drivers/mtd/devices/block2mtd.c

   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 #include <linux/module.h>
  13 #include <linux/fs.h>
  14 #include <linux/blkdev.h>
  15 #include <linux/bio.h>
  16 #include <linux/pagemap.h>
  17 #include <linux/list.h>
  18 #include <linux/init.h>
  19 #include <linux/mtd/mtd.h>
  20 #include <linux/mutex.h>
  21 #include <linux/mount.h>
  22 #include <linux/slab.h>
  23 #include <linux/major.h>
  24
  25 /* Info for the block device */
  26 struct block2mtd_dev {
  27         struct list_head list;
  28         struct block_device *blkdev;
  29         struct mtd_info mtd;
  30         struct mutex write_mutex;
  31 };
  32
  33
  34 /* Static info about the MTD, used in cleanup_module */
  35 static LIST_HEAD(blkmtd_device_list);
  36
  37
  38 static struct page *page_read(struct address_space *mapping, int index)
  39 {
  40         return read_mapping_page(mapping, index, NULL);
  41 }
  42
  43 /* erase a specified part of the device */
  44 static int _block2mtd_erase(struct block2mtd_dev *dev, loff_t to, size_t len)
  45 {
  46         struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
  47         struct page *page;
  48         int index = to >> PAGE_SHIFT;   // page index
  49         int pages = len >> PAGE_SHIFT;
  50         u_long *p;
  51         u_long *max;
  52
  53         while (pages) {
  54                 page = page_read(mapping, index);
  55                 if (IS_ERR(page))
  56                         return PTR_ERR(page);
  57
  58                 max = page_address(page) + PAGE_SIZE;
  59                 for (p=page_address(page); p<max; p++)
  60                         if (*p != -1UL) {
  61                                 lock_page(page);
  62                                 memset(page_address(page), 0xff, PAGE_SIZE);
  63                                 set_page_dirty(page);
  64                                 unlock_page(page);
  65                                 balance_dirty_pages_ratelimited(mapping);
  66                                 break;
  67                         }
  68
  69                 page_cache_release(page);
  70                 pages--;
  71                 index++;
  72         }
  73         return 0;
  74 }
  75 static int block2mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
  76 {
  77         struct block2mtd_dev *dev = mtd->priv;
  78         size_t from = instr->addr;
  79         size_t len = instr->len;
  80         int err;
  81
  82         instr->state = MTD_ERASING;
  83         mutex_lock(&dev->write_mutex);
  84         err = _block2mtd_erase(dev, from, len);
  85         mutex_unlock(&dev->write_mutex);
  86         if (err) {
  87                 pr_err("erase failed err = %d\n", err);
  88                 instr->state = MTD_ERASE_FAILED;
  89         } else
  90                 instr->state = MTD_ERASE_DONE;
  91
  92         mtd_erase_callback(instr);
  93         return err;
  94 }
  95
  96
  97 static int block2mtd_read(struct mtd_info *mtd, loff_t from, size_t len,
  98                 size_t *retlen, u_char *buf)
  99 {
 100         struct block2mtd_dev *dev = mtd->priv;
 101         struct page *page;
 102         int index = from >> PAGE_SHIFT;
 103         int offset = from & (PAGE_SIZE-1);
 104         int cpylen;
 105
 106         while (len) {
 107                 if ((offset + len) > PAGE_SIZE)
 108                         cpylen = PAGE_SIZE - offset;    // multiple pages
 109                 else
 110                         cpylen = len;   // this page
 111                 len = len - cpylen;
 112
 113                 page = page_read(dev->blkdev->bd_inode->i_mapping, index);
 114                 if (IS_ERR(page))
 115                         return PTR_ERR(page);
 116
 117                 memcpy(buf, page_address(page) + offset, cpylen);
 118                 page_cache_release(page);
 119
 120                 if (retlen)
