On Wed, 2008-10-08 at 11:47 -0400, Tom Talpey wrote:
> From: Tom Tucker <talpey@xxxxxxxxxx>
Now I'm really confused!
> 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@xxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Tom Talpey <talpey@xxxxxxxxxx>
> ---
>
> net/sunrpc/xprtrdma/verbs.c | 51 ++++++++++++-------------------------------
> 1 files changed, 14 insertions(+), 37 deletions(-)
>
> diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
> index 39a1652..e3fe905 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__);
>
> --
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