block2mtd.c revision ee0e87b174bb41f0310cf089262bf5dd8f95a212 
1/*
2 * block2mtd.c - create an mtd from a block device
3 *
4 * Copyright (C) 2001,2002	Simon Evans <spse@secret.org.uk>
5 * Copyright (C) 2004-2006	Joern Engel <joern@wh.fh-wedel.de>
6 *
7 * Licence: GPL
8 */
9#include <linux/module.h>
10#include <linux/fs.h>
11#include <linux/blkdev.h>
12#include <linux/bio.h>
13#include <linux/pagemap.h>
14#include <linux/list.h>
15#include <linux/init.h>
16#include <linux/mtd/mtd.h>
17#include <linux/buffer_head.h>
18#include <linux/mutex.h>
19#include <linux/mount.h>
20#include <linux/slab.h>
21
22#define ERROR(fmt, args...) printk(KERN_ERR "block2mtd: " fmt "\n" , ## args)
23#define INFO(fmt, args...) printk(KERN_INFO "block2mtd: " fmt "\n" , ## args)
24
25
26/* Info for the block device */
27struct block2mtd_dev {
28	struct list_head list;
29	struct block_device *blkdev;
30	struct mtd_info mtd;
31	struct mutex write_mutex;
32};
33
34
35/* Static info about the MTD, used in cleanup_module */
36static LIST_HEAD(blkmtd_device_list);
37
38
39static struct page *page_read(struct address_space *mapping, int index)
40{
41	return read_mapping_page(mapping, index, NULL);
42}
43
44/* erase a specified part of the device */
45static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
46{
47	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
48	struct page *page;
49	int index = to >> PAGE_SHIFT;	// page index
50	int pages = len >> PAGE_SHIFT;
51	u_long *p;
52	u_long *max;
53
54	while (pages) {
55		page = page_read(mapping, index);
56		if (!page)
57			return -ENOMEM;
58		if (IS_ERR(page))
59			return PTR_ERR(page);
60
61		max = page_address(page) + PAGE_SIZE;
62		for (p=page_address(page); p<max; p++)
63			if (*p != -1UL) {
64				lock_page(page);
65				memset(page_address(page), 0xff, PAGE_SIZE);
66				set_page_dirty(page);
67				unlock_page(page);
68				break;
69			}
70
71		page_cache_release(page);
72		pages--;
73		index++;
74	}
75	return 0;
76}
77static int block2mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
78{
79	struct block2mtd_dev *dev = mtd->priv;
80	size_t from = instr->addr;
81	size_t len = instr->len;
82	int err;
83
84	instr->state = MTD_ERASING;
85	mutex_lock(&dev->write_mutex);
86	err = _block2mtd_erase(dev, from, len);
87	mutex_unlock(&dev->write_mutex);
88	if (err) {
89		ERROR("erase failed err = %d", err);
90		instr->state = MTD_ERASE_FAILED;
91	} else
92		instr->state = MTD_ERASE_DONE;
93
94	mtd_erase_callback(instr);
95	return err;
96}
97
98
99static int block2mtd_read(struct mtd_info *mtd, loff_t from, size_t len,
100		size_t *retlen, u_char *buf)
101{
102	struct block2mtd_dev *dev = mtd->priv;
103	struct page *page;
104	int index = from >> PAGE_SHIFT;
105	int offset = from & (PAGE_SIZE-1);
106	int cpylen;
107
108	if (from > mtd->size)
109		return -EINVAL;
110	if (from + len > mtd->size)
111		len = mtd->size - from;
112
113	if (retlen)
114		*retlen = 0;
115
116	while (len) {
117		if ((offset + len) > PAGE_SIZE)
118			cpylen = PAGE_SIZE - offset;	// multiple pages
119		else
120			cpylen = len;	// this page
121		len = len - cpylen;
122
123		page = page_read(dev->blkdev->bd_inode->i_mapping, index);
124		if (!page)
125			return -ENOMEM;
126		if (IS_ERR(page))
127			return PTR_ERR(page);
128
129		memcpy(buf, page_address(page) + offset, cpylen);
130		page_cache_release(page);
131
132		if (retlen)
133			*retlen += cpylen;
134		buf += cpylen;
135		offset = 0;
136		index++;
137	}
138	return 0;
139}
140
141
142/* write data to the underlying device */
143static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
144		loff_t to, size_t len, size_t *retlen)
145{
146	struct page *page;
147	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
148	int index = to >> PAGE_SHIFT;	// page index
149	int offset = to & ~PAGE_MASK;	// page offset
150	int cpylen;
151
152	if (retlen)
153		*retlen = 0;
154	while (len) {
155		if ((offset+len) > PAGE_SIZE)
156			cpylen = PAGE_SIZE - offset;	// multiple pages
157		else
158			cpylen = len;			// this page
