[PATCH] RPC: separate TCP and UDP socket write paths

 Split the RPC client's main socket write path into a TCP version and a UDP
 version to eliminate another dependency on the "xprt->stream" variable.

 Compiler optimization removes unneeded code from xs_sendpages, as this
 function is now called with some constant arguments.

 We can now cleanly perform transport protocol-specific return code testing
 and error recovery in each path.

 Test-plan:
 Millions of fsx operations.  Performance characterization such as
 "sio" or "iozone".  Examine oprofile results for any changes before and
 after this patch is applied.

 Version: Thu, 11 Aug 2005 16:08:46 -0400

 Signed-off-by: Chuck Lever <cel@netapp.com>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 128 insertions, 87 deletions

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index f91529787b9b..57988300640a 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -40,6 +40,12 @@
  */
 #define XS_MAX_RESVPORT         (800U)
 
+/*
+ * How many times to try sending a request on a socket before waiting
+ * for the socket buffer to clear.
+ */
+#define XS_SENDMSG_RETRY        (10U)
+
 #ifdef RPC_DEBUG
 # undef  RPC_DEBUG_DATA
 # define RPCDBG_FACILITY        RPCDBG_TRANS
@@ -114,13 +120,18 @@ static int xs_send_tail(struct socket *sock, struct xdr_buf *xdr, unsigned int b
  * @base: starting position in the buffer
  *
  */
-static int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base)
+static inline int xs_sendpages(struct socket *sock, struct sockaddr *addr, int addrlen, struct xdr_buf *xdr, unsigned int base)
 {
         struct page **ppage = xdr->pages;
         unsigned int len, pglen = xdr->page_len;
         int err, ret = 0;
         ssize_t (*sendpage)(struct socket *, struct page *, int, size_t, int);
 
+        if (unlikely(!sock))
+                return -ENOTCONN;
+
+        clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
+
         len = xdr->head[0].iov_len;
         if (base < len || (addr != NULL && base == 0)) {
                 err = xs_send_head(sock, addr, addrlen, xdr, base, len);
@@ -187,140 +198,162 @@ out:
 }
 
 /**
- * xs_sendmsg - write an RPC request to a socket
- * @xprt: generic transport
- * @req: the RPC request to write
+ * xs_nospace - place task on wait queue if transmit was incomplete
+ * @task: task to put to sleep
  *
  */
-static int xs_sendmsg(struct rpc_xprt *xprt, struct rpc_rqst *req)
+static void xs_nospace(struct rpc_task *task)
 {
-        struct socket *sock = xprt->sock;
-        struct xdr_buf *xdr = &req->rq_snd_buf;
-        struct sockaddr *addr = NULL;
-        int addrlen = 0;
-        unsigned int skip;
-        int result;
+        struct rpc_rqst *req = task->tk_rqstp;
+        struct rpc_xprt *xprt = req->rq_xprt;
 
-        if (!sock)
-                return -ENOTCONN;
+        dprintk("RPC: %4d xmit incomplete (%u left of %u)\n",
+                        task->tk_pid, req->rq_slen - req->rq_bytes_sent,
+                        req->rq_slen);
+
+        if (test_bit(SOCK_ASYNC_NOSPACE, &xprt->sock->flags)) {
+                /* Protect against races with write_space */
+                spin_lock_bh(&xprt->transport_lock);
+
+                /* Don't race with disconnect */
+                if (!xprt_connected(xprt))
+                        task->tk_status = -ENOTCONN;
+                else if (test_bit(SOCK_NOSPACE, &xprt->sock->flags))
+                        xprt_wait_for_buffer_space(task);
+
+                spin_unlock_bh(&xprt->transport_lock);
+        } else
+                /* Keep holding the socket if it is blocked */
+                rpc_delay(task, HZ>>4);
+}
+
+/**
+ * xs_udp_send_request - write an RPC request to a UDP socket
+ * @task: address of RPC task that manages the state of an RPC request
+ *
+ * Return values:
+ *        0:    The request has been sent
+ *   EAGAIN:    The socket was blocked, please call again later to
+ *              complete the request
+ * ENOTCONN:    Caller needs to invoke connect logic then call again
+ *    other:    Some other error occured, the request was not sent
+ */
+static int xs_udp_send_request(struct rpc_task *task)
+{
+        struct rpc_rqst *req = task->tk_rqstp;
+        struct rpc_xprt *xprt = req->rq_xprt;
+        struct xdr_buf *xdr = &req->rq_snd_buf;
+        int status;
 
         xs_pktdump("packet data:",
                                 req->rq_svec->iov_base,
                                 req->rq_svec->iov_len);
 
