2008-05-05 19:31:41

by [email protected]

[permalink] [raw]
Subject: Re: [PATCH 1/17] svcrdma: Simplify receive buffer posting

On Fri, May 02, 2008 at 11:28:27AM -0500, Tom Tucker wrote:
> The svcrdma transport provider currently allocates receive buffers
> to the RQ through the xpo_release_rqst method. This approach is overly
> complicated since it means that the rqstp rq_xprt_ctxt has to be
> selectively set based on whether the RPC is going to be processed
> immediately or deferred. Instead, just post the receive buffer when
> we are certain that we are replying in the send_reply function.

Makes sense to me. But, by the way:

> index af408fc..1e0af2f 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
> @@ -910,27 +910,8 @@ static struct svc_xprt *svc_rdma_accept(struct svc_xprt *xprt)
> return NULL;
> }
>
> -/*
> - * Post an RQ WQE to the RQ when the rqst is being released. This
> - * effectively returns an RQ credit to the client. The rq_xprt_ctxt
> - * will be null if the request is deferred due to an RDMA_READ or the
> - * transport had no data ready (EAGAIN). Note that an RPC deferred in
> - * svc_process will still return the credit, this is because the data
> - * is copied and no longer consume a WQE/WC.
> - */
> static void svc_rdma_release_rqst(struct svc_rqst *rqstp)
> {
> - int err;
> - struct svcxprt_rdma *rdma =
> - container_of(rqstp->rq_xprt, struct svcxprt_rdma, sc_xprt);
> - if (rqstp->rq_xprt_ctxt) {
> - BUG_ON(rqstp->rq_xprt_ctxt != rdma);
> - err = svc_rdma_post_recv(rdma);
> - if (err)
> - dprintk("svcrdma: failed to post an RQ WQE error=%d\n",
> - err);
> - }
> - rqstp->rq_xprt_ctxt = NULL;
> }

Why is it that the svcsock equivalent (svc_release_skb) frees
rqstp->rq_deferred, but this doesn't? Don't we need to free that in the
rdma case too?

--b.