block2mtd.c revision 2e24e32e2759348c9290404abad4f729f791bfad 
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/mutex.h>
18#include <linux/mount.h>
19#include <linux/slab.h>
20
21#define ERROR(fmt, args...) printk(KERN_ERR "block2mtd: " fmt "\n" , ## args)
22#define INFO(fmt, args...) printk(KERN_INFO "block2mtd: " fmt "\n" , ## args)
23
24
25/* Info for the block device */
26struct block2mtd_dev {
27	struct list_head list;
28	struct block_device *blkdev;
29	struct mtd_info mtd;
30	struct mutex write_mutex;
31};
32
33
34/* Static info about the MTD, used in cleanup_module */
35static LIST_HEAD(blkmtd_device_list);
36
37
38static struct page *page_read(struct address_space *mapping, int index)
39{
40	return read_mapping_page(mapping, index, NULL);
41}
42
43/* erase a specified part of the device */
44static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
45{
46	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
47	struct page *page;
48	int index = to >> PAGE_SHIFT;	// page index
49	int pages = len >> PAGE_SHIFT;
50	u_long *p;
51	u_long *max;
52
53	while (pages) {
54		page = page_read(mapping, index);
55		if (IS_ERR(page))
56			return PTR_ERR(page);
57
58		max = page_address(page) + PAGE_SIZE;
59		for (p=page_address(page); p<max; p++)
60			if (*p != -1UL) {
61				lock_page(page);
62				memset(page_address(page), 0xff, PAGE_SIZE);
63				set_page_dirty(page);
64				unlock_page(page);
65				break;
66			}
67
68		page_cache_release(page);
69		pages--;
70		index++;
71	}
72	return 0;
73}
74static int block2mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
75{
76	struct block2mtd_dev *dev = mtd->priv;
77	size_t from = instr->addr;
78	size_t len = instr->len;
79	int err;
80
81	instr->state = MTD_ERASING;
82	mutex_lock(&dev->write_mutex);
83	err = _block2mtd_erase(dev, from, len);
84	mutex_unlock(&dev->write_mutex);
85	if (err) {
86		ERROR("erase failed err = %d", err);
87		instr->state = MTD_ERASE_FAILED;
88	} else
89		instr->state = MTD_ERASE_DONE;
90
91	mtd_erase_callback(instr);
92	return err;
93}
94
95
96static int block2mtd_read(struct mtd_info *mtd, loff_t from, size_t len,
97		size_t *retlen, u_char *buf)
98{
99	struct block2mtd_dev *dev = mtd->priv;
100	struct page *page;
101	int index = from >> PAGE_SHIFT;
102	int offset = from & (PAGE_SIZE-1);
103	int cpylen;
104
105	while (len) {
106		if ((offset + len) > PAGE_SIZE)
107			cpylen = PAGE_SIZE - offset;	// multiple pages
108		else
109			cpylen = len;	// this page
110		len = len - cpylen;
111
112		page = page_read(dev->blkdev->bd_inode->i_mapping, index);
113		if (IS_ERR(page))
114			return PTR_ERR(page);
115
116		memcpy(buf, page_address(page) + offset, cpylen);
117		page_cache_release(page);
118
119		if (retlen)
120			*retlen += cpylen;
121		buf += cpylen;
122		offset = 0;
123		index++;
124	}
125	return 0;
126}
127
128
129/* write data to the underlying device */
130static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
131		loff_t to, size_t len, size_t *retlen)
132{
133	struct page *page;
134	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
135	int index = to >> PAGE_SHIFT;	// page index
136	int offset = to & ~PAGE_MASK;	// page offset
137	int cpylen;
138
139	while (len) {
140		if ((offset+len) > PAGE_SIZE)
141			cpylen = PAGE_SIZE - offset;	// multiple pages
142		else
143			cpylen = len;			// this page
144		len = len - cpylen;
145
146		page = page_read(mapping, index);
147		if (IS_ERR(page))
148			return PTR_ERR(page);
149
150		if (memcmp(page_address(page)+offset, buf, cpylen)) {
151			lock_page(page);
152			memcpy(page_address(page) + offset, buf, cpylen);
153			set_page_dirty(page);
154			unlock_page(page);
155		}
156		page_cache_release(page);
157
158		if (retlen)
159			*retlen += cpylen;