 121                         *retlen += cpylen;
 122                 buf += cpylen;
 123                 offset = 0;
 124                 index++;
 125         }
 126         return 0;
 127 }
 128
 129
 130 /* write data to the underlying device */
 131 static int _block2mtd_write(struct block2mtd_dev *dev, const u_char *buf,
 132                 loff_t to, size_t len, size_t *retlen)
 133 {
 134         struct page *page;
 135         struct address_space *mapping = dev->blkdev->bd_inode->i_mapping;
 136         int index = to >> PAGE_SHIFT;   // page index
 137         int offset = to & ~PAGE_MASK;   // page offset
 138         int cpylen;
 139
 140         while (len) {
 141                 if ((offset+len) > PAGE_SIZE)
 142                         cpylen = PAGE_SIZE - offset;    // multiple pages
 143                 else
 144                         cpylen = len;                   // this page
 145                 len = len - cpylen;
 146
 147                 page = page_read(mapping, index);
 148                 if (IS_ERR(page))
 149                         return PTR_ERR(page);
 150
 151                 if (memcmp(page_address(page)+offset, buf, cpylen)) {
 152                         lock_page(page);
 153                         memcpy(page_address(page) + offset, buf, cpylen);
 154                         set_page_dirty(page);
 155                         unlock_page(page);
 156                         balance_dirty_pages_ratelimited(mapping);
 157                 }
 158                 page_cache_release(page);
 159
 160                 if (retlen)
 161                         *retlen += cpylen;
 162
 163                 buf += cpylen;
 164                 offset = 0;
 165                 index++;
 166         }
 167         return 0;
 168 }
 169
 170
 171 static int block2mtd_write(struct mtd_info *mtd, loff_t to, size_t len,
 172                 size_t *retlen, const u_char *buf)
 173 {
 174         struct block2mtd_dev *dev = mtd->priv;
 175         int err;
 176
 177         mutex_lock(&dev->write_mutex);
 178         err = _block2mtd_write(dev, buf, to, len, retlen);
 179         mutex_unlock(&dev->write_mutex);
 180         if (err > 0)
 181                 err = 0;
 182         return err;
 183 }
 184
 185
 186 /* sync the device - wait until the write queue is empty */
 187 static void block2mtd_sync(struct mtd_info *mtd)
 188 {
 189         struct block2mtd_dev *dev = mtd->priv;
 190         sync_blockdev(dev->blkdev);
 191         return;
 192 }
 193
 194
 195 static void block2mtd_free_device(struct block2mtd_dev *dev)
 196 {
 197         if (!dev)
 198                 return;
 199
 200         kfree(dev->mtd.name);
 201
 202         if (dev->blkdev) {
 203                 invalidate_mapping_pages(dev->blkdev->bd_inode->i_mapping,
 204                                         0, -1);
 205                 blkdev_put(dev->blkdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
 206         }
 207
 208         kfree(dev);
 209 }
 210
 211
 212 static struct block2mtd_dev *add_device(char *devname, int erase_size)
 213 {
 214         const fmode_t mode = FMODE_READ | FMODE_WRITE | FMODE_EXCL;
 215         struct block_device *bdev;
 216         struct block2mtd_dev *dev;
 217         char *name;
 218
 219         if (!devname)
 220                 return NULL;
 221
 222         dev = kzalloc(sizeof(struct block2mtd_dev), GFP_KERNEL);
 223         if (!dev)
 224                 return NULL;
 225
 226         /* Get a handle on the device */
 227         bdev = blkdev_get_by_path(devname, mode, dev);
 228 #ifndef MODULE
 229         if (IS_ERR(bdev)) {
 230
 231                 /* We might not have rootfs mounted at this point. Try
 232                    to resolve the device name by other means. */
 233
 234                 dev_t devt = name_to_dev_t(devname);
 235                 if (devt)
 236                         bdev = blkdev_get_by_dev(devt, mode, dev);
