libceph: tcp_nodelay support

TCP_NODELAY socket option set on connection sockets,
disables Nagle’s algorithm and improves latency characteristics.
tcp_nodelay(default)/notcp_nodelay option flags provided to
enable/disable setting the socket option.

Signed-off-by: Chaitanya Huilgol <chaitanya.huilgol@sandisk.com>
[idryomov@redhat.com: NO_TCP_NODELAY -> TCP_NODELAY, minor adjustments]
Signed-off-by: Ilya Dryomov <idryomov@redhat.com>

include/linux/ceph/libceph.h

@@ -30,8 +30,9 @@
 #define CEPH_OPT_MYIP             (1<<2) /* specified my ip */
 #define CEPH_OPT_NOCRC            (1<<3) /* no data crc on writes */
 #define CEPH_OPT_NOMSGAUTH	  (1<<4) /* not require cephx message signature */
+#define CEPH_OPT_TCP_NODELAY	  (1<<5) /* TCP_NODELAY on TCP sockets */
 
-#define CEPH_OPT_DEFAULT   (0)
+#define CEPH_OPT_DEFAULT   (CEPH_OPT_TCP_NODELAY)
 
 #define ceph_set_opt(client, opt) \
 	(client)->options->flags |= CEPH_OPT_##opt;

include/linux/ceph/messenger.h

@@ -57,6 +57,7 @@ struct ceph_messenger {
 
 	atomic_t stopping;
 	bool nocrc;
+	bool tcp_nodelay;
 
 	/*
 	 * the global_seq counts connections i (attempt to) initiate
@@ -264,7 +265,8 @@ extern void ceph_messenger_init(struct ceph_messenger *msgr,
 			struct ceph_entity_addr *myaddr,
 			u64 supported_features,
 			u64 required_features,
-			bool nocrc);
+			bool nocrc,
+			bool tcp_nodelay);
 
 extern void ceph_con_init(struct ceph_connection *con, void *private,
 			const struct ceph_connection_operations *ops,