ksm: define MADV_MERGEABLE and MADV_UNMERGEABLE

The out-of-tree KSM used ioctls on fds cloned from /dev/ksm to register a
memory area for merging: we prefer now to use an madvise(2) interface.

This patch just defines MADV_MERGEABLE (to tell KSM it may merge pages in
this area found identical to pages in other mergeable areas) and
MADV_UNMERGEABLE (to undo that).

Most architectures use asm-generic, but alpha, mips, parisc, xtensa need
their own definitions: included here for mmotm convenience, but we'll
probably want to split this and feed pieces to arch maintainers.

Based upon earlier patches by Chris Wright and Izik Eidus.
Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Signed-off-by: Chris Wright <chrisw@redhat.com>
Signed-off-by: Izik Eidus <ieidus@redhat.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Kyle McMartin <kyle@mcmartin.ca>
Cc: Helge Deller <deller@gmx.de>
Cc: Chris Zankel <chris@zankel.net>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lee Schermerhorn <lee.schermerhorn@hp.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/alpha/include/asm/mman.h

@@ -48,6 +48,9 @@
 #define MADV_DONTFORK	10		/* don't inherit across fork */
 #define MADV_DOFORK	11		/* do inherit across fork */
 
+#define MADV_MERGEABLE   12		/* KSM may merge identical pages */
+#define MADV_UNMERGEABLE 13		/* KSM may not merge identical pages */
+
 /* compatibility flags */
 #define MAP_FILE	0
 

arch/mips/include/asm/mman.h

@@ -71,6 +71,9 @@
 #define MADV_DONTFORK	10		/* don't inherit across fork */
 #define MADV_DOFORK	11		/* do inherit across fork */
 
+#define MADV_MERGEABLE   12		/* KSM may merge identical pages */
+#define MADV_UNMERGEABLE 13		/* KSM may not merge identical pages */
+
 /* compatibility flags */
 #define MAP_FILE	0
 

arch/parisc/include/asm/mman.h

@@ -54,6 +54,9 @@
 #define MADV_16M_PAGES  24              /* Use 16 Megabyte pages */
 #define MADV_64M_PAGES  26              /* Use 64 Megabyte pages */
 
+#define MADV_MERGEABLE   65		/* KSM may merge identical pages */
+#define MADV_UNMERGEABLE 66		/* KSM may not merge identical pages */
+
 /* compatibility flags */
 #define MAP_FILE	0
 #define MAP_VARIABLE	0

arch/xtensa/include/asm/mman.h

@@ -78,6 +78,9 @@
 #define MADV_DONTFORK	10		/* don't inherit across fork */
 #define MADV_DOFORK	11		/* do inherit across fork */
 
+#define MADV_MERGEABLE   12		/* KSM may merge identical pages */
+#define MADV_UNMERGEABLE 13		/* KSM may not merge identical pages */
+
 /* compatibility flags */
 #define MAP_FILE	0
 

include/asm-generic/mman-common.h

@@ -35,6 +35,9 @@
 #define MADV_DONTFORK	10		/* don't inherit across fork */
 #define MADV_DOFORK	11		/* do inherit across fork */
 
+#define MADV_MERGEABLE   12		/* KSM may merge identical pages */
+#define MADV_UNMERGEABLE 13		/* KSM may not merge identical pages */
+
 /* compatibility flags */
 #define MAP_FILE	0