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 char *name;
269
270 if (!devname)
271 return NULL;
272
273 dev = kzalloc(size: sizeof(struct block2mtd_dev), GFP_KERNEL);
274 if (!dev)
275 return NULL;
276
277 /* Get a handle on the device */
278 bdev_file = bdev_file_open_by_path(path: devname, mode, holder: dev, NULL);
279 if (IS_ERR(ptr: bdev_file))
280 bdev_file = mdtblock_early_get_bdev(devname, mode, timeout,
281 dev);
282 if (IS_ERR(ptr: bdev_file)) {
283 pr_err("error: cannot open device %s\n", devname);
284 goto err_free_block2mtd;
285 }
286 dev->bdev_file = bdev_file;
287 bdev = file_bdev(bdev_file);
288
289 if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
290 pr_err("attempting to use an MTD device as a block device\n");
291 goto err_free_block2mtd;
292 }
293
294 if ((long)bdev->bd_inode->i_size % erase_size) {
295 pr_err("erasesize must be a divisor of device size\n");
296 goto err_free_block2mtd;
297 }
298
299 mutex_init(&dev->write_mutex);
300
301 /* Setup the MTD structure */
302 /* make the name contain the block device in */
303 if (!label)
304 name = kasprintf(GFP_KERNEL, fmt: "block2mtd: %s", devname);
305 else
306 name = kstrdup(s: label, GFP_KERNEL);
307 if (!name)
308 goto err_destroy_mutex;
309
310 dev->mtd.name = name;
311
312 dev->mtd.size = bdev->bd_inode->i_size & PAGE_MASK;
313 dev->mtd.erasesize = erase_size;
314 dev->mtd.writesize = 1;
315 dev->mtd.writebufsize = PAGE_SIZE;
316 dev->mtd.type = MTD_RAM;
317 dev->mtd.flags = MTD_CAP_RAM;
318 dev->mtd._erase = block2mtd_erase;
319 dev->mtd._write = block2mtd_write;
320 dev->mtd._sync = block2mtd_sync;
321 dev->mtd._read = block2mtd_read;
322 dev->mtd.priv = dev;
323 dev->mtd.owner = THIS_MODULE;
324
325 if (mtd_device_register(&dev->mtd, NULL, 0)) {
326 /* Device didn't get added, so free the entry */
327 goto err_destroy_mutex;
328 }
329
330 list_add(new: &dev->list, head: &blkmtd_device_list);
331 pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n",
332 dev->mtd.index,
333 label ? label : dev->mtd.name + strlen("block2mtd: "),
334 dev->mtd.erasesize >> 10, dev->mtd.erasesize);
335 return dev;
336
337err_destroy_mutex:
338 mutex_destroy(lock: &dev->write_mutex);
339err_free_block2mtd:
340 block2mtd_free_device(dev);
341 return NULL;
342}
343
344
345/* This function works similar to reguler strtoul. In addition, it
346 * allows some suffixes for a more human-readable number format:
347 * ki, Ki, kiB, KiB - multiply result with 1024
348 * Mi, MiB - multiply result with 1024^2
349 * Gi, GiB - multiply result with 1024^3
350 */
351static int ustrtoul(const char *cp, char **endp, unsigned int base)
352{
353 unsigned long result = simple_strtoul(cp, endp, base);
354 switch (**endp) {
355 case 'G' :
356 result *= 1024;
357 fallthrough;
358 case 'M':
359 result *= 1024;
360 fallthrough;
361 case 'K':
362 case 'k':
363 result *= 1024;
364 /* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
365 if ((*endp)[1] == 'i') {
366 if ((*endp)[2] == 'B')
367 (*endp) += 3;
368 else
369 (*endp) += 2;
370 }
371 }
372 return result;
373}
374
375
376static int parse_num(size_t *num, const char *token)
377{
378 char *endp;
379 size_t n;
380
381 n = (size_t) ustrtoul(cp: token, endp: &endp, base: 0);
382 if (*endp)
383 return -EINVAL;
384
385 *num = n;
386 return 0;
387}
388
389
390static inline void kill_final_newline(char *str)
391{
392 char *newline = strrchr(str, '\n');
393 if (newline && !newline[1])
394 *newline = 0;
395}
396
397
398#ifndef MODULE
399static int block2mtd_init_called = 0;