160
161		buf += cpylen;
162		offset = 0;
163		index++;
164	}
165	return 0;
166}
167
168
169static int block2mtd_write(struct mtd_info *mtd, loff_t to, size_t len,
170		size_t *retlen, const u_char *buf)
171{
172	struct block2mtd_dev *dev = mtd->priv;
173	int err;
174
175	mutex_lock(&dev->write_mutex);
176	err = _block2mtd_write(dev, buf, to, len, retlen);
177	mutex_unlock(&dev->write_mutex);
178	if (err > 0)
179		err = 0;
180	return err;
181}
182
183
184/* sync the device - wait until the write queue is empty */
185static void block2mtd_sync(struct mtd_info *mtd)
186{
187	struct block2mtd_dev *dev = mtd->priv;
188	sync_blockdev(dev->blkdev);
189	return;
190}
191
192
193static void block2mtd_free_device(struct block2mtd_dev *dev)
194{
195	if (!dev)
196		return;
197
198	kfree(dev->mtd.name);
199
200	if (dev->blkdev) {
201		invalidate_mapping_pages(dev->blkdev->bd_inode->i_mapping,
202					0, -1);
203		blkdev_put(dev->blkdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
204	}
205
206	kfree(dev);
207}
208
209
210/* FIXME: ensure that mtd->size % erase_size == 0 */
211static struct block2mtd_dev *add_device(char *devname, int erase_size)
212{
213	const fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
214	struct block_device *bdev;
215	struct block2mtd_dev *dev;
216	char *name;
217
218	if (!devname)
219		return NULL;
220
221	dev = kzalloc(sizeof(struct block2mtd_dev), GFP_KERNEL);
222	if (!dev)
223		return NULL;
224
225	/* Get a handle on the device */
226	bdev = blkdev_get_by_path(devname, mode, dev);
227#ifndef MODULE
228	if (IS_ERR(bdev)) {
229
230		/* We might not have rootfs mounted at this point. Try
231		   to resolve the device name by other means. */
232
233		dev_t devt = name_to_dev_t(devname);
234		if (devt)
235			bdev = blkdev_get_by_dev(devt, mode, dev);
236	}
237#endif
238
239	if (IS_ERR(bdev)) {
240		ERROR("error: cannot open device %s", devname);
241		goto devinit_err;
242	}
243	dev->blkdev = bdev;
244
245	if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
246		ERROR("attempting to use an MTD device as a block device");
247		goto devinit_err;
248	}
249
250	mutex_init(&dev->write_mutex);
251
252	/* Setup the MTD structure */
253	/* make the name contain the block device in */
254	name = kasprintf(GFP_KERNEL, "block2mtd: %s", devname);
255	if (!name)
256		goto devinit_err;
257
258	dev->mtd.name = name;
259
260	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
261	dev->mtd.erasesize = erase_size;
262	dev->mtd.writesize = 1;
263	dev->mtd.writebufsize = PAGE_SIZE;
264	dev->mtd.type = MTD_RAM;
265	dev->mtd.flags = MTD_CAP_RAM;
266	dev->mtd._erase = block2mtd_erase;
267	dev->mtd._write = block2mtd_write;
268	dev->mtd._sync = block2mtd_sync;
269	dev->mtd._read = block2mtd_read;
270	dev->mtd.priv = dev;
271	dev->mtd.owner = THIS_MODULE;
272
273	if (mtd_device_register(&dev->mtd, NULL, 0)) {
274		/* Device didn't get added, so free the entry */
275		goto devinit_err;
276	}
277	list_add(&dev->list, &blkmtd_device_list);
278	INFO("mtd%d: [%s] erase_size = %dKiB [%d]", dev->mtd.index,
279			dev->mtd.name + strlen("block2mtd: "),
280			dev->mtd.erasesize >> 10, dev->mtd.erasesize);
281	return dev;
282
283devinit_err:
284	block2mtd_free_device(dev);
285	return NULL;
286}
287
288
289/* This function works similar to reguler strtoul.  In addition, it
290 * allows some suffixes for a more human-readable number format:
291 * ki, Ki, kiB, KiB	- multiply result with 1024
292 * Mi, MiB		- multiply result with 1024^2
293 * Gi, GiB		- multiply result with 1024^3
294 */
295static int ustrtoul(const char *cp, char **endp, unsigned int base)
296{
297	unsigned long result = simple_strtoul(cp, endp, base);
298	switch (**endp) {
299	case 'G' :
300		result *= 1024;
