linux/drivers/mtd/devices/block2mtd.c
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   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 */
  35struct 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 */
  44static LIST_HEAD(blkmtd_device_list);
  45
  46
  47static 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 */
  53static 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}
  84static 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
 101static 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 */
 135static 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
 175static 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 */
 191static 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
 199static 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
 216static 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
 312err_destroy_mutex:
 313        mutex_destroy(&dev->write_mutex);
 314err_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 */
 326static 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
 351static 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
 365static 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
 374static int block2mtd_init_called = 0;
 375/* 80 for device, 12 for erase size */
 376static char block2mtd_paramline[80 + 12];
 377#endif
 378
 379static 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
 431static 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
 458module_param_call(block2mtd, block2mtd_setup, NULL, NULL, 0200);
 459MODULE_PARM_DESC(block2mtd, "Device to use. \"block2mtd=<dev>[,<erasesize>]\"");
 460
 461static 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
 475static 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
 493late_initcall(block2mtd_init);
 494module_exit(block2mtd_exit);
 495
 496MODULE_LICENSE("GPL");
 497MODULE_AUTHOR("Joern Engel <joern@lazybastard.org>");
 498MODULE_DESCRIPTION("Emulate an MTD using a block device");
 499
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