drm/i915: Add a few more sanity checks for stolen handling

We should never be called via obj->ops->release() on anything other than
a fully formed stolen object, so raise that to an assert. In the process
tidy up a comment and variable no longer used outside of a conditional
BUG.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/20161117155846.4631-1-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.auld@intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
index 9b182ed93f3e82cfd5694709b66140f2c1f14174..5bc9f699fdd2ca8d366a9349599378b4b21d6960 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
@@ -513,11 +513,10 @@ i915_pages_create_for_stolen(struct drm_device *dev,
                             u32 offset, u32 size)
 {
        struct drm_i915_private *dev_priv = to_i915(dev);
-       struct i915_ggtt *ggtt = &dev_priv->ggtt;
        struct sg_table *st;
        struct scatterlist *sg;
 
-       GEM_BUG_ON(offset > ggtt->stolen_size - size);
+       GEM_BUG_ON(offset > dev_priv->ggtt.stolen_size - size);
 
        /* We hide that we have no struct page backing our stolen object
         * by wrapping the contiguous physical allocation with a fake
@@ -554,7 +553,7 @@ i915_gem_object_get_pages_stolen(struct drm_i915_gem_object *obj)
 static void i915_gem_object_put_pages_stolen(struct drm_i915_gem_object *obj,
                                             struct sg_table *pages)
 {
-       /* Should only be called during free */
+       /* Should only be called from i915_gem_object_release_stolen() */
        sg_free_table(pages);
        kfree(pages);
 }
@@ -563,15 +562,16 @@ static void
 i915_gem_object_release_stolen(struct drm_i915_gem_object *obj)
 {
        struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
+       struct drm_mm_node *stolen = fetch_and_zero(&obj->stolen);
+
+       GEM_BUG_ON(!stolen);
 
        __i915_gem_object_unpin_pages(obj);
 
-       if (obj->stolen) {
-               i915_gem_stolen_remove_node(dev_priv, obj->stolen);
-               kfree(obj->stolen);
-               obj->stolen = NULL;
-       }
+       i915_gem_stolen_remove_node(dev_priv, stolen);
+       kfree(stolen);
 }
+
 static const struct drm_i915_gem_object_ops i915_gem_object_stolen_ops = {
        .get_pages = i915_gem_object_get_pages_stolen,
        .put_pages = i915_gem_object_put_pages_stolen,