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SubjectRe: [for-next PATCH v2 1/2] RDMA/rxe: Remove unnecessary mr testing
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On 21/10/2022 22:39, Zhu Yanjun wrote:
> On Fri, Oct 21, 2022 at 3:53 PM Li Zhijian <lizhijian@fujitsu.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,
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@fujitsu.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
>>

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