path: root/drivers/mtd/devices/block2mtd.c

/*
 * $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) 2004-2006	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>
#include <linux/mutex.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 mutex 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;
	mutex_lock(&dev->write_mutex);
	err = _block2mtd_erase(dev, from, len);
	mutex_unlock(&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;

	mutex_lock(&dev->write_mutex);
	err = _block2mtd_write(dev, buf, to, len, retlen);
	mutex_unlock(&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 */n1489' href='#n1489'>1489