[PATCH] knfsd: use new lock for svc_sock deferred list

Protect the svc_sock->sk_deferred list with a new lock svc_sock->sk_defer_lock
instead of svc_serv->sv_lock.  Using the more fine-grained lock reduces the
number of places we need to take the svc_serv lock.

Signed-off-by: Greg Banks <gnb@melbourne.sgi.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 7 insertions, 6 deletions

diff --git a/include/linux/sunrpc/svcsock.h b/include/linux/sunrpc/svcsock.h
index 17cb834a748c..7766a1001660 100644
--- a/include/linux/sunrpc/svcsock.h
+++ b/include/linux/sunrpc/svcsock.h
@@ -36,6 +36,7 @@ struct svc_sock {
 
         int                     sk_reserved;    /* space on outq that is reserved */
 
+        spinlock_t              sk_defer_lock;  /* protects sk_deferred */
         struct list_head        sk_deferred;    /* deferred requests that need to
                                                  * be revisted */
         struct mutex            sk_mutex;       /* to serialize sending data */
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index d836031e4581..bdb5c2841db7 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -47,6 +47,7 @@
 /* SMP locking strategy:
  *
  *      svc_serv->sv_lock protects most stuff for that service.
+ *      svc_sock->sk_defer_lock protects the svc_sock->sk_deferred list
  *
  *      Some flags can be set to certain values at any time
  *      providing that certain rules are followed:
@@ -1416,6 +1417,7 @@ svc_setup_socket(struct svc_serv *serv, struct socket *sock,
         svsk->sk_server = serv;
         atomic_set(&svsk->sk_inuse, 0);
         svsk->sk_lastrecv = get_seconds();
+        spin_lock_init(&svsk->sk_defer_lock);
         INIT_LIST_HEAD(&svsk->sk_deferred);
         INIT_LIST_HEAD(&svsk->sk_ready);
         mutex_init(&svsk->sk_mutex);
@@ -1594,7 +1596,6 @@ svc_makesock(struct svc_serv *serv, int protocol, unsigned short port)
 static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
 {
         struct svc_deferred_req *dr = container_of(dreq, struct svc_deferred_req, handle);
-        struct svc_serv *serv = dreq->owner;
         struct svc_sock *svsk;
 
         if (too_many) {
@@ -1605,9 +1606,9 @@ static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
         dprintk("revisit queued\n");
         svsk = dr->svsk;
         dr->svsk = NULL;
-        spin_lock_bh(&serv->sv_lock);
+        spin_lock_bh(&svsk->sk_defer_lock);
         list_add(&dr->handle.recent, &svsk->sk_deferred);
-        spin_unlock_bh(&serv->sv_lock);
+        spin_unlock_bh(&svsk->sk_defer_lock);
         set_bit(SK_DEFERRED, &svsk->sk_flags);
         svc_sock_enqueue(svsk);
         svc_sock_put(svsk);
@@ -1667,11 +1668,10 @@ static int svc_deferred_recv(struct svc_rqst *rqstp)
 static struct svc_deferred_req *svc_deferred_dequeue(struct svc_sock *svsk)
 {
         struct svc_deferred_req *dr = NULL;
-        struct svc_serv *serv = svsk->sk_server;
         
         if (!test_bit(SK_DEFERRED, &svsk->sk_flags))
                 return NULL;
-        spin_lock_bh(&serv->sv_lock);
+        spin_lock_bh(&svsk->sk_defer_lock);
         clear_bit(SK_DEFERRED, &svsk->sk_flags);
         if (!list_empty(&svsk->sk_deferred)) {
                 dr = list_entry(svsk->sk_deferred.next,
@@ -1680,6 +1680,6 @@ static struct svc_deferred_req *svc_deferred_dequeue(struct svc_sock *svsk)
                 list_del_init(&dr->handle.recent);
                 set_bit(SK_DEFERRED, &svsk->sk_flags);
         }
-        spin_unlock_bh(&serv->sv_lock);
+        spin_unlock_bh(&svsk->sk_defer_lock);
         return dr;
 }