drm/i915: Move __i915_gem_free_object to ttm_bo_destroy

When we implement delayed destroy, we may have a second
call to the delete_mem_notify() handler, while free_object()
only should be called once.

Move it to bo->destroy(), to ensure it's only called once.
This fixes some weird memory corruption issues with delayed
destroy when async eviction is used.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210830121006.2978297-2-maarten.lankhorst@linux.intel.com
Fixes: 213d5092 ("drm/i915/ttm: Introduce a TTM i915 gem object backend")
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

drivers/gpu/drm/i915/gem/i915_gem_ttm.c

@@ -356,11 +356,8 @@ static void i915_ttm_delete_mem_notify(struct ttm_buffer_object *bo)
 {
 	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
 
-	if (likely(obj)) {
-		/* This releases all gem object bindings to the backend. */
+	if (likely(obj))
 		i915_ttm_free_cached_io_st(obj);
-		__i915_gem_free_object(obj);
-	}
 }
 
 static struct intel_memory_region *
@@ -886,8 +883,12 @@ void i915_ttm_bo_destroy(struct ttm_buffer_object *bo)
 {
 	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
 
+	/* This releases all gem object bindings to the backend. */
+	__i915_gem_free_object(obj);
+
 	i915_gem_object_release_memory_region(obj);
 	mutex_destroy(&obj->ttm.get_io_page.lock);
+
 	if (obj->ttm.created)
 		call_rcu(&obj->rcu, __i915_gem_free_object_rcu);
 }