block2mtd.c revision 92cbfdcc3661d7670b01b92b89811cd3a2412297 
1/*
2 * $Id: block2mtd.c,v 1.30 2005/11/29 14:48:32 gleixner Exp $
3 *
4 * block2mtd.c - create an mtd from a block device
5 *
6 * Copyright (C) 2001,2002	Simon Evans <spse@secret.org.uk>
7 * Copyright (C) 2004-2006	Jörn Engel <joern@wh.fh-wedel.de>
8 *
9 * Licence: GPL
10 */
11#include <linux/config.h>
12#include <linux/module.h>
13#include <linux/fs.h>
14#include <linux/blkdev.h>
15#include <linux/bio.h>
16#include <linux/pagemap.h>
17#include <linux/list.h>
18#include <linux/init.h>
19#include <linux/mtd/mtd.h>
20#include <linux/buffer_head.h>
21#include <linux/mutex.h>
22
23#define VERSION "$Revision: 1.30 $"
24
25
26#define ERROR(fmt, args...) printk(KERN_ERR "block2mtd: " fmt "\n" , ## args)
27#define INFO(fmt, args...) printk(KERN_INFO "block2mtd: " fmt "\n" , ## args)
28
29
30/* Info for the block device */
31struct block2mtd_dev {
32	struct list_head list;
33	struct block_device *blkdev;
34	struct mtd_info mtd;
35	struct mutex write_mutex;
36};
37
38
39/* Static info about the MTD, used in cleanup_module */
40static LIST_HEAD(blkmtd_device_list);
41
42
43#define PAGE_READAHEAD 64
44static void cache_readahead(struct address_space *mapping, int index)
45{
46	filler_t *filler = (filler_t*)mapping->a_ops->readpage;
47	int i, pagei;
48	unsigned ret = 0;
49	unsigned long end_index;
50	struct page *page;
51	LIST_HEAD(page_pool);
52	struct inode *inode = mapping->host;
53	loff_t isize = i_size_read(inode);
54
55	if (!isize) {
56		INFO("iSize=0 in cache_readahead\n");
57		return;
58	}
59
60	end_index = ((isize - 1) >> PAGE_CACHE_SHIFT);
61
62	read_lock_irq(&mapping->tree_lock);
63	for (i = 0; i < PAGE_READAHEAD; i++) {
64		pagei = index + i;
65		if (pagei > end_index) {
66			INFO("Overrun end of disk in cache readahead\n");
67			break;
68		}
69		page = radix_tree_lookup(&mapping->page_tree, pagei);
70		if (page && (!i))
71			break;
72		if (page)
73			continue;
74		read_unlock_irq(&mapping->tree_lock);
75		page = page_cache_alloc_cold(mapping);
76		read_lock_irq(&mapping->tree_lock);
77		if (!page)
78			break;
79		page->index = pagei;
80		list_add(&page->lru, &page_pool);
81		ret++;
82	}
83	read_unlock_irq(&mapping->tree_lock);
84	if (ret)
85		read_cache_pages(mapping, &page_pool, filler, NULL);
86}
87
88
89static struct page* page_readahead(struct address_space *mapping, int index)
90{
91	filler_t *filler = (filler_t*)mapping->a_ops->readpage;
92	cache_readahead(mapping, index);
93	return read_cache_page(mapping, index, filler, NULL);
94}
95
96
97/* erase a specified part of the device */
98static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
99{
100	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
101	struct page *page;
102	int index = to >> PAGE_SHIFT;	// page index
103	int pages = len >> PAGE_SHIFT;
104	u_long *p;
105	u_long *max;
106
107	while (pages) {
108		page = page_readahead(mapping, index);
109		if (!page)
110			return -ENOMEM;
111		if (IS_ERR(page))
112			return PTR_ERR(page);
113
114		max = (u_long*)page_address(page) + PAGE_SIZE;
115		for (p=(u_long*)page_address(page); p<max; p++)
116			if (*p != -1UL) {
117				lock_page(page);
118				memset(page_address(page), 0xff, PAGE_SIZE);
119				set_page_dirty(page);
120				unlock_page(page);
121				break;
122			}
123
124		page_cache_release(page);
125		pages--;
126		index++;
127	}
128	return 0;
129}
130static int block2mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
131{
132	struct block2mtd_dev *dev = mtd->priv;
133	size_t from = instr->addr;
134	size_t len = instr->len;
135	int err;
136
137	instr->state = MTD_ERASING;
138	mutex_lock(&dev->write_mutex);
139	err = _block2mtd_erase(dev, from, len);
140	mutex_unlock(&dev->write_mutex);
141	if (err) {
142		ERROR("erase failed err = %d", err);
143		instr->state = MTD_ERASE_FAILED;
144	} else
145		instr->state = MTD_ERASE_DONE;
146
147	instr->state = MTD_ERASE_DONE;
148	mtd_erase_callback(instr);
149	return err;
150}
151
152
153static int block2mtd_read(struct mtd_info *mtd, loff_t from, size_t len,
154		size_t *retlen, u_char *buf)
155{
156	struct block2mtd_dev *dev = mtd->priv;
157	struct page *page;
158	int index = from >> PAGE_SHIFT;
