linux-imx

/*

 * z3fold.c

 *

 * Author: Vitaly Wool <vitaly.wool@konsulko.com>

 * Copyright (C) 2016, Sony Mobile Communications Inc.

 *

 * This implementation is based on zbud written by Seth Jennings.

 *

 * z3fold is an special purpose allocator for storing compressed pages. It

 * can store up to three compressed pages per page which improves the

 * compression ratio of zbud while retaining its main concepts (e. g. always

 * storing an integral number of objects per page) and simplicity.

 * It still has simple and deterministic reclaim properties that make it

 * preferable to a higher density approach (with no requirement on integral

 * number of object per page) when reclaim is used.

 *

 * As in zbud, pages are divided into "chunks".  The size of the chunks is

 * fixed at compile time and is determined by NCHUNKS_ORDER below.

 *

 * z3fold doesn't export any API and is meant to be used via zpool API.

 */

​

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

​

#include <linux/atomic.h>

#include <linux/sched.h>

#include <linux/list.h>

#include <linux/mm.h>

#include <linux/module.h>

#include <linux/percpu.h>

#include <linux/preempt.h>

#include <linux/workqueue.h>

#include <linux/slab.h>

#include <linux/spinlock.h>

#include <linux/zpool.h>

​

/*****************

 * Structures

*****************/

struct z3fold_pool;

struct z3fold_ops {

    int (*evict)(struct z3fold_pool *pool, unsigned long handle);

};

​

enum buddy {

    HEADLESS = 0,

    FIRST,

    MIDDLE,

    LAST,

    BUDDIES_MAX

};

​

/*

 * struct z3fold_header - z3fold page metadata occupying first chunks of each

 *          z3fold page, except for HEADLESS pages

 * @buddy:      links the z3fold page into the relevant list in the

 *          pool

 * @page_lock:      per-page lock

 * @refcount:       reference count for the z3fold page

 * @work:       work_struct for page layout optimization

 * @pool:       pointer to the pool which this page belongs to

 * @cpu:        CPU which this page "belongs" to

 * @first_chunks:   the size of the first buddy in chunks, 0 if free