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