159	int offset = from & (PAGE_SIZE-1);
160	int cpylen;
161
162	if (from > mtd->size)
163		return -EINVAL;
164	if (from + len > mtd->size)
165		len = mtd->size - from;
166
167	if (retlen)
168		*retlen = 0;
169
170	while (len) {
171		if ((offset + len) > PAGE_SIZE)
172			cpylen = PAGE_SIZE - offset;	// multiple pages
173		else
174			cpylen = len;	// this page
175		len = len - cpylen;
176
177		//      Get page
178		page = page_readahead(dev->blkdev->bd_inode->i_mapping, index);
179		if (!page)
180			return -ENOMEM;
181		if (IS_ERR(page))
182			return PTR_ERR(page);
183
184		memcpy(buf, page_address(page) + offset, cpylen);
185		page_cache_release(page);
186
187		if (retlen)
188			*retlen += cpylen;
189		buf += cpylen;
190		offset = 0;
191		index++;
192	}
193	return 0;
194}
195
196
197/* write data to the underlying device */
198static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
199		loff_t to, size_t len, size_t *retlen)
200{
201	struct page *page;
202	struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
203	int index = to >> PAGE_SHIFT;	// page index
204	int offset = to & ~PAGE_MASK;	// page offset
205	int cpylen;
206
207	if (retlen)
208		*retlen = 0;
209	while (len) {
210		if ((offset+len) > PAGE_SIZE)
211			cpylen = PAGE_SIZE - offset;	// multiple pages
212		else
213			cpylen = len;			// this page
214		len = len - cpylen;
215
216		//	Get page
217		page = page_readahead(mapping, index);
218		if (!page)
219			return -ENOMEM;
220		if (IS_ERR(page))
221			return PTR_ERR(page);
222
223		if (memcmp(page_address(page)+offset, buf, cpylen)) {
224			lock_page(page);
225			memcpy(page_address(page) + offset, buf, cpylen);
226			set_page_dirty(page);
227			unlock_page(page);
228		}
229		page_cache_release(page);
230
231		if (retlen)
232			*retlen += cpylen;
233
234		buf += cpylen;
235		offset = 0;
236		index++;
237	}
238	return 0;
239}
240static int block2mtd_write(struct mtd_info *mtd, loff_t to, size_t len,
241		size_t *retlen, const u_char *buf)
242{
243	struct block2mtd_dev *dev = mtd->priv;
244	int err;
245
246	if (!len)
247		return 0;
248	if (to >= mtd->size)
249		return -ENOSPC;
250	if (to + len > mtd->size)
251		len = mtd->size - to;
252
253	mutex_lock(&dev->write_mutex);
254	err = _block2mtd_write(dev, buf, to, len, retlen);
255	mutex_unlock(&dev->write_mutex);
256	if (err > 0)
257		err = 0;
258	return err;
259}
260
261
262/* sync the device - wait until the write queue is empty */
263static void block2mtd_sync(struct mtd_info *mtd)
264{
265	struct block2mtd_dev *dev = mtd->priv;
266	sync_blockdev(dev->blkdev);
267	return;
268}
269
270
271static void block2mtd_free_device(struct block2mtd_dev *dev)
272{
273	if (!dev)
274		return;
275
276	kfree(dev->mtd.name);
277
278	if (dev->blkdev) {
279		invalidate_inode_pages(dev->blkdev->bd_inode->i_mapping);
280		close_bdev_excl(dev->blkdev);
281	}
282
283	kfree(dev);
284}
285
286
287/* FIXME: ensure that mtd->size % erase_size == 0 */
288static struct block2mtd_dev *add_device(char *devname, int erase_size)
289{
290	struct block_device *bdev;
291	struct block2mtd_dev *dev;
292
293	if (!devname)
294		return NULL;
295
296	dev = kmalloc(sizeof(struct block2mtd_dev), GFP_KERNEL);
297	if (!dev)
298		return NULL;
299	memset(dev, 0, sizeof(*dev));
300
301	/* Get a handle on the device */
302	bdev = open_bdev_excl(devname, O_RDWR, NULL);
303	if (IS_ERR(bdev)) {
304		ERROR("error: cannot open device %s", devname);
305		goto devinit_err;
306	}
307	dev->blkdev = bdev;
308
309	if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
310		ERROR("attempting to use an MTD device as a block device");
311		goto devinit_err;
312	}
313
314	mutex_init(&dev->write_mutex);
315
316	/* Setup the MTD structure */
317	/* make the name contain the block device in */
318	dev->mtd.name = kmalloc(sizeof("block2mtd: ") + strlen(devname),
319			GFP_KERNEL);
320	if (!dev->mtd.name)
321		goto devinit_err;
322
323	sprintf(dev->mtd.name, "block2mtd: %s", devname);
324
325	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
326	dev->mtd.erasesize = erase_size;
327	dev->mtd.type = MTD_GENERIC_TYPE;
328	dev->mtd.flags = MTD_CAP_RAM;
329	dev->mtd.erase = block2mtd_erase;
