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

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Message-ID: <d933e865-2b6b-41c1-a0f2-46f8fef3cc17@linux.dev>
Date: Thu, 22 Aug 2024 19:59:32 +0800
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: zhenwei pi <pizhenwei@...edance.com>, linux-rdma@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: zyjzyj2000@...il.com, jgg@...dia.com, leonro@...dia.com
Subject: Re: [PATCH 1/3] RDMA/rxe: Use sizeof instead of hard code number

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.

But in this,

sizeof(struct iphdr) (20) + sizeof(struct udphdr) (8) + sizeof(struct 
rxe_bth) (12) = 40

Not sure if we should use sizeof(union rdma_network_hdr) or 
(sizeof(struct iphdr) + sizeof(struct udphdr) + sizeof(struct rxe_bth)) 
in this place.

Best Regards,
Zhu Yanjun


>   			rxe_dbg_qp(qp, "The receive buffer is too small for this UD packet.\n");
>   			return RESPST_ERR_LENGTH;
>   		}