[MTD] New blockdev-backed 'fake' MTD device.

Rewritten alternative driver by Gareth Bult and Jörn Engel.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

drivers/mtd/devices/Kconfig

 # drivers/mtd/maps/Kconfig
-# $Id: Kconfig,v 1.14 2004/11/29 22:40:45 dwmw2 Exp $
+# $Id: Kconfig,v 1.15 2004/12/22 17:51:15 joern Exp $
 
 menu "Self-contained MTD device drivers"
 	depends on MTD!=n
@@ -125,6 +125,15 @@ config MTD_BLKMTD
 	  Testing MTD users (eg JFFS2) on large media and media that might
 	  be removed during a write (using the floppy drive).
 
+config MTD_BLOCK2MTD
+	tristate "MTD using block device (rewrite)"
+	depends on MTD || EXPERIMENTAL
+	help
+	  This driver is basically the same at MTD_BLKMTD above, but
+	  experienced some interface changes plus serious speedups.  In
+	  the long term, it should replace MTD_BLKMTD.  Right now, you
+	  shouldn't entrust important data to it yet.
+
 comment "Disk-On-Chip Device Drivers"
 
 config MTD_DOC2000

drivers/mtd/devices/Makefile

 #
 # linux/drivers/devices/Makefile
 #
-# $Id: Makefile.common,v 1.6 2004/07/12 16:07:30 dwmw2 Exp $
+# $Id: Makefile.common,v 1.7 2004/12/22 17:51:15 joern Exp $
 
 #                       *** BIG UGLY NOTE ***
 #
@@ -22,3 +22,4 @@ obj-$(CONFIG_MTD_MS02NV)	+= ms02-nv.o
 obj-$(CONFIG_MTD_MTDRAM)	+= mtdram.o
 obj-$(CONFIG_MTD_LART)		+= lart.o
 obj-$(CONFIG_MTD_BLKMTD)	+= blkmtd.o
+obj-$(CONFIG_MTD_BLOCK2MTD)	+= block2mtd.o

