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
10#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
11
12/*
13 * When the first attempt at device initialization fails, we may need to
14 * wait a little bit and retry. This timeout, by default 3 seconds, gives
15 * device time to start up. Required on BCM2708 and a few other chipsets.
16 */
17#define MTD_DEFAULT_TIMEOUT 3
18
19#include <linux/module.h>
20#include <linux/delay.h>
21#include <linux/fs.h>
22#include <linux/blkdev.h>
23#include <linux/backing-dev.h>
24#include <linux/bio.h>
25#include <linux/pagemap.h>
26#include <linux/list.h>
27#include <linux/init.h>
28#include <linux/mtd/mtd.h>
29#include <linux/mutex.h>
30#include <linux/mount.h>
31#include <linux/slab.h>
32#include <linux/major.h>
33
34/* Maximum number of comma-separated items in the 'block2mtd=' parameter */
35#define BLOCK2MTD_PARAM_MAX_COUNT 3
36
37/* Info for the block device */
38struct block2mtd_dev {
39 struct list_head list;
40 struct file *bdev_file;
41 struct mtd_info mtd;
42 struct mutex write_mutex;
43};
44
45
46/* Static info about the MTD, used in cleanup_module */
47static LIST_HEAD(blkmtd_device_list);
48
49
50static struct page *page_read(struct address_space *mapping, pgoff_t index)
51{
52 return read_mapping_page(mapping, index, NULL);
53}
54
55/* erase a specified part of the device */
56static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
57{
58 struct address_space *mapping = dev->bdev_file->f_mapping;
59 struct page *page;
60 pgoff_t index = to >> PAGE_SHIFT; // page index
61 int pages = len >> PAGE_SHIFT;
62 u_long *p;
63 u_long *max;
64
65 while (pages) {
66 page = page_read(mapping, index);
67 if (IS_ERR(ptr: page))
68 return PTR_ERR(ptr: page);
69
70 max = page_address(page) + PAGE_SIZE;
71 for (p=page_address(page); p<max; p++)
72 if (*p != -1UL) {
73 lock_page(page);
74 memset(page_address(page), 0xff, PAGE_SIZE);
75 set_page_dirty(page);
76 unlock_page(page);
77 balance_dirty_pages_ratelimited(mapping);
78 break;
79 }
80
81 put_page(page);
82 pages--;
83 index++;
84 }
85 return 0;
86}
87static int block2mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
88{
89 struct block2mtd_dev *dev = mtd->priv;
90 size_t from = instr->addr;
91 size_t len = instr->len;
92 int err;
93
94 mutex_lock(&dev->write_mutex);
95 err = _block2mtd_erase(dev, to: from, len);
96 mutex_unlock(lock: &dev->write_mutex);
97 if (err)
98 pr_err("erase failed err = %d\n", err);
99
100 return err;
101}
102
103
104static int block2mtd_read(struct mtd_info *mtd, loff_t from, size_t len,
105 size_t *retlen, u_char *buf)
106{
107 struct block2mtd_dev *dev = mtd->priv;
108 struct address_space *mapping = dev->bdev_file->f_mapping;
109 struct page *page;
110 pgoff_t index = from >> PAGE_SHIFT;
111 int offset = from & (PAGE_SIZE-1);
112 int cpylen;
113
114 while (len) {
115 if ((offset + len) > PAGE_SIZE)
116 cpylen = PAGE_SIZE - offset; // multiple pages
117 else
118 cpylen = len; // this page
119 len = len - cpylen;
120
121 page = page_read(mapping, index);
122 if (IS_ERR(ptr: page))
