linux/drivers/mtd/ubi/gluebi.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Copyright (c) International Business Machines Corp., 2006
   4 *
   5 * Author: Artem Bityutskiy (Битюцкий Артём), Joern Engel
   6 */
   7
   8/*
   9 * This is a small driver which implements fake MTD devices on top of UBI
  10 * volumes. This sounds strange, but it is in fact quite useful to make
  11 * MTD-oriented software (including all the legacy software) work on top of
  12 * UBI.
  13 *
  14 * Gluebi emulates MTD devices of "MTD_UBIVOLUME" type. Their minimal I/O unit
  15 * size (@mtd->writesize) is equivalent to the UBI minimal I/O unit. The
  16 * eraseblock size is equivalent to the logical eraseblock size of the volume.
  17 */
  18
  19#include <linux/err.h>
  20#include <linux/list.h>
  21#include <linux/slab.h>
  22#include <linux/sched.h>
  23#include <linux/math64.h>
  24#include <linux/module.h>
  25#include <linux/mutex.h>
  26#include <linux/mtd/ubi.h>
  27#include <linux/mtd/mtd.h>
  28#include "ubi-media.h"
  29
  30#define err_msg(fmt, ...)                                   \
  31        pr_err("gluebi (pid %d): %s: " fmt "\n",            \
  32               current->pid, __func__, ##__VA_ARGS__)
  33
  34/**
  35 * struct gluebi_device - a gluebi device description data structure.
  36 * @mtd: emulated MTD device description object
  37 * @refcnt: gluebi device reference count
  38 * @desc: UBI volume descriptor
  39 * @ubi_num: UBI device number this gluebi device works on
  40 * @vol_id: ID of UBI volume this gluebi device works on
  41 * @list: link in a list of gluebi devices
  42 */
  43struct gluebi_device {
  44        struct mtd_info mtd;
  45        int refcnt;
  46        struct ubi_volume_desc *desc;
  47        int ubi_num;
  48        int vol_id;
  49        struct list_head list;
  50};
  51
  52/* List of all gluebi devices */
  53static LIST_HEAD(gluebi_devices);
  54static DEFINE_MUTEX(devices_mutex);
  55
  56/**
  57 * find_gluebi_nolock - find a gluebi device.
  58 * @ubi_num: UBI device number
  59 * @vol_id: volume ID
  60 *
  61 * This function seraches for gluebi device corresponding to UBI device
  62 * @ubi_num and UBI volume @vol_id. Returns the gluebi device description
  63 * object in case of success and %NULL in case of failure. The caller has to
  64 * have the &devices_mutex locked.
  65 */
  66static struct gluebi_device *find_gluebi_nolock(int ubi_num, int vol_id)
  67{
  68        struct gluebi_device *gluebi;
  69
  70        list_for_each_entry(gluebi, &gluebi_devices, list)
  71                if (gluebi->ubi_num == ubi_num && gluebi->vol_id == vol_id)
  72                        return gluebi;
  73        return NULL;
  74}
  75
  76/**
  77 * gluebi_get_device - get MTD device reference.
  78 * @mtd: the MTD device description object
  79 *
  80 * This function is called every time the MTD device is being opened and
  81 * implements the MTD get_device() operation. Returns zero in case of success
  82 * and a negative error code in case of failure.
  83 */
  84static int gluebi_get_device(struct mtd_info *mtd)
  85{
  86        struct gluebi_device *gluebi;
  87        int ubi_mode = UBI_READONLY;
  88
  89        if (mtd->flags & MTD_WRITEABLE)
  90                ubi_mode = UBI_READWRITE;
  91
  92        gluebi = container_of(mtd, struct gluebi_device, mtd);
  93        mutex_lock(&devices_mutex);
  94        if (gluebi->refcnt > 0) {
  95                /*
  96                 * The MTD device is already referenced and this is just one
  97                 * more reference. MTD allows many users to open the same
  98                 * volume simultaneously and do not distinguish between
  99                 * readers/writers/exclusive/meta openers as UBI does. So we do
 100                 * not open the UBI volume again - just increase the reference
 101                 * counter and return.
 102                 */
 103                gluebi->refcnt += 1;
 104                mutex_unlock(&devices_mutex);
 105                return 0;
 106        }
 107
 108        /*
 109         * This is the first reference to this UBI volume via the MTD device
 110         * interface. Open the corresponding volume in read-write mode.
 111         */
 112        gluebi->desc = ubi_open_volume(gluebi->ubi_num, gluebi->vol_id,
 113                                       ubi_mode);
 114        if (IS_ERR(gluebi->desc)) {
 115                mutex_unlock(&devices_mutex);
 116                return PTR_ERR(gluebi->desc);
 117        }
 118        gluebi->refcnt += 1;
 119        mutex_unlock(&devices_mutex);
 120        return 0;
 121}
 122
 123/**
 124 * gluebi_put_device - put MTD device reference.
