linux-kernel - Re: [PATCH] ioat/dca: Use struct

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Date:   Wed, 28 Aug 2019 12:38:35 -0700
From:   Dave Jiang <dave.jiang@...el.com>
To:     "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Vinod Koul <vkoul@...nel.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>
Cc:     "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ioat/dca: Use struct_size() helper



On 8/28/19 11:40 AM, Gustavo A. R. Silva wrote:
> One of the more common cases of allocation size calculations is finding
> the size of a structure that has a zero-sized array at the end, along
> with memory for some number of elements for that array. For example:
> 
> struct ioat_dca_priv {
> 	...
>         struct ioat_dca_slot     req_slots[0];
> };
> 
> Make use of the struct_size() helper instead of an open-coded version
> in order to avoid any potential type mistakes.
> 
> So, replace the following form:
> 
> sizeof(*ioatdca) + (sizeof(struct ioat_dca_slot) * slots)
> 
> with:
> 
> struct_size(ioatdca, req_slots, slots)
> 
> This code was detected with the help of Coccinelle.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>

Acked-by: Dave Jiang <dave.jiang@...el.com>

> ---
>  drivers/dma/ioat/dca.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/dma/ioat/dca.c b/drivers/dma/ioat/dca.c
> index 70fd8454d002..be61c32a876f 100644
> --- a/drivers/dma/ioat/dca.c
> +++ b/drivers/dma/ioat/dca.c
> @@ -286,8 +286,7 @@ struct dca_provider *ioat_dca_init(struct pci_dev *pdev, void __iomem *iobase)
>  		return NULL;
>  
>  	dca = alloc_dca_provider(&ioat_dca_ops,
> -				 sizeof(*ioatdca)
> -				      + (sizeof(struct ioat_dca_slot) * slots));
> +				 struct_size(ioatdca, req_slots, slots));
>  	if (!dca)
>  		return NULL;
>  
>