Re: [PATCH] drm: Declare that create drm_mm nodes with size 0 is illegal

On Wed, Aug 3, 2016 at 8:26 PM, Chris Wilson chris@chris-wilson.co.uk wrote:

At a higher level, all objects are created with definite size i.e. 0 is illegal. In forthcoming patches, this assumption is dependent upon in the drm_mm range manager, i.e. trying to create a drm_mm node with size 0 will have undefined behaviour. Add a couple of WARNs upon creating the drm_mm node to prevent later bugs.

Signed-off-by: Chris Wilson chris@chris-wilson.co.uk

drivers/gpu/drm/drm_mm.c | 9 +++++++++ 1 file changed, 9 insertions(+)

Reviewed-by: David Herrmann dh.herrmann@gmail.com

Thanks David

diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c index cb39f45d6a16..e8c15795386d 100644 --- a/drivers/gpu/drm/drm_mm.c +++ b/drivers/gpu/drm/drm_mm.c @@ -185,6 +185,9 @@ int drm_mm_reserve_node(struct drm_mm *mm, struct drm_mm_node *node)

    BUG_ON(node == NULL);

•   if (WARN_ON(node->size == 0))
  

•           return -EINVAL;
  

•   end = node->start + node->size;
  
    /* Find the relevant hole to add our node to */
  

@@ -239,6 +242,9 @@ int drm_mm_insert_node_generic(struct drm_mm *mm, struct drm_mm_node *node, { struct drm_mm_node *hole_node;

•   if (WARN_ON(size == 0))
  

•           return -EINVAL;
  

•   hole_node = drm_mm_search_free_generic(mm, size, alignment,
                                           color, sflags);
    if (!hole_node)
  

@@ -340,6 +346,9 @@ int drm_mm_insert_node_in_range_generic(struct drm_mm *mm, struct drm_mm_node *n { struct drm_mm_node *hole_node;

•   if (WARN_ON(size == 0))
  

•           return -EINVAL;
  

•   hole_node = drm_mm_search_free_in_range_generic(mm,
                                                    size, alignment, color,
                                                    start, end, sflags);
  

-- 2.8.1

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