 125 * @mtd: the MTD device description object
 126 *
 127 * This function is called every time the MTD device is being put. Returns
 128 * zero in case of success and a negative error code in case of failure.
 129 */
 130static void gluebi_put_device(struct mtd_info *mtd)
 131{
 132        struct gluebi_device *gluebi;
 133
 134        gluebi = container_of(mtd, struct gluebi_device, mtd);
 135        mutex_lock(&devices_mutex);
 136        gluebi->refcnt -= 1;
 137        if (gluebi->refcnt == 0)
 138                ubi_close_volume(gluebi->desc);
 139        mutex_unlock(&devices_mutex);
 140}
 141
 142/**
 143 * gluebi_read - read operation of emulated MTD devices.
 144 * @mtd: MTD device description object
 145 * @from: absolute offset from where to read
 146 * @len: how many bytes to read
 147 * @retlen: count of read bytes is returned here
 148 * @buf: buffer to store the read data
 149 *
 150 * This function returns zero in case of success and a negative error code in
 151 * case of failure.
 152 */
 153static int gluebi_read(struct mtd_info *mtd, loff_t from, size_t len,
 154                       size_t *retlen, unsigned char *buf)
 155{
 156        int err = 0, lnum, offs, bytes_left;
 157        struct gluebi_device *gluebi;
 158
 159        gluebi = container_of(mtd, struct gluebi_device, mtd);
 160        lnum = div_u64_rem(from, mtd->erasesize, &offs);
 161        bytes_left = len;
 162        while (bytes_left) {
 163                size_t to_read = mtd->erasesize - offs;
 164
 165                if (to_read > bytes_left)
 166                        to_read = bytes_left;
 167
 168                err = ubi_read(gluebi->desc, lnum, buf, offs, to_read);
 169                if (err)
 170                        break;
 171
 172                lnum += 1;
 173                offs = 0;
 174                bytes_left -= to_read;
 175                buf += to_read;
 176        }
 177
 178        *retlen = len - bytes_left;
 179        return err;
 180}
 181
 182/**
 183 * gluebi_write - write operation of emulated MTD devices.
 184 * @mtd: MTD device description object
 185 * @to: absolute offset where to write
 186 * @len: how many bytes to write
 187 * @retlen: count of written bytes is returned here
 188 * @buf: buffer with data to write
 189 *
 190 * This function returns zero in case of success and a negative error code in
 191 * case of failure.
 192 */
 193static int gluebi_write(struct mtd_info *mtd, loff_t to, size_t len,
 194                        size_t *retlen, const u_char *buf)
 195{
 196        int err = 0, lnum, offs, bytes_left;
 197        struct gluebi_device *gluebi;
 198
 199        gluebi = container_of(mtd, struct gluebi_device, mtd);
 200        lnum = div_u64_rem(to, mtd->erasesize, &offs);
 201
 202        if (len % mtd->writesize || offs % mtd->writesize)
 203                return -EINVAL;
 204
 205        bytes_left = len;
 206        while (bytes_left) {
 207                size_t to_write = mtd->erasesize - offs;
 208
 209                if (to_write > bytes_left)
 210                        to_write = bytes_left;
 211
 212                err = ubi_leb_write(gluebi->desc, lnum, buf, offs, to_write);
 213                if (err)
 214                        break;
 215
 216                lnum += 1;
 217                offs = 0;
 218                bytes_left -= to_write;
 219                buf += to_write;
 220        }
 221
 222        *retlen = len - bytes_left;
 223        return err;
 224}
 225
 226/**
 227 * gluebi_erase - erase operation of emulated MTD devices.
 228 * @mtd: the MTD device description object
 229 * @instr: the erase operation description
 230 *
 231 * This function calls the erase callback when finishes. Returns zero in case
 232 * of success and a negative error code in case of failure.
 233 */
 234static int gluebi_erase(struct mtd_info *mtd, struct erase_info *instr)
 235{
 236        int err, i, lnum, count;
 237        struct gluebi_device *gluebi;
 238
 239        if (mtd_mod_by_ws(instr->addr, mtd) || mtd_mod_by_ws(instr->len, mtd))
 240                return -EINVAL;
 241
 242        lnum = mtd_div_by_eb(instr->addr, mtd);
 243        count = mtd_div_by_eb(instr->len, mtd);
 244        gluebi = container_of(mtd, struct gluebi_device, mtd);
 245
 246        for (i = 0; i < count - 1; i++) {
 247                err = ubi_leb_unmap(gluebi->desc, lnum + i);
 248                if (err)
 249                        goto out_err;
 250        }
 251        /*
 252         * MTD erase operations are synchronous, so we have to make sure the
 253         * physical eraseblock is wiped out.
