[Intel-gfx] [PATCH 6/7] drm: Don't walk fb list twice in getresources

[Chris Wilson]

On Fri, Dec 09, 2016 at 03:19:43PM +0100, Daniel Vetter wrote:
> We can be more clever than that and merge the 2 list walking loops.
> It's all under the one mutex critical section anyway, so nothing funny
> can happen.
> 
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> ---
>  drivers/gpu/drm/drm_mode_config.c | 28 +++++++++++-----------------
>  1 file changed, 11 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_mode_config.c b/drivers/gpu/drm/drm_mode_config.c
> index 64c2971478db..a6205a92dfee 100644
> --- a/drivers/gpu/drm/drm_mode_config.c
> +++ b/drivers/gpu/drm/drm_mode_config.c
> @@ -84,7 +84,6 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
>  			  struct drm_file *file_priv)
>  {
>  	struct drm_mode_card_res *card_res = data;
> -	struct list_head *lh;
>  	struct drm_framebuffer *fb;
>  	struct drm_connector *connector;
>  	struct drm_crtc *crtc;
> @@ -105,25 +104,20 @@ int drm_mode_getresources(struct drm_device *dev, void *data,
>  
>  
>  	mutex_lock(&file_priv->fbs_lock);
> -	/*
> -	 * For the non-control nodes we need to limit the list of resources
> -	 * by IDs in the group list for this node
> -	 */
> -	list_for_each(lh, &file_priv->fbs)
> -		fb_count++;
> -
>  	/* handle this in 4 parts */
>  	/* FBs */
> -	if (card_res->count_fbs >= fb_count) {
> -		copied = 0;
> -		fb_id = (uint32_t __user *)(unsigned long)card_res->fb_id_ptr;
> -		list_for_each_entry(fb, &file_priv->fbs, filp_head) {
> -			if (put_user(fb->base.id, fb_id + copied)) {
> -				mutex_unlock(&file_priv->fbs_lock);
> -				return -EFAULT;
> -			}
> -			copied++;
> +	copied = 0;
> +	fb_id = (uint32_t __user *)(unsigned long)card_res->fb_id_ptr;
> +	list_for_each_entry(fb, &file_priv->fbs, filp_head) {
> +		fb_count++;
> +		if (fb_count > card_res->count_fbs)
> +			continue;
> +
> +		if (put_user(fb->base.id, fb_id + copied)) {
> +			mutex_unlock(&file_priv->fbs_lock);
> +			return -EFAULT;
>  		}
> +		copied++;

if (fb_count < card_res->count_fbs &&
    put_user(fb->base.id fb_id + fb_count) {
}
fb_count++; // no need for copied

I'd just like for one style :) Otoh, this seems reasonable to apply to
crtc/encoders/connectors as well, and on the other we already have a
counter for the others. Hmm, setting count = copied in the previous
patch is thereby wrong (change in uABI).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre