SHRINKER_NONSLAB
compr_pool.shrinker = shrinker_alloc(SHRINKER_NONSLAB, "btrfs-compr-pages");
mp->m_inodegc_shrinker = shrinker_alloc(SHRINKER_NONSLAB,
SHRINKER_NONSLAB,
!(shrinker->flags & SHRINKER_NONSLAB))