fs: dlm: add comment about lkb IFL flags

This patch adds comments about the difference between the lower 2 bytes
of lkb flags and the 2 upper bytes of the lkb IFL flags. In short the
upper 2 bytes will be handled as internal flags whereas the lower 2
bytes are part of the DLM protocol and are used to exchange messages.
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

fs/dlm/dlm_internal.h

@@ -207,6 +207,14 @@ struct dlm_args {
 #define DLM_IFL_TIMEOUT_CANCEL	0x00800000
 #define DLM_IFL_DEADLOCK_CANCEL	0x01000000
 #define DLM_IFL_STUB_MS		0x02000000 /* magic number for m_flags */
+/* least significant 2 bytes are message changed, they are full transmitted
+ * but at receive side only the 2 bytes LSB will be set.
+ *
+ * Even wireshark dlm dissector does only evaluate the lower bytes and note
+ * that they may not be used on transceiver side, we assume the higher bytes
+ * are for internal use or reserved so long they are not parsed on receiver
+ * side.
+ */
 #define DLM_IFL_USER		0x00000001
 #define DLM_IFL_ORPHAN		0x00000002