net: add socket option for low latency polling

adds a socket option for low latency polling.
This allows overriding the global sysctl value with a per-socket one.
Unexport sysctl_net_ll_poll since for now it's not needed in modules.
Signed-off-by: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/alpha/include/uapi/asm/socket.h

@@ -81,4 +81,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* _UAPI_ASM_SOCKET_H */

arch/avr32/include/uapi/asm/socket.h

@@ -74,4 +74,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* __ASM_AVR32_SOCKET_H */

arch/cris/include/uapi/asm/socket.h

@@ -76,6 +76,8 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* _ASM_SOCKET_H */
 
 

arch/frv/include/uapi/asm/socket.h

@@ -74,5 +74,7 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* _ASM_SOCKET_H */
 

arch/h8300/include/uapi/asm/socket.h

@@ -74,4 +74,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* _ASM_SOCKET_H */

arch/ia64/include/uapi/asm/socket.h

@@ -83,4 +83,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* _ASM_IA64_SOCKET_H */

arch/m32r/include/uapi/asm/socket.h

@@ -74,4 +74,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* _ASM_M32R_SOCKET_H */

arch/mips/include/uapi/asm/socket.h

@@ -92,4 +92,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* _UAPI_ASM_SOCKET_H */

arch/mn10300/include/uapi/asm/socket.h

@@ -74,4 +74,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* _ASM_SOCKET_H */

arch/parisc/include/uapi/asm/socket.h

@@ -73,6 +73,8 @@
 
 #define SO_SELECT_ERR_QUEUE	0x4026
 
+#define SO_LL			0x4027
+
 /* O_NONBLOCK clashes with the bits used for socket types.  Therefore we
  * have to define SOCK_NONBLOCK to a different value here.
  */

arch/powerpc/include/uapi/asm/socket.h

@@ -81,4 +81,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif	/* _ASM_POWERPC_SOCKET_H */

arch/s390/include/uapi/asm/socket.h

@@ -80,4 +80,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* _ASM_SOCKET_H */

arch/sparc/include/uapi/asm/socket.h

@@ -70,6 +70,8 @@
 
 #define SO_SELECT_ERR_QUEUE	0x0029
 
+#define SO_LL			0x0030
+
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION		0x5001
 #define SO_SECURITY_ENCRYPTION_TRANSPORT	0x5002

arch/xtensa/include/uapi/asm/socket.h

@@ -85,4 +85,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif	/* _XTENSA_SOCKET_H */

include/net/ll_poll.h

@@ -39,12 +39,12 @@ extern unsigned int sysctl_net_ll_poll __read_mostly;
 /* we can use sched_clock() because we don't care much about precision
  * we only care that the average is bounded
  */
-static inline u64 ll_end_time(void)
+static inline u64 ll_end_time(struct sock *sk)
 {
-	u64 end_time = ACCESS_ONCE(sysctl_net_ll_poll);
+	u64 end_time = ACCESS_ONCE(sk->sk_ll_usec);
 
 	/* we don't mind a ~2.5% imprecision
-	 * sysctl_net_ll_poll is a u_int so this can't overflow
+	 * sk->sk_ll_usec is a u_int so this can't overflow
 	 */
 	end_time = (end_time << 10) + sched_clock();
 
@@ -53,7 +53,7 @@ static inline u64 ll_end_time(void)
 
 static inline bool sk_valid_ll(struct sock *sk)
 {
-	return sysctl_net_ll_poll && sk->sk_napi_id &&
+	return sk->sk_ll_usec && sk->sk_napi_id &&
 	       !need_resched() && !signal_pending(current);
 }
 
@@ -65,7 +65,7 @@ static inline bool can_poll_ll(u64 end_time)
 static inline bool sk_poll_ll(struct sock *sk, int nonblock)
 {
 	const struct net_device_ops *ops;
-	u64 end_time = ll_end_time();
+	u64 end_time = ll_end_time(sk);
 	struct napi_struct *napi;
 	int rc = false;
 
@@ -118,7 +118,7 @@ static inline void sk_mark_ll(struct sock *sk, struct sk_buff *skb)
 
 #else /* CONFIG_NET_LL_RX_POLL */
 
-static inline u64 ll_end_time(void)
+static inline u64 ll_end_time(struct sock *sk)
 {
 	return 0;
 }

include/net/sock.h

@@ -230,6 +230,7 @@ struct cg_proto;
   *	@sk_wmem_queued: persistent queue size
   *	@sk_forward_alloc: space allocated forward
   *	@sk_napi_id: id of the last napi context to receive data for sk
+  *	@sk_ll_usec: usecs to busypoll when there is no data
   *	@sk_allocation: allocation mode
   *	@sk_sndbuf: size of send buffer in bytes
   *	@sk_flags: %SO_LINGER (l_onoff), %SO_BROADCAST, %SO_KEEPALIVE,
@@ -328,6 +329,7 @@ struct sock {
 #endif
 #ifdef CONFIG_NET_LL_RX_POLL
 	unsigned int		sk_napi_id;
+	unsigned int		sk_ll_usec;
 #endif
 	atomic_t		sk_drops;
 	int			sk_rcvbuf;

include/uapi/asm-generic/socket.h

@@ -76,4 +76,6 @@
 
 #define SO_SELECT_ERR_QUEUE	45
 
+#define SO_LL			46
+
 #endif /* __ASM_GENERIC_SOCKET_H */

net/core/sock.c

@@ -913,6 +913,19 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 		sock_valbool_flag(sk, SOCK_SELECT_ERR_QUEUE, valbool);
 		break;
 
+#ifdef CONFIG_NET_LL_RX_POLL
+	case SO_LL:
+		/* allow unprivileged users to decrease the value */
+		if ((val > sk->sk_ll_usec) && !capable(CAP_NET_ADMIN))
+			ret = -EPERM;
+		else {
+			if (val < 0)
+				ret = -EINVAL;
+			else
+				sk->sk_ll_usec = val;
+		}
+		break;
+#endif
 	default:
 		ret = -ENOPROTOOPT;
 		break;
@@ -1170,6 +1183,12 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 		v.val = sock_flag(sk, SOCK_SELECT_ERR_QUEUE);
 		break;
 
+#ifdef CONFIG_NET_LL_RX_POLL
+	case SO_LL:
+		v.val = sk->sk_ll_usec;
+		break;
+#endif
+
 	default:
 		return -ENOPROTOOPT;
 	}
@@ -2288,6 +2307,7 @@ void sock_init_data(struct socket *sock, struct sock *sk)
 
 #ifdef CONFIG_NET_LL_RX_POLL
 	sk->sk_napi_id		=	0;
+	sk->sk_ll_usec		=	sysctl_net_ll_poll;
 #endif
 
 	/*

net/socket.c

@@ -108,7 +108,6 @@
 
 #ifdef CONFIG_NET_LL_RX_POLL
 unsigned int sysctl_net_ll_poll __read_mostly;
-EXPORT_SYMBOL_GPL(sysctl_net_ll_poll);
 #endif
 
 static int sock_no_open(struct inode *irrelevant, struct file *dontcare);