RPC/RDMA: fix connection IRD/ORD setting

This logic sets the connection parameter that configures the local device
and informs the remote peer how many concurrent incoming RDMA_READ
requests are supported. The original logic didn't really do what was
intended for two reasons:

- The max number supported by the device is typically smaller than
any one factor in the calculation used, and

- The field in the connection parameter structure where the value is
stored is a u8 and always overflows for the default settings.

So what really happens is the value requested for responder resources
is the left over 8 bits from the "desired value". If the desired value
happened to be a multiple of 256, the result was zero and it wouldn't
connect at all.

Given the above and the fact that max_requests is almost always larger
than the max responder resources supported by the adapter, this patch
simplifies this logic and simply requests the max supported by the device,
subject to a reasonable limit.

This bug was found by Jim Schutt at Sandia.

Signed-off-by: Tom Tucker <tom@opengridcomputing.com>
Acked-by: Tom Talpey <talpey@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 14 insertions, 37 deletions

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 39a165202d8f..e3fe9054fef6 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -705,30 +705,13 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia,
         ep->rep_remote_cma.private_data_len = 0;
 
         /* Client offers RDMA Read but does not initiate */
-        switch (ia->ri_memreg_strategy) {
-        case RPCRDMA_BOUNCEBUFFERS:
+        ep->rep_remote_cma.initiator_depth = 0;
+        if (ia->ri_memreg_strategy == RPCRDMA_BOUNCEBUFFERS)
                 ep->rep_remote_cma.responder_resources = 0;
-                break;
-        case RPCRDMA_MTHCAFMR:
-        case RPCRDMA_REGISTER:
-        case RPCRDMA_FRMR:
-                ep->rep_remote_cma.responder_resources = cdata->max_requests *
-                                (RPCRDMA_MAX_DATA_SEGS / 8);
-                break;
-        case RPCRDMA_MEMWINDOWS:
-        case RPCRDMA_MEMWINDOWS_ASYNC:
-#if RPCRDMA_PERSISTENT_REGISTRATION
-        case RPCRDMA_ALLPHYSICAL:
-#endif
-                ep->rep_remote_cma.responder_resources = cdata->max_requests *
-                                (RPCRDMA_MAX_DATA_SEGS / 2);
-                break;
-        default:
-                break;
-        }
-        if (ep->rep_remote_cma.responder_resources > devattr.max_qp_rd_atom)
+        else if (devattr.max_qp_rd_atom > 32)   /* arbitrary but <= 255 */
+                ep->rep_remote_cma.responder_resources = 32;
+        else
                 ep->rep_remote_cma.responder_resources = devattr.max_qp_rd_atom;
-        ep->rep_remote_cma.initiator_depth = 0;
 
         ep->rep_remote_cma.retry_count = 7;
         ep->rep_remote_cma.flow_control = 0;
@@ -858,14 +841,6 @@ if (strnicmp(ia->ri_id->device->dma_device->bus->name, "pci", 3) == 0) {
         }
 }
 
-        /* Theoretically a client initiator_depth > 0 is not needed,
-         * but many peers fail to complete the connection unless they
-         * == responder_resources! */
-        if (ep->rep_remote_cma.initiator_depth !=
-                                ep->rep_remote_cma.responder_resources)
-                ep->rep_remote_cma.initiator_depth =
-                        ep->rep_remote_cma.responder_resources;
-
         ep->rep_connected = 0;
 
         rc = rdma_connect(ia->ri_id, &ep->rep_remote_cma);
@@ -894,14 +869,16 @@ if (strnicmp(ia->ri_id->device->dma_device->bus->name, "pci", 3) == 0) {
         if (ep->rep_connected <= 0) {
                 /* Sometimes, the only way to reliably connect to remote
                  * CMs is to use same nonzero values for ORD and IRD. */
-                ep->rep_remote_cma.initiator_depth =
-                                        ep->rep_remote_cma.responder_resources;
-                if (ep->rep_remote_cma.initiator_depth == 0)
-                        ++ep->rep_remote_cma.initiator_depth;
-                if (ep->rep_remote_cma.responder_resources == 0)
-                        ++ep->rep_remote_cma.responder_resources;
-                if (retry_count++ == 0)
+                if (retry_count++ <= RDMA_CONNECT_RETRY_MAX + 1 &&
+                    (ep->rep_remote_cma.responder_resources == 0 ||
+                     ep->rep_remote_cma.initiator_depth !=
+                                ep->rep_remote_cma.responder_resources)) {
+                        if (ep->rep_remote_cma.responder_resources == 0)
+                                ep->rep_remote_cma.responder_resources = 1;
+                        ep->rep_remote_cma.initiator_depth =
+                                ep->rep_remote_cma.responder_resources;
                         goto retry;
+                }
                 rc = ep->rep_connected;
         } else {
                 dprintk("RPC:       %s: connected\n", __func__);