start adding the tag to iov_iter

For now, just use the same thing we pass to ->direct_IO() - it's all
iovec-based at the moment.  Pass it explicitly to iov_iter_init() and
account for kvec vs. iovec in there, by the same kludge NFS ->direct_IO()
uses.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/mm/filemap.c b/mm/filemap.c
index a7f79e9..3aeaf2d 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1730,7 +1730,7 @@
 	size_t count = iov_length(iov, nr_segs);
 	struct iov_iter i;
 
-	iov_iter_init(&i, iov, nr_segs, count, 0);
+	iov_iter_init(&i, READ, iov, nr_segs, count);
 	return generic_file_read_iter(iocb, &i);
 }
 EXPORT_SYMBOL(generic_file_aio_read);
@@ -2596,7 +2596,7 @@
 	if (err)
 		goto out;
 
-	iov_iter_init(&from, iov, nr_segs, count, 0);
+	iov_iter_init(&from, WRITE, iov, nr_segs, count);
 
 	/* coalesce the iovecs and go direct-to-BIO for O_DIRECT */
 	if (unlikely(file->f_flags & O_DIRECT)) {