linux-kernel - Re: [PATCH 1/3] RDMA/rxe: Use sizeof instead of hard code number

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Message-ID: <20240822123649.GP3773488@nvidia.com>
Date: Thu, 22 Aug 2024 09:36:49 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Zhu Yanjun <yanjun.zhu@...ux.dev>
Cc: zhenwei pi <pizhenwei@...edance.com>, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org, zyjzyj2000@...il.com,
	leonro@...dia.com
Subject: Re: [PATCH 1/3] RDMA/rxe: Use sizeof instead of hard code number

On Thu, Aug 22, 2024 at 07:59:32PM +0800, Zhu Yanjun wrote:
> 在 2024/8/22 14:52, zhenwei pi 写道:
> > Use 'sizeof(union rdma_network_hdr)' instead of hard code GRH length
> > for GSI and UD.
> > 
> > Signed-off-by: zhenwei pi <pizhenwei@...edance.com>
> > ---
> >   drivers/infiniband/sw/rxe/rxe_resp.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/infiniband/sw/rxe/rxe_resp.c b/drivers/infiniband/sw/rxe/rxe_resp.c
> > index 6596a85723c9..bf8f4bc8c5c8 100644
> > --- a/drivers/infiniband/sw/rxe/rxe_resp.c
> > +++ b/drivers/infiniband/sw/rxe/rxe_resp.c
> > @@ -351,7 +351,7 @@ static enum resp_states rxe_resp_check_length(struct rxe_qp *qp,
> >   		for (i = 0; i < qp->resp.wqe->dma.num_sge; i++)
> >   			recv_buffer_len += qp->resp.wqe->dma.sge[i].length;
> > -		if (payload + 40 > recv_buffer_len) {
> > +		if (payload + sizeof(union rdma_network_hdr) > recv_buffer_len) {
> 
> The definition of union rdma_network_hdr is as below
> 
>  797 union rdma_network_hdr {
>  798         struct ib_grh ibgrh;
>  799         struct {
>  800                 /* The IB spec states that if it's IPv4, the header
>  801                  * is located in the last 20 bytes of the header.
>  802                  */
>  803                 u8              reserved[20];
>  804                 struct iphdr    roce4grh;
>  805         };
>  806 };
> 
> The length is 40 byte.

This looks like the right struct to me if this is talking about the
special 40 byte blob that is placed in front of UD verbs completions.

Jason