net: refactor socket_poll

Factor out two busy poll related helpers for late reuse, and remove
a command that isn't very helpful, especially with the __poll_t
annotations in place.
Signed-off-by: NChristoph Hellwig <hch@lst.de>

include/net/busy_poll.h

@@ -121,6 +121,21 @@ static inline void sk_busy_loop(struct sock *sk, int nonblock)
 #endif
 }
 
+static inline void sock_poll_busy_loop(struct socket *sock, __poll_t events)
+{
+	if (sk_can_busy_loop(sock->sk) &&
+	    events && (events & POLL_BUSY_LOOP)) {
+		/* once, only if requested by syscall */
+		sk_busy_loop(sock->sk, 1);
+	}
+}
+
+/* if this socket can poll_ll, tell the system call */
+static inline __poll_t sock_poll_busy_flag(struct socket *sock)
+{
+	return sk_can_busy_loop(sock->sk) ? POLL_BUSY_LOOP : 0;
+}
+
 /* used in the NIC receive handler to mark the skb */
 static inline void skb_mark_napi_id(struct sk_buff *skb,
 				    struct napi_struct *napi)

net/socket.c

@@ -1117,24 +1117,11 @@ EXPORT_SYMBOL(sock_create_lite);
 /* No kernel lock held - perfect */
 static __poll_t sock_poll(struct file *file, poll_table *wait)
 {
-	__poll_t busy_flag = 0;
-	struct socket *sock;
-
-	/*
-	 *      We can't return errors to poll, so it's either yes or no.
-	 */
-	sock = file->private_data;
-
-	if (sk_can_busy_loop(sock->sk)) {
-		/* this socket can poll_ll so tell the system call */
-		busy_flag = POLL_BUSY_LOOP;
-
-		/* once, only if requested by syscall */
-		if (wait && (wait->_key & POLL_BUSY_LOOP))
-			sk_busy_loop(sock->sk, 1);
-	}
+	struct socket *sock = file->private_data;
+	__poll_t events = poll_requested_events(wait);
 
-	return busy_flag | sock->ops->poll(file, sock, wait);
+	sock_poll_busy_loop(sock, events);
+	return sock->ops->poll(file, sock, wait) | sock_poll_busy_flag(sock);
 }
 
 static int sock_mmap(struct file *file, struct vm_area_struct *vma)