Re: [PATCH] list: introduce list_bulk_move_tail helper

[Huang Rui <ray.huang-5C7GfCeVMHo@public.gmane.org>]

On Mon, Sep 17, 2018 at 02:08:34PM +0200, Christian König wrote:
> Move all entries between @first and including @last before @head.
> 
> This is useful for LRU lists where a whole block of entries should be
> moved to the end of the list.
> 
> Used as a band aid in TTM, but better placed in the common list headers.
> 
> Signed-off-by: Christian König <christian.koenig@amd.com>
> ---

For TTM change, patch is Reviewed-by: Huang Rui <ray.huang@amd.com>

For new list_bulk_move_tail helper in hinclude/linux/list.h, may we have
your comments from LKML?

Thanks,
Ray

>  drivers/gpu/drm/ttm/ttm_bo.c | 25 +++++--------------------
>  include/linux/list.h         | 23 +++++++++++++++++++++++
>  2 files changed, 28 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
> index b2a33bf1ef10..26b889f86670 100644
> --- a/drivers/gpu/drm/ttm/ttm_bo.c
> +++ b/drivers/gpu/drm/ttm/ttm_bo.c
> @@ -247,20 +247,6 @@ void ttm_bo_move_to_lru_tail(struct ttm_buffer_object *bo,
>  }
>  EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
>  
> -static void ttm_list_move_bulk_tail(struct list_head *list,
> -				    struct list_head *first,
> -				    struct list_head *last)
> -{
> -	first->prev->next = last->next;
> -	last->next->prev = first->prev;
> -
> -	list->prev->next = first;
> -	first->prev = list->prev;
> -
> -	last->next = list;
> -	list->prev = last;
> -}
> -
>  void ttm_bo_bulk_move_lru_tail(struct ttm_lru_bulk_move *bulk)
>  {
>  	unsigned i;
> @@ -276,8 +262,8 @@ void ttm_bo_bulk_move_lru_tail(struct ttm_lru_bulk_move *bulk)
>  		reservation_object_assert_held(pos->last->resv);
>  
>  		man = &pos->first->bdev->man[TTM_PL_TT];
> -		ttm_list_move_bulk_tail(&man->lru[i], &pos->first->lru,
> -					&pos->last->lru);
> +		list_bulk_move_tail(&man->lru[i], &pos->first->lru,
> +				    &pos->last->lru);
>  	}
>  
>  	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
> @@ -291,8 +277,8 @@ void ttm_bo_bulk_move_lru_tail(struct ttm_lru_bulk_move *bulk)
>  		reservation_object_assert_held(pos->last->resv);
>  
>  		man = &pos->first->bdev->man[TTM_PL_VRAM];
> -		ttm_list_move_bulk_tail(&man->lru[i], &pos->first->lru,
> -					&pos->last->lru);
> +		list_bulk_move_tail(&man->lru[i], &pos->first->lru,
> +				    &pos->last->lru);
>  	}
>  
>  	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
> @@ -306,8 +292,7 @@ void ttm_bo_bulk_move_lru_tail(struct ttm_lru_bulk_move *bulk)
>  		reservation_object_assert_held(pos->last->resv);
>  
>  		lru = &pos->first->bdev->glob->swap_lru[i];
> -		ttm_list_move_bulk_tail(lru, &pos->first->swap,
> -					&pos->last->swap);
> +		list_bulk_move_tail(lru, &pos->first->swap, &pos->last->swap);
>  	}
>  }
>  EXPORT_SYMBOL(ttm_bo_bulk_move_lru_tail);
> diff --git a/include/linux/list.h b/include/linux/list.h
> index de04cc5ed536..edb7628e46ed 100644
> --- a/include/linux/list.h
> +++ b/include/linux/list.h
> @@ -183,6 +183,29 @@ static inline void list_move_tail(struct list_head *list,
>  	list_add_tail(list, head);
>  }
>  
> +/**
> + * list_bulk_move_tail - move a subsection of a list to its tail
> + * @head: the head that will follow our entry
> + * @first: first entry to move
> + * @last: last entry to move, can be the same as first
> + *
> + * Move all entries between @first and including @last before @head.
> + * All three entries must belong to the same linked list.
> + */
> +static inline void list_bulk_move_tail(struct list_head *head,
> +				       struct list_head *first,
> +				       struct list_head *last)
> +{
> +	first->prev->next = last->next;
> +	last->next->prev = first->prev;
> +
> +	head->prev->next = first;
> +	first->prev = head->prev;
> +
> +	last->next = head;
> +	head->prev = last;
> +}
> +
>  /**
>   * list_is_last - tests whether @list is the last entry in list @head
>   * @list: the entry to test
> -- 
> 2.14.1
> 
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