Re: [Intel-gfx] [PATCH] drm: remove min_order BUG_ON check

[Jani Nikula <jani.nikula@linux.intel.com>]

On Mon, 07 Mar 2022, Arunpravin <Arunpravin.PaneerSelvam@amd.com> wrote:
> place BUG_ON(order < min_order) outside do..while
> loop as it fails Unigine Heaven benchmark.
>
> Unigine Heaven has buffer allocation requests for
> example required pages are 161 and alignment request
> is 128. To allocate the remaining 33 pages, continues
> the iteration to find the order value which is 5 and
> when it compares with min_order = 7, enables the
> BUG_ON(). To avoid this problem, placed the BUG_ON
> check outside of do..while loop.

How about turning these BUG_ON()s to WARN_ON()s with an error return?
What's the point in oopsing?

BR,
Jani.


>
> Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@amd.com>
> ---
>  drivers/gpu/drm/drm_buddy.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
> index 72f52f293249..ed94c56b720f 100644
> --- a/drivers/gpu/drm/drm_buddy.c
> +++ b/drivers/gpu/drm/drm_buddy.c
> @@ -669,10 +669,11 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
>  	order = fls(pages) - 1;
>  	min_order = ilog2(min_page_size) - ilog2(mm->chunk_size);
>  
> +	BUG_ON(order < min_order);
> +
>  	do {
>  		order = min(order, (unsigned int)fls(pages) - 1);
>  		BUG_ON(order > mm->max_order);
> -		BUG_ON(order < min_order);
>  
>  		do {
>  			if (flags & DRM_BUDDY_RANGE_ALLOCATION)
>
> base-commit: 8025c79350b90e5a8029234d433578f12abbae2b

-- 
Jani Nikula, Intel Open Source Graphics Center