159		len = len - cpylen;
160
161		page = page_read(mapping, index);
162		if (!page)
163			return -ENOMEM;
164		if (IS_ERR(page))
165			return PTR_ERR(page);
166
167		if (memcmp(page_address(page)+offset, buf, cpylen)) {
168			lock_page(page);
169			memcpy(page_address(page) + offset, buf, cpylen);
170			set_page_dirty(page);
171			unlock_page(page);
172		}
173		page_cache_release(page);
174
175		if (retlen)
176			*retlen += cpylen;
177
178		buf += cpylen;
179		offset = 0;
180		index++;
181	}
182	return 0;
183}
184
185
186static int block2mtd_write(struct mtd_info *mtd, loff_t to, size_t len,
187		size_t *retlen, const u_char *buf)
188{
189	struct block2mtd_dev *dev = mtd->priv;
190	int err;
191
192	if (!len)
193		return 0;
194	if (to >= mtd->size)
195		return -ENOSPC;
196	if (to + len > mtd->size)
197		len = mtd->size - to;
198
199	mutex_lock(&dev->write_mutex);
200	err = _block2mtd_write(dev, buf, to, len, retlen);
201	mutex_unlock(&dev->write_mutex);
202	if (err > 0)
203		err = 0;
204	return err;
205}
206
207
208/* sync the device - wait until the write queue is empty */
209static void block2mtd_sync(struct mtd_info *mtd)
210{
211	struct block2mtd_dev *dev = mtd->priv;
212	sync_blockdev(dev->blkdev);
213	return;
214}
215
216
217static void block2mtd_free_device(struct block2mtd_dev *dev)
218{
219	if (!dev)
220		return;
221
222	kfree(dev->mtd.name);
223
224	if (dev->blkdev) {
225		invalidate_mapping_pages(dev->blkdev->bd_inode->i_mapping,
226					0, -1);
227		blkdev_put(dev->blkdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
228	}
229
230	kfree(dev);
231}
232
233
234/* FIXME: ensure that mtd->size % erase_size == 0 */
235static struct block2mtd_dev *add_device(char *devname, int erase_size)
236{
237	const fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
238	struct block_device *bdev;
239	struct block2mtd_dev *dev;
240	char *name;
241
242	if (!devname)
243		return NULL;
244
245	dev = kzalloc(sizeof(struct block2mtd_dev), GFP_KERNEL);
246	if (!dev)
247		return NULL;
248
249	/* Get a handle on the device */
250	bdev = blkdev_get_by_path(devname, mode, dev);
251#ifndef MODULE
252	if (IS_ERR(bdev)) {
253
254		/* We might not have rootfs mounted at this point. Try
255		   to resolve the device name by other means. */
256
257		dev_t devt = name_to_dev_t(devname);
258		if (devt)
259			bdev = blkdev_get_by_dev(devt, mode, dev);
260	}
261#endif
262
263	if (IS_ERR(bdev)) {
264		ERROR("error: cannot open device %s", devname);
265		goto devinit_err;
266	}
267	dev->blkdev = bdev;
268
269	if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
270		ERROR("attempting to use an MTD device as a block device");
271		goto devinit_err;
272	}
273
274	mutex_init(&dev->write_mutex);
275
276	/* Setup the MTD structure */
277	/* make the name contain the block device in */
278	name = kasprintf(GFP_KERNEL, "block2mtd: %s", devname);
279	if (!name)
280		goto devinit_err;
281
282	dev->mtd.name = name;
283
284	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
285	dev->mtd.erasesize = erase_size;
286	dev->mtd.writesize = 1;
287	dev->mtd.type = MTD_RAM;
288	dev->mtd.flags = MTD_CAP_RAM;
289	dev->mtd.erase = block2mtd_erase;
290	dev->mtd.write = block2mtd_write;
291	dev->mtd.writev = default_mtd_writev;
292	dev->mtd.sync = block2mtd_sync;
293	dev->mtd.read = block2mtd_read;
294	dev->mtd.priv = dev;
295	dev->mtd.owner = THIS_MODULE;
296
297	if (mtd_device_register(&dev->mtd, NULL, 0)) {
298		/* Device didn't get added, so free the entry */
299		goto devinit_err;
300	}
301	list_add(&dev->list, &blkmtd_device_list);
302	INFO("mtd%d: [%s] erase_size = %dKiB [%d]", dev->mtd.index,
303			dev->mtd.name + strlen("block2mtd: "),
304			dev->mtd.erasesize >> 10, dev->mtd.erasesize);
305	return dev;
306
307devinit_err:
308	block2mtd_free_device(dev);
309	return NULL;
310}
311
312
313/* This function works similar to reguler strtoul.  In addition, it
314 * allows some suffixes for a more human-readable number format:
315 * ki, Ki, kiB, KiB	- multiply result with 1024
