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Subject: Re: [PATCH] list: introduce list_bulk_move_tail helper
To:     =?UTF-8?Q?Christian_K=c3=b6nig?= <ckoenig.leichtzumerken@gmail.com>,
        <linux-kernel@vger.kernel.org>, <dri-devel@lists.freedesktop.org>,
        <amd-gfx@lists.freedesktop.org>
References: <20180917120834.13993-1-christian.koenig@amd.com>
From:   "Zhang, Jerry(Junwei)" <Jerry.Zhang@amd.com>
Message-ID: <84fbcd38-8433-1e87-e6e9-90dcb96168a9@amd.com>
Date:   Tue, 18 Sep 2018 14:00:04 +0800
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On 09/17/2018 08:08 PM, 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>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
> ---
>   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