Reviewed-by: Sage Weil <sage at inktank.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/ceph/osd_client.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index eb9a444..b7b980d 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -1339,13 +1339,13 @@ static void kick_requests(struct ceph_osd_client *osdc, int force_resend)
 		__register_request(osdc, req);
 		__unregister_linger_request(osdc, req);
 	}
+	reset_changed_osds(osdc);
 	mutex_unlock(&osdc->request_mutex);

 	if (needmap) {
 		dout("%d requests for down osds, need new map\n", needmap);
 		ceph_monc_request_next_osdmap(&osdc->client->monc);
 	}
-	reset_changed_osds(osdc);
 }


--
1.8.1.2





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