Re: [PATCH v4 2/6] drm: improve drm_buddy_alloc function

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Hi

Am 01.12.21 um 17:39 schrieb Arunpravin:
- Make drm_buddy_alloc a single function to handle
   range allocation and non-range allocation demands

- Implemented a new function alloc_range() which allocates
   the requested power-of-two block comply with range limitations

- Moved order computation and memory alignment logic from
   i915 driver to drm buddy

v2:
   merged below changes to keep the build unbroken
    - drm_buddy_alloc_range() becomes obsolete and may be removed
    - enable ttm range allocation (fpfn / lpfn) support in i915 driver
    - apply enhanced drm_buddy_alloc() function to i915 driver

v3(Matthew Auld):
   - Fix alignment issues and remove unnecessary list_empty check
   - add more validation checks for input arguments
   - make alloc_range() block allocations as bottom-up
   - optimize order computation logic
   - replace uint64_t with u64, which is preferred in the kernel

v4(Matthew Auld):
   - keep drm_buddy_alloc_range() function implementation for generic
     actual range allocations
   - keep alloc_range() implementation for end bias allocations

Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@xxxxxxx>
---
  drivers/gpu/drm/drm_buddy.c                   | 316 +++++++++++++-----
  drivers/gpu/drm/i915/i915_ttm_buddy_manager.c |  67 ++--
  drivers/gpu/drm/i915/i915_ttm_buddy_manager.h |   2 +
  include/drm/drm_buddy.h                       |  22 +-
  4 files changed, 285 insertions(+), 122 deletions(-)

diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 9340a4b61c5a..7f47632821f4 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -280,23 +280,97 @@ void drm_buddy_free_list(struct drm_buddy_mm *mm, struct list_head *objects)
  }
  EXPORT_SYMBOL(drm_buddy_free_list);
-/**
- * drm_buddy_alloc - allocate power-of-two blocks
- *
- * @mm: DRM buddy manager to allocate from
- * @order: size of the allocation
- *
- * The order value here translates to:
- *
- * 0 = 2^0 * mm->chunk_size
- * 1 = 2^1 * mm->chunk_size
- * 2 = 2^2 * mm->chunk_size
- *
- * Returns:
- * allocated ptr to the &drm_buddy_block on success
- */
-struct drm_buddy_block *
-drm_buddy_alloc(struct drm_buddy_mm *mm, unsigned int order)
+static inline bool overlaps(u64 s1, u64 e1, u64 s2, u64 e2)
+{
+	return s1 <= e2 && e1 >= s2;
+}
+
+static inline bool contains(u64 s1, u64 e1, u64 s2, u64 e2)
+{
+	return s1 <= s2 && e1 >= e2;
+}
+
+static struct drm_buddy_block *
+alloc_range_bias(struct drm_buddy_mm *mm,
+		 u64 start, u64 end,
+		 unsigned int order)
+{
+	struct drm_buddy_block *block;
+	struct drm_buddy_block *buddy;
+	LIST_HEAD(dfs);
+	int err;
+	int i;
+
+	end = end - 1;
+
+	for (i = 0; i < mm->n_roots; ++i)
+		list_add_tail(&mm->roots[i]->tmp_link, &dfs);
+
+	do {
+		u64 block_start;
+		u64 block_end;
+
+		block = list_first_entry_or_null(&dfs,
+						 struct drm_buddy_block,
+						 tmp_link);
+		if (!block)
+			break;
+
+		list_del(&block->tmp_link);
+
+		if (drm_buddy_block_order(block) < order)
+			continue;
+
+		block_start = drm_buddy_block_offset(block);
+		block_end = block_start + drm_buddy_block_size(mm, block) - 1;
+
+		if (!overlaps(start, end, block_start, block_end))
+			continue;
+
+		if (drm_buddy_block_is_allocated(block))
+			continue;
+
+		if (contains(start, end, block_start, block_end) &&
+		    order == drm_buddy_block_order(block)) {
+			/*
+			 * Find the free block within the range.
+			 */
+			if (drm_buddy_block_is_free(block))
+				return block;
+
+			continue;
+		}
+
+		if (!drm_buddy_block_is_split(block)) {
+			err = split_block(mm, block);
+			if (unlikely(err))
+				goto err_undo;
+		}
+
+		list_add(&block->right->tmp_link, &dfs);
+		list_add(&block->left->tmp_link, &dfs);
+	} while (1);
+
+	return ERR_PTR(-ENOSPC);
+
+err_undo:
+	/*
+	 * We really don't want to leave around a bunch of split blocks, since
+	 * bigger is better, so make sure we merge everything back before we
+	 * free the allocated blocks.
+	 */
+	buddy = get_buddy(block);
+	if (buddy &&
+	    (drm_buddy_block_is_free(block) &&
+	     drm_buddy_block_is_free(buddy)))
+		__drm_buddy_free(mm, block);
+	return ERR_PTR(err);
+}
+
+static struct drm_buddy_block *
+alloc_from_freelist(struct drm_buddy_mm *mm,
+		    unsigned int order,
+		    unsigned long flags)
  {
  	struct drm_buddy_block *block = NULL;
  	unsigned int i;
@@ -318,78 +392,28 @@ drm_buddy_alloc(struct drm_buddy_mm *mm, unsigned int order)
  	while (i != order) {
  		err = split_block(mm, block);
  		if (unlikely(err))
-			goto out_free;
+			goto err_undo;
- /* Go low */
-		block = block->left;
+		block = block->right;
  		i--;
  	}
-
-	mark_allocated(block);
-	mm->avail -= drm_buddy_block_size(mm, block);
-	kmemleak_update_trace(block);
  	return block;
-out_free:
+err_undo:
  	if (i != order)
  		__drm_buddy_free(mm, block);
  	return ERR_PTR(err);
  }
-EXPORT_SYMBOL(drm_buddy_alloc);
-
-static inline bool overlaps(u64 s1, u64 e1, u64 s2, u64 e2)
-{
-	return s1 <= e2 && e1 >= s2;
-}
-static inline bool contains(u64 s1, u64 e1, u64 s2, u64 e2)
-{
-	return s1 <= s2 && e1 >= e2;
-}
-
-/**
- * drm_buddy_alloc_range - allocate range
- *
- * @mm: DRM buddy manager to allocate from
- * @blocks: output list head to add allocated blocks
- * @start: start of the allowed range for this block
- * @size: size of the allocation
- *
- * Intended for pre-allocating portions of the address space, for example to