123 return PTR_ERR(ptr: page);
124
125 memcpy(buf, page_address(page) + offset, cpylen);
126 put_page(page);
127
128 if (retlen)
129 *retlen += cpylen;
130 buf += cpylen;
131 offset = 0;
132 index++;
133 }
134 return 0;
135}
136
137
138/* write data to the underlying device */
139static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
140 loff_t to, size_t len, size_t *retlen)
141{
142 struct page *page;
143 struct address_space *mapping = dev->bdev_file->f_mapping;
144 pgoff_t index = to >> PAGE_SHIFT; // page index
145 int offset = to & ~PAGE_MASK; // page offset
146 int cpylen;
147
148 while (len) {
149 if ((offset+len) > PAGE_SIZE)
150 cpylen = PAGE_SIZE - offset; // multiple pages
151 else
152 cpylen = len; // this page
153 len = len - cpylen;
154
155 page = page_read(mapping, index);
156 if (IS_ERR(ptr: page))
157 return PTR_ERR(ptr: page);
158
159 if (memcmp(page_address(page)+offset, q: buf, size: cpylen)) {
160 lock_page(page);
161 memcpy(page_address(page) + offset, buf, cpylen);
162 set_page_dirty(page);
163 unlock_page(page);
164 balance_dirty_pages_ratelimited(mapping);
165 }
166 put_page(page);
167
168 if (retlen)
169 *retlen += cpylen;
170
171 buf += cpylen;
172 offset = 0;
173 index++;
174 }
175 return 0;
176}
177
178
179static int block2mtd_write(struct mtd_info *mtd, loff_t to, size_t len,
180 size_t *retlen, const u_char *buf)
181{
182 struct block2mtd_dev *dev = mtd->priv;
183 int err;
184
185 mutex_lock(&dev->write_mutex);
186 err = _block2mtd_write(dev, buf, to, len, retlen);
187 mutex_unlock(lock: &dev->write_mutex);
188 if (err > 0)
189 err = 0;
190 return err;
191}
192
193
194/* sync the device - wait until the write queue is empty */
195static void block2mtd_sync(struct mtd_info *mtd)
196{
197 struct block2mtd_dev *dev = mtd->priv;
198 sync_blockdev(bdev: file_bdev(bdev_file: dev->bdev_file));
199 return;
200}
201
202
203static void block2mtd_free_device(struct block2mtd_dev *dev)
204{
205 if (!dev)
206 return;
207
208 kfree(objp: dev->mtd.name);
209
210 if (dev->bdev_file) {
211 invalidate_mapping_pages(mapping: dev->bdev_file->f_mapping, start: 0, end: -1);
212 bdev_fput(bdev_file: dev->bdev_file);
213 }
214
215 kfree(objp: dev);
216}
217
218/*
219 * This function is marked __ref because it calls the __init marked
220 * early_lookup_bdev when called from the early boot code.
221 */
222static struct file __ref *mdtblock_early_get_bdev(const char *devname,
223 blk_mode_t mode, int timeout, struct block2mtd_dev *dev)
224{
225 struct file *bdev_file = ERR_PTR(error: -ENODEV);
226#ifndef MODULE
227 int i;
228
229 /*
230 * We can't use early_lookup_bdev from a running system.
231 */
232 if (system_state >= SYSTEM_RUNNING)
233 return bdev_file;
234
235 /*
236 * We might not have the root device mounted at this point.
237 * Try to resolve the device name by other means.
238 */
239 for (i = 0; i <= timeout; i++) {
240 dev_t devt;
241
242 if (i)
243 /*
244 * Calling wait_for_device_probe in the first loop
245 * was not enough, sleep for a bit in subsequent
246 * go-arounds.
