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

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Message-ID: <YPbALA/P5+NsC7MO@unreal>
Date:   Tue, 20 Jul 2021 15:23:08 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>
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
Subject: Re: [PATCH] RDMA/irdma: Improve the way 'cqp_request' structures are
 cleaned when they are recycled

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.

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@...adoo.fr>
> ---
>  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
>