/*
* Memory merging support.
*
* This code enables dynamic sharing of identical pages found in different
* memory areas, even if they are not shared by fork()
*
* Copyright (C) 2008-2009 Red Hat, Inc.
* Authors:
* Izik Eidus
* Andrea Arcangeli
* Chris Wright
* Hugh Dickins
*
* This work is licensed under the terms of the GNU GPL, version 2.
*/
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/mman.h>
#include <linux/sched.h>
#include <linux/rwsem.h>
#include <linux/pagemap.h>
#include <linux/rmap.h>
#include <linux/spinlock.h>
#include <linux/jhash.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/wait.h>
#include <linux/slab.h>
#include <linux/rbtree.h>
#include <linux/mmu_notifier.h>
#include <linux/ksm.h>
#include <asm/tlbflush.h>
/*
* A few notes about the KSM scanning process,
* to make it easier to understand the data structures below:
*
* In order to reduce excessive scanning, KSM sorts the memory pages by their
* contents into a data structure that holds pointers to the pages' locations.
*
* Since the contents of the pages may change at any moment, KSM cannot just
* insert the pages into a normal sorted tree and expect it to find anything.
* Therefore KSM uses two data structures - the stable and the unstable tree.
*
* The stable tree holds pointers to all the merged pages (ksm pages), sorted
* by their contents. Because each such page is write-protected, searching on
* this tree is fully assured to be working (except when pages are unmapped),
