__I915_MADV_PURGED
obj->mm.madv = __I915_MADV_PURGED;
case __I915_MADV_PURGED:
GEM_BUG_ON(obj->mm.madv == __I915_MADV_PURGED);
if (obj->mm.madv == __I915_MADV_PURGED)
obj->mm.madv = __I915_MADV_PURGED;
case __I915_MADV_PURGED:
if (obj->mm.madv != __I915_MADV_PURGED) {
args->retained = obj->mm.madv != __I915_MADV_PURGED;