[DLM] Add support for tcp communications

The following patch adds a TCP based communications layer
to the DLM which is compile time selectable. The existing SCTP
layer gives the advantage of allowing multihoming, whereas
the TCP layer has been heavily tested in previous versions of
the DLM and is known to be robust and therefore can be used as
a baseline for performance testing.

Signed-off-by: Patrick Caulfield <pcaulfie@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/dlm/Kconfig

@@ -9,6 +9,23 @@ config DLM
 	A general purpose distributed lock manager for kernel or userspace
 	applications.
 
+choice
+	prompt "Select DLM communications protocol"
+	depends on DLM
+	default DLM_TCP
+	help
+	The DLM Can use TCP or SCTP for it's network communications.
+	SCTP supports multi-homed operations whereas TCP doesn't.
+	However, SCTP seems to have stability problems at the moment.
+
+config DLM_TCP
+	bool "TCP/IP"
+
+config DLM_SCTP
+	bool "SCTP"
+
+endchoice
+
 config DLM_DEBUG
 	bool "DLM debugging"
 	depends on DLM

fs/dlm/Makefile

@@ -4,7 +4,6 @@ dlm-y :=			ast.o \
 				dir.o \
 				lock.o \
 				lockspace.o \
-				lowcomms.o \
 				main.o \
 				member.o \
 				memory.o \
@@ -17,3 +16,6 @@ dlm-y :=			ast.o \
 				util.o
 dlm-$(CONFIG_DLM_DEBUG) +=	debug_fs.o
 
+dlm-$(CONFIG_DLM_TCP)   += lowcomms-tcp.o
+
+dlm-$(CONFIG_DLM_SCTP)  += lowcomms-sctp.o