linux-kernel - Re: [PATCH 2/2] dma-mapping: benchmark: prevent potential kthread hang

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Date: Fri, 3 May 2024 18:39:29 +0300
From: Fedor Pchelkin <pchelkin@...ras.ru>
To: Barry Song <21cnbao@...il.com>
Cc: Xiang Chen <chenxiang66@...ilicon.com>, Christoph Hellwig <hch@....de>, 
	Marek Szyprowski <m.szyprowski@...sung.com>, Robin Murphy <robin.murphy@....com>, 
	Barry Song <song.bao.hua@...ilicon.com>, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	Alexey Khoroshilov <khoroshilov@...ras.ru>, lvc-project@...uxtesting.org
Subject: Re: [PATCH 2/2] dma-mapping: benchmark: prevent potential kthread
 hang

On Fri, 03. May 13:44, Barry Song wrote:
> On Fri, May 3, 2024 at 4:29 AM Fedor Pchelkin <pchelkin@...ras.ru> wrote:
> 

[...]

> do we still need to do copy_to_user(argp, &map->bparam, sizeof(map->bparam)
> after  do_map_benchmark(map) fails?
> do we also need the below?
> diff --git a/kernel/dma/map_benchmark.c b/kernel/dma/map_benchmark.c
> index 02205ab53b7e..28ca165cb62c 100644
> --- a/kernel/dma/map_benchmark.c
> +++ b/kernel/dma/map_benchmark.c
> @@ -252,6 +252,9 @@ static long map_benchmark_ioctl(struct file *file,
> unsigned int cmd,
>                  * dma_mask changed by benchmark
>                  */
>                 dma_set_mask(map->dev, old_dma_mask);
> +
> +               if (ret)
> +                       return ret;
>                 break;
>         default:
>                 return -EINVAL;
> 
> 

Good point, thank you! If benchmark failed, nothing new to be copied back
to user, indeed.

I'll add this as the third patch of the series and post v2.