staging: zcache: host services and PAM services

[PATCH V2 2/3] drivers/staging: zcache: host services and PAM services

Zcache provides host services (memory allocation) for tmem,
a "shim" to interface cleancache and frontswap to tmem, and
two different page-addressable memory implemenations using
lzo1x compression.  The first, "compression buddies" ("zbud")
compresses pairs of pages and supplies a shrinker interface
that allows entire pages to be reclaimed.  The second is
a shim to xvMalloc which is more space-efficient but
less receptive to page reclamation.  The first is used
for ephemeral pools and the second for persistent pools.
All ephemeral pools share the same memory, that is, even
pages from different pools can share the same page.
Signed-off-by: NDan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: NNitin Gupta <ngupta@vflare.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>