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