[ 3.5.y.z extended stable ] Patch "svcrpc: make svc_age_temp_xprts enqueue under sv_lock" has been added to staging queue

[Luis Henriques]

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

    svcrpc: make svc_age_temp_xprts enqueue under sv_lock

to the linux-3.5.y-queue branch of the 3.5.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-3.5.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.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From c050375de24d473b6745f0d21219e272c8a669f5 Mon Sep 17 00:00:00 2001
From: "J. Bruce Fields" <bfields at redhat.com>
Date: Sun, 10 Feb 2013 11:33:48 -0500
Subject: [PATCH] svcrpc: make svc_age_temp_xprts enqueue under sv_lock
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit e75bafbff2270993926abcc31358361db74a9bc2 upstream.

svc_age_temp_xprts expires xprts in a two-step process: first it takes
the sv_lock and moves the xprts to expire off their server-wide list
(sv_tempsocks or sv_permsocks) to a local list.  Then it drops the
sv_lock and enqueues and puts each one.

I see no reason for this: svc_xprt_enqueue() will take sp_lock, but the
sv_lock and sp_lock are not otherwise nested anywhere (and documentation
at the top of this file claims it's correct to nest these with sp_lock
inside.)

Tested-by: Jason Tibbitts <tibbs at math.uh.edu>
Tested-by: Paweł Sikora <pawel.sikora at agmk.net>
Signed-off-by: J. Bruce Fields <bfields at redhat.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/sunrpc/svc_xprt.c | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index bac973a..3e74e01 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -814,7 +814,6 @@ static void svc_age_temp_xprts(unsigned long closure)
 	struct svc_serv *serv = (struct svc_serv *)closure;
 	struct svc_xprt *xprt;
 	struct list_head *le, *next;
-	LIST_HEAD(to_be_aged);

 	dprintk("svc_age_temp_xprts\n");

@@ -835,25 +834,15 @@ static void svc_age_temp_xprts(unsigned long closure)
 		if (atomic_read(&xprt->xpt_ref.refcount) > 1 ||
 		    test_bit(XPT_BUSY, &xprt->xpt_flags))
 			continue;
-		svc_xprt_get(xprt);
-		list_move(le, &to_be_aged);
+		list_del_init(le);
 		set_bit(XPT_CLOSE, &xprt->xpt_flags);
 		set_bit(XPT_DETACHED, &xprt->xpt_flags);
-	}
-	spin_unlock_bh(&serv->sv_lock);
-
-	while (!list_empty(&to_be_aged)) {
-		le = to_be_aged.next;
-		/* fiddling the xpt_list node is safe 'cos we're XPT_DETACHED */
-		list_del_init(le);
-		xprt = list_entry(le, struct svc_xprt, xpt_list);
-
 		dprintk("queuing xprt %p for closing\n", xprt);

 		/* a thread will dequeue and close it soon */
 		svc_xprt_enqueue(xprt);
-		svc_xprt_put(xprt);
 	}
+	spin_unlock_bh(&serv->sv_lock);

 	mod_timer(&serv->sv_temptimer, jiffies + svc_conn_age_period * HZ);
 }
--
1.8.1.2