Subject: Re: [PATCH v1 05/12] xprtrdma: Account for RPC/RDMA header size when
 deciding to inline
To: Chuck Lever <chuck.lever@oracle.com>, <linux-rdma@vger.kernel.org>,
        <linux-nfs@vger.kernel.org>
References: <20150709203242.26247.4848.stgit@manet.1015granger.net>
 <20150709204227.26247.51111.stgit@manet.1015granger.net>
From: Anna Schumaker <Anna.Schumaker@netapp.com>
Message-ID: <55A02650.1050809@Netapp.com>
Date: Fri, 10 Jul 2015 16:08:48 -0400
MIME-Version: 1.0
In-Reply-To: <20150709204227.26247.51111.stgit@manet.1015granger.net>
Content-Type: text/plain; charset="utf-8"
Sender: linux-nfs-owner@vger.kernel.org

Hi Chuck,

On 07/09/2015 04:42 PM, Chuck Lever wrote:
> When marshaling RPC/RDMA requests, ensure the combined size of
> RPC/RDMA header and RPC header do not exceed the inline threshold.
> Endpoints typically reject RPC/RDMA messages that exceed the size
> of their receive buffers.
> 
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  net/sunrpc/xprtrdma/rpc_rdma.c |   29 +++++++++++++++++++++++++++--
>  1 file changed, 27 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
> index 84ea37d..8cf9402 100644
> --- a/net/sunrpc/xprtrdma/rpc_rdma.c
> +++ b/net/sunrpc/xprtrdma/rpc_rdma.c
> @@ -71,6 +71,31 @@ static const char transfertypes[][12] = {
>  };
>  #endif
>  
> +/* The client can send a request inline as long as the RPCRDMA header
> + * plus the RPC call fit under the transport's inline limit. If the
> + * combined call message size exceeds that limit, the client must use
> + * the read chunk list for this operation.
> + */
> +static bool rpcrdma_args_inline(struct rpc_rqst *rqst)
> +{
> +	unsigned int callsize = RPCRDMA_HDRLEN_MIN + rqst->rq_snd_buf.len;
> +
> +	return callsize <= RPCRDMA_INLINE_WRITE_THRESHOLD(rqst);
> +}
> +
> +/* The client can’t know how large the actual reply will be. Thus it
                 ^^^^^
This is showing up as "can<80><99>t" in git-show, leading me to think that the apostrophe was replaced with a unicode-apostrophe.  Google might have made the switch, but can you double check the patch on your side just in case?

Thanks,
Anna

> + * plans for the largest possible reply for that particular ULP
> + * operation. If the maximum combined reply message size exceeds that
> + * limit, the client must provide a write list or a reply chunk for
> + * this request.
> + */
> +static bool rpcrdma_results_inline(struct rpc_rqst *rqst)
> +{
> +	unsigned int repsize = RPCRDMA_HDRLEN_MIN + rqst->rq_rcv_buf.buflen;
> +
> +	return repsize <= RPCRDMA_INLINE_READ_THRESHOLD(rqst);
> +}
> +
>  /*
>   * Chunk assembly from upper layer xdr_buf.
>   *
> @@ -418,7 +443,7 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
>  	 * a READ, then use write chunks to separate the file data
>  	 * into pages; otherwise use reply chunks.
>  	 */
> -	if (rqst->rq_rcv_buf.buflen <= RPCRDMA_INLINE_READ_THRESHOLD(rqst))
> +	if (rpcrdma_results_inline(rqst))
>  		wtype = rpcrdma_noch;
>  	else if (rqst->rq_rcv_buf.page_len == 0)
>  		wtype = rpcrdma_replych;
> @@ -441,7 +466,7 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
>  	 * implies the op is a write.
>  	 * TBD check NFSv4 setacl
>  	 */
> -	if (rqst->rq_snd_buf.len <= RPCRDMA_INLINE_WRITE_THRESHOLD(rqst))
> +	if (rpcrdma_args_inline(rqst))
>  		rtype = rpcrdma_noch;
>  	else if (rqst->rq_snd_buf.page_len == 0)
>  		rtype = rpcrdma_areadch;
> 
> --
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