/*
 * $Id: block2mtd.c,v 1.30 2005/11/29 14:48:32 gleixner Exp $
 *
 * block2mtd.c - create an mtd from a block device
 *
 * Copyright (C) 2001,2002	Simon Evans <spse@secret.org.uk>
 * Copyright (C) 2004,2005	Jörn Engel <joern@wh.fh-wedel.de>
 *
 * Licence: GPL
 */
#include <linux/config.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/pagemap.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/mtd/mtd.h>
#include <linux/buffer_head.h>

#define VERSION "$Revision: 1.30 $"


#define ERROR(fmt, args...) printk(KERN_ERR "block2mtd: " fmt "\n" , ## args)
#define INFO(fmt, args...) printk(KERN_INFO "block2mtd: " fmt "\n" , ## args)


/* Info for the block device */
struct block2mtd_dev {
	struct list_head list;
	struct block_device *blkdev;
	struct mtd_info mtd;
	struct semaphore write_mutex;
};


/* Static info about the MTD, used in cleanup_module */
static LIST_HEAD(blkmtd_device_list);


#define PAGE_READAHEAD 64
static void cache_readahead(struct address_space *mapping, int index)
{
	filler_t *filler = (filler_t*)mapping->a_ops->readpage;
	int i, pagei;
	unsigned ret = 0;
	unsigned long end_index;
	struct page *page;
	LIST_HEAD(page_pool);
	struct inode *inode = mapping->host;
	loff_t isize = i_size_read(inode);

	if (!isize) {
		INFO("iSize=0 in cache_readahead\n");
		return;
	}

	end_index = ((isize - 1) >> PAGE_CACHE_SHIFT);

	read_lock_irq(&mapping->tree_lock);
	for (i = 0; i < PAGE_READAHEAD; i++) {
		pagei = index + i;
		if (pagei > end_index) {
			INFO("Overrun end of disk in cache readahead\n");
			break;
		}
		page = radix_tree_lookup(&mapping->page_tree, pagei);
		if (page && (!i))
			break;
		if (page)
			continue;
		read_unlock_irq(&mapping->tree_lock);
		page = page_cache_alloc_cold(mapping);
		read_lock_irq(&mapping->tree_lock);
		if (!page)
			break;
		page->index = pagei;
		list_add(&page->lru, &page_pool);
		ret++;
	}
	read_unlock_irq(&mapping->tree_lock);
	if (ret)
		read_cache_pages(mapping, &page_pool, filler, NULL);
}


static struct page* page_readahead(struct address_space *mapping, int index)
{
	filler_t *filler = (filler_t*)mapping->a_ops->readpage;
	cache_readahead(mapping, index);
	return read_cache_page(mapping, index, filler, NULL);
}


/* erase a specified part of the device */
static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
{
	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
	struct page *page;
	int index = to >> PAGE_SHIFT;	// page index
	int pages = len >> PAGE_SHIFT;
	u_long *p;
	u_long *max;

	while (pages) {
		page = page_readahead(mapping, index);
		if (!page)
			return -ENOMEM;
		if (IS_ERR(page))
			return PTR_ERR(page);

		max = (u_long*)page_address(page) + PAGE_SIZE;
		for (p=(u_long*)page_address(page); p<max; p++)
			if (*p != -1UL) {
				lock_page(page);
				memset(page_address(page), 0xff, PAGE_SIZE);
				set_page_dirty(page);
				unlock_page(page);
				break;
			}

		page_cache_release(page);
		pages--;
		index++;
	}
	return 0;
}
static int block2mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
{
	struct block2mtd_dev *dev = mtd->priv;
	size_t from = instr->addr;
	size_t len = instr->len;
	int err;

	instr->state = MTD_ERASING;
	down(&dev->write_mutex);
	err = _block2mtd_erase(dev, from, len);
	up(&dev->write_mutex);
	if (err) {
		ERROR("erase failed err = %d", err);
		instr->state = MTD_ERASE_FAILED;
	} else
		instr->state = MTD_ERASE_DONE;

	instr->state = MTD_ERASE_DONE;
	mtd_erase_callback(instr);
	return err;
}


static int block2mtd_read(struct mtd_info *mtd, loff_t from, size_t len,
		size_t *retlen, u_char *buf)
{
	struct block2mtd_dev *dev = mtd->priv;
	struct page *page;
	int index = from >> PAGE_SHIFT;
	int offset = from & (PAGE_SIZE-1);
	int cpylen;

	if (from > mtd->size)
		return -EINVAL;
	if (from + len > mtd->size)
		len = mtd->size - from;

	if (retlen)
		*retlen = 0;

	while (len) {
		if ((offset + len) > PAGE_SIZE)
			cpylen = PAGE_SIZE - offset;	// multiple pages
		else
			cpylen = len;	// this page
		len = len - cpylen;

