> On Jan 7, 2017, at 12:17, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>
> Replace C structure-based XDR decoding with pointer arithmetic.
> Pointer arithmetic is considered more portable.
>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> include/linux/sunrpc/svc_rdma.h | 2 +-
> net/sunrpc/xprtrdma/svc_rdma_backchannel.c | 17 +++++++++++++----
> net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 27 +++++++++++++++------------
> 3 files changed, 29 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
> index 531980b..9866e94 100644
> --- a/include/linux/sunrpc/svc_rdma.h
> +++ b/include/linux/sunrpc/svc_rdma.h
> @@ -184,7 +184,7 @@ static inline void svc_rdma_count_mappings(struct svcxprt_rdma *rdma,
>
> /* svc_rdma_backchannel.c */
> extern int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt,
> - struct rpcrdma_msg *rmsgp,
> + __be32 *rdma_resp,
> struct xdr_buf *rcvbuf);
>
> /* svc_rdma_marshal.c */
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
> index 7d49545..6b3bbb6 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_backchannel.c
> @@ -11,7 +11,16 @@
>
> #undef SVCRDMA_BACKCHANNEL_DEBUG
>
> -int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, struct rpcrdma_msg *rmsgp,
> +/**
> + * svc_rdma_handle_bc_reply - Process incoming backchannel reply
> + * @xprt: controlling backchannel transport
> + * @rdma_resp: pointer to incoming transport header
> + * @rcvbuf: XDR buffer into which to decode the reply
> + *
> + * Returns zero and fills @rcvbuf if successful. Otherwise a
> + * negative errno is returned.
> + */
> +int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, __be32 *rdma_resp,
> struct xdr_buf *rcvbuf)
> {
> struct rpcrdma_xprt *r_xprt = rpcx_to_rdmax(xprt);
> @@ -26,13 +35,13 @@ int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, struct rpcrdma_msg *rmsgp,
>
> p = (__be32 *)src->iov_base;
> len = src->iov_len;
> - xid = rmsgp->rm_xid;
> + xid = *rdma_resp;
>
> #ifdef SVCRDMA_BACKCHANNEL_DEBUG
> pr_info("%s: xid=%08x, length=%zu\n",
> __func__, be32_to_cpu(xid), len);
> pr_info("%s: RPC/RDMA: %*ph\n",
> - __func__, (int)RPCRDMA_HDRLEN_MIN, rmsgp);
> + __func__, (int)RPCRDMA_HDRLEN_MIN, rdma_resp);
> pr_info("%s: RPC: %*ph\n",
> __func__, (int)len, p);
> #endif
> @@ -52,7 +61,7 @@ int svc_rdma_handle_bc_reply(struct rpc_xprt *xprt, struct rpcrdma_msg *rmsgp,
> goto out_unlock;
> memcpy(dst->iov_base, p, len);
>
> - credits = be32_to_cpu(rmsgp->rm_credit);
> + credits = be32_to_cpup(rdma_resp + 2);
> if (credits == 0)
> credits = 1; /* don't deadlock */
> else if (credits > r_xprt->rx_buf.rb_bc_max_requests)
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> index f1b5bbf..c9ea2e9 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> @@ -565,28 +565,30 @@ static void rdma_read_complete(struct svc_rqst *rqstp,
> * the RPC/RDMA header small and fixed in size, so it is
> * straightforward to check the RPC header's direction field.
> */
> -static bool
> -svc_rdma_is_backchannel_reply(struct svc_xprt *xprt, struct rpcrdma_msg *rmsgp)
> +static bool svc_rdma_is_backchannel_reply(struct svc_xprt *xprt,
> + __be32 *rdma_resp)
> {
> - __be32 *p = (__be32 *)rmsgp;
> + __be32 *p;
>
> if (!xprt->xpt_bc_xprt)
> return false;
>
> - if (rmsgp->rm_type != rdma_msg)
> + p = rdma_resp + 3;
> + if (*p++ != rdma_msg)
> return false;
> - if (rmsgp->rm_body.rm_chunks[0] != xdr_zero)
> +
> + if (*p++ != xdr_zero)
> return false;
> - if (rmsgp->rm_body.rm_chunks[1] != xdr_zero)
> + if (*p++ != xdr_zero)
> return false;
> - if (rmsgp->rm_body.rm_chunks[2] != xdr_zero)
> + if (*p++ != xdr_zero)
> return false;
>
> - /* sanity */
> - if (p[7] != rmsgp->rm_xid)
> + /* XID sanity */
> + if (*p++ != *rdma_resp)
> return false;
> /* call direction */
> - if (p[8] == cpu_to_be32(RPC_CALL))
> + if (*p == cpu_to_be32(RPC_CALL))
> return false;
>
> return true;
> @@ -652,8 +654,9 @@ int svc_rdma_recvfrom(struct svc_rqst *rqstp)
> goto out_drop;
> rqstp->rq_xprt_hlen = ret;
>
> - if (svc_rdma_is_backchannel_reply(xprt, rmsgp)) {
> - ret = svc_rdma_handle_bc_reply(xprt->xpt_bc_xprt, rmsgp,
> + if (svc_rdma_is_backchannel_reply(xprt, (__be32 *)rmsgp)) {
> + ret = svc_rdma_handle_bc_reply(xprt->xpt_bc_xprt,
> + (__be32 *)rmsgp,
Shouldn’t that be &rmsgp->rm_xid in order to be strictly equivalent?
> &rqstp->rq_arg);
> svc_rdma_put_context(ctxt, 0);
> if (ret)
>
> --
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