-        /* For UDP, we need to provide an address */
-        if (!xprt->stream) {
-                addr = (struct sockaddr *) &xprt->addr;
-                addrlen = sizeof(xprt->addr);
-        }
-        /* Don't repeat bytes */
-        skip = req->rq_bytes_sent;
+        req->rq_xtime = jiffies;
+        status = xs_sendpages(xprt->sock, (struct sockaddr *) &xprt->addr,
+                                sizeof(xprt->addr), xdr, req->rq_bytes_sent);
 
-        clear_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
-        result = xs_sendpages(sock, addr, addrlen, xdr, skip);
+        dprintk("RPC:      xs_udp_send_request(%u) = %d\n",
+                        xdr->len - req->rq_bytes_sent, status);
 
-        dprintk("RPC:      xs_sendmsg(%d) = %d\n", xdr->len - skip, result);
+        if (likely(status >= (int) req->rq_slen))
+                return 0;
 
-        if (result >= 0)
-                return result;
+        /* Still some bytes left; set up for a retry later. */
+        if (status > 0)
+                status = -EAGAIN;
 
-        switch (result) {
+        switch (status) {
+        case -ENETUNREACH:
+        case -EPIPE:
         case -ECONNREFUSED:
                 /* When the server has died, an ICMP port unreachable message
                  * prompts ECONNREFUSED. */
-        case -EAGAIN:
                 break;
-        case -ECONNRESET:
-        case -ENOTCONN:
-        case -EPIPE:
-                /* connection broken */
-                if (xprt->stream)
-                        result = -ENOTCONN;
+        case -EAGAIN:
+                xs_nospace(task);
                 break;
         default:
+                dprintk("RPC:      sendmsg returned unrecognized error %d\n",
+                        -status);
                 break;
         }
-        return result;
+
+        return status;
 }
 
 /**
- * xs_send_request - write an RPC request to a socket
+ * xs_tcp_send_request - write an RPC request to a TCP socket
  * @task: address of RPC task that manages the state of an RPC request
  *
  * Return values:
- *      0:  The request has been sent
- * EAGAIN:  The socket was blocked, please call again later to
- *          complete the request
- *  other:  Some other error occured, the request was not sent
+ *        0:    The request has been sent
+ *   EAGAIN:    The socket was blocked, please call again later to
+ *              complete the request
+ * ENOTCONN:    Caller needs to invoke connect logic then call again
+ *    other:    Some other error occured, the request was not sent
  *
  * XXX: In the case of soft timeouts, should we eventually give up
- *      if the socket is not able to make progress?
+ *      if sendmsg is not able to make progress?
  */
-static int xs_send_request(struct rpc_task *task)
+static int xs_tcp_send_request(struct rpc_task *task)
 {
         struct rpc_rqst *req = task->tk_rqstp;
         struct rpc_xprt *xprt = req->rq_xprt;
+        struct xdr_buf *xdr = &req->rq_snd_buf;
+        u32 *marker = req->rq_svec[0].iov_base;
         int status, retry = 0;
 
-        /* set up everything as needed. */
         /* Write the record marker */
-        if (xprt->stream) {
-                u32 *marker = req->rq_svec[0].iov_base;
+        *marker = htonl(0x80000000|(req->rq_slen-sizeof(*marker)));
 
-                *marker = htonl(0x80000000|(req->rq_slen-sizeof(*marker)));
-        }
+        xs_pktdump("packet data:",
+                                req->rq_svec->iov_base,
+                                req->rq_svec->iov_len);
 
         /* Continue transmitting the packet/record. We must be careful
          * to cope with writespace callbacks arriving _after_ we have
-         * called sendmsg().
-         */
+         * called sendmsg(). */
         while (1) {
                 req->rq_xtime = jiffies;
-                status = xs_sendmsg(xprt, req);
+                status = xs_sendpages(xprt->sock, NULL, 0, xdr,
+                                                req->rq_bytes_sent);
 
