Re: [PATCH v3 02/21] drm/ttm: Slightly clean up LRU list iteration

[Matthew Brost <matthew.brost@intel.com>]

On Tue, May 21, 2024 at 09:16:20AM +0200, Thomas Hellström wrote:
> To make the transition to using lru hitches easier,
> simplify the ttm_resource_manager_next() interface to only take
> the cursor and reuse ttm_resource_manager_next() functionality
> from ttm_resource_manager_first().
> 
> Cc: Christian König <christian.koenig@amd.com>
> Cc: Somalapuram Amaranath <Amaranath.Somalapuram@amd.com>
> Cc: Matthew Brost <matthew.brost@intel.com>

Reviewed-by: Matthew Brost <matthew.brost@intel.com>

> Cc: <dri-devel@lists.freedesktop.org>
> Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> ---
>  drivers/gpu/drm/ttm/ttm_resource.c | 48 +++++++++++++-----------------
>  include/drm/ttm/ttm_resource.h     | 10 ++++---
>  2 files changed, 27 insertions(+), 31 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_resource.c b/drivers/gpu/drm/ttm/ttm_resource.c
> index db9a7a3717c4..8bfbddddc0e8 100644
> --- a/drivers/gpu/drm/ttm/ttm_resource.c
> +++ b/drivers/gpu/drm/ttm/ttm_resource.c
> @@ -496,50 +496,44 @@ struct ttm_resource *
>  ttm_resource_manager_first(struct ttm_resource_manager *man,
>  			   struct ttm_resource_cursor *cursor)
>  {
> -	struct ttm_lru_item *lru;
> -
>  	lockdep_assert_held(&man->bdev->lru_lock);
>  
> -	for (cursor->priority = 0; cursor->priority < TTM_MAX_BO_PRIORITY;
> -	     ++cursor->priority)
> -		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
> -			if (ttm_lru_item_is_res(lru))
> -				return ttm_lru_item_to_res(lru);
> -		}
> -
> -	return NULL;
> +	cursor->priority = 0;
> +	cursor->man = man;
> +	cursor->cur = &man->lru[cursor->priority];
> +	return ttm_resource_manager_next(cursor);
>  }
>  
>  /**
>   * ttm_resource_manager_next
>   *
> - * @man: resource manager to iterate over
>   * @cursor: cursor to record the position
> - * @res: the current resource pointer
>   *
> - * Returns the next resource from the resource manager.
> + * Return: the next resource from the resource manager.
>   */
>  struct ttm_resource *
> -ttm_resource_manager_next(struct ttm_resource_manager *man,
> -			  struct ttm_resource_cursor *cursor,
> -			  struct ttm_resource *res)
> +ttm_resource_manager_next(struct ttm_resource_cursor *cursor)
>  {
> -	struct ttm_lru_item *lru = &res->lru;
> +	struct ttm_resource_manager *man = cursor->man;
> +	struct ttm_lru_item *lru;
>  
>  	lockdep_assert_held(&man->bdev->lru_lock);
>  
> -	list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
> -		if (ttm_lru_item_is_res(lru))
> -			return ttm_lru_item_to_res(lru);
> -	}
> -
> -	for (++cursor->priority; cursor->priority < TTM_MAX_BO_PRIORITY;
> -	     ++cursor->priority)
> -		list_for_each_entry(lru, &man->lru[cursor->priority], link) {
> -			if (ttm_lru_item_is_res(lru))
> -				ttm_lru_item_to_res(lru);
> +	for (;;) {
> +		lru = list_entry(cursor->cur, typeof(*lru), link);
> +		list_for_each_entry_continue(lru, &man->lru[cursor->priority], link) {
> +			if (ttm_lru_item_is_res(lru)) {
> +				cursor->cur = &lru->link;
> +				return ttm_lru_item_to_res(lru);
> +			}
>  		}
>  
> +		if (++cursor->priority >= TTM_MAX_BO_PRIORITY)
> +			break;
> +
> +		cursor->cur = &man->lru[cursor->priority];
> +	}
> +
>  	return NULL;
>  }
>  
> diff --git a/include/drm/ttm/ttm_resource.h b/include/drm/ttm/ttm_resource.h
> index 1511d91e290d..7d81fd5b5b83 100644
> --- a/include/drm/ttm/ttm_resource.h
> +++ b/include/drm/ttm/ttm_resource.h
> @@ -272,11 +272,15 @@ ttm_lru_item_to_res(struct ttm_lru_item *item)
>  /**
>   * struct ttm_resource_cursor
>   *
> + * @man: The resource manager currently being iterated over.
> + * @cur: The list head the cursor currently points to.
>   * @priority: the current priority
>   *
>   * Cursor to iterate over the resources in a manager.
>   */
>  struct ttm_resource_cursor {
> +	struct ttm_resource_manager *man;
> +	struct list_head *cur;
>  	unsigned int priority;
>  };
>  
> @@ -438,9 +442,7 @@ struct ttm_resource *
>  ttm_resource_manager_first(struct ttm_resource_manager *man,
>  			   struct ttm_resource_cursor *cursor);
>  struct ttm_resource *
> -ttm_resource_manager_next(struct ttm_resource_manager *man,
> -			  struct ttm_resource_cursor *cursor,
> -			  struct ttm_resource *res);
> +ttm_resource_manager_next(struct ttm_resource_cursor *cursor);
>  
>  struct ttm_resource *
>  ttm_lru_first_res_or_null(struct list_head *head);
> @@ -455,7 +457,7 @@ ttm_lru_first_res_or_null(struct list_head *head);
>   */
>  #define ttm_resource_manager_for_each_res(man, cursor, res)		\
>  	for (res = ttm_resource_manager_first(man, cursor); res;	\
> -	     res = ttm_resource_manager_next(man, cursor, res))
> +	     res = ttm_resource_manager_next(cursor))
>  
>  struct ttm_kmap_iter *
>  ttm_kmap_iter_iomap_init(struct ttm_kmap_iter_iomap *iter_io,
> -- 
> 2.44.0
>