		//      Get page
		page = page_readahead(dev->blkdev->bd_inode->i_mapping, index);
		if (!page)
			return -ENOMEM;
		if (IS_ERR(page))
			return PTR_ERR(page);

		memcpy(buf, page_address(page) + offset, cpylen);
		page_cache_release(page);

		if (retlen)
			*retlen += cpylen;
		buf += cpylen;
		offset = 0;
		index++;
	}
	return 0;
}


/* write data to the underlying device */
static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
		loff_t to, size_t len, size_t *retlen)
{
	struct page *page;
	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
	int index = to >> PAGE_SHIFT;	// page index
	int offset = to & ~PAGE_MASK;	// page offset
	int cpylen;

	if (retlen)
		*retlen = 0;
	while (len) {
		if ((offset+len) > PAGE_SIZE)
			cpylen = PAGE_SIZE - offset;	// multiple pages
		else
			cpylen = len;			// this page
		len = len - cpylen;

		//	Get page
		page = page_readahead(mapping, index);
		if (!page)
			return -ENOMEM;
		if (IS_ERR(page))
			return PTR_ERR(page);

		if (memcmp(page_address(page)+offset, buf, cpylen)) {
			lock_page(page);
			memcpy(page_address(page) + offset, buf, cpylen);
			set_page_dirty(page);
			unlock_page(page);
		}
		page_cache_release(page);

		if (retlen)
			*retlen += cpylen;

		buf += cpylen;
		offset = 0;
		index++;
	}
	return 0;
}
static int block2mtd_write(struct mtd_info *mtd, loff_t to, size_t len,
		size_t *retlen, const u_char *buf)
{
	struct block2mtd_dev *dev = mtd->priv;
	int err;

	if (!len)
		return 0;
	if (to >= mtd->size)
		return -ENOSPC;
	if (to + len > mtd->size)
		len = mtd->size - to;

	down(&dev->write_mutex);
	err = _block2mtd_write(dev, buf, to, len, retlen);
	up(&dev->write_mutex);
	if (err > 0)
		err = 0;
	return err;
}


/* sync the device - wait until the write queue is empty */
static void block2mtd_sync(struct mtd_info *mtd)
{
	struct block2mtd_dev *dev = mtd->priv;
	sync_blockdev(dev->blkdev);
	return;
}


static void block2mtd_free_device(struct block2mtd_dev *dev)
{
	if (!dev)
		return;

	kfree(dev->mtd.name);

	if (dev->blkdev) {
		invalidate_inode_pages(dev->blkdev->bd_inode->i_mapping);
		close_bdev_excl(dev->blkdev);
	}

	kfree(dev);
}


/* FIXME: ensure that mtd->size % erase_size == 0 */
static struct block2mtd_dev *add_device(char *devname, int erase_size)
{
	struct block_device *bdev;
	struct block2mtd_dev *dev;

	if (!devname)
		return NULL;

	dev = kmalloc(sizeof(struct block2mtd_dev), GFP_KERNEL);
	if (!dev)
		return NULL;
	memset(dev, 0, sizeof(*dev));

	/* Get a handle on the device */
	bdev = open_bdev_excl(devname, O_RDWR, NULL);
	if (IS_ERR(bdev)) {
		ERROR("error: cannot open device %s", devname);
		goto devinit_err;
	}
	dev->blkdev = bdev;

	if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
		ERROR("attempting to use an MTD device as a block device");
		goto devinit_err;
	}

	init_MUTEX(&dev->write_mutex);

	/* Setup the MTD structure */
	/* make the name contain the block device in */
	dev->mtd.name = kmalloc(sizeof("block2mtd: ") + strlen(devname),
			GFP_KERNEL);
	if (!dev->mtd.name)
		goto devinit_err;

	sprintf(dev->mtd.name, "block2mtd: %s", devname);

