->splice_write() via ->write_iter()

iter_file_splice_write() - a ->splice_write() instance that gathers the
pipe buffers, builds a bio_vec-based iov_iter covering those and feeds
it to ->write_iter().  A bunch of simple cases coverted to that...

[AV: fixed the braino spotted by Cyrill]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
static void *ubifs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	struct ubifs_inode *ui = ubifs_inode(dentry->d_inode);

	nd_set_link(nd, ui->data);
	return NULL;
}

static void *ubifs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	struct ubifs_inode *ui = ubifs_inode(dentry->d_inode);

	nd_set_link(nd, ui->data);
	return NULL;
}