- * reserve a block for the initial framebuffer or similar, hence the expectation
- * here is that drm_buddy_alloc() is still the main vehicle for
- * allocations, so if that's not the case then the drm_mm range allocator is
- * probably a much better fit, and so you should probably go use that instead.
- *
- * Note that it's safe to chain together multiple alloc_ranges
- * with the same blocks list
- *
- * Returns:
- * 0 on success, error code on failure.
- */
-int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
-			  struct list_head *blocks,
-			  u64 start, u64 size)
+static int __alloc_range(struct drm_buddy_mm *mm,
+			 struct list_head *dfs,
+			 u64 start, u64 size,
+			 struct list_head *blocks)
  {
  	struct drm_buddy_block *block;
  	struct drm_buddy_block *buddy;
-	LIST_HEAD(allocated);
-	LIST_HEAD(dfs);
  	u64 end;
  	int err;
-	int i;
-
-	if (size < mm->chunk_size)
-		return -EINVAL;
-
-	if (!IS_ALIGNED(size | start, mm->chunk_size))
-		return -EINVAL;
-
-	if (range_overflows(start, size, mm->size))
-		return -EINVAL;
-
-	for (i = 0; i < mm->n_roots; ++i)
-		list_add_tail(&mm->roots[i]->tmp_link, &dfs);
end = start + size - 1; @@ -397,7 +421,7 @@ int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
  		u64 block_start;
  		u64 block_end;
- block = list_first_entry_or_null(&dfs,
+		block = list_first_entry_or_null(dfs,
  						 struct drm_buddy_block,
  						 tmp_link);
  		if (!block)
@@ -424,7 +448,7 @@ int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
mark_allocated(block);
  			mm->avail -= drm_buddy_block_size(mm, block);
-			list_add_tail(&block->link, &allocated);
+			list_add_tail(&block->link, blocks);
  			continue;
  		}
@@ -434,11 +458,10 @@ int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
  				goto err_undo;
  		}
- list_add(&block->right->tmp_link, &dfs);
-		list_add(&block->left->tmp_link, &dfs);
+		list_add(&block->right->tmp_link, dfs);
+		list_add(&block->left->tmp_link, dfs);
  	} while (1);
- list_splice_tail(&allocated, blocks);
  	return 0;
err_undo:
@@ -453,11 +476,144 @@ int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
  	     drm_buddy_block_is_free(buddy)))
  		__drm_buddy_free(mm, block);
+err_free:
+	drm_buddy_free_list(mm, blocks);
+	return err;
+}
+
+/**
+ * __drm_buddy_alloc_range - actual range allocation
+ *
+ * @mm: DRM buddy manager to allocate from
+ * @start: start of the allowed range for this block
+ * @size: size of the allocation
+ * @blocks: output list head to add allocated blocks
+ *
+ * Intended for pre-allocating portions of the address space, for example to
+ * reserve a block for the initial framebuffer or similar
+ *
+ * Note that it's safe to chain together multiple alloc_ranges
+ * with the same blocks list
+ *
+ * Returns:
+ * 0 on success, error code on failure.
+ */
+static int __drm_buddy_alloc_range(struct drm_buddy_mm *mm,
+				   u64 start,
+				   u64 size,
+				   struct list_head *blocks)
+{
+	LIST_HEAD(dfs);
+	int i;
+
+	for (i = 0; i < mm->n_roots; ++i)
+		list_add_tail(&mm->roots[i]->tmp_link, &dfs);
+
+	return __alloc_range(mm, &dfs, start, size, blocks);
+}
+
+/**
+ * drm_buddy_alloc - allocate power-of-two blocks
+ *
+ * @mm: DRM buddy manager to allocate from
+ * @start: start of the allowed range for this block
+ * @end: end of the allowed range for this block
+ * @size: size of the allocation
+ * @min_page_size: alignment of the allocation
+ * @blocks: output list head to add allocated blocks
+ * @flags: DRM_BUDDY_*_ALLOCATION flags
+ *
+ * alloc_range_bias() called on range limitations, which traverses
+ * the tree and returns the desired block.
+ *
+ * alloc_from_freelist() called when *no* range restrictions
+ * are enforced, which picks the block from the freelist.
+ *
+ * blocks are allocated in order, the order value here translates to:
+ *
+ * 0 = 2^0 * mm->chunk_size
