[PATCH 1/2] list: introduce list_bulk_move_tail helper

[PATCH 1/2] list: introduce list_bulk_move_tail helper

[Christian König]

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 an list.

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 include/linux/list.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

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

[PATCH 2/2] drm/ttm: once more fix ttm_bo_bulk_move_lru_tail v2

[Christian König]

While cutting the lists we sometimes accidentally added a list_head from
the stack to the LRUs, effectively corrupting the list.

Remove the list cutting and use explicit list manipulation instead.

v2: separate out new list_bulk_move_tail helper

Signed-off-by: Christian König <christian.koenig@amd.com>
---
 drivers/gpu/drm/ttm/ttm_bo.c | 46 +++++++++++++++++++-------------------------
 1 file changed, 20 insertions(+), 26 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 138c98902033..26b889f86670 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -247,47 +247,38 @@ void ttm_bo_move_to_lru_tail(struct ttm_buffer_object *bo,
 }
 EXPORT_SYMBOL(ttm_bo_move_to_lru_tail);
 
-static void ttm_bo_bulk_move_helper(struct ttm_lru_bulk_move_pos *pos,
-				    struct list_head *lru, bool is_swap)
-{
-	struct list_head *list;
-	LIST_HEAD(entries);
-	LIST_HEAD(before);
-
-	reservation_object_assert_held(pos->last->resv);
-	list = is_swap ? &pos->last->swap : &pos->last->lru;
-	list_cut_position(&entries, lru, list);
-
-	reservation_object_assert_held(pos->first->resv);
-	list = is_swap ? pos->first->swap.prev : pos->first->lru.prev;
-	list_cut_position(&before, &entries, list);
-
-	list_splice(&before, lru);
-	list_splice_tail(&entries, lru);
-}
-
 void ttm_bo_bulk_move_lru_tail(struct ttm_lru_bulk_move *bulk)
 {
 	unsigned i;
 
 	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
+		struct ttm_lru_bulk_move_pos *pos = &bulk->tt[i];
 		struct ttm_mem_type_manager *man;
 
-		if (!bulk->tt[i].first)
+		if (!pos->first)
 			continue;
 
-		man = &bulk->tt[i].first->bdev->man[TTM_PL_TT];
-		ttm_bo_bulk_move_helper(&bulk->tt[i], &man->lru[i], false);
+		reservation_object_assert_held(pos->first->resv);
+		reservation_object_assert_held(pos->last->resv);
+
+		man = &pos->first->bdev->man[TTM_PL_TT];
+		list_bulk_move_tail(&man->lru[i], &pos->first->lru,
+				    &pos->last->lru);
 	}
 
 	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
+		struct ttm_lru_bulk_move_pos *pos = &bulk->vram[i];
 		struct ttm_mem_type_manager *man;
 
-		if (!bulk->vram[i].first)
+		if (!pos->first)
 			continue;
 
-		man = &bulk->vram[i].first->bdev->man[TTM_PL_VRAM];
-		ttm_bo_bulk_move_helper(&bulk->vram[i], &man->lru[i], false);
+		reservation_object_assert_held(pos->first->resv);
+		reservation_object_assert_held(pos->last->resv);
+
+		man = &pos->first->bdev->man[TTM_PL_VRAM];
+		list_bulk_move_tail(&man->lru[i], &pos->first->lru,
+				    &pos->last->lru);
 	}
 
 	for (i = 0; i < TTM_MAX_BO_PRIORITY; ++i) {
@@ -297,8 +288,11 @@ void ttm_bo_bulk_move_lru_tail(struct ttm_lru_bulk_move *bulk)
 		if (!pos->first)
 			continue;
 
+		reservation_object_assert_held(pos->first->resv);
+		reservation_object_assert_held(pos->last->resv);
+
 		lru = &pos->first->bdev->glob->swap_lru[i];
-		ttm_bo_bulk_move_helper(&bulk->swap[i], lru, true);
+		list_bulk_move_tail(lru, &pos->first->swap, &pos->last->swap);
 	}
 }
 EXPORT_SYMBOL(ttm_bo_bulk_move_lru_tail);
-- 
2.14.1

Re: [PATCH 1/2] list: introduce list_bulk_move_tail helper

[Huang Rui]

On Thu, Sep 13, 2018 at 01:22:07PM +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 an list.
> 
> Signed-off-by: Christian König <christian.koenig@amd.com>

Bulk move helper is useful for TTM driver to improve the LRU moving
efficiency. Please go on with my RB.

Series are Reviewed-and-Tested-by: Huang Rui <ray.huang@amd.com>

> ---
>  include/linux/list.h | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> 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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