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Subject: Re: [PATCH v2 04/18] media/v4l2-core: set pages dirty upon releasing
 DMA buffers
To: John Hubbard <jhubbard@nvidia.com>,
 Andrew Morton <akpm@linux-foundation.org>
References: <20191103211813.213227-1-jhubbard@nvidia.com>
 <20191103211813.213227-5-jhubbard@nvidia.com>
From: Hans Verkuil <hverkuil@xs4all.nl>
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Date: Sun, 10 Nov 2019 11:10:10 +0100
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Cc: Michal Hocko <mhocko@suse.com>, Jan Kara <jack@suse.cz>,
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 =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= <bjorn.topel@intel.com>,
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 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

On 11/3/19 10:17 PM, John Hubbard wrote:
> After DMA is complete, and the device and CPU caches are synchronized,
> it's still required to mark the CPU pages as dirty, if the data was
> coming from the device. However, this driver was just issuing a
> bare put_page() call, without any set_page_dirty*() call.
> 
> Fix the problem, by calling set_page_dirty_lock() if the CPU pages
> were potentially receiving data from the device.
> 
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>

Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Looks good, thanks!

	Hans

> ---
>  drivers/media/v4l2-core/videobuf-dma-sg.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c
> index 66a6c6c236a7..28262190c3ab 100644
> --- a/drivers/media/v4l2-core/videobuf-dma-sg.c
> +++ b/drivers/media/v4l2-core/videobuf-dma-sg.c
> @@ -349,8 +349,11 @@ int videobuf_dma_free(struct videobuf_dmabuf *dma)
>  	BUG_ON(dma->sglen);
>  
>  	if (dma->pages) {
> -		for (i = 0; i < dma->nr_pages; i++)
> +		for (i = 0; i < dma->nr_pages; i++) {
> +			if (dma->direction == DMA_FROM_DEVICE)
> +				set_page_dirty_lock(dma->pages[i]);
>  			put_page(dma->pages[i]);
> +		}
>  		kfree(dma->pages);
>  		dma->pages = NULL;
>  	}
>