 237         }
 238 #endif
 239
 240         if (IS_ERR(bdev)) {
 241                 pr_err("error: cannot open device %s\n", devname);
 242                 goto err_free_block2mtd;
 243         }
 244         dev->blkdev = bdev;
 245
 246         if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
 247                 pr_err("attempting to use an MTD device as a block device\n");
 248                 goto err_free_block2mtd;
 249         }
 250
 251         if ((long)dev->blkdev->bd_inode->i_size % erase_size) {
 252                 pr_err("erasesize must be a divisor of device size\n");
 253                 goto err_free_block2mtd;
 254         }
 255
 256         mutex_init(&dev->write_mutex);
 257
 258         /* Setup the MTD structure */
 259         /* make the name contain the block device in */
 260         name = kasprintf(GFP_KERNEL, "block2mtd: %s", devname);
 261         if (!name)
 262                 goto err_destroy_mutex;
 263
 264         dev->mtd.name = name;
 265
 266         dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
 267         dev->mtd.erasesize = erase_size;
 268         dev->mtd.writesize = 1;
 269         dev->mtd.writebufsize = PAGE_SIZE;
 270         dev->mtd.type = MTD_RAM;
 271         dev->mtd.flags = MTD_CAP_RAM;
 272         dev->mtd._erase = block2mtd_erase;
 273         dev->mtd._write = block2mtd_write;
 274         dev->mtd._sync = block2mtd_sync;
 275         dev->mtd._read = block2mtd_read;
 276         dev->mtd.priv = dev;
 277         dev->mtd.owner = THIS_MODULE;
 278
 279         if (mtd_device_register(&dev->mtd, NULL, 0)) {
 280                 /* Device didn't get added, so free the entry */
 281                 goto err_destroy_mutex;
 282         }
 283         list_add(&dev->list, &blkmtd_device_list);
 284         pr_info("mtd%d: [%s] erase_size = %dKiB [%d]\n",
 285                 dev->mtd.index,
 286                 dev->mtd.name + strlen("block2mtd: "),
 287                 dev->mtd.erasesize >> 10, dev->mtd.erasesize);
 288         return dev;
 289
 290 err_destroy_mutex:
 291         mutex_destroy(&dev->write_mutex);
 292 err_free_block2mtd:
 293         block2mtd_free_device(dev);
 294         return NULL;
 295 }
 296
 297
 298 /* This function works similar to reguler strtoul.  In addition, it
 299  * allows some suffixes for a more human-readable number format:
 300  * ki, Ki, kiB, KiB     - multiply result with 1024
 301  * Mi, MiB              - multiply result with 1024^2
 302  * Gi, GiB              - multiply result with 1024^3
 303  */
 304 static int ustrtoul(const char *cp, char **endp, unsigned int base)
 305 {
 306         unsigned long result = simple_strtoul(cp, endp, base);
 307         switch (**endp) {
 308         case 'G' :
 309                 result *= 1024;
 310         case 'M':
 311                 result *= 1024;
 312         case 'K':
 313         case 'k':
 314                 result *= 1024;
 315         /* By dwmw2 editorial decree, "ki", "Mi" or "Gi" are to be used. */
 316                 if ((*endp)[1] == 'i') {
 317                         if ((*endp)[2] == 'B')
 318                                 (*endp) += 3;
 319                         else
 320                                 (*endp) += 2;
 321                 }
 322         }
 323         return result;
 324 }
 325
 326
 327 static int parse_num(size_t *num, const char *token)
 328 {
 329         char *endp;
 330         size_t n;
 331
 332         n = (size_t) ustrtoul(token, &endp, 0);
 333         if (*endp)
 334                 return -EINVAL;
 335
 336         *num = n;
 337         return 0;
 338 }
 339
 340
 341 static inline void kill_final_newline(char *str)
 342 {
 343         char *newline = strrchr(str, '\n');
 344         if (newline && !newline[1])
 345                 *newline = 0;
 346 }
 347
 348
 349 #ifndef MODULE
 350 static int block2mtd_init_called = 0;
