linux-kernel - Re: [for-next PATCH v2 1/2] RDMA/rxe: Remove unnecessary mr testing

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Date:   Fri, 21 Oct 2022 22:39:28 +0800
From:   Zhu Yanjun <zyjzyj2000@...il.com>
To:     Li Zhijian <lizhijian@...itsu.com>
Cc:     jgg@...pe.ca, leon@...nel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [for-next PATCH v2 1/2] RDMA/rxe: Remove unnecessary mr testing

On Fri, Oct 21, 2022 at 3:53 PM Li Zhijian <lizhijian@...itsu.com> wrote:
>
> Before the testing, we already passed it to rxe_mr_copy() where mr could
> be dereferenced. so this checking is not exactly correct.
>
> I tried to figure out the details how/when mr could be NULL, but failed
> at last. Add a WARN_ON(!mr) to that path to tell us more when it
> happends.

If I get you correctly, you confronted a problem, but you can not figure it out.
So you send it upstream as a patch?

I am not sure if it is a good idea.

Zhu Yanjun

>
> Signed-off-by: Li Zhijian <lizhijian@...itsu.com>
> ---
>  drivers/infiniband/sw/rxe/rxe_resp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/infiniband/sw/rxe/rxe_resp.c b/drivers/infiniband/sw/rxe/rxe_resp.c
> index ed5a09e86417..218c14fb07c6 100644
> --- a/drivers/infiniband/sw/rxe/rxe_resp.c
> +++ b/drivers/infiniband/sw/rxe/rxe_resp.c
> @@ -778,6 +778,7 @@ static enum resp_states read_reply(struct rxe_qp *qp,
>         if (res->state == rdatm_res_state_new) {
>                 if (!res->replay) {
>                         mr = qp->resp.mr;
> +                       WARN_ON(!mr);
>                         qp->resp.mr = NULL;
>                 } else {
>                         mr = rxe_recheck_mr(qp, res->read.rkey);
> @@ -811,8 +812,7 @@ static enum resp_states read_reply(struct rxe_qp *qp,
>
>         rxe_mr_copy(mr, res->read.va, payload_addr(&ack_pkt),
>                     payload, RXE_FROM_MR_OBJ);
> -       if (mr)
> -               rxe_put(mr);
> +       rxe_put(mr);
>
>         if (bth_pad(&ack_pkt)) {
>                 u8 *pad = payload_addr(&ack_pkt) + payload;
> --
> 2.31.1
>