+ * 1 = 2^1 * mm->chunk_size
+ * 2 = 2^2 * mm->chunk_size
+ *
+ * Returns:
+ * 0 on success, error code on failure.
+ */
+int drm_buddy_alloc(struct drm_buddy_mm *mm,
+		    u64 start, u64 end, u64 size,
+		    u64 min_page_size,
+		    struct list_head *blocks,
+		    unsigned long flags)
+{
+	struct drm_buddy_block *block = NULL;
+	unsigned int min_order, order;
+	unsigned long pages;
+	LIST_HEAD(allocated);
+	int err;
+
+	if (size < mm->chunk_size)
+		return -EINVAL;
+
+	if (min_page_size < mm->chunk_size)
+		return -EINVAL;
+
+	if (!is_power_of_2(min_page_size))
+		return -EINVAL;
+
+	if (!IS_ALIGNED(start | end | size, mm->chunk_size))
+		return -EINVAL;
+
+	if (check_range_overflow(start, end, size, mm->size))
+		return -EINVAL;
+
+	/* Actual range allocation */
+	if (start + size == end)
+		return __drm_buddy_alloc_range(mm, start, size, blocks);
+
+	pages = size >> ilog2(mm->chunk_size);
+	order = fls(pages) - 1;
+	min_order = ilog2(min_page_size) - ilog2(mm->chunk_size);
+
+	do {
+		order = min(order, (unsigned int)fls(pages) - 1);
+		BUG_ON(order > mm->max_order);
+		BUG_ON(order < min_order);
+
+		do {
+			if (flags & DRM_BUDDY_RANGE_ALLOCATION)
+				/* Allocate traversing within the range */
+				block = alloc_range_bias(mm, start, end, order);
+			else
+				/* Allocate from freelist */
+				block = alloc_from_freelist(mm, order, flags);
+
+			if (!IS_ERR(block))
+				break;
+
+			if (order-- == min_order) {
+				err = -ENOSPC;
+				goto err_free;
+			}
+		} while (1);
+
+		mark_allocated(block);
+		mm->avail -= drm_buddy_block_size(mm, block);
+		kmemleak_update_trace(block);
+		list_add_tail(&block->link, &allocated);
+
+		pages -= BIT(order);
+
+		if (!pages)
+			break;
+	} while (1);
+
+	list_splice_tail(&allocated, blocks);
+	return 0;
+
  err_free:
  	drm_buddy_free_list(mm, &allocated);
  	return err;
  }
-EXPORT_SYMBOL(drm_buddy_alloc_range);
+EXPORT_SYMBOL(drm_buddy_alloc);
/**
   * drm_buddy_block_print - print block information
diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
index c4b70cb8c248..7621d42155e6 100644
--- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
+++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.c
@@ -36,13 +36,14 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
  	struct i915_ttm_buddy_manager *bman = to_buddy_manager(man);
  	struct i915_ttm_buddy_resource *bman_res;
  	struct drm_buddy_mm *mm = &bman->mm;
-	unsigned long n_pages;
-	unsigned int min_order;
+	unsigned long n_pages, lpfn;
  	u64 min_page_size;
  	u64 size;
  	int err;
- GEM_BUG_ON(place->fpfn || place->lpfn);
+	lpfn = place->lpfn;
+	if (!lpfn)
+		lpfn = man->size;
bman_res = kzalloc(sizeof(*bman_res), GFP_KERNEL);
  	if (!bman_res)
@@ -52,6 +53,9 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
  	INIT_LIST_HEAD(&bman_res->blocks);
  	bman_res->mm = mm;
+ if (place->fpfn || lpfn != man->size)
+		bman_res->flags |= DRM_BUDDY_RANGE_ALLOCATION;
+
  	GEM_BUG_ON(!bman_res->base.num_pages);
  	size = bman_res->base.num_pages << PAGE_SHIFT;
@@ -60,10 +64,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
  		min_page_size = bo->page_alignment << PAGE_SHIFT;
GEM_BUG_ON(min_page_size < mm->chunk_size);
-	min_order = ilog2(min_page_size) - ilog2(mm->chunk_size);
+
  	if (place->flags & TTM_PL_FLAG_CONTIGUOUS) {
+		unsigned long pages;
+
  		size = roundup_pow_of_two(size);
-		min_order = ilog2(size) - ilog2(mm->chunk_size);
+		min_page_size = size;
+
+		pages = size >> ilog2(mm->chunk_size);
+		if (pages > lpfn)
+			lpfn = pages;
  	}
if (size > mm->size) {
@@ -73,34 +83,16 @@ static int i915_ttm_buddy_man_alloc(struct ttm_resource_manager *man,
n_pages = size >> ilog2(mm->chunk_size); - do {
-		struct drm_buddy_block *block;
-		unsigned int order;
-
-		order = fls(n_pages) - 1;
-		GEM_BUG_ON(order > mm->max_order);
-		GEM_BUG_ON(order < min_order);
-
-		do {
-			mutex_lock(&bman->lock);
