ttm_tt_swapout
num_pages = ttm_tt_swapout(devs->ttm_dev, tt, GFP_KERNEL);
ret = ttm_tt_swapout(bdev, tt, swapout_walk->gfp_flags);
EXPORT_SYMBOL_FOR_TESTS_ONLY(ttm_tt_swapout);
int ttm_tt_swapout(struct ttm_device *bdev, struct ttm_tt *ttm,