[PATCH] Rearrange setting of snd/rcv buf size to avoid locking issue

Currently svc_sock_setbuf can be called under a spinlock,
but it can try to lock a socket, which can block....

Now when we decide that changing the size might be good we
set a flag (SK_CHNGBUF) and then later (when the next
packet arrives) we change the sizes appropriately.

include/linux/sunrpc/svcsock.h

@@ -30,6 +30,7 @@ struct svc_sock {
 #define	SK_TEMP		4			/* temp (TCP) socket */
 #define	SK_QUED		5			/* on serv->sk_sockets */
 #define	SK_DEAD		6			/* socket closed */
+#define	SK_CHNGBUF	7			/* need to change snd/rcv buffer sizes */
 
 	int			sk_reserved;	/* space on outq that is reserved */
 

net/sunrpc/svcsock.c

@@ -481,6 +481,16 @@ svc_udp_recvfrom(struct svc_rqst *rqstp)
 	u32		*data;
 	int		err, len;
 
+	if (test_and_clear_bit(SK_CHNGBUF, &svsk->sk_flags))
+	    /* udp sockets need large rcvbuf as all pending
+	     * requests are still in that buffer.  sndbuf must
+	     * also be large enough that there is enough space
+	     * for one reply per thread.
+	     */
+	    svc_sock_setbufsize(svsk->sk_sock,
+				(serv->sv_nrthreads+3) * serv->sv_bufsz,
+				(serv->sv_nrthreads+3) * serv->sv_bufsz);
+
 	clear_bit(SK_DATA, &svsk->sk_flags);
 	while ((skb = skb_recv_datagram(svsk->sk_sk, 0, 1, &err)) == NULL) {
 		svc_sock_received(svsk);
@@ -564,6 +574,8 @@ svc_udp_init(struct svc_sock *svsk)
 	svsk->sk_recvfrom = svc_udp_recvfrom;
 	svsk->sk_sendto = svc_udp_sendto;
 
+	set_bit(SK_CHNGBUF, &svsk->sk_flags);
+
 	return 0;
 }
 
@@ -771,6 +783,18 @@ svc_tcp_recvfrom(struct svc_rqst *rqstp)
 		return 0;
 	}
 
+	if (test_and_clear_bit(SK_CHNGBUF, &svsk->sk_flags))
+		/* sndbuf needs to have room for one request
+		 * per thread, otherwise we can stall even when the
+		 * network isn't a bottleneck.
+		 * rcvbuf just needs to be able to hold a few requests.
+		 * Normally they will be removed from the queue 
+		 * as soon a a complete request arrives.
+		 */
+		svc_sock_setbufsize(svsk->sk_sock,
+				    (serv->sv_nrthreads+3) * serv->sv_bufsz,
+				    3 * serv->sv_bufsz);
+
 	clear_bit(SK_DATA, &svsk->sk_flags);
 
 	/* Receive data. If we haven't got the record length yet, get
@@ -916,17 +940,7 @@ svc_tcp_init(struct svc_sock *svsk)
 		svsk->sk_reclen = 0;
 		svsk->sk_tcplen = 0;
 
-		/* sndbuf needs to have room for one request
-		 * per thread, otherwise we can stall even when the
-		 * network isn't a bottleneck.
-		 * rcvbuf just needs to be able to hold a few requests.
-		 * Normally they will be removed from the queue 
-		 * as soon a a complete request arrives.
-		 */
-		svc_sock_setbufsize(svsk->sk_sock,
-				    (svsk->sk_server->sv_nrthreads+3) *
-				    svsk->sk_server->sv_bufsz,
-				    3 * svsk->sk_server->sv_bufsz);
+		set_bit(SK_CHNGBUF, &svsk->sk_flags);
 	}
 
 	return 0;
@@ -945,30 +959,12 @@ svc_sock_update_bufs(struct svc_serv *serv)
 	list_for_each(le, &serv->sv_permsocks) {
 		struct svc_sock *svsk = 
 			list_entry(le, struct svc_sock, sk_list);
-		struct socket *sock = svsk->sk_sock;
-		if (sock->type == SOCK_DGRAM) {
-			/* udp sockets need large rcvbuf as all pending
-			 * requests are still in that buffer.
-			 */
-			svc_sock_setbufsize(sock,
-					    (serv->sv_nrthreads+3) * serv->sv_bufsz,
-					    (serv->sv_nrthreads+3) * serv->sv_bufsz);
-		} else if (svsk->sk_sk->state != TCP_LISTEN) {
-			printk(KERN_ERR "RPC update_bufs: permanent sock neither UDP or TCP_LISTEN\n");
-		}
+		set_bit(SK_CHNGBUF, &svsk->sk_flags);
 	}
 	list_for_each(le, &serv->sv_tempsocks) {
 		struct svc_sock *svsk =
 			list_entry(le, struct svc_sock, sk_list);
-		struct socket *sock = svsk->sk_sock;
-		if (sock->type == SOCK_STREAM) {
-			/* See svc_tcp_init above for rationale on buffer sizes */
-			svc_sock_setbufsize(sock,
-					    (serv->sv_nrthreads+3) *
-					    serv->sv_bufsz,
-					    3 * serv->sv_bufsz);
-		} else 
-			printk(KERN_ERR "RPC update_bufs: temp sock not TCP\n");
+		set_bit(SK_CHNGBUF, &svsk->sk_flags);
 	}
 	spin_unlock_bh(&serv->sv_lock);
 }