SUNRPC: Fix suspicious enobufs issues.

The current test is racy when dealing with fast NICs.

Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>

1 files changed, 25 insertions, 6 deletions

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 646170d0cb86..6b3efeb3edc5 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -642,6 +642,7 @@ static int xs_tcp_send_request(struct rpc_task *task)
         struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
         struct xdr_buf *xdr = &req->rq_snd_buf;
         bool zerocopy = true;
+        bool vm_wait = false;
         int status;
         int sent;
 
@@ -677,15 +678,33 @@ static int xs_tcp_send_request(struct rpc_task *task)
                         return 0;
                 }
 
+                WARN_ON_ONCE(sent == 0 && status == 0);
+
+                if (status == -EAGAIN ) {
+                        /*
+                         * Return EAGAIN if we're sure we're hitting the
+                         * socket send buffer limits.
+                         */
+                        if (test_bit(SOCK_NOSPACE, &transport->sock->flags))
+                                break;
+                        /*
+                         * Did we hit a memory allocation failure?
+                         */
+                        if (sent == 0) {
+                                status = -ENOBUFS;
+                                if (vm_wait)
+                                        break;
+                                /* Retry, knowing now that we're below the
+                                 * socket send buffer limit
+                                 */
+                                vm_wait = true;
+                        }
+                        continue;
+                }
                 if (status < 0)
                         break;
-                if (sent == 0) {
-                        status = -EAGAIN;
-                        break;
-                }
+                vm_wait = false;
         }
-        if (status == -EAGAIN && sk_stream_is_writeable(transport->inet))
-                status = -ENOBUFS;
 
         switch (status) {
         case -ENOTSOCK: