NFS: Reduce the stack footprint of nfs_follow_remote_path()

static int nfs_follow_remote_path(struct vfsmount *root_mnt,

		const char *export_path, struct vfsmount *mnt_target)

{

	struct nameidata *nd = NULL;

	struct mnt_namespace *ns_private;

	struct nameidata nd;

	struct super_block *s;

	int ret;

	nd = kmalloc(sizeof(*nd), GFP_KERNEL);

	if (nd == NULL)

		return -ENOMEM;

	ns_private = create_mnt_ns(root_mnt);

	ret = PTR_ERR(ns_private);

	if (IS_ERR(ns_private))

		goto out_mntput;

	ret = vfs_path_lookup(root_mnt->mnt_root, root_mnt,

			export_path, LOOKUP_FOLLOW, &nd);

			export_path, LOOKUP_FOLLOW, nd);

	put_mnt_ns(ns_private);

	if (ret != 0)

		goto out_err;

	s = nd.path.mnt->mnt_sb;

	s = nd->path.mnt->mnt_sb;

	atomic_inc(&s->s_active);

	mnt_target->mnt_sb = s;

	mnt_target->mnt_root = dget(nd.path.dentry);

	mnt_target->mnt_root = dget(nd->path.dentry);

	/* Correct the device pathname */

	nfs_fix_devname(&nd.path, mnt_target);

	nfs_fix_devname(&nd->path, mnt_target);

	path_put(&nd.path);

	path_put(&nd->path);

	kfree(nd);

	down_write(&s->s_umount);

	return 0;

out_mntput:

	mntput(root_mnt);

out_err:

	kfree(nd);

	return ret;

}