400/* 80 for device, 12 for erase size */
401static char block2mtd_paramline[80 + 12];
402#endif
403
404static int block2mtd_setup2(const char *val)
405{
406 /* 80 for device, 12 for erase size, 80 for name, 8 for timeout */
407 char buf[80 + 12 + 80 + 8];
408 char *str = buf;
409 char *token[BLOCK2MTD_PARAM_MAX_COUNT];
410 char *name;
411 char *label = NULL;
412 size_t erase_size = PAGE_SIZE;
413 unsigned long timeout = MTD_DEFAULT_TIMEOUT;
414 int i, ret;
415
416 if (strnlen(p: val, maxlen: sizeof(buf)) >= sizeof(buf)) {
417 pr_err("parameter too long\n");
418 return 0;
419 }
420
421 strcpy(p: str, q: val);
422 kill_final_newline(str);
423
424 for (i = 0; i < BLOCK2MTD_PARAM_MAX_COUNT; i++)
425 token[i] = strsep(&str, ",");
426
427 if (str) {
428 pr_err("too many arguments\n");
429 return 0;
430 }
431
432 if (!token[0]) {
433 pr_err("no argument\n");
434 return 0;
435 }
436
437 name = token[0];
438 if (strlen(name) + 1 > 80) {
439 pr_err("device name too long\n");
440 return 0;
441 }
442
443 /* Optional argument when custom label is used */
444 if (token[1] && strlen(token[1])) {
445 ret = parse_num(num: &erase_size, token: token[1]);
446 if (ret) {
447 pr_err("illegal erase size\n");
448 return 0;
449 }
450 }
451
452 if (token[2]) {
453 label = token[2];
454 pr_info("Using custom MTD label '%s' for dev %s\n", label, name);
455 }
456
457 add_device(devname: name, erase_size, label, timeout);
458
459 return 0;
460}
461
462
463static int block2mtd_setup(const char *val, const struct kernel_param *kp)
464{
465#ifdef MODULE
466 return block2mtd_setup2(val);
467#else
468 /* If more parameters are later passed in via
469 /sys/module/block2mtd/parameters/block2mtd
470 and block2mtd_init() has already been called,
471 we can parse the argument now. */
472
473 if (block2mtd_init_called)
474 return block2mtd_setup2(val);
475
476 /* During early boot stage, we only save the parameters
477 here. We must parse them later: if the param passed
478 from kernel boot command line, block2mtd_setup() is
479 called so early that it is not possible to resolve
480 the device (even kmalloc() fails). Deter that work to
481 block2mtd_setup2(). */
482
483 strscpy(block2mtd_paramline, val, sizeof(block2mtd_paramline));
484
485 return 0;
486#endif
487}
488
489
490module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
491MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,[<erasesize>][,<label>]]\"");
492
493static int __init block2mtd_init(void)
494{
495 int ret = 0;
496
497#ifndef MODULE
498 if (strlen(block2mtd_paramline))
499 ret = block2mtd_setup2(val: block2mtd_paramline);
500 block2mtd_init_called = 1;
501#endif
502
503 return ret;
504}
505
506
507static void block2mtd_exit(void)
508{
509 struct list_head *pos, *next;
510
511 /* Remove the MTD devices */
512 list_for_each_safe(pos, next, &blkmtd_device_list) {
513 struct block2mtd_dev *dev = list_entry(pos, typeof(*dev), list);
514 block2mtd_sync(mtd: &dev->mtd);
515 mtd_device_unregister(master: &dev->mtd);
516 mutex_destroy(lock: &dev->write_mutex);
517 pr_info("mtd%d: [%s] removed\n",
518 dev->mtd.index,
519 dev->mtd.name + strlen("block2mtd: "));
520 list_del(entry: &dev->list);
521 block2mtd_free_device(dev);
522 }
523}
524
525late_initcall(block2mtd_init);
526module_exit(block2mtd_exit);
527
528MODULE_LICENSE("GPL");
529MODULE_AUTHOR("Joern Engel <joern@lazybastard.org>");
530MODULE_DESCRIPTION("Emulate an MTD using a block device");
531

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