247 */
248 msleep(msecs: 1000);
249 wait_for_device_probe();
250
251 if (!early_lookup_bdev(pathname: devname, dev: &devt)) {
252 bdev_file = bdev_file_open_by_dev(dev: devt, mode, holder: dev, NULL);
253 if (!IS_ERR(ptr: bdev_file))
254 break;
255 }
256 }
257#endif
258 return bdev_file;
259}
260
261static struct block2mtd_dev *add_device(char *devname, int erase_size,
262 char *label, int timeout)
263{
264 const blk_mode_t mode = BLK_OPEN_READ | BLK_OPEN_WRITE;
265 struct file *bdev_file;
266 struct block_device *bdev;
267 struct block2mtd_dev *dev;
268 loff_t size;
269 char *name;
270
271 if (!devname)
272 return NULL;
273
274 dev = kzalloc(sizeof(struct block2mtd_dev), GFP_KERNEL);
275 if (!dev)
276 return NULL;
277
278 /* Get a handle on the device */
279 bdev_file = bdev_file_open_by_path(path: devname, mode, holder: dev, NULL);
280 if (IS_ERR(ptr: bdev_file))
281 bdev_file = mdtblock_early_get_bdev(devname, mode, timeout,
282 dev);
283 if (IS_ERR(ptr: bdev_file)) {
284 pr_err("error: cannot open device %s\n", devname);
285 goto err_free_block2mtd;
286 }
287 dev->bdev_file = bdev_file;
288 bdev = file_bdev(bdev_file);
289
290 if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
291 pr_err("attempting to use an MTD device as a block device\n");
292 goto err_free_block2mtd;
293 }
294
295 size = bdev_nr_bytes(bdev);
296 if ((long)size % erase_size) {
297 pr_err("erasesize must be a divisor of device size\n");
298 goto err_free_block2mtd;
299 }
300
301 mutex_init(&dev->write_mutex);
302
303 /* Setup the MTD structure */
304 /* make the name contain the block device in */
305 if (!label)
306 name = kasprintf(GFP_KERNEL, fmt: "block2mtd: %s", devname);
307 else
308 name = kstrdup(s: label, GFP_KERNEL);
309 if (!name)
310 goto err_destroy_mutex;
311
312 dev->mtd.name = name;
313
314 dev->mtd.size = size & PAGE_MASK;
315 dev->mtd.erasesize = erase_size;
316 dev->mtd.writesize = 1;
317 dev->mtd.writebufsize = PAGE_SIZE;
318 dev->mtd.type = MTD_RAM;
319 dev->mtd.flags = MTD_CAP_RAM;
320 dev->mtd._erase = block2mtd_erase;
321 dev->mtd._write = block2mtd_write;
322 dev->mtd._sync = block2mtd_sync;
323 dev->mtd._read = block2mtd_read;
324 dev->mtd.priv = dev;
325 dev->mtd.owner = THIS_MODULE;
326
327 if (mtd_device_register(&dev->mtd, NULL, 0)) {
328 /* Device didn't get added, so free the entry */
329 goto err_destroy_mutex;
330 }
331
332 list_add(new: &dev->list, head: &blkmtd_device_list);
333 pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n",
334 dev->mtd.index,
335 label ? label : dev->mtd.name + strlen("block2mtd: "),
336 dev->mtd.erasesize >> 10, dev->mtd.erasesize);
337 return dev;
338
339err_destroy_mutex:
340 mutex_destroy(lock: &dev->write_mutex);
341err_free_block2mtd:
342 block2mtd_free_device(dev);
343 return NULL;
344}
345
346
347/* This function works similar to reguler strtoul. In addition, it
348 * allows some suffixes for a more human-readable number format:
349 * ki, Ki, kiB, KiB - multiply result with 1024
350 * Mi, MiB - multiply result with 1024^2
351 * Gi, GiB - multiply result with 1024^3
352 */
353static int ustrtoul(const char *cp, char **endp, unsigned int base)
354{
355 unsigned long result = simple_strtoul(cp, endp, base);
356 switch (**endp) {
357 case 'G' :
358 result *= 1024;
359 fallthrough;
360 case 'M':
361 result *= 1024;
362 fallthrough;
363 case 'K':
364 case 'k':
365 result *= 1024;
366 /* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
367 if ((*endp)[1] == 'i') {
368 if ((*endp)[2] == 'B')
369 (*endp) += 3;
370 else
371 (*endp) += 2;
372 }
373 }
374 return result;
375}
376
377
378static int parse_num(size_t *num, const char *token)
379{
380 char *endp;
381 size_t n;
382
383 n = (size_t) ustrtoul(cp: token, endp: &endp, base: 0);
384 if (*endp)
