pipe: change the ->pin() operation to ->confirm()

The name 'pin' was badly chosen, it doesn't pin a pipe buffer
in the most commonly used sense in the kernel. So change the
name to 'confirm', after debating this issue with Hugh
Dickins a bit.

A good return from ->confirm() means that the buffer is really
there, and that the contents are good.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
index 44c2e2a..4979b66 100644
--- a/fs/ocfs2/file.c
+++ b/fs/ocfs2/file.c
@@ -1583,7 +1583,7 @@
 	ssize_t copied = 0;
 	struct ocfs2_splice_write_priv sp;
 
-	ret = buf->ops->pin(pipe, buf);
+	ret = buf->ops->confirm(pipe, buf);
 	if (ret)
 		goto out;
 
@@ -1604,7 +1604,7 @@
 		 * might enter ocfs2_buffered_write_cluster() more
 		 * than once, so keep track of our progress here.
 		 */
-		copied = ocfs2_buffered_write_cluster(sd->file,
+		copied = ocfs2_buffered_write_cluster(sd->u.file,
 						      (loff_t)sd->pos + total,
 						      count,
 						      ocfs2_map_and_write_splice_data,