drm/i915/userptr: Deactivate a failed userptr if the worker reports an EFAULT

If the worker fails, it no longer has pages to release and can be
immediately removed from the invalidate-tree.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170307205851.32578-1-chris@chris-wilson.co.uk
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

drivers/gpu/drm/i915/i915_gem_userptr.c

@@ -541,6 +541,8 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
 		}
 
 		obj->userptr.work = ERR_CAST(pages);
+		if (IS_ERR(pages))
+			__i915_gem_userptr_set_active(obj, false);
 	}
 	mutex_unlock(&obj->mm.lock);