linux-kernel - Re: [PATCH 19/26] ivtv: Convert driver to use get_user_pages

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Date:	Sat, 05 Oct 2013 08:02:21 -0400
From:	Andy Walls <awalls@...metrocast.net>
To:	Jan Kara <jack@...e.cz>
Cc:	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	linux-media@...r.kernel.org
Subject: Re: [PATCH 19/26] ivtv: Convert driver to use
 get_user_pages_unlocked()

Hi Jan:

<rant>
This patch alone does not have suffcient information for me to evaluate
it.  get_user_pages_unlocked() is added in another patch which I did not
receive, and which I cannot find in any list archives.

I wasted quite a bit of time looking for this additional patch:

https://git.kernel.org/cgit/linux/kernel/git/jack/linux-fs.git/commit/?h=get_user_pages&id=624fc1bfb70fb65d32d31fbd16427ad9c234653e

</rant>

If I found the correct patch for adding get_user_pages_unlocked(), then
the patch below looks fine.

Reviewed-by: Andy Walls <awalls@...metrocast.net>
Acked-by: Andy Walls <awalls@...metrocast.net>

Regards,
Andy

On Wed, 2013-10-02 at 16:28 +0200, Jan Kara wrote:
> CC: Andy Walls <awalls@...metrocast.net>
> CC: linux-media@...r.kernel.org
> Signed-off-by: Jan Kara <jack@...e.cz>
> ---
>  drivers/media/pci/ivtv/ivtv-udma.c |  6 ++----
>  drivers/media/pci/ivtv/ivtv-yuv.c  | 12 ++++++------
>  2 files changed, 8 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/media/pci/ivtv/ivtv-udma.c b/drivers/media/pci/ivtv/ivtv-udma.c
> index 7338cb2d0a38..6012e5049076 100644
> --- a/drivers/media/pci/ivtv/ivtv-udma.c
> +++ b/drivers/media/pci/ivtv/ivtv-udma.c
> @@ -124,10 +124,8 @@ int ivtv_udma_setup(struct ivtv *itv, unsigned long ivtv_dest_addr,
>  	}
>  
>  	/* Get user pages for DMA Xfer */
> -	down_read(&current->mm->mmap_sem);
> -	err = get_user_pages(current, current->mm,
> -			user_dma.uaddr, user_dma.page_count, 0, 1, dma->map, NULL);
> -	up_read(&current->mm->mmap_sem);
> +	err = get_user_pages_unlocked(current, current->mm, user_dma.uaddr,
> +				      user_dma.page_count, 0, 1, dma->map);
>  
>  	if (user_dma.page_count != err) {
>  		IVTV_DEBUG_WARN("failed to map user pages, returned %d instead of %d\n",
> diff --git a/drivers/media/pci/ivtv/ivtv-yuv.c b/drivers/media/pci/ivtv/ivtv-yuv.c
> index 2ad65eb29832..9365995917d8 100644
> --- a/drivers/media/pci/ivtv/ivtv-yuv.c
> +++ b/drivers/media/pci/ivtv/ivtv-yuv.c
> @@ -75,15 +75,15 @@ static int ivtv_yuv_prep_user_dma(struct ivtv *itv, struct ivtv_user_dma *dma,
>  	ivtv_udma_get_page_info (&uv_dma, (unsigned long)args->uv_source, 360 * uv_decode_height);
>  
>  	/* Get user pages for DMA Xfer */
> -	down_read(&current->mm->mmap_sem);
> -	y_pages = get_user_pages(current, current->mm, y_dma.uaddr, y_dma.page_count, 0, 1, &dma->map[0], NULL);
> +	y_pages = get_user_pages_unlocked(current, current->mm, y_dma.uaddr,
> +					  y_dma.page_count, 0, 1, &dma->map[0]);
>  	uv_pages = 0; /* silence gcc. value is set and consumed only if: */
>  	if (y_pages == y_dma.page_count) {
> -		uv_pages = get_user_pages(current, current->mm,
> -					  uv_dma.uaddr, uv_dma.page_count, 0, 1,
> -					  &dma->map[y_pages], NULL);
> +		uv_pages = get_user_pages_unlocked(current, current->mm,
> +						   uv_dma.uaddr,
> +						   uv_dma.page_count, 0, 1,
> +						   &dma->map[y_pages]);
>  	}
> -	up_read(&current->mm->mmap_sem);
>  
>  	if (y_pages != y_dma.page_count || uv_pages != uv_dma.page_count) {
>  		int rc = -EFAULT;


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