-			block = drm_buddy_alloc(mm, order);
-			mutex_unlock(&bman->lock);
-			if (!IS_ERR(block))
-				break;
-
-			if (order-- == min_order) {
-				err = -ENOSPC;
-				goto err_free_blocks;
-			}
-		} while (1);
-
-		n_pages -= BIT(order);
-
-		list_add_tail(&block->link, &bman_res->blocks);
-
-		if (!n_pages)
-			break;
-	} while (1);
+	mutex_lock(&bman->lock);
+	err = drm_buddy_alloc(mm, (u64)place->fpfn << PAGE_SHIFT,
+			(u64)place->lpfn << PAGE_SHIFT,
+			(u64)n_pages << PAGE_SHIFT,
+			 min_page_size,
+			 &bman_res->blocks,
+			 bman_res->flags);
+	mutex_unlock(&bman->lock);
+	if (unlikely(err))
+		goto err_free_blocks;
*res = &bman_res->base;
  	return 0;
@@ -266,10 +258,17 @@ int i915_ttm_buddy_man_reserve(struct ttm_resource_manager *man,
  {
  	struct i915_ttm_buddy_manager *bman = to_buddy_manager(man);
  	struct drm_buddy_mm *mm = &bman->mm;
+	unsigned long flags = 0;
  	int ret;
+ flags |= DRM_BUDDY_RANGE_ALLOCATION;
+
  	mutex_lock(&bman->lock);
-	ret = drm_buddy_alloc_range(mm, &bman->reserved, start, size);
+	ret = drm_buddy_alloc(mm, start,
+			start + size,
+			size, mm->chunk_size,
+			&bman->reserved,
+			flags);
  	mutex_unlock(&bman->lock);
return ret;
diff --git a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
index fa644b512c2e..5ba490875f66 100644
--- a/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
+++ b/drivers/gpu/drm/i915/i915_ttm_buddy_manager.h
@@ -20,6 +20,7 @@ struct drm_buddy_mm;
   *
   * @base: struct ttm_resource base class we extend
   * @blocks: the list of struct i915_buddy_block for this resource/allocation
+ * @flags: DRM_BUDDY_*_ALLOCATION flags
   * @mm: the struct i915_buddy_mm for this resource
   *
   * Extends the struct ttm_resource to manage an address space allocation with
@@ -28,6 +29,7 @@ struct drm_buddy_mm;
  struct i915_ttm_buddy_resource {
  	struct ttm_resource base;
  	struct list_head blocks;
+	unsigned long flags;
  	struct drm_buddy_mm *mm;
  };
diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
index f9ff48a3f3a6..221de702e909 100644
--- a/include/drm/drm_buddy.h
+++ b/include/drm/drm_buddy.h
@@ -13,15 +13,22 @@
#include <drm/drm_print.h> -#define range_overflows(start, size, max) ({ \
+#define check_range_overflow(start, end, size, max) ({ \
  	typeof(start) start__ = (start); \
+	typeof(end) end__ = (end);\
  	typeof(size) size__ = (size); \
  	typeof(max) max__ = (max); \
  	(void)(&start__ == &size__); \
  	(void)(&start__ == &max__); \
-	start__ >= max__ || size__ > max__ - start__; \
+	(void)(&start__ == &end__); \
+	(void)(&end__ == &size__); \
+	(void)(&end__ == &max__); \
+	start__ >= max__ || end__ > max__ || \
+	size__ > end__ - start__; \
  })
+#define DRM_BUDDY_RANGE_ALLOCATION (1 << 0)
+
  struct drm_buddy_block {
  #define DRM_BUDDY_HEADER_OFFSET GENMASK_ULL(63, 12)
  #define DRM_BUDDY_HEADER_STATE  GENMASK_ULL(11, 10)
@@ -132,12 +139,11 @@ int drm_buddy_init(struct drm_buddy_mm *mm, u64 size, u64 chunk_size);
void drm_buddy_fini(struct drm_buddy_mm *mm); -struct drm_buddy_block *
-drm_buddy_alloc(struct drm_buddy_mm *mm, unsigned int order);

Just a style issue. The structure is called drm_buddy_mm. For consistency, I like to suggest to name all the public interfaces and defines drm_buddy_mm_* instead of just drm_buddy_*.


-
-int drm_buddy_alloc_range(struct drm_buddy_mm *mm,
-			  struct list_head *blocks,
-			  u64 start, u64 size);
+int drm_buddy_alloc(struct drm_buddy_mm *mm,
+		    u64 start, u64 end, u64 size,
+		    u64 min_page_size,
+		    struct list_head *blocks,
+		    unsigned long flags);
void drm_buddy_free(struct drm_buddy_mm *mm, struct drm_buddy_block *block);

I'd call those *_alloc_blocks() and _free_blocks(). Right now it sounds as if they allocate and free instances of drm_buddy_mm.

Best regards
Thomas

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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