Re: [PATCH v6 5/5] svcrdma: Mark Read chunks

[Mike Snitzer <snitzer@kernel.org>]

On Wed, Oct 22, 2025 at 03:22:08PM -0400, Chuck Lever wrote:
> From: Chuck Lever <chuck.lever@oracle.com>
> 
> The upper layer may want to know when the receive buffer's .pages
> array is guaranteed to contain only an opaque payload. This permits
> the upper layer to optimize its buffer handling.
> 
> NB: Since svc_rdma_recvfrom.c is under net/, we use the comment
> style that is preferred in the networking layer.
> 
> Reviewed-by: Jeff Layton <jlayton@kernel.org>
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  net/sunrpc/xprtrdma/svc_rdma_recvfrom.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> index e7e4a39ca6c6..b1a0c72f73de 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> @@ -815,6 +815,11 @@ static void svc_rdma_read_complete_one(struct svc_rqst *rqstp,
>  	buf->page_len = length;
>  	buf->len += length;
>  	buf->buflen += length;
> +
> +	/* Transport guarantees that only the chunk payload
> +	 * appears in buf->pages.
> +	 */
> +	buf->flags |= XDRBUF_READ;
>  }
>  
>  /* Finish constructing the RPC Call message in rqstp::rq_arg.
> -- 
> 2.51.0
> 
> 

This patch header leaves me unclear on your thinking for upper layer
optimization that would look for XDRBUF_READ.

I see rpcrdma_marshal_req() is checking XDRBUF_READ but...

I'm left hoping for a clearer payoff on this change's benefit (and
relation to the rest of the patchset).