On 25/10/2021 14:00, Arunpravin wrote:
On contiguous allocation, we round up the size
to the *next* power of 2, implement a function
to free the unused pages after the newly allocate block.
Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@xxxxxxx>
Ideally this gets added with some user, so we can see it in action?
Maybe squash the next patch here?
---
drivers/gpu/drm/drm_buddy.c | 103 ++++++++++++++++++++++++++++++++++++
include/drm/drm_buddy.h | 4 ++
2 files changed, 107 insertions(+)
diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 9d3547bcc5da..0da8510736eb 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -284,6 +284,109 @@ static inline bool contains(u64 s1, u64 e1, u64 s2, u64 e2)
return s1 <= s2 && e1 >= e2;
}
+/**
+ * drm_buddy_free_unused_pages - free unused pages
+ *
+ * @mm: DRM buddy manager
+ * @actual_size: original size requested
+ * @blocks: output list head to add allocated blocks
+ *
+ * For contiguous allocation, we round up the size to the nearest
+ * power of two value, drivers consume *actual* size, so remaining
+ * portions are unused and it can be freed.
+ *
+ * Returns:
+ * 0 on success, error code on failure.
+ */
+int drm_buddy_free_unused_pages(struct drm_buddy_mm *mm,
drm_buddy_block_trim?
+ u64 actual_size,
new_size?
+ struct list_head *blocks)
+{
+ struct drm_buddy_block *block;
+ struct drm_buddy_block *buddy;
+ u64 actual_start;
+ u64 actual_end;
+ LIST_HEAD(dfs);
+ u64 count = 0;
+ int err;
+
+ if (!list_is_singular(blocks))
+ return -EINVAL;
+
+ block = list_first_entry_or_null(blocks,
+ struct drm_buddy_block,
+ link);
+
+ if (!block)
+ return -EINVAL;
list_is_singular() already ensures that I guess?
+
+ if (actual_size > drm_buddy_block_size(mm, block))
+ return -EINVAL;
+
+ if (actual_size == drm_buddy_block_size(mm, block))
+ return 0;
Probably need to check the alignment of the actual_size, and also check
that it is non-zero?
+
+ list_del(&block->link);
+
+ actual_start = drm_buddy_block_offset(block);
+ actual_end = actual_start + actual_size - 1;
+
+ if (drm_buddy_block_is_allocated(block))
That should rather be a programmer error.
+ mark_free(mm, block);
+
+ list_add(&block->tmp_link, &dfs);
+
+ while (1) {
+ block = list_first_entry_or_null(&dfs,
+ struct drm_buddy_block,
+ tmp_link);
+
+ if (!block)
+ break;
+
+ list_del(&block->tmp_link);
+
+ if (count == actual_size)
+ return 0;
Check for overlaps somewhere here to avoid needless searching and splitting?
+
+ if (contains(actual_start, actual_end, drm_buddy_block_offset(block),
+ (drm_buddy_block_offset(block) + drm_buddy_block_size(mm, block) - 1))) {
Could maybe record the start/end for better readability?
+ BUG_ON(!drm_buddy_block_is_free(block));
+
+ /* Allocate only required blocks */
+ mark_allocated(block);
+ mm->avail -= drm_buddy_block_size(mm, block);
+ list_add_tail(&block->link, blocks);
+ count += drm_buddy_block_size(mm, block);
+ continue;
+ }
+
+ if (drm_buddy_block_order(block) == 0)
+ continue;
Should be impossible with overlaps check added.
+
+ if (!drm_buddy_block_is_split(block)) {
That should always be true.
+ 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);
+ }
+
+ return -ENOSPC;
Would it make sense to factor out part of the alloc_range for this? It
looks roughly the same.
+
+err_undo:
+ 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;
Where do we add the block back to the original list? Did we not just
leak it?
+}
+EXPORT_SYMBOL(drm_buddy_free_unused_pages);
+
static struct drm_buddy_block *
alloc_range(struct drm_buddy_mm *mm,
u64 start, u64 end,
diff --git a/include/drm/drm_buddy.h b/include/drm/drm_buddy.h
index cd8021d2d6e7..1dfc80c88e1f 100644
--- a/include/drm/drm_buddy.h
+++ b/include/drm/drm_buddy.h
@@ -145,6 +145,10 @@ int drm_buddy_alloc(struct drm_buddy_mm *mm,
struct list_head *blocks,
unsigned long flags);
+int drm_buddy_free_unused_pages(struct drm_buddy_mm *mm,
+ u64 actual_size,
+ struct list_head *blocks);
+
void drm_buddy_free(struct drm_buddy_mm *mm, struct drm_buddy_block *block);
void drm_buddy_free_list(struct drm_buddy_mm *mm, struct list_head *objects);
