[ 3.5.yuz extended stable ] Patch "libceph: only kunmap kmapped pages" has been added to staging queue

[Herton Ronaldo Krzesinski]

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

    libceph: only kunmap kmapped pages

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

------

>From 38c1cfbc01e54212f13710a2175289fbaa391cfa Mon Sep 17 00:00:00 2001
From: Alex Elder <elder at inktank.com>
Date: Fri, 21 Sep 2012 17:59:58 -0500
Subject: [PATCH 72/78] libceph: only kunmap kmapped pages

commit 5ce765a540f34d1e2005e1210f49f67fdf11e997 upstream.

In write_partial_msg_pages(), pages need to be kmapped in order to
perform a CRC-32c calculation on them.  As an artifact of the way
this code used to be structured, the kunmap() call was separated
from the kmap() call and both were done conditionally.  But the
conditions under which the kmap() and kunmap() calls were made
differed, so there was a chance a kunmap() call would be done on a
page that had not been mapped.

The symptom of this was tripping a BUG() in kunmap_high() when
pkmap_count[nr] became 0.

Reported-by: Bryan K. Wright <bryan at virginia.edu>
Signed-off-by: Alex Elder <elder at inktank.com>
Reviewed-by: Sage Weil <sage at inktank.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 net/ceph/messenger.c |    5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c
index b141c86..8ba0eee 100644
--- a/net/ceph/messenger.c
+++ b/net/ceph/messenger.c
@@ -1069,16 +1069,13 @@ static int write_partial_msg_pages(struct ceph_connection *con)
 			BUG_ON(kaddr == NULL);
 			base = kaddr + con->out_msg_pos.page_pos + bio_offset;
 			crc = crc32c(crc, base, len);
+			kunmap(page);
 			msg->footer.data_crc = cpu_to_le32(crc);
 			con->out_msg_pos.did_page_crc = true;
 		}
 		ret = ceph_tcp_sendpage(con->sock, page,
 				      con->out_msg_pos.page_pos + bio_offset,
 				      len, 1);
-
-		if (do_datacrc)
-			kunmap(page);
-
 		if (ret <= 0)
 			goto out;

--
1.7.9.5