SUNRPC: Fix the TCP server's send buffer accounting

Currently, the sunrpc server is refusing to allow us to process new RPC
calls if the TCP send buffer is 2/3 full, even if we do actually have
enough free space to guarantee that we can send another request.
The following patch fixes svc_tcp_has_wspace() so that we only stop
processing requests if we know that the socket buffer cannot possibly fit
another reply.

It also fixes the tcp write_space() callback so that we only clear the
SOCK_NOSPACE flag when the TCP send buffer is less than 2/3 full.
This should ensure that the send window will grow as per the standard TCP
socket code.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 18 insertions, 17 deletions

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 004a2f9dc432..b09c80c56ee3 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -380,6 +380,7 @@ static void svc_sock_setbufsize(struct socket *sock, unsigned int snd,
         sock->sk->sk_sndbuf = snd * 2;
         sock->sk->sk_rcvbuf = rcv * 2;
         sock->sk->sk_userlocks |= SOCK_SNDBUF_LOCK|SOCK_RCVBUF_LOCK;
+        sock->sk->sk_write_space(sock->sk);
         release_sock(sock->sk);
 #endif
 }
@@ -421,6 +422,15 @@ static void svc_write_space(struct sock *sk)
         }
 }
 
+static void svc_tcp_write_space(struct sock *sk)
+{
+        struct socket *sock = sk->sk_socket;
+
+        if (sk_stream_wspace(sk) >= sk_stream_min_wspace(sk) && sock)
+                clear_bit(SOCK_NOSPACE, &sock->flags);
+        svc_write_space(sk);
+}
+
 /*
  * Copy the UDP datagram's destination address to the rqstp structure.
  * The 'destination' address in this case is the address to which the
@@ -1015,25 +1025,16 @@ static void svc_tcp_prep_reply_hdr(struct svc_rqst *rqstp)
 static int svc_tcp_has_wspace(struct svc_xprt *xprt)
 {
         struct svc_sock *svsk = container_of(xprt, struct svc_sock, sk_xprt);
-        struct svc_serv *serv = svsk->sk_xprt.xpt_server;
+        struct svc_serv *serv = svsk->sk_xprt.xpt_server;
         int required;
-        int wspace;
 
-        /*
-         * Set the SOCK_NOSPACE flag before checking the available
-         * sock space.
-         */
+        if (test_bit(XPT_LISTENER, &xprt->xpt_flags))
+                return 1;
+        required = atomic_read(&xprt->xpt_reserved) + serv->sv_max_mesg;
+        if (sk_stream_wspace(svsk->sk_sk) >= required)
+                return 1;
         set_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);
-        required = atomic_read(&svsk->sk_xprt.xpt_reserved) + serv->sv_max_mesg;
-        wspace = sk_stream_wspace(svsk->sk_sk);
-
-        if (wspace < sk_stream_min_wspace(svsk->sk_sk))
-                return 0;
-        if (required * 2 > wspace)
-                return 0;
-
-        clear_bit(SOCK_NOSPACE, &svsk->sk_sock->flags);
-        return 1;
+        return 0;
 }
 
 static struct svc_xprt *svc_tcp_create(struct svc_serv *serv,
@@ -1089,7 +1090,7 @@ static void svc_tcp_init(struct svc_sock *svsk, struct svc_serv *serv)
                 dprintk("setting up TCP socket for reading\n");
                 sk->sk_state_change = svc_tcp_state_change;
                 sk->sk_data_ready = svc_tcp_data_ready;
-                sk->sk_write_space = svc_write_space;
+                sk->sk_write_space = svc_tcp_write_space;
 
                 svsk->sk_reclen = 0;
                 svsk->sk_tcplen = 0;