-                if (status < 0)
-                        break;
+                dprintk("RPC:      xs_tcp_send_request(%u) = %d\n",
+                                xdr->len - req->rq_bytes_sent, status);
 
-                if (xprt->stream) {
-                        req->rq_bytes_sent += status;
-
-                        /* If we've sent the entire packet, immediately
-                         * reset the count of bytes sent. */
-                        if (req->rq_bytes_sent >= req->rq_slen) {
-                                req->rq_bytes_sent = 0;
-                                return 0;
-                        }
-                } else {
-                        if (status >= req->rq_slen)
-                                return 0;
-                        status = -EAGAIN;
+                if (unlikely(status < 0))
                         break;
-                }
 
-                dprintk("RPC: %4d xmit incomplete (%d left of %d)\n",
-                                task->tk_pid, req->rq_slen - req->rq_bytes_sent,
-                                req->rq_slen);
+                /* If we've sent the entire packet, immediately
+                 * reset the count of bytes sent. */
+                req->rq_bytes_sent += status;
+                if (likely(req->rq_bytes_sent >= req->rq_slen)) {
+                        req->rq_bytes_sent = 0;
+                        return 0;
+                }
 
                 status = -EAGAIN;
-                if (retry++ > 50)
+                if (retry++ > XS_SENDMSG_RETRY)
                         break;
         }
 
-        if (status == -EAGAIN) {
-                if (test_bit(SOCK_ASYNC_NOSPACE, &xprt->sock->flags)) {
-                        /* Protect against races with write_space */
-                        spin_lock_bh(&xprt->transport_lock);
-                        /* Don't race with disconnect */
-                        if (!xprt_connected(xprt))
-                                task->tk_status = -ENOTCONN;
-                        else if (test_bit(SOCK_NOSPACE, &xprt->sock->flags))
-                                xprt_wait_for_buffer_space(task);
-                        spin_unlock_bh(&xprt->transport_lock);
-                        return status;
-                }
-                /* Keep holding the socket if it is blocked */
-                rpc_delay(task, HZ>>4);
+        switch (status) {
+        case -EAGAIN:
+                xs_nospace(task);
+                break;
+        case -ECONNREFUSED:
+        case -ECONNRESET:
+        case -ENOTCONN:
+        case -EPIPE:
+                status = -ENOTCONN;
+                break;
+        default:
+                dprintk("RPC:      sendmsg returned unrecognized error %d\n",
+                        -status);
+                break;
         }
+
         return status;
 }
 
@@ -992,10 +1025,18 @@ static void xs_connect(struct rpc_task *task)
         }
 }
 
-static struct rpc_xprt_ops xs_ops = {
+static struct rpc_xprt_ops xs_udp_ops = {
+        .set_buffer_size        = xs_set_buffer_size,
+        .connect                = xs_connect,
+        .send_request           = xs_udp_send_request,
+        .close                  = xs_close,
+        .destroy                = xs_destroy,
+};
+
+static struct rpc_xprt_ops xs_tcp_ops = {
         .set_buffer_size        = xs_set_buffer_size,
         .connect                = xs_connect,
-        .send_request           = xs_send_request,
+        .send_request           = xs_tcp_send_request,
         .close                  = xs_close,
         .destroy                = xs_destroy,
 };
@@ -1033,7 +1074,7 @@ int xs_setup_udp(struct rpc_xprt *xprt, struct rpc_timeout *to)
 
         INIT_WORK(&xprt->connect_worker, xs_udp_connect_worker, xprt);
 
-        xprt->ops = &xs_ops;
+        xprt->ops = &xs_udp_ops;
 
         if (to)
                 xprt->timeout = *to;
@@ -1072,7 +1113,7 @@ int xs_setup_tcp(struct rpc_xprt *xprt, struct rpc_timeout *to)
 
         INIT_WORK(&xprt->connect_worker, xs_tcp_connect_worker, xprt);
 
-        xprt->ops = &xs_ops;
+        xprt->ops = &xs_tcp_ops;
 
         if (to)
                 xprt->timeout = *to;