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