blkmtd-25.c

linux下的MTD设备驱动源代码,配合jffs2 yaffss2文件系统.

/*
 * $Id: blkmtd-25.c,v 1.5 2003/07/16 06:48:27 spse Exp $
 *
 * blkmtd.c - use a block device as a fake MTD
 *
 * Author: Simon Evans <[e-mail]>
 *
 * Copyright (C) 2001,2002 Simon Evans
 *
 * Licence: GPL
 *
 * How it works:
 *	The driver uses raw/io to read/write the device and the page
 *	cache to cache access. Writes update the page cache with the
 *	new data and mark it dirty and add the page into a BIO which
 *	is then written out.
 *
 *	It can be loaded Read-Only to prevent erases and writes to the
 *	medium.
 *
 */

#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>


#define err(format, arg...) printk(KERN_ERR "blkmtd: " format "\n" , ## arg)
#define info(format, arg...) printk(KERN_INFO "blkmtd: " format "\n" , ## arg)
#define warn(format, arg...) printk(KERN_WARNING "blkmtd: " format "\n" , ## arg)
#define crit(format, arg...) printk(KERN_CRIT "blkmtd: " format "\n" , ## arg)


/* Default erase size in K, always make it a multiple of PAGE_SIZE */
#define CONFIG_MTD_BLKDEV_ERASESIZE (128 << 10)	/* 128KiB */
#define VERSION "$Revision: 1.5 $"

/* Info for the block device */
struct blkmtd_dev {
	struct list_head list;
	struct block_device *blkdev;
	struct mtd_info mtd_info;
	struct semaphore wrbuf_mutex;
};


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


static void blkmtd_sync(struct mtd_info *mtd);

#define MAX_DEVICES 4

/* Module parameters passed by insmod/modprobe */
char *device[MAX_DEVICES];    /* the block device to use */
int erasesz[MAX_DEVICES];     /* optional default erase size */
int ro[MAX_DEVICES];          /* optional read only flag */
int sync;


MODULE_LICENSE("GPL");
MODULE_AUTHOR("Simon Evans <[e-mail]>");
MODULE_DESCRIPTION("Emulate an MTD using a block device");
MODULE_PARM(device, "1-4s");
MODULE_PARM_DESC(device, "block device to use");
MODULE_PARM(erasesz, "1-4i");
MODULE_PARM_DESC(erasesz, "optional erase size to use in KiB. eg 4=4KiB.");
MODULE_PARM(ro, "1-4i");
MODULE_PARM_DESC(ro, "1=Read only, writes and erases cause errors");
MODULE_PARM(sync, "i");
MODULE_PARM_DESC(sync, "1=Synchronous writes");


/* completion handler for BIO reads */
static int bi_read_complete(struct bio *bio, unsigned int bytes_done, int error)
{
	if (bio->bi_size)
		return 1;

	complete((struct completion*)bio->bi_private);
	return 0;
}


/* completion handler for BIO writes */
static int bi_write_complete(struct bio *bio, unsigned int bytes_done, int error)
{
	const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
	struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;

	if (bio->bi_size)
		return 1;

	if(!uptodate) 
		err("bi_write_complete: not uptodate\n");

	do {
		struct page *page = bvec->bv_page;
		DEBUG(3, "Cleaning up page %ld\n", page->index);
		if (--bvec >= bio->bi_io_vec)
			prefetchw(&bvec->bv_page->flags);

		if (uptodate) {
			SetPageUptodate(page);
		} else {
			ClearPageUptodate(page);
			SetPageError(page);
		}
		ClearPageDirty(page);
		unlock_page(page);
		page_cache_release(page);
	} while (bvec >= bio->bi_io_vec);
	
	complete((struct completion*)bio->bi_private);
	return 0;
}


/* read one page from the block device */                 
static int blkmtd_readpage(struct blkmtd_dev *dev, struct page *page)
{
	struct bio *bio;
	struct completion event;
	int err = -ENOMEM;

	if(PageUptodate(page)) {
		DEBUG(2, "blkmtd: readpage page %ld is already upto date\n", page->index);
		unlock_page(page);
		return 0;
	}
	
