linux-kernel - Re: [PATCH] RDMA/irdma: Improve the way 'cqp_request' structures are cleaned when they are recycled

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Date:   Tue, 20 Jul 2021 15:05:55 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     leon@...nel.org
Cc:     mustafa.ismail@...el.com, shiraz.saleem@...el.com,
        dledford@...hat.com, jgg@...pe.ca, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        christophe.jaillet@...adoo.fr
Subject: Re: [PATCH] RDMA/irdma: Improve the way 'cqp_request' structures are
 cleaned when they are recycled

Le 20/07/2021 à 14:23, Leon Romanovsky a écrit :
> On Mon, Jul 19, 2021 at 07:02:15PM +0200, Christophe JAILLET wrote:
>> A set of IRDMA_CQP_SW_SQSIZE_2048 (i.e. 2048) 'cqp_request' are
>> pre-allocated and zeroed in 'irdma_create_cqp()' (hw.c).  These
>> structures are managed with the 'cqp->cqp_avail_reqs' list which keeps
>> track of available entries.
>>
>> In 'irdma_free_cqp_request()' (utils.c), when an entry is recycled and goes
>> back to the 'cqp_avail_reqs' list, some fields are reseted.
>>
>> However, one of these fields, 'compl_info', is initialized within
>> 'irdma_alloc_and_get_cqp_request()'.
>>
>> Move the corresponding memset to 'irdma_free_cqp_request()' so that the
>> clean-up is done in only one place. This makes the logic more easy to
>> understand.
> 
> I'm not so sure. The function irdma_alloc_and_get_cqp_request() returns
> prepared cqp_request and all users expect that it will returned cleaned
> one. The reliance on some other place to clear part of the structure is
> prone to errors.

Ok, so maybe, moving:
	cqp_request->request_done = false;
	cqp_request->callback_fcn = NULL;
	cqp_request->waiting = false;
from 'irdma_free_cqp_request()' to 'irdma_alloc_and_get_cqp_request()' 
to make explicit what is reseted makes more sense?

 From my point of view, it is same same: all (re)initialization are done 
at 1 place only.

This would also avoid setting 'waiting' twice (once to false in 
'irdma_free_cqp_request()' and one to 'wait' 
'irdma_alloc_and_get_cqp_request()')


CJ
> 
> Thanks
> 
>>
>> This also saves this memset in the case that the 'cqp_avail_reqs' list is
>> empty and a new 'cqp_request' structure must be allocated. This memset is
>> useless, because the structure is already kzalloc'ed.
>>
>> Signed-off-by: Christophe JAILLET <christophe.jaillet-39ZsbGIQGT5GWvitb5QawA@...lic.gmane.org>
>> ---
>>   drivers/infiniband/hw/irdma/utils.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/infiniband/hw/irdma/utils.c b/drivers/infiniband/hw/irdma/utils.c
>> index 5bbe44e54f9a..66711024d38b 100644
>> --- a/drivers/infiniband/hw/irdma/utils.c
>> +++ b/drivers/infiniband/hw/irdma/utils.c
>> @@ -445,7 +445,6 @@ struct irdma_cqp_request *irdma_alloc_and_get_cqp_request(struct irdma_cqp *cqp,
>>   
>>   	cqp_request->waiting = wait;
>>   	refcount_set(&cqp_request->refcnt, 1);
>> -	memset(&cqp_request->compl_info, 0, sizeof(cqp_request->compl_info));
>>   
>>   	return cqp_request;
>>   }
>> @@ -475,6 +474,7 @@ void irdma_free_cqp_request(struct irdma_cqp *cqp,
>>   		cqp_request->request_done = false;
>>   		cqp_request->callback_fcn = NULL;
>>   		cqp_request->waiting = false;
>> +		memset(&cqp_request->compl_info, 0, sizeof(cqp_request->compl_info));
>>   
>>   		spin_lock_irqsave(&cqp->req_lock, flags);
>>   		list_add_tail(&cqp_request->list, &cqp->cqp_avail_reqs);
>> -- 
>> 2.30.2
>>
>