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

[Li Zhijian]

On 21/10/2022 22:39, Zhu Yanjun wrote:
> On Fri, Oct 21, 2022 at 3:53 PM Li Zhijian <lizhijian@xxxxxxxxxxx> 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,
Not exactly,  I removed the mr checking since i think this checking is not correct.
the newly added WARN_ON(!mr) is the only once place where the mr can be NULL but not handled correctly.
At least with/without this patch, once WARN_ON(!mr) is triggered, kernel will go something wrong.

so i want to place this  WARN_ON(!mr) to point to the problem.

Thanks
Zhijian

>   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@xxxxxxxxxxx>
> > ---
> >   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