> On Oct 16, 2015, at 9:30 AM, Chuck Lever <[email protected]> wrote:
>
> Minor optimization: when dealing with write chunk XDR roundup, do
> not post a Write WR for the zero bytes in the pad. Simply update
> the write segment in the RPC-over-RDMA header to reflect the extra
> pad bytes.
>
> The Reply chunk is also a write chunk, but the server does not use
> send_write_chunks() to send the Reply chunk. That's OK in this case:
> the server Upper Layer typically marshals the Reply chunk contents
> in a single contiguous buffer, without a separate tail for the XDR
> pad.
>
> The comments and the variable naming refer to "chunks" but what is
> really meant is "segments." The existing code sends only one
> xdr_write_chunk per RPC reply.
>
> The fix assumes this as well. When the XDR pad in the first write
> chunk is reached, the assumption is the Write list is complete and
> send_write_chunks() returns.
>
> That will remain a valid assumption until the server Upper Layer can
> support multiple bulk payload results per RPC.
>
> Signed-off-by: Chuck Lever <[email protected]>
> --
Bruce, can you take this for 4.4 ?
> net/sunrpc/xprtrdma/svc_rdma_sendto.c | 7 +++++++
> 1 files changed, 7 insertions(+), 0 deletions(-)
>
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
> b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
> index 1dfae83..6c48901 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
> @@ -342,6 +342,13 @@ static int send_write_chunks(struct svcxprt_rdma *xprt,
> arg_ch->rs_handle,
> arg_ch->rs_offset,
> write_len);
> +
> + /* Do not send XDR pad bytes */
> + if (chunk_no && write_len < 4) {
> + chunk_no++;
> + break;
> + }
> +
> chunk_off = 0;
> while (write_len) {
> ret = send_write(xprt, rqstp,
>
> --
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—
Chuck Lever
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