	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
	dev->mtd.erasesize = erase_size;
	dev->mtd.type = MTD_RAM;
	dev->mtd.flags = MTD_CAP_RAM;
	dev->mtd.erase = block2mtd_erase;
	dev->mtd.write = block2mtd_write;
	dev->mtd.writev = default_mtd_writev;
	dev->mtd.sync = block2mtd_sync;
	dev->mtd.read = block2mtd_read;
	dev->mtd.readv = default_mtd_readv;
	dev->mtd.priv = dev;
	dev->mtd.owner = THIS_MODULE;

	if (add_mtd_device(&dev->mtd)) {
		/* Device didnt get added, so free the entry */
		goto devinit_err;
	}
	list_add(&dev->list, &blkmtd_device_list);
	INFO("mtd%d: [%s] erase_size = %dKiB [%d]", dev->mtd.index,
			dev->mtd.name + strlen("blkmtd: "),
			dev->mtd.erasesize >> 10, dev->mtd.erasesize);
	return dev;

devinit_err:
	block2mtd_free_device(dev);
	return NULL;
}


static int ustrtoul(const char *cp, char **endp, unsigned int base)
{
	unsigned long result = simple_strtoul(cp, endp, base);
	switch (**endp) {
	case 'G' :
		result *= 1024;
	case 'M':
		result *= 1024;
	case 'k':
		result *= 1024;
	/* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
		if ((*endp)[1] == 'i')
			(*endp) += 2;
	}
	return result;
}


static int parse_num(size_t *num, const char *token)
{
	char *endp;
	size_t n;

	n = (size_t) ustrtoul(token, &endp, 0);
	if (*endp)
		return -EINVAL;

	*num = n;
	return 0;
}


static int parse_name(char **pname, const char *token, size_t limit)
{
	size_t len;
	char *name;

	len = strlen(token) + 1;
	if (len > limit)
		return -ENOSPC;

	name = kmalloc(len, GFP_KERNEL);
	if (!name)
		return -ENOMEM;

	strcpy(name, token);

	*pname = name;
	return 0;
}


static inline void kill_final_newline(char *str)
{
	char *newline = strrchr(str, '\n');
	if (newline && !newline[1])
		*newline = 0;
}


#define parse_err(fmt, args...) do {		\
	ERROR("block2mtd: " fmt "\n", ## args);	\
	return 0;				\
} while (0)

static int block2mtd_setup(const char *val, struct kernel_param *kp)
{
	char buf[80+12], *str=buf; /* 80 for device, 12 for erase size */
	char *token[2];
	char *name;
	size_t erase_size = PAGE_SIZE;
	int i, ret;

	if (strnlen(val, sizeof(buf)) >= sizeof(buf))
		parse_err("parameter too long");

	strcpy(str, val);
	kill_final_newline(str);

	for (i=0; i<2; i++)
		token[i] = strsep(&str, ",");

	if (str)
		parse_err("too many arguments");

	if (!token[0])
		parse_err("no argument");

	ret = parse_name(&name, token[0], 80);
	if (ret == -ENOMEM)
		parse_err("out of memory");
	if (ret == -ENOSPC)
		parse_err("name too long");
	if (ret)
		return 0;

	if (token[1]) {
		ret = parse_num(&erase_size, token[1]);
		if (ret)
			parse_err("illegal erase size");
	}

	add_device(name, erase_size);

	return 0;
}


module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");

static int __init block2mtd_init(void)
{
	INFO("version " VERSION);
	return 0;
}


static void __devexit block2mtd_exit(void)
{
	struct list_head *pos, *next;

	/* Remove the MTD devices */
	list_for_each_safe(pos, next, &blkmtd_device_list) {
		struct block2mtd_dev *dev = list_entry(pos, typeof(*dev), list);
		block2mtd_sync(&dev->mtd);
		del_mtd_device(&dev->mtd);
		INFO("mtd%d: [%s] removed", dev->mtd.index,
				dev->mtd.name + strlen("blkmtd: "));
		list_del(&dev->list);
		block2mtd_free_device(dev);
	}
}


module_init(block2mtd_init);
module_exit(block2mtd_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Simon Evans <spse@secret.org.uk> and others");
MODULE_DESCRIPTION("Emulate an MTD using a block device");