Re: [PATCH] media: v4l2: make allocation algorithm more robust and flexible

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Hi Zhaowei,

On Wed, Jul 30, 2014 at 9:39 AM, Zhaowei Yuan <zhaowei.yuan@xxxxxxxxxxx> wrote:
> Current algorithm relies on the fact that caller will align the
> size to PAGE_SIZE, otherwise order will be decreased to negative
> when remain size is less than PAGE_SIZE, it makes the function
> hard to be migrated.
> This patch sloves the hidden problem.
>
> Signed-off-by: Zhaowei Yuan <zhaowei.yuan@xxxxxxxxxxx>
> ---
>  drivers/media/v4l2-core/videobuf2-dma-sg.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-sg.c b/drivers/media/v4l2-core/videobuf2-dma-sg.c
> index adefc31..40d18aa 100644
> --- a/drivers/media/v4l2-core/videobuf2-dma-sg.c
> +++ b/drivers/media/v4l2-core/videobuf2-dma-sg.c
> @@ -58,7 +58,7 @@ static int vb2_dma_sg_alloc_compacted(struct vb2_dma_sg_buf *buf,
>
>                 order = get_order(size);
>                 /* Dont over allocate*/
> -               if ((PAGE_SIZE << order) > size)
> +               if (order > 0 && (PAGE_SIZE << order) > size)
>                         order--;

If size is not page aligned, then wouldn't decrementing the order
under-allocate the memory?

-- 
Regards,
Sachin.
--
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