path: root/drivers/mtd/mtdswap.c

/*
 * Swap block device support for MTDs
 * Turns an MTD device into a swap device with block wear leveling
 *
 * Copyright © 2007,2011 Nokia Corporation. All rights reserved.
 *
 * Authors: Jarkko Lavinen <jarkko.lavinen@nokia.com>
 *
 * Based on Richard Purdie's earlier implementation in 2007. Background
 * support and lock-less operation written by Adrian Hunter.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mtd/mtd.h>
#include <linux/mtd/blktrans.h>
#include <linux/rbtree.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/genhd.h>
#include <linux/swap.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/device.h>
#include <linux/math64.h>

#define MTDSWAP_PREFIX "mtdswap"

/*
 * The number of free eraseblocks when GC should stop
 */
#define CLEAN_BLOCK_THRESHOLD	20

/*
 * Number of free eraseblocks below which GC can also collect low frag
 * blocks.
 */
#define LOW_FRAG_GC_TRESHOLD	5

/*
 * Wear level cost amortization. We want to do wear leveling on the background
 * without disturbing gc too much. This is made by defining max GC frequency.
 * Frequency value 6 means 1/6 of the GC passes will pick an erase block based
 * on the biggest wear difference rather than the biggest dirtiness.
 *
 * The lower freq2 should be chosen so that it makes sure the maximum erase
 * difference will decrease even if a malicious application is deliberately
 * trying to make erase differences large.
 */
#define MAX_ERASE_DIFF		4000
#define COLLECT_NONDIRTY_BASE	MAX_ERASE_DIFF
#define COLLECT_NONDIRTY_FREQ1	6
#define COLLECT_NONDIRTY_FREQ2	4

#define PAGE_UNDEF		UINT_MAX
#define BLOCK_UNDEF		UINT_MAX
#define BLOCK_ERROR		(UINT_MAX - 1)
#define BLOCK_MAX		(UINT_MAX - 2)

#define EBLOCK_BAD		(1 << 0)
#define EBLOCK_NOMAGIC		(1 << 1)
#define EBLOCK_BITFLIP		(1 << 2)
#define EBLOCK_FAILED		(1 << 3)
#define EBLOCK_READERR		(1 << 4)
#define EBLOCK_IDX_SHIFT	5

struct swap_eb {
	struct rb_node rb;
	struct rb_root *root;

	unsigned int flags;
	unsigned int active_count;
	unsigned int erase_count;
	unsigned int pad;		/* speeds up pointer decrement */
};

#define MTDSWAP_ECNT_MIN(rbroot) (rb_entry(rb_first(rbroot), struct swap_eb, \
				rb)->erase_count)
#define MTDSWAP_ECNT_MAX(rbroot) (rb_entry(rb_last(rbroot), struct swap_eb, \
				rb)->erase_count)

struct mtdswap_tree {
	struct rb_root root;
	unsigned int count;
};

enum {
	MTDSWAP_CLEAN,
	MTDSWAP_USED,
	MTDSWAP_LOWFRAG,
	MTDSWAP_HIFRAG,
	MTDSWAP_DIRTY,
	MTDSWAP_BITFLIP,
	MTDSWAP_FAILING,
	MTDSWAP_TREE_CNT,
};

struct mtdswap_dev {
	struct mtd_blktrans_dev *mbd_dev;
	struct mtd_info *mtd;
	struct device *dev;

	unsigned int *page_data;
	unsigned int *revmap;

	unsigned int eblks;
	unsigned int spare_eblks;
	unsigned int pages_per_eblk;
	unsigned int max_erase_count;
	struct swap_eb *eb_data;

	struct mtdswap_tree trees[MTDSWAP_TREE_CNT];

	unsigned long long sect_read_count;
	unsigned long long sect_write_count;
	unsigned long long mtd_write_count;
	unsigned long long mtd_read_count;
	unsigned long long discard_count;
	unsigned long long discard_page_count;

	unsigned int curr_write_pos;
	struct swap_eb *curr_write;

	char *page_buf;
	char *oob_buf;

	struct dentry *debugfs_root;
};

struct mtdswap_oobdata {
	__le16 magic;
	__le32 count;
} __packed;

#define MTDSWAP_MAGIC_CLEAN	0x2095
#define MTDSWAP_MAGIC_DIRTY	(MTDSWAP_MAGIC_CLEAN + 1)
#define MTDSWAP_TYPE_CLEAN	0
#define MTDSWAP_TYPE_DIRTY	1
#define MTDSWAP_OOBSIZE		sizeof(struct mtdswap_oobdata)

#define MTDSWAP_ERASE_RETRIES	3 /* Before marking erase block bad */
#define MTDSWAP_IO_RETRIES	3

enum {
	MTDSWAP_SCANNED_CLEAN,
	MTDSWAP_SCANNED_DIRTY,
	MTDSWAP_SCANNED_BITFLIP,
	MTDSWAP_SCANNED_BAD,
};

/*
 * In the worst case mtdswap_writesect() has allocated the last clean
 * page from the current block and is then pre-empted by the GC
 * thread. The thread can consume a full erase block when moving a
 * block.
 */
#define MIN_SPARE_EBLOCKS	2
#define MIN_ERASE_BLOCKS	(MIN_SPARE_EBLOCKS + 1)

#define TREE_ROOT(d, name) (&d->trees[MTDSWAP_ ## name].root)
#define TREE_EMPTY(d, name) (TREE_ROOT(d, name)->rb_node == NULL)
#define TREE_NONEMPTY(d, name) (!TREE_EMPTY(d, name))
#define TREE_COUNT(d, name) (d->trees[MTDSWAP_ ## name].count)

#define MTDSWAP_MBD_TO_MTDSWAP(dev) ((struct mtdswap_dev *)dev->priv)

static char partitions[128] = "";
module_param_string(partitions, partitions, sizeof(partitions), 0444);
MODULE_PARM_DESC(partitions, "MTD partition numbers to use as swap "
		"partitions=\"1,3,5\"");

static unsigned int spare_eblocks = 10;
module_param(spare_eblocks, uint, 0444);
MODULE_PARM_DESC(spare_eblocks, "Percentage of spare erase blocks for "
		"garbage collection (default 10%)");

static bool header; /* false */
module_param(header, bool, 0444);
MODULE_PARM_DESC(header,
		"Include builtin swap header (default 0, without he