staging: ramster: local compression + tmem

RAMster implements peer-to-peer transcendent memory, allowing a "cluster"
of kernels to dynamically pool their RAM.

This patch copies files from drivers/staging/zcache.  RAMster compresses
pages locally before transmitting them to another node, so we can
leverage the zcache and tmem code directly.  Note: there are
no ramster-specific changes yet to these files.

(Why copy?  The ramster tmem.c/tmem.h changes are definitely shareable
between zcache and ramster; the eventual destination for tmem.c
is the linux lib directory.  Ramster changes to zcache are more substantial
and zcache is currently undergoing some significant unrelated changes
(including a new allocator and breaking zcache-main.c into smaller files),
so it seemed best to branch temporarily and merge later.)

Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/ramster/Kconfig

@@ -0,0 +1,13 @@
+config ZCACHE
+	tristate "Dynamic compression of swap pages and clean pagecache pages"
+	depends on CLEANCACHE || FRONTSWAP
+	select XVMALLOC
+	select LZO_COMPRESS
+	select LZO_DECOMPRESS
+	default n
+	help
+	  Zcache doubles RAM efficiency while providing a significant
+	  performance boosts on many workloads.  Zcache uses lzo1x
+	  compression and an in-kernel implementation of transcendent
+	  memory to store clean page cache pages and swap in RAM,
+	  providing a noticeable reduction in disk I/O.

drivers/staging/ramster/Makefile

@@ -0,0 +1,3 @@
+zcache-y	:=	zcache-main.o tmem.o
+
+obj-$(CONFIG_ZCACHE)	+=	zcache.o