ocfs2: Define the contents of the slot_map file.

The slot map file is merely an array of __le16.  Wrap it in a structure for
cleaner reference.

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

fs/ocfs2/ocfs2_fs.h

@@ -474,6 +474,18 @@ struct ocfs2_extent_block
 /* Actual on-disk size is one block */
 };
 
+/*
+ * On disk slot map for OCFS2.  This defines the contents of the "slot_map"
+ * system file.
+ */
+struct ocfs2_slot_map {
+/*00*/	__le16 sm_slots[0];
+/*
+ * Actual on-disk size is one block.  OCFS2_MAX_SLOTS is 255,
+ * 255 * sizeof(__le16) == 512B, within the 512B block minimum blocksize.
+ */
+};
+
 /*
  * On disk superblock for OCFS2
  * Note that it is contained inside an ocfs2_dinode, so all offsets