static struct mountpoint *lock_mount(struct path *path)
{
	struct vfsmount *mnt;
	struct dentry *dentry = path->dentry;
retry:
	inode_lock(dentry->d_inode);
	if (unlikely(cant_mount(dentry))) {
		inode_unlock(dentry->d_inode);
		return ERR_PTR(-ENOENT);
	}
	namespace_lock();
	mnt = lookup_mnt(path);
	if (likely(!mnt)) {
		struct mountpoint *mp = get_mountpoint(dentry);
		if (IS_ERR(mp)) {
			namespace_unlock();
			inode_unlock(dentry->d_inode);
			return mp;
		}
		return mp;
	}
	namespace_unlock();
	inode_unlock(path->dentry->d_inode);
	path_put(path);
	path->mnt = mnt;
	dentry = path->dentry = dget(mnt->mnt_root);
	goto retry;
}