Re: [PATCH] drm/buddy: Fix alloc_range() error handling code

[Matthew Auld <matthew.auld@intel.com>]

On 07/02/2024 17:44, Arunpravin Paneer Selvam wrote:
> Few users have observed display corruption when they boot
> the machine to KDE Plasma or playing games. We have root
> caused the problem that whenever alloc_range() couldn't
> find the required memory blocks the function was returning
> SUCCESS in some of the corner cases.

Can you please give an example here?

> 
> The right approach would be if the total allocated size
> is less than the required size, the function should
> return -ENOSPC.
> 
> Gitlab ticket link - https://gitlab.freedesktop.org/drm/amd/-/issues/3097
> Fixes: 0a1844bf0b53 ("drm/buddy: Improve contiguous memory allocation")
> Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam@amd.com>
> Tested-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
>   drivers/gpu/drm/drm_buddy.c | 6 ++++++
>   1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
> index f57e6d74fb0e..c1a99bf4dffd 100644
> --- a/drivers/gpu/drm/drm_buddy.c
> +++ b/drivers/gpu/drm/drm_buddy.c
> @@ -539,6 +539,12 @@ static int __alloc_range(struct drm_buddy *mm,
>   	} while (1);
>   
>   	list_splice_tail(&allocated, blocks);
> +
> +	if (total_allocated < size) {
> +		err = -ENOSPC;
> +		goto err_free;
> +	}
> +
>   	return 0;
>   
>   err_undo: