+int nilfs_checkpoint_is_mounted(struct super_block *sb, __u64 cno)
+{
+ struct the_nilfs *nilfs = NILFS_SB(sb)->s_nilfs;
+ struct nilfs_root *root;
+ struct inode *inode;
+ struct dentry *dentry;
+ int ret;
+
+ if (cno < 0 || cno > nilfs->ns_cno)
+ return false;
+
+ if (cno >= nilfs_last_cno(nilfs))
+ return true; /* protect recent checkpoints */
+
+ ret = false;
+ root = nilfs_lookup_root(NILFS_SB(sb)->s_nilfs, cno);
+ if (root) {
+ inode = nilfs_ilookup(sb, root, NILFS_ROOT_INO);
+ if (inode) {
+ dentry = d_find_alias(inode);
+ if (dentry) {
+ if (nilfs_tree_was_touched(dentry))
+ ret = nilfs_try_to_shrink_tree(dentry);
+ dput(dentry);
+ }
+ iput(inode);
+ }
+ nilfs_put_root(root);
+ }
+ return ret;
+}
+