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