	ClearPageUptodate(page);
	ClearPageError(page);

	bio = bio_alloc(GFP_KERNEL, 1);
	if(bio) {
		init_completion(&event);
		bio->bi_bdev = dev->blkdev;
		bio->bi_sector = page->index << (PAGE_SHIFT-9);
		bio->bi_private = &event;
		bio->bi_end_io = bi_read_complete;
		if(bio_add_page(bio, page, PAGE_SIZE, 0) == PAGE_SIZE) {
			submit_bio(READ, bio);
			blk_run_queues();
			wait_for_completion(&event);
			err = test_bit(BIO_UPTODATE, &bio->bi_flags) ? 0 : -EIO;
			bio_put(bio);
		}
	}

	if(err)
		SetPageError(page);
	else
		SetPageUptodate(page);
	flush_dcache_page(page);
	unlock_page(page);
	return err;
}


/* write out the current BIO and wait for it to finish */
static int blkmtd_write_out(struct bio *bio)
{
	struct completion event;
	int err;

	if(!bio->bi_vcnt) {
		bio_put(bio);
		return 0;
	}

	init_completion(&event);
	bio->bi_private = &event;
	bio->bi_end_io = bi_write_complete;
	submit_bio(WRITE, bio);
	blk_run_queues();
	wait_for_completion(&event);
	DEBUG(3, "submit_bio completed, bi_vcnt = %d\n", bio->bi_vcnt);
	err = test_bit(BIO_UPTODATE, &bio->bi_flags) ? 0 : -EIO;
	bio_put(bio);
	return err; 
}


/**
 * blkmtd_add_page - add a page to the current BIO
 * @bio: bio to add to (NULL to alloc initial bio)
 * @blkdev: block device
 * @page: page to add
 * @pagecnt: pages left to add
 *
 * Adds a page to the current bio, allocating it if necessary. If it cannot be
 * added, the current bio is written out and a new one is allocated. Returns
 * the new bio to add or NULL on error
 */
static struct bio *blkmtd_add_page(struct bio *bio, struct block_device *blkdev,
				   struct page *page, int pagecnt)
{

 retry:
	if(!bio) {
		bio = bio_alloc(GFP_KERNEL, pagecnt);
		if(!bio)
			return NULL;
		bio->bi_sector = page->index << (PAGE_SHIFT-9);
		bio->bi_bdev = blkdev;
	}

	if(bio_add_page(bio, page, PAGE_SIZE, 0) != PAGE_SIZE) {
		blkmtd_write_out(bio);
		bio = NULL;
		goto retry;
	}
	return bio;
}


/**
 * write_pages - write block of data to device via the page cache
 * @dev: device to write to
 * @buf: data source or NULL if erase (output is set to 0xff)
 * @to: offset into output device
 * @len: amount to data to write
 * @retlen: amount of data written
 *
 * Grab pages from the page cache and fill them with the source data.
 * Non page aligned start and end result in a readin of the page and
 * part of the page being modified. Pages are added to the bio and then written
 * out.
 */
static int write_pages(struct blkmtd_dev *dev, const u_char *buf, loff_t to,
		    size_t len, size_t *retlen)
{
	int pagenr, offset;
	size_t start_len = 0, end_len;
	int pagecnt = 0;
	int err = 0;
	struct bio *bio = NULL;
	size_t thislen = 0;

	pagenr = to >> PAGE_SHIFT;
	offset = to & ~PAGE_MASK;

	DEBUG(2, "blkmtd: write_pages: buf = %p to = %ld len = %d pagenr = %d offset = %d\n",
	      buf, (long)to, len, pagenr, offset);

	/* see if we have to do a partial write at the start */
	if(offset) {
		start_len = ((offset + len) > PAGE_SIZE) ? PAGE_SIZE - offset : len;
		len -= start_len;
	}

	/* calculate the length of the other two regions */
	end_len = len & ~PAGE_MASK;
	len -= end_len;

	if(start_len)
		pagecnt++;

	if(len)
		pagecnt += len >> PAGE_SHIFT;

	if(end_len)
		pagecnt++;

	down(&dev->wrbuf_mutex);

	DEBUG(3, "blkmtd: write: start_len = %d len = %d end_len = %d pagecnt = %d\n",
	      start_len, len, end_len, pagecnt);

	if(start_len) {
		/* do partial start region */
		struct page *page;

		DEBUG(3, "blkmtd: write: doing partial start, page = %d len = %d offset = %d\n",
		      pagenr, start_len, offset);