330	dev->mtd.write = block2mtd_write;
331	dev->mtd.writev = default_mtd_writev;
332	dev->mtd.sync = block2mtd_sync;
333	dev->mtd.read = block2mtd_read;
334	dev->mtd.priv = dev;
335	dev->mtd.owner = THIS_MODULE;
336
337	if (add_mtd_device(&dev->mtd)) {
338		/* Device didnt get added, so free the entry */
339		goto devinit_err;
340	}
341	list_add(&dev->list, &blkmtd_device_list);
342	INFO("mtd%d: [%s] erase_size = %dKiB [%d]", dev->mtd.index,
343			dev->mtd.name + strlen("blkmtd: "),
344			dev->mtd.erasesize >> 10, dev->mtd.erasesize);
345	return dev;
346
347devinit_err:
348	block2mtd_free_device(dev);
349	return NULL;
350}
351
352
353/* This function works similar to reguler strtoul.  In addition, it
354 * allows some suffixes for a more human-readable number format:
355 * ki, Ki, kiB, KiB	- multiply result with 1024
356 * Mi, MiB		- multiply result with 1024^2
357 * Gi, GiB		- multiply result with 1024^3
358 */
359static int ustrtoul(const char *cp, char **endp, unsigned int base)
360{
361	unsigned long result = simple_strtoul(cp, endp, base);
362	switch (**endp) {
363	case 'G' :
364		result *= 1024;
365	case 'M':
366		result *= 1024;
367	case 'K':
368	case 'k':
369		result *= 1024;
370	/* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
371		if ((*endp)[1] == 'i') {
372			if ((*endp)[2] == 'B')
373				(*endp) += 3;
374			else
375				(*endp) += 2;
376		}
377	}
378	return result;
379}
380
381
382static int parse_num(size_t *num, const char *token)
383{
384	char *endp;
385	size_t n;
386
387	n = (size_t) ustrtoul(token, &endp, 0);
388	if (*endp)
389		return -EINVAL;
390
391	*num = n;
392	return 0;
393}
394
395
396static int parse_name(char **pname, const char *token, size_t limit)
397{
398	size_t len;
399	char *name;
400
401	len = strlen(token) + 1;
402	if (len > limit)
403		return -ENOSPC;
404
405	name = kmalloc(len, GFP_KERNEL);
406	if (!name)
407		return -ENOMEM;
408
409	strcpy(name, token);
410
411	*pname = name;
412	return 0;
413}
414
415
416static inline void kill_final_newline(char *str)
417{
418	char *newline = strrchr(str, '\n');
419	if (newline && !newline[1])
420		*newline = 0;
421}
422
423
424#define parse_err(fmt, args...) do {		\
425	ERROR("block2mtd: " fmt "\n", ## args);	\
426	return 0;				\
427} while (0)
428
429static int block2mtd_setup(const char *val, struct kernel_param *kp)
430{
431	char buf[80+12]; /* 80 for device, 12 for erase size */
432	char *str = buf;
433	char *token[2];
434	char *name;
435	size_t erase_size = PAGE_SIZE;
436	int i, ret;
437
438	if (strnlen(val, sizeof(buf)) >= sizeof(buf))
439		parse_err("parameter too long");
440
441	strcpy(str, val);
442	kill_final_newline(str);
443
444	for (i = 0; i < 2; i++)
445		token[i] = strsep(&str, ",");
446
447	if (str)
448		parse_err("too many arguments");
449
450	if (!token[0])
451		parse_err("no argument");
452
453	ret = parse_name(&name, token[0], 80);
454	if (ret == -ENOMEM)
455		parse_err("out of memory");
456	if (ret == -ENOSPC)
457		parse_err("name too long");
458	if (ret)
459		return 0;
460
461	if (token[1]) {
462		ret = parse_num(&erase_size, token[1]);
463		if (ret) {
464			kfree(name);
465			parse_err("illegal erase size");
466		}
467	}
468
469	add_device(name, erase_size);
470
471	return 0;
472}
473
474
475module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
476MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");
477
478static int __init block2mtd_init(void)
479{
480	INFO("version " VERSION);
481	return 0;
482}
483
484
485static void __devexit block2mtd_exit(void)
486{
487	struct list_head *pos, *next;
488
489	/* Remove the MTD devices */
490	list_for_each_safe(pos, next, &blkmtd_device_list) {
491		struct block2mtd_dev *dev = list_entry(pos, typeof(*dev), list);
492		block2mtd_sync(&dev->mtd);
493		del_mtd_device(&dev->mtd);
494		INFO("mtd%d: [%s] removed", dev->mtd.index,
495				dev->mtd.name + strlen("blkmtd: "));
496		list_del(&dev->list);
497		block2mtd_free_device(dev);
498	}
499}
500
501
502module_init(block2mtd_init);
503module_exit(block2mtd_exit);
504
505MODULE_LICENSE("GPL");
506MODULE_AUTHOR("Simon Evans <spse@secret.org.uk> and others");
507MODULE_DESCRIPTION("Emulate an MTD using a block device");
508