ipvs: convert app locks

We use locks like tcp_app_lock, udp_app_lock,
sctp_app_lock to protect access to the protocol hash tables
from readers in packet context while the application
instances (inc) are [un]registered under global mutex.

As the hash tables are mostly read when conns are
created and bound to app, use RCU for readers and reclaim
app instance after grace period.

Simplify ip_vs_app_inc_get because we use usecnt
only for statistics and rely on module refcounting.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off by: Hans Schillstrom <hans@schillstrom.com>
Signed-off-by: Simon Horman <horms@verge.net.au>
diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index a150ff5..84ca171 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -823,6 +823,7 @@
 	struct ip_vs_app	*app;		/* its real application */
 	__be16			port;		/* port number in net order */
 	atomic_t		usecnt;		/* usage counter */
+	struct rcu_head		rcu_head;
 
 	/*
 	 * output hook: Process packet in inout direction, diff set for TCP.
@@ -908,7 +909,6 @@
 	#define	TCP_APP_TAB_SIZE	(1 << TCP_APP_TAB_BITS)
 	#define	TCP_APP_TAB_MASK	(TCP_APP_TAB_SIZE - 1)
 	struct list_head	tcp_apps[TCP_APP_TAB_SIZE];
-	spinlock_t		tcp_app_lock;
 #endif
 	/* ip_vs_proto_udp */
 #ifdef CONFIG_IP_VS_PROTO_UDP
@@ -916,7 +916,6 @@
 	#define	UDP_APP_TAB_SIZE	(1 << UDP_APP_TAB_BITS)
 	#define	UDP_APP_TAB_MASK	(UDP_APP_TAB_SIZE - 1)
 	struct list_head	udp_apps[UDP_APP_TAB_SIZE];
-	spinlock_t		udp_app_lock;
 #endif
 	/* ip_vs_proto_sctp */
 #ifdef CONFIG_IP_VS_PROTO_SCTP
@@ -925,7 +924,6 @@
 	#define SCTP_APP_TAB_MASK	(SCTP_APP_TAB_SIZE - 1)
 	/* Hash table for SCTP application incarnations	 */
 	struct list_head	sctp_apps[SCTP_APP_TAB_SIZE];
-	spinlock_t		sctp_app_lock;
 #endif
 	/* ip_vs_conn */
 	atomic_t		conn_count;      /*  connection counter */