		BUG_ON(!buf);
		page = read_cache_page(dev->blkdev->bd_inode->i_mapping, pagenr, (filler_t *)blkmtd_readpage, dev);
		lock_page(page);
		if(PageDirty(page)) {
			err("to = %lld start_len = %d len = %d end_len = %d pagenr = %d\n",
			    to, start_len, len, end_len, pagenr);
			BUG();
		}
		memcpy(page_address(page)+offset, buf, start_len);
		SetPageDirty(page);
		SetPageUptodate(page);
		buf += start_len;
		thislen = start_len;
		bio = blkmtd_add_page(bio, dev->blkdev, page, pagecnt);
		if(!bio) {
			err = -ENOMEM;
			err("bio_add_page failed\n");
			goto write_err;
		}
		pagecnt--;
		pagenr++;
	}

	/* Now do the main loop to a page aligned, n page sized output */
	if(len) {
		int pagesc = len >> PAGE_SHIFT;
		DEBUG(3, "blkmtd: write: whole pages start = %d, count = %d\n",
		      pagenr, pagesc);
		while(pagesc) {
			struct page *page;

			/* see if page is in the page cache */
			DEBUG(3, "blkmtd: write: grabbing page %d from page cache\n", pagenr);
			page = grab_cache_page(dev->blkdev->bd_inode->i_mapping, pagenr);
			if(PageDirty(page)) {
				BUG();
			}
			if(!page) {
				warn("write: cannot grab cache page %d", pagenr);
				err = -ENOMEM;
				goto write_err;
			}
			if(!buf) {
				memset(page_address(page), 0xff, PAGE_SIZE);
			} else {
				memcpy(page_address(page), buf, PAGE_SIZE);
				buf += PAGE_SIZE;
			}
			bio = blkmtd_add_page(bio, dev->blkdev, page, pagecnt);
			if(!bio) {
				err = -ENOMEM;
				err("bio_add_page failed\n");
				goto write_err;
			}
			pagenr++;
			pagecnt--;
			SetPageDirty(page);
			SetPageUptodate(page);
			pagesc--;
			thislen += PAGE_SIZE;
		}
	}

	if(end_len) {
		/* do the third region */
		struct page *page;
		DEBUG(3, "blkmtd: write: doing partial end, page = %d len = %d\n",
		      pagenr, end_len);
		BUG_ON(!buf);
		page = read_cache_page(dev->blkdev->bd_inode->i_mapping, pagenr, (filler_t *)blkmtd_readpage, dev);
		lock_page(page);
		if(PageDirty(page)) {
			err("to = %lld start_len = %d len = %d end_len = %d pagenr = %d\n",
			    to, start_len, len, end_len, pagenr);
			BUG();
		}
		memcpy(page_address(page), buf, end_len);
		SetPageDirty(page);
		SetPageUptodate(page);
		DEBUG(3, "blkmtd: write: writing out partial end\n");
		thislen += end_len;
		bio = blkmtd_add_page(bio, dev->blkdev, page, pagecnt);
		if(!bio) {
			err = -ENOMEM;
			err("bio_add_page failed\n");
			goto write_err;
		}
		pagenr++;
	}

	DEBUG(3, "blkmtd: write: got %d vectors to write\n", bio->bi_vcnt);
 write_err:
	if(bio)
		blkmtd_write_out(bio);

	DEBUG(2, "blkmtd: write: end, retlen = %d, err = %d\n", *retlen, err);
	up(&dev->wrbuf_mutex);

	if(retlen)
		*retlen = thislen;
	return err;
}


/* erase a specified part of the device */
static int blkmtd_erase(struct mtd_info *mtd, struct erase_info *instr)
{
	struct blkmtd_dev *dev = mtd->priv;
	struct mtd_erase_region_info *einfo = mtd->eraseregions;
	int numregions = mtd->numeraseregions;
	size_t from;
	u_long len;
	int err = -EIO;
	int retlen;

	instr->state = MTD_ERASING;
	from = instr->addr;
	len = instr->len;

	/* check erase region has valid start and length */
	DEBUG(2, "blkmtd: erase: dev = `%s' from = 0x%x len = 0x%lx\n",
	      mtd->name+9, from, len);
	while(numregions) {
		DEBUG(3, "blkmtd: checking erase region = 0x%08X size = 0x%X num = 0x%x\n",
		      einfo->offset, einfo->erasesize, einfo->numblocks);
		if(from >= einfo->offset
		   && from < einfo->offset + (einfo->erasesize * einfo->numblocks)) {
			if(len == einfo->erasesize
			   && ( (from - einfo->offset) % einfo->erasesize == 0))
				break;