 254         *
 255         * Thus, perform leb_erase instead of leb_unmap operation - leb_erase
 256         * will wait for the end of operations
 257         */
 258        err = ubi_leb_erase(gluebi->desc, lnum + i);
 259        if (err)
 260                goto out_err;
 261
 262        return 0;
 263
 264out_err:
 265        instr->fail_addr = (long long)lnum * mtd->erasesize;
 266        return err;
 267}
 268
 269/**
 270 * gluebi_create - create a gluebi device for an UBI volume.
 271 * @di: UBI device description object
 272 * @vi: UBI volume description object
 273 *
 274 * This function is called when a new UBI volume is created in order to create
 275 * corresponding fake MTD device. Returns zero in case of success and a
 276 * negative error code in case of failure.
 277 */
 278static int gluebi_create(struct ubi_device_info *di,
 279                         struct ubi_volume_info *vi)
 280{
 281        struct gluebi_device *gluebi, *g;
 282        struct mtd_info *mtd;
 283
 284        gluebi = kzalloc(sizeof(struct gluebi_device), GFP_KERNEL);
 285        if (!gluebi)
 286                return -ENOMEM;
 287
 288        mtd = &gluebi->mtd;
 289        mtd->name = kmemdup(vi->name, vi->name_len + 1, GFP_KERNEL);
 290        if (!mtd->name) {
 291                kfree(gluebi);
 292                return -ENOMEM;
 293        }
 294
 295        gluebi->vol_id = vi->vol_id;
 296        gluebi->ubi_num = vi->ubi_num;
 297        mtd->type = MTD_UBIVOLUME;
 298        if (!di->ro_mode)
 299                mtd->flags = MTD_WRITEABLE;
 300        mtd->owner      = THIS_MODULE;
 301        mtd->writesize  = di->min_io_size;
 302        mtd->erasesize  = vi->usable_leb_size;
 303        mtd->_read       = gluebi_read;
 304        mtd->_write      = gluebi_write;
 305        mtd->_erase      = gluebi_erase;
 306        mtd->_get_device = gluebi_get_device;
 307        mtd->_put_device = gluebi_put_device;
 308
 309        /*
 310         * In case of dynamic a volume, MTD device size is just volume size. In
 311         * case of a static volume the size is equivalent to the amount of data
 312         * bytes.
 313         */
 314        if (vi->vol_type == UBI_DYNAMIC_VOLUME)
 315                mtd->size = (unsigned long long)vi->usable_leb_size * vi->size;
 316        else
 317                mtd->size = vi->used_bytes;
 318
 319        /* Just a sanity check - make sure this gluebi device does not exist */
 320        mutex_lock(&devices_mutex);
 321        g = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
 322        if (g)
 323                err_msg("gluebi MTD device %d form UBI device %d volume %d already exists",
 324                        g->mtd.index, vi->ubi_num, vi->vol_id);
 325        mutex_unlock(&devices_mutex);
 326
 327        if (mtd_device_register(mtd, NULL, 0)) {
 328                err_msg("cannot add MTD device");
 329                kfree(mtd->name);
 330                kfree(gluebi);
 331                return -ENFILE;
 332        }
 333
 334        mutex_lock(&devices_mutex);
 335        list_add_tail(&gluebi->list, &gluebi_devices);
 336        mutex_unlock(&devices_mutex);
 337        return 0;
 338}
 339
 340/**
 341 * gluebi_remove - remove a gluebi device.
 342 * @vi: UBI volume description object
 343 *
 344 * This function is called when an UBI volume is removed and it removes
 345 * corresponding fake MTD device. Returns zero in case of success and a
 346 * negative error code in case of failure.
 347 */
 348static int gluebi_remove(struct ubi_volume_info *vi)
 349{
 350        int err = 0;
 351        struct mtd_info *mtd;
 352        struct gluebi_device *gluebi;
 353
 354        mutex_lock(&devices_mutex);
 355        gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
 356        if (!gluebi) {
 357                err_msg("got remove notification for unknown UBI device %d volume %d",
 358                        vi->ubi_num, vi->vol_id);
 359                err = -ENOENT;
 360        } else if (gluebi->refcnt)
 361                err = -EBUSY;
 362        else
 363                list_del(&gluebi->list);
 364        mutex_unlock(&devices_mutex);
 365        if (err)
 366                return err;
 367
 368        mtd = &gluebi->mtd;
 369        err = mtd_device_unregister(mtd);
 370        if (err) {
 371                err_msg("cannot remove fake MTD device %d, UBI device %d, volume %d, error %d",
 372                        mtd->index, gluebi->ubi_num, gluebi->vol_id, err);
 373                mutex_lock(&devices_mutex);
 374                list_add_tail(&gluebi->list, &gluebi_devices);
 375                mutex_unlock(&devices_mutex);
 376                return err;
 377        }
 378
 379        kfree(mtd->name);
 380        kfree(gluebi);
 381        return 0;
 382}
 383
 384/**
 385 * gluebi_updated - UBI volume was updated notifier.