301	case 'M':
302		result *= 1024;
303	case 'K':
304	case 'k':
305		result *= 1024;
306	/* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
307		if ((*endp)[1] == 'i') {
308			if ((*endp)[2] == 'B')
309				(*endp) += 3;
310			else
311				(*endp) += 2;
312		}
313	}
314	return result;
315}
316
317
318static int parse_num(size_t *num, const char *token)
319{
320	char *endp;
321	size_t n;
322
323	n = (size_t) ustrtoul(token, &endp, 0);
324	if (*endp)
325		return -EINVAL;
326
327	*num = n;
328	return 0;
329}
330
331
332static inline void kill_final_newline(char *str)
333{
334	char *newline = strrchr(str, '\n');
335	if (newline && !newline[1])
336		*newline = 0;
337}
338
339
340#define parse_err(fmt, args...) do {	\
341	ERROR(fmt, ## args);		\
342	return 0;			\
343} while (0)
344
345#ifndef MODULE
346static int block2mtd_init_called = 0;
347static char block2mtd_paramline[80 + 12]; /* 80 for device, 12 for erase size */
348#endif
349
350
351static int block2mtd_setup2(const char *val)
352{
353	char buf[80 + 12]; /* 80 for device, 12 for erase size */
354	char *str = buf;
355	char *token[2];
356	char *name;
357	size_t erase_size = PAGE_SIZE;
358	int i, ret;
359
360	if (strnlen(val, sizeof(buf)) >= sizeof(buf))
361		parse_err("parameter too long");
362
363	strcpy(str, val);
364	kill_final_newline(str);
365
366	for (i = 0; i < 2; i++)
367		token[i] = strsep(&str, ",");
368
369	if (str)
370		parse_err("too many arguments");
371
372	if (!token[0])
373		parse_err("no argument");
374
375	name = token[0];
376	if (strlen(name) + 1 > 80)
377		parse_err("device name too long");
378
379	if (token[1]) {
380		ret = parse_num(&erase_size, token[1]);
381		if (ret) {
382			parse_err("illegal erase size");
383		}
384	}
385
386	add_device(name, erase_size);
387
388	return 0;
389}
390
391
392static int block2mtd_setup(const char *val, struct kernel_param *kp)
393{
394#ifdef MODULE
395	return block2mtd_setup2(val);
396#else
397	/* If more parameters are later passed in via
398	   /sys/module/block2mtd/parameters/block2mtd
399	   and block2mtd_init() has already been called,
400	   we can parse the argument now. */
401
402	if (block2mtd_init_called)
403		return block2mtd_setup2(val);
404
405	/* During early boot stage, we only save the parameters
406	   here. We must parse them later: if the param passed
407	   from kernel boot command line, block2mtd_setup() is
408	   called so early that it is not possible to resolve
409	   the device (even kmalloc() fails). Deter that work to
410	   block2mtd_setup2(). */
411
412	strlcpy(block2mtd_paramline, val, sizeof(block2mtd_paramline));
413
414	return 0;
415#endif
416}
417
418
419module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
420MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");
421
422static int __init block2mtd_init(void)
423{
424	int ret = 0;
425
426#ifndef MODULE
427	if (strlen(block2mtd_paramline))
428		ret = block2mtd_setup2(block2mtd_paramline);
429	block2mtd_init_called = 1;
430#endif
431
432	return ret;
433}
434
435
436static void __devexit block2mtd_exit(void)
437{
438	struct list_head *pos, *next;
439
440	/* Remove the MTD devices */
441	list_for_each_safe(pos, next, &blkmtd_device_list) {
442		struct block2mtd_dev *dev = list_entry(pos, typeof(*dev), list);
443		block2mtd_sync(&dev->mtd);
444		mtd_device_unregister(&dev->mtd);
445		INFO("mtd%d: [%s] removed", dev->mtd.index,
446				dev->mtd.name + strlen("block2mtd: "));
447		list_del(&dev->list);
448		block2mtd_free_device(dev);
449	}
450}
451
452
453module_init(block2mtd_init);
454module_exit(block2mtd_exit);
455
456MODULE_LICENSE("GPL");
457MODULE_AUTHOR("Joern Engel <joern@lazybastard.org>");
458MODULE_DESCRIPTION("Emulate an MTD using a block device");
459