316 * Mi, MiB		- multiply result with 1024^2
317 * Gi, GiB		- multiply result with 1024^3
318 */
319static int ustrtoul(const char *cp, char **endp, unsigned int base)
320{
321	unsigned long result = simple_strtoul(cp, endp, base);
322	switch (**endp) {
323	case 'G' :
324		result *= 1024;
325	case 'M':
326		result *= 1024;
327	case 'K':
328	case 'k':
329		result *= 1024;
330	/* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
331		if ((*endp)[1] == 'i') {
332			if ((*endp)[2] == 'B')
333				(*endp) += 3;
334			else
335				(*endp) += 2;
336		}
337	}
338	return result;
339}
340
341
342static int parse_num(size_t *num, const char *token)
343{
344	char *endp;
345	size_t n;
346
347	n = (size_t) ustrtoul(token, &endp, 0);
348	if (*endp)
349		return -EINVAL;
350
351	*num = n;
352	return 0;
353}
354
355
356static inline void kill_final_newline(char *str)
357{
358	char *newline = strrchr(str, '\n');
359	if (newline && !newline[1])
360		*newline = 0;
361}
362
363
364#define parse_err(fmt, args...) do {	\
365	ERROR(fmt, ## args);		\
366	return 0;			\
367} while (0)
368
369#ifndef MODULE
370static int block2mtd_init_called = 0;
371static char block2mtd_paramline[80 + 12]; /* 80 for device, 12 for erase size */
372#endif
373
374
375static int block2mtd_setup2(const char *val)
376{
377	char buf[80 + 12]; /* 80 for device, 12 for erase size */
378	char *str = buf;
379	char *token[2];
380	char *name;
381	size_t erase_size = PAGE_SIZE;
382	int i, ret;
383
384	if (strnlen(val, sizeof(buf)) >= sizeof(buf))
385		parse_err("parameter too long");
386
387	strcpy(str, val);
388	kill_final_newline(str);
389
390	for (i = 0; i < 2; i++)
391		token[i] = strsep(&str, ",");
392
393	if (str)
394		parse_err("too many arguments");
395
396	if (!token[0])
397		parse_err("no argument");
398
399	name = token[0];
400	if (strlen(name) + 1 > 80)
401		parse_err("device name too long");
402
403	if (token[1]) {
404		ret = parse_num(&erase_size, token[1]);
405		if (ret) {
406			parse_err("illegal erase size");
407		}
408	}
409
410	add_device(name, erase_size);
411
412	return 0;
413}
414
415
416static int block2mtd_setup(const char *val, struct kernel_param *kp)
417{
418#ifdef MODULE
419	return block2mtd_setup2(val);
420#else
421	/* If more parameters are later passed in via
422	   /sys/module/block2mtd/parameters/block2mtd
423	   and block2mtd_init() has already been called,
424	   we can parse the argument now. */
425
426	if (block2mtd_init_called)
427		return block2mtd_setup2(val);
428
429	/* During early boot stage, we only save the parameters
430	   here. We must parse them later: if the param passed
431	   from kernel boot command line, block2mtd_setup() is
432	   called so early that it is not possible to resolve
433	   the device (even kmalloc() fails). Deter that work to
434	   block2mtd_setup2(). */
435
436	strlcpy(block2mtd_paramline, val, sizeof(block2mtd_paramline));
437
438	return 0;
439#endif
440}
441
442
443module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
444MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");
445
446static int __init block2mtd_init(void)
447{
448	int ret = 0;
449
450#ifndef MODULE
451	if (strlen(block2mtd_paramline))
452		ret = block2mtd_setup2(block2mtd_paramline);
453	block2mtd_init_called = 1;
454#endif
455
456	return ret;
457}
458
459
460static void __devexit block2mtd_exit(void)
461{
462	struct list_head *pos, *next;
463
464	/* Remove the MTD devices */
465	list_for_each_safe(pos, next, &blkmtd_device_list) {
466		struct block2mtd_dev *dev = list_entry(pos, typeof(*dev), list);
467		block2mtd_sync(&dev->mtd);
468		mtd_device_unregister(&dev->mtd);
469		INFO("mtd%d: [%s] removed", dev->mtd.index,
470				dev->mtd.name + strlen("block2mtd: "));
471		list_del(&dev->list);
472		block2mtd_free_device(dev);
473	}
474}
475
476
477module_init(block2mtd_init);
478module_exit(block2mtd_exit);
479
480MODULE_LICENSE("GPL");
481MODULE_AUTHOR("Joern Engel <joern@lazybastard.org>");
482MODULE_DESCRIPTION("Emulate an MTD using a block device");
483