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