ocfs2: Support creation of unwritten extents

This can now be trivially supported with re-use of our existing extend code.

ocfs2_allocate_unwritten_extents() takes a start offset and a byte length
and iterates over the inode, adding extents (marked as unwritten) until len
is reached. Existing extents are skipped over.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
index 36289e6..d430fda 100644
--- a/fs/ocfs2/namei.c
+++ b/fs/ocfs2/namei.c
@@ -1674,7 +1674,7 @@
 		u32 offset = 0;
 
 		inode->i_op = &ocfs2_symlink_inode_operations;
-		status = ocfs2_do_extend_allocation(osb, inode, &offset, 1,
+		status = ocfs2_do_extend_allocation(osb, inode, &offset, 1, 0,
 						    new_fe_bh,
 						    handle, data_ac, NULL,
 						    NULL);