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

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Message-ID: <70f73586-670e-43d0-adf4-0950a9b3940d@linux.dev>
Date: Fri, 23 Aug 2024 13:56:02 +0800
From: Zhu Yanjun <yanjun.zhu@...ux.dev>
To: zhenwei pi <pizhenwei@...edance.com>, Jason Gunthorpe <jgg@...dia.com>
Cc: 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


在 2024/8/23 10:30, zhenwei pi 写道:
>
> On 8/22/24 20:36, Jason Gunthorpe wrote:
> > 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
> >>> ---
> >>> 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
>
> Yes, this is the front part(40 bytes) of UD/GSI verbs completion.
>
When running, you can print the value of the front part (40 bytes) of 
UD/GSI to confirm that these 40 bytes are the union rdma_network_hdr.

If these 40 bytes are the union rdma_network_hdr,

Reviewed-by: Zhu Yanjun <yanjun.zhu@...ux.dev>

Best Regards,

Zhu Yanjun

>
> -- 
> zhenwei pi
>
-- 
Best Regards,
Yanjun.Zhu