root_anon_vma     511 mm/rmap.c      	struct anon_vma *root_anon_vma;
root_anon_vma     522 mm/rmap.c      	root_anon_vma = READ_ONCE(anon_vma->root);
root_anon_vma     523 mm/rmap.c      	if (down_read_trylock(&root_anon_vma->rwsem)) {
root_anon_vma     530 mm/rmap.c      			up_read(&root_anon_vma->rwsem);