[PATCH v3] drm: add a check to verify the size alignment

[Arunpravin Paneer Selvam]

Add a simple check to reject any size not aligned to the
min_page_size.

when size is not aligned to min_page_size, driver module
should handle in their own way either to round_up() the
size value to min_page_size or just to enable WARN_ON().

If we dont handle the alignment properly, we may hit the
following bug, Unigine Heaven has allocation requests for
example required pages are 257 and alignment request is 256.
To allocate the left over 1 page, continues the iteration to
find the order value which is 0 and when it compares with
min_order = 8, triggers the BUG_ON(order < min_order).

v2: add more commit description
v3: remove WARN_ON()

Signed-off-by: Arunpravin Paneer Selvam <Arunpravin.PaneerSelvam at amd.com>
Suggested-by: Matthew Auld <matthew.auld at intel.com>
---
 drivers/gpu/drm/drm_buddy.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
index 72f52f293249..11bb59399471 100644
--- a/drivers/gpu/drm/drm_buddy.c
+++ b/drivers/gpu/drm/drm_buddy.c
@@ -665,6 +665,9 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm,
 	if (start + size == end)
 		return __drm_buddy_alloc_range(mm, start, size, blocks);
 
+	if (!IS_ALIGNED(size, min_page_size))
+		return -EINVAL;
+
 	pages = size >> ilog2(mm->chunk_size);
 	order = fls(pages) - 1;
 	min_order = ilog2(min_page_size) - ilog2(mm->chunk_size);

base-commit: 4dcdb745569d8eef8db09e24e8ff2e5dffc0664c
-- 
2.25.1