 351 static char block2mtd_paramline[80 + 12]; /* 80 for device, 12 for erase size */
 352 #endif
 353
 354 static int block2mtd_setup2(const char *val)
 355 {
 356         char buf[80 + 12]; /* 80 for device, 12 for erase size */
 357         char *str = buf;
 358         char *token[2];
 359         char *name;
 360         size_t erase_size = PAGE_SIZE;
 361         int i, ret;
 362
 363         if (strnlen(val, sizeof(buf)) >= sizeof(buf)) {
 364                 pr_err("parameter too long\n");
 365                 return 0;
 366         }
 367
 368         strcpy(str, val);
 369         kill_final_newline(str);
 370
 371         for (i = 0; i < 2; i++)
 372                 token[i] = strsep(&str, ",");
 373
 374         if (str) {
 375                 pr_err("too many arguments\n");
 376                 return 0;
 377         }
 378
 379         if (!token[0]) {
 380                 pr_err("no argument\n");
 381                 return 0;
 382         }
 383
 384         name = token[0];
 385         if (strlen(name) + 1 > 80) {
 386                 pr_err("device name too long\n");
 387                 return 0;
 388         }
 389
 390         if (token[1]) {
 391                 ret = parse_num(&erase_size, token[1]);
 392                 if (ret) {
 393                         pr_err("illegal erase size\n");
 394                         return 0;
 395                 }
 396         }
 397
 398         add_device(name, erase_size);
 399
 400         return 0;
 401 }
 402
 403
 404 static int block2mtd_setup(const char *val, struct kernel_param *kp)
 405 {
 406 #ifdef MODULE
 407         return block2mtd_setup2(val);
 408 #else
 409         /* If more parameters are later passed in via
 410            /sys/module/block2mtd/parameters/block2mtd
 411            and block2mtd_init() has already been called,
 412            we can parse the argument now. */
 413
 414         if (block2mtd_init_called)
 415                 return block2mtd_setup2(val);
 416
 417         /* During early boot stage, we only save the parameters
 418            here. We must parse them later: if the param passed
 419            from kernel boot command line, block2mtd_setup() is
 420            called so early that it is not possible to resolve
 421            the device (even kmalloc() fails). Deter that work to
 422            block2mtd_setup2(). */
 423
 424         strlcpy(block2mtd_paramline, val, sizeof(block2mtd_paramline));
 425
 426         return 0;
 427 #endif
 428 }
 429
 430
 431 module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
 432 MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");
 433
 434 static int __init block2mtd_init(void)
 435 {
 436         int ret = 0;
 437
 438 #ifndef MODULE
 439         if (strlen(block2mtd_paramline))
 440                 ret = block2mtd_setup2(block2mtd_paramline);
 441         block2mtd_init_called = 1;
 442 #endif
 443
 444         return ret;
 445 }
 446
 447
 448 static void block2mtd_exit(void)
 449 {
 450         struct list_head *pos, *next;
 451
 452         /* Remove the MTD devices */
 453         list_for_each_safe(pos, next, &blkmtd_device_list) {
 454                 struct block2mtd_dev *dev = list_entry(pos, typeof(*dev), list);
 455                 block2mtd_sync(&dev->mtd);
 456                 mtd_device_unregister(&dev->mtd);
 457                 mutex_destroy(&dev->write_mutex);
 458                 pr_info("mtd%d: [%s] removed\n",
 459                         dev->mtd.index,
 460                         dev->mtd.name + strlen("block2mtd: "));
 461                 list_del(&dev->list);
 462                 block2mtd_free_device(dev);
 463         }
 464 }
 465
 466
 467 module_init(block2mtd_init);
 468 module_exit(block2mtd_exit);
 469
 470 MODULE_LICENSE("GPL");
 471 MODULE_AUTHOR("Joern Engel <joern@lazybastard.org>");
 472 MODULE_DESCRIPTION("Emulate an MTD using a block device");