Merge branch 'master' into for-next

Sync with Linus' tree to be able to apply patches against new
code I have in queue.

1 files changed, 23 insertions, 0 deletions

diff --git a/mm/Kconfig b/mm/Kconfig
index e9c0c61f2ddd..8ca47a5ee9c8 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -347,3 +347,26 @@ config NEED_PER_CPU_KM
         depends on !SMP
         bool
         default y
+
+config CLEANCACHE
+        bool "Enable cleancache driver to cache clean pages if tmem is present"
+        default n
+        help
+          Cleancache can be thought of as a page-granularity victim cache
+          for clean pages that the kernel's pageframe replacement algorithm
+          (PFRA) would like to keep around, but can't since there isn't enough
+          memory.  So when the PFRA "evicts" a page, it first attempts to use
+          cleancacne code to put the data contained in that page into
+          "transcendent memory", memory that is not directly accessible or
+          addressable by the kernel and is of unknown and possibly
+          time-varying size.  And when a cleancache-enabled
+          filesystem wishes to access a page in a file on disk, it first
+          checks cleancache to see if it already contains it; if it does,
+          the page is copied into the kernel and a disk access is avoided.
+          When a transcendent memory driver is available (such as zcache or
+          Xen transcendent memory), a significant I/O reduction
+          may be achieved.  When none is available, all cleancache calls
+          are reduced to a single pointer-compare-against-NULL resulting
+          in a negligible performance hit.
+
+          If unsure, say Y to enable cleancache