Re: [PATCH 13/19] media/v4l2-core: pin_longterm_pages (FOLL_PIN) and put_user_page() conversion

[Ira Weiny]

On Wed, Oct 30, 2019 at 03:49:24PM -0700, John Hubbard wrote:
> 1. Change v4l2 from get_user_pages(FOLL_LONGTERM), to
> pin_longterm_pages(), which sets both FOLL_LONGTERM and FOLL_PIN.
> 
> 2. Because all FOLL_PIN-acquired pages must be released via
> put_user_page(), also convert the put_page() call over to
> put_user_pages_dirty_lock().
> 

Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>

> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
> ---
>  drivers/media/v4l2-core/videobuf-dma-sg.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/videobuf-dma-sg.c b/drivers/media/v4l2-core/videobuf-dma-sg.c
> index 28262190c3ab..9b9c5b37bf59 100644
> --- a/drivers/media/v4l2-core/videobuf-dma-sg.c
> +++ b/drivers/media/v4l2-core/videobuf-dma-sg.c
> @@ -183,12 +183,12 @@ static int videobuf_dma_init_user_locked(struct videobuf_dmabuf *dma,
>  	dprintk(1, "init user [0x%lx+0x%lx => %d pages]\n",
>  		data, size, dma->nr_pages);
>  
> -	err = get_user_pages(data & PAGE_MASK, dma->nr_pages,
> -			     flags | FOLL_LONGTERM, dma->pages, NULL);
> +	err = pin_longterm_pages(data & PAGE_MASK, dma->nr_pages,
> +				 flags, dma->pages, NULL);
>  
>  	if (err != dma->nr_pages) {
>  		dma->nr_pages = (err >= 0) ? err : 0;
> -		dprintk(1, "get_user_pages: err=%d [%d]\n", err,
> +		dprintk(1, "pin_longterm_pages: err=%d [%d]\n", err,
>  			dma->nr_pages);
>  		return err < 0 ? err : -EINVAL;
>  	}
> @@ -349,11 +349,8 @@ int videobuf_dma_free(struct videobuf_dmabuf *dma)
>  	BUG_ON(dma->sglen);
>  
>  	if (dma->pages) {
> -		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]);
> -		}
> +		put_user_pages_dirty_lock(dma->pages, dma->nr_pages,
> +					  dma->direction == DMA_FROM_DEVICE);
>  		kfree(dma->pages);
>  		dma->pages = NULL;
>  	}
> -- 
> 2.23.0
>