385 return -EINVAL;
386
387 *num = n;
388 return 0;
389}
390
391
392static inline void kill_final_newline(char *str)
393{
394 char *newline = strrchr(str, '\n');
395 if (newline && !newline[1])
396 *newline = 0;
397}
398
399
400#ifndef MODULE
401static int block2mtd_init_called = 0;
402/* 80 for device, 12 for erase size */
403static char block2mtd_paramline[80 + 12];
404#endif
405
406static int block2mtd_setup2(const char *val)
407{
408 /* 80 for device, 12 for erase size, 80 for name, 8 for timeout */
409 char buf[80 + 12 + 80 + 8];
410 char *str = buf;
411 char *token[BLOCK2MTD_PARAM_MAX_COUNT];
412 char *name;
413 char *label = NULL;
414 size_t erase_size = PAGE_SIZE;
415 unsigned long timeout = MTD_DEFAULT_TIMEOUT;
416 int i, ret;
417
418 if (strnlen(p: val, maxlen: sizeof(buf)) >= sizeof(buf)) {
419 pr_err("parameter too long\n");
420 return 0;
421 }
422
423 strcpy(p: str, q: val);
424 kill_final_newline(str);
425
426 for (i = 0; i < BLOCK2MTD_PARAM_MAX_COUNT; i++)
427 token[i] = strsep(&str, ",");
428
429 if (str) {
430 pr_err("too many arguments\n");
431 return 0;
432 }
433
434 if (!token[0]) {
435 pr_err("no argument\n");
436 return 0;
437 }
438
439 name = token[0];
440 if (strlen(name) + 1 > 80) {
441 pr_err("device name too long\n");
442 return 0;
443 }
444
445 /* Optional argument when custom label is used */
446 if (token[1] && strlen(token[1])) {
447 ret = parse_num(num: &erase_size, token: token[1]);
448 if (ret) {
449 pr_err("illegal erase size\n");
450 return 0;
451 }
452 }
453
454 if (token[2]) {
455 label = token[2];
456 pr_info("Using custom MTD label '%s' for dev %s\n", label, name);
457 }
458
459 add_device(devname: name, erase_size, label, timeout);
460
461 return 0;
462}
463
464
465static int block2mtd_setup(const char *val, const struct kernel_param *kp)
466{
467#ifdef MODULE
468 return block2mtd_setup2(val);
469#else
470 /* If more parameters are later passed in via
471 /sys/module/block2mtd/parameters/block2mtd
472 and block2mtd_init() has already been called,
473 we can parse the argument now. */
474
475 if (block2mtd_init_called)
476 return block2mtd_setup2(val);
477
478 /* During early boot stage, we only save the parameters
479 here. We must parse them later: if the param passed
480 from kernel boot command line, block2mtd_setup() is
481 called so early that it is not possible to resolve
482 the device (even kmalloc() fails). Deter that work to
483 block2mtd_setup2(). */
484
485 strscpy(block2mtd_paramline, val, sizeof(block2mtd_paramline));
486
487 return 0;
488#endif
489}
490
491
492module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
493MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,[<erasesize>][,<label>]]\"");
494
495static int __init block2mtd_init(void)
496{
497 int ret = 0;
498
499#ifndef MODULE
500 if (strlen(block2mtd_paramline))
501 ret = block2mtd_setup2(val: block2mtd_paramline);
502 block2mtd_init_called = 1;
503#endif
504
505 return ret;
506}
507
508
509static void block2mtd_exit(void)
510{
511 struct list_head *pos, *next;
512
513 /* Remove the MTD devices */
514 list_for_each_safe(pos, next, &blkmtd_device_list) {
515 struct block2mtd_dev *dev = list_entry(pos, typeof(*dev), list);
516 block2mtd_sync(mtd: &dev->mtd);
517 mtd_device_unregister(master: &dev->mtd);
518 mutex_destroy(lock: &dev->write_mutex);
519 pr_info("mtd%d: [%s] removed\n",
520 dev->mtd.index,
521 dev->mtd.name + strlen("block2mtd: "));
522 list_del(entry: &dev->list);
523 block2mtd_free_device(dev);
524 }
525}
526
527late_initcall(block2mtd_init);
528module_exit(block2mtd_exit);
529
530MODULE_LICENSE("GPL");
531MODULE_AUTHOR("Joern Engel <joern@lazybastard.org>");
532MODULE_DESCRIPTION("Emulate an MTD using a block device");
533

source code of linux/drivers/mtd/devices/block2mtd.c