drivers/mtd/devices/block2mtd.c

+/*
+ * $Id: block2mtd.c,v 1.23 2005/01/05 17:05:46 dwmw2 Exp $
+ *
+ * blockmtd.c - use a block device as a fake MTD
+ *
+ * Author: Simon Evans <spse@secret.org.uk>
+ *
+ * Copyright (C) 2001,2002	Simon Evans
+ * Copyright (C) 2004		
+ * Copyright (C) 2004		Jörn Engel <joern@wh.fh-wedel.de>
+ *
+ * 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>
+#include <linux/buffer_head.h>
+
+#define ERROR(fmt, args...) printk(KERN_ERR "blockmtd: " fmt "\n" , ## args)
+#define INFO(fmt, args...) printk(KERN_INFO "blockmtd: " fmt "\n" , ## args)
+
+
+/* Default erase size in K, always make it a multiple of PAGE_SIZE */
+#define VERSION "$Revision: 1.23 $"
+
+/* Info for the block device */
+struct blockmtd_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
+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) {
+		printk(KERN_INFO "iSize=0 in cache_readahead\n");
+		return;
+	}
+
+	end_index = ((isize - 1) >> PAGE_CACHE_SHIFT);
+
+	spin_lock_irq(&mapping->tree_lock);
+	for (i = 0; i < PAGE_READAHEAD; i++) {
+		pagei = index + i;
+		if (pagei > end_index) {
+			printk(KERN_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;
+		spin_unlock_irq(&mapping->tree_lock);
+		page = page_cache_alloc_cold(mapping);
+		spin_lock_irq(&mapping->tree_lock);
+		if (!page)
+			break;
+		page->index = pagei;
+		list_add(&page->lru, &page_pool);
+		ret++;
+	}
+	spin_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 _blockmtd_erase(struct blockmtd_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 blockmtd_erase(struct mtd_info *mtd, struct erase_info *instr)
+{
+	struct blockmtd_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 = _blockmtd_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 blockmtd_read(struct mtd_info *mtd, loff_t from, size_t len,
+		size_t *retlen, u_char *buf)
+{
+	struct blockmtd_dev *dev = mtd->priv;
+	struct page *page;
+	int index = from >> PAGE_SHIFT;
+	int offset = from & (PAGE_SHIFT-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 _blockmtd_write(struct blockmtd_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 blockmtd_write(struct mtd_info *mtd, loff_t to, size_t len,
+		size_t *retlen, const u_char *buf)
+{
+	struct blockmtd_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 = _blockmtd_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 blockmtd_sync(struct mtd_info *mtd)
+{
+	struct blockmtd_dev *dev = mtd->priv;
+	sync_blockdev(dev->blkdev);
+	return;
+}
+
+
+static void blockmtd_free_device(struct blockmtd_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 blockmtd_dev *add_device(char *devname, int erase_size)
+{
+	struct block_device *bdev;
+	struct blockmtd_dev *dev;
+
+	if (!devname)
+		return NULL;
+
+	dev = kmalloc(sizeof(struct blockmtd_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;
+	}
+
+	atomic_set(&bdev->bd_inode->i_mapping->truncate_count, 0);
+	init_MUTEX(&dev->write_mutex);
+
+	/* Setup the MTD structure */
+	/* make the name contain the block device in */
+	dev->mtd.name = kmalloc(sizeof("blockmtd: ") + strlen(devname),
+			GFP_KERNEL);
+	if (!dev->mtd.name)
+		goto devinit_err;
+
+	sprintf(dev->mtd.name, "blockmtd: %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 = blockmtd_erase;
+	dev->mtd.write = blockmtd_write;
+	dev->mtd.writev = default_mtd_writev;
+	dev->mtd.sync = blockmtd_sync;
+	dev->mtd.read = blockmtd_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 [%ld]", dev->mtd.index,
+			dev->mtd.name + strlen("blkmtd: "),
+			dev->mtd.erasesize >> 10, PAGE_SIZE);
+	return dev;
+
+devinit_err:
+	blockmtd_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_num32(u32 *num32, const char *token)
+{
+	char *endp;
+	unsigned long n;
+
+	n = ustrtoul(token, &endp, 0);
+	if (*endp)
+		return -EINVAL;
+
+	*num32 = 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;
+}
+
+
+#define parse_err(fmt, args...) do {		\
+	ERROR("blockmtd: " fmt "\n", ## args);	\
+	return 0;				\
+} while (0)
+
+static int blockmtd_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);
+
+	for (i=0; i<2; i++)
+		token[i] = strsep(&str, ",");
+
+	{ /* people dislike typing "echo -n".  and it's simple enough */
+		char *newline = strrchr(token[1], '\n');
+		if (newline && !newline[1])
+			*newline = 0;
+	}
+
+	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_num32(&erase_size, token[1]);
+		if (ret)
+			parse_err("illegal erase size");
+	}
+
+	add_device(name, erase_size);
+
+	return 0;
+}
+
+
+module_param_call(blockmtd, blockmtd_setup, NULL, NULL, 0200);
+MODULE_PARM_DESC(blockmtd, "Device to use. \"blockmtd=<dev>[,<erasesize>]\"");
+
+static int __init blockmtd_init(void)
+{
+	INFO("version " VERSION);
+	return 0;
+}
+
+
+static void __devexit blockmtd_exit(void)
+{
+	struct list_head *pos, *next;
+
+	/* Remove the MTD devices */
+	list_for_each_safe(pos, next, &blkmtd_device_list) {
+		struct blockmtd_dev *dev = list_entry(pos, typeof(*dev), list);
+		blockmtd_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);
+		blockmtd_free_device(dev);
+	}
+}
+
+
+module_init(blockmtd_init);
+module_exit(blockmtd_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Simon Evans <spse@secret.org.uk> and others");
+MODULE_DESCRIPTION("Emulate an MTD using a block device");