diff mbox series

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

Message ID 1666338764-2-2-git-send-email-lizhijian@fujitsu.com
State New
Headers
Series [for-next,v2,1/2] RDMA/rxe: Remove unnecessary mr testing |

Commit Message

Zhijian Li (Fujitsu) Oct. 21, 2022, 7:52 a.m. UTC 
  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.

Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
---
 drivers/infiniband/sw/rxe/rxe_resp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Zhu Yanjun Oct. 21, 2022, 2:39 p.m. UTC | #1 
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, 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
>
Zhijian Li (Fujitsu) Oct. 22, 2022, 1:09 a.m. UTC | #2 
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
>>
Bob Pearson Oct. 23, 2022, 6:05 p.m. UTC | #3 
On 10/21/22 20:09, Li Zhijian wrote:
> 
> 
> 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
>>>
> 

Li is correct that the only way mr could be NULL is if qp->resp.mr == NULL. So the
'if (mr)' is not needed if that is the case. The read_reply subroutine is reached
from a new rdma read operation after going through check_rkey or from a previous
rdma read operations from get_req if qp->resp.res != NULL or from a duplicate request
where the previous responder resource is found. In all these cases the mr is set.
Initially in check_rkey where if it can't find the mr it causes an RKEY_VIOLATION.
Thereafter the rkey is stored in the responder resources and looked up for each
packet to get an mr or cause an RKEY_VIOLATION. So the mr can't be NULL. I think
you can leave out the WARN and just drop the if (mr).

Bob
Zhu Yanjun Oct. 24, 2022, 2:25 a.m. UTC | #4 
On Mon, Oct 24, 2022 at 2:05 AM Bob Pearson <rpearsonhpe@gmail.com> wrote:
>
> On 10/21/22 20:09, Li Zhijian wrote:
> >
> >
> > 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
> >>>
> >
>
> Li is correct that the only way mr could be NULL is if qp->resp.mr == NULL. So the

What I am concerned about is if "WARN_ON(!mr);" should be added or not.
IMO, if the root cause remains unclear, this should be a problem.
Currently this problem is not fixed. It is useless to send a debug
statement to the maillist.

Zhu Yanjun

> 'if (mr)' is not needed if that is the case. The read_reply subroutine is reached
> from a new rdma read operation after going through check_rkey or from a previous
> rdma read operations from get_req if qp->resp.res != NULL or from a duplicate request
> where the previous responder resource is found. In all these cases the mr is set.
> Initially in check_rkey where if it can't find the mr it causes an RKEY_VIOLATION.
> Thereafter the rkey is stored in the responder resources and looked up for each
> packet to get an mr or cause an RKEY_VIOLATION. So the mr can't be NULL. I think
> you can leave out the WARN and just drop the if (mr).
>
> Bob
>
Zhijian Li (Fujitsu) Oct. 24, 2022, 3:15 a.m. UTC | #5 
On 24/10/2022 10:25, Zhu Yanjun wrote:
>>>>> +++ 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
>>>>>
>> Li is correct that the only way mr could be NULL is if qp->resp.mr == NULL. So the
> What I am concerned about is if "WARN_ON(!mr);" should be added or not.
> IMO, if the root cause remains unclear, this should be a problem.
> Currently this problem is not fixed. It is useless to send a debug
> statement to the maillist.

As per Bob's explanation,  no 'WARN_ON(!mr)' is needed.
I will update the patch soon.

> Zhu Yanjun
>
>> 'if (mr)' is not needed if that is the case. The read_reply subroutine is reached
>> from a new rdma read operation after going through check_rkey or from a previous
>> rdma read operations from get_req if qp->resp.res != NULL or from a duplicate request
>> where the previous responder resource is found. In all these cases the mr is set.
>> Initially in check_rkey where if it can't find the mr it causes an RKEY_VIOLATION.
>> Thereafter the rkey is stored in the responder resources and looked up for each
>> packet to get an mr or cause an RKEY_VIOLATION. So the mr can't be NULL. I think
>> you can leave out the WARN and just drop the if (mr).
Very thanks for your explanation

Thanks
Zhijian

>>
>> Bob
>>
Zhijian Li (Fujitsu) Oct. 24, 2022, 3:26 a.m. UTC | #6 
Just noticed i didn't post [2/2] successfully, will sent it in next version.



On 21/10/2022 15:52, Li Zhijian 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.
>
> 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;
Bob Pearson Oct. 24, 2022, 2:09 p.m. UTC | #7 
On 10/23/22 21:25, Zhu Yanjun wrote:
> On Mon, Oct 24, 2022 at 2:05 AM Bob Pearson <rpearsonhpe@gmail.com> wrote:
>>
>> On 10/21/22 20:09, Li Zhijian wrote:
>>>
>>>
>>> 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
>>>>>
>>>
>>
>> Li is correct that the only way mr could be NULL is if qp->resp.mr == NULL. So the
> 
> What I am concerned about is if "WARN_ON(!mr);" should be added or not.
> IMO, if the root cause remains unclear, this should be a problem.
> Currently this problem is not fixed. It is useless to send a debug
> statement to the maillist.

Li was fixing a bug that no one ever saw. mr is not NULL in this case.

Bob
> 
> Zhu Yanjun
> 
>> 'if (mr)' is not needed if that is the case. The read_reply subroutine is reached
>> from a new rdma read operation after going through check_rkey or from a previous
>> rdma read operations from get_req if qp->resp.res != NULL or from a duplicate request
>> where the previous responder resource is found. In all these cases the mr is set.
>> Initially in check_rkey where if it can't find the mr it causes an RKEY_VIOLATION.
>> Thereafter the rkey is stored in the responder resources and looked up for each
>> packet to get an mr or cause an RKEY_VIOLATION. So the mr can't be NULL. I think
>> you can leave out the WARN and just drop the if (mr).
>>
>> Bob
>>
diff mbox series

Patch

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;