net: sk_sleep() helper

Define a new function to return the waitqueue of a "struct sock".

static inline wait_queue_head_t *sk_sleep(struct sock *sk)
{
	return sk->sk_sleep;
}

Change all read occurrences of sk_sleep by a call to this function.

Needed for a future RCU conversion. sk_sleep wont be a field directly
available.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/rds/send.c b/net/rds/send.c
index 53d6795..9c1c6bc 100644
--- a/net/rds/send.c
+++ b/net/rds/send.c
@@ -915,7 +915,7 @@
 			goto out;
 		}
 
-		timeo = wait_event_interruptible_timeout(*sk->sk_sleep,
+		timeo = wait_event_interruptible_timeout(*sk_sleep(sk),
 					rds_send_queue_rm(rs, conn, rm,
 							  rs->rs_bound_port,
 							  dport,