UMAP_PAGES_LOCKED
KASSERT((umap->flags & UMAP_PAGES_LOCKED) == 0);
umap->flags |= UMAP_PAGES_LOCKED;
KASSERT((umap->flags & UMAP_PAGES_LOCKED) == 0);
if (umap->flags & UMAP_PAGES_LOCKED) {
umap->flags &= ~UMAP_PAGES_LOCKED;