 386 * @vi: volume info structure
 387 *
 388 * This function is called every time an UBI volume is updated. It does nothing
 389 * if te volume @vol is dynamic, and changes MTD device size if the
 390 * volume is static. This is needed because static volumes cannot be read past
 391 * data they contain. This function returns zero in case of success and a
 392 * negative error code in case of error.
 393 */
 394static int gluebi_updated(struct ubi_volume_info *vi)
 395{
 396        struct gluebi_device *gluebi;
 397
 398        mutex_lock(&devices_mutex);
 399        gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
 400        if (!gluebi) {
 401                mutex_unlock(&devices_mutex);
 402                err_msg("got update notification for unknown UBI device %d volume %d",
 403                        vi->ubi_num, vi->vol_id);
 404                return -ENOENT;
 405        }
 406
 407        if (vi->vol_type == UBI_STATIC_VOLUME)
 408                gluebi->mtd.size = vi->used_bytes;
 409        mutex_unlock(&devices_mutex);
 410        return 0;
 411}
 412
 413/**
 414 * gluebi_resized - UBI volume was re-sized notifier.
 415 * @vi: volume info structure
 416 *
 417 * This function is called every time an UBI volume is re-size. It changes the
 418 * corresponding fake MTD device size. This function returns zero in case of
 419 * success and a negative error code in case of error.
 420 */
 421static int gluebi_resized(struct ubi_volume_info *vi)
 422{
 423        struct gluebi_device *gluebi;
 424
 425        mutex_lock(&devices_mutex);
 426        gluebi = find_gluebi_nolock(vi->ubi_num, vi->vol_id);
 427        if (!gluebi) {
 428                mutex_unlock(&devices_mutex);
 429                err_msg("got update notification for unknown UBI device %d volume %d",
 430                        vi->ubi_num, vi->vol_id);
 431                return -ENOENT;
 432        }
 433        gluebi->mtd.size = vi->used_bytes;
 434        mutex_unlock(&devices_mutex);
 435        return 0;
 436}
 437
 438/**
 439 * gluebi_notify - UBI notification handler.
 440 * @nb: registered notifier block
 441 * @l: notification type
 442 * @ptr: pointer to the &struct ubi_notification object
 443 */
 444static int gluebi_notify(struct notifier_block *nb, unsigned long l,
 445                         void *ns_ptr)
 446{
 447        struct ubi_notification *nt = ns_ptr;
 448
 449        switch (l) {
 450        case UBI_VOLUME_ADDED:
 451                gluebi_create(&nt->di, &nt->vi);
 452                break;
 453        case UBI_VOLUME_REMOVED:
 454                gluebi_remove(&nt->vi);
 455                break;
 456        case UBI_VOLUME_RESIZED:
 457                gluebi_resized(&nt->vi);
 458                break;
 459        case UBI_VOLUME_UPDATED:
 460                gluebi_updated(&nt->vi);
 461                break;
 462        default:
 463                break;
 464        }
 465        return NOTIFY_OK;
 466}
 467
 468static struct notifier_block gluebi_notifier = {
 469        .notifier_call  = gluebi_notify,
 470};
 471
 472static int __init ubi_gluebi_init(void)
 473{
 474        return ubi_register_volume_notifier(&gluebi_notifier, 0);
 475}
 476
 477static void __exit ubi_gluebi_exit(void)
 478{
 479        struct gluebi_device *gluebi, *g;
 480
 481        list_for_each_entry_safe(gluebi, g, &gluebi_devices, list) {
 482                int err;
 483                struct mtd_info *mtd = &gluebi->mtd;
 484
 485                err = mtd_device_unregister(mtd);
 486                if (err)
 487                        err_msg("error %d while removing gluebi MTD device %d, UBI device %d, volume %d - ignoring",
 488                                err, mtd->index, gluebi->ubi_num,
 489                                gluebi->vol_id);
 490                kfree(mtd->name);
 491                kfree(gluebi);
 492        }
 493        ubi_unregister_volume_notifier(&gluebi_notifier);
 494}
 495
 496module_init(ubi_gluebi_init);
 497module_exit(ubi_gluebi_exit);
 498MODULE_DESCRIPTION("MTD emulation layer over UBI volumes");
 499MODULE_AUTHOR("Artem Bityutskiy, Joern Engel");
 500MODULE_LICENSE("GPL");
 501