block/partitions/core.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 1991-1998  Linus Torvalds
   4  * Re-organised Feb 1998 Russell King
   5  * Copyright (C) 2020 Christoph Hellwig
   6  */
   7 #include <linux/fs.h>
   8 #include <linux/slab.h>
   9 #include <linux/ctype.h>
  10 #include <linux/genhd.h>
  11 #include <linux/vmalloc.h>
  12 #include <linux/blktrace_api.h>
  13 #include <linux/raid/detect.h>
  14 #include "check.h"
  15
  16 static int (*check_part[])(struct parsed_partitions *) = {
  17         /*
  18          * Probe partition formats with tables at disk address 0
  19          * that also have an ADFS boot block at 0xdc0.
  20          */
  21 #ifdef CONFIG_ACORN_PARTITION_ICS
  22         adfspart_check_ICS,
  23 #endif
  24 #ifdef CONFIG_ACORN_PARTITION_POWERTEC
  25         adfspart_check_POWERTEC,
  26 #endif
  27 #ifdef CONFIG_ACORN_PARTITION_EESOX
  28         adfspart_check_EESOX,
  29 #endif
  30
  31         /*
  32          * Now move on to formats that only have partition info at
  33          * disk address 0xdc0.  Since these may also have stale
  34          * PC/BIOS partition tables, they need to come before
  35          * the msdos entry.
  36          */
  37 #ifdef CONFIG_ACORN_PARTITION_CUMANA
  38         adfspart_check_CUMANA,
  39 #endif
  40 #ifdef CONFIG_ACORN_PARTITION_ADFS
  41         adfspart_check_ADFS,
  42 #endif
  43
  44 #ifdef CONFIG_CMDLINE_PARTITION
  45         cmdline_partition,
  46 #endif
  47 #ifdef CONFIG_EFI_PARTITION
  48         efi_partition,          /* this must come before msdos */
  49 #endif
  50 #ifdef CONFIG_SGI_PARTITION
  51         sgi_partition,
  52 #endif
  53 #ifdef CONFIG_LDM_PARTITION
  54         ldm_partition,          /* this must come before msdos */
  55 #endif
  56 #ifdef CONFIG_MSDOS_PARTITION
  57         msdos_partition,
  58 #endif
  59 #ifdef CONFIG_OSF_PARTITION
  60         osf_partition,
  61 #endif
  62 #ifdef CONFIG_SUN_PARTITION
  63         sun_partition,
  64 #endif
  65 #ifdef CONFIG_AMIGA_PARTITION
  66         amiga_partition,
  67 #endif
  68 #ifdef CONFIG_ATARI_PARTITION
  69         atari_partition,
  70 #endif
  71 #ifdef CONFIG_MAC_PARTITION
  72         mac_partition,
  73 #endif
  74 #ifdef CONFIG_ULTRIX_PARTITION
  75         ultrix_partition,
  76 #endif
  77 #ifdef CONFIG_IBM_PARTITION
  78         ibm_partition,
  79 #endif
  80 #ifdef CONFIG_KARMA_PARTITION
  81         karma_partition,
  82 #endif
  83 #ifdef CONFIG_SYSV68_PARTITION
  84         sysv68_partition,
  85 #endif
  86         NULL
  87 };
  88
  89 static void bdev_set_nr_sectors(struct block_device *bdev, sector_t sectors)
  90 {
  91         spin_lock(&bdev->bd_size_lock);
  92         i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
  93         spin_unlock(&bdev->bd_size_lock);
  94 }
  95
  96 static struct parsed_partitions *allocate_partitions(struct gendisk *hd)
  97 {
  98         struct parsed_partitions *state;
  99         int nr;
 100
 101         state = kzalloc(sizeof(*state), GFP_KERNEL);
 102         if (!state)
 103                 return NULL;
 104
 105         nr = disk_max_parts(hd);
 106         state->parts = vzalloc(array_size(nr, sizeof(state->parts[0])));
 107         if (!state->parts) {
 108                 kfree(state);
 109                 return NULL;
 110         }
 111
 112         state->limit = nr;
 113
 114         return state;
 115 }
 116
 117 static void free_partitions(struct parsed_partitions *state)
 118 {
 119         vfree(state->parts);
 120         kfree(state);
 121 }
 122
 123 static struct parsed_partitions *check_partition(struct gendisk *hd,
 124                 struct block_device *bdev)
 125 {
 126         struct parsed_partitions *state;
 127         int i, res, err;
 128
 129         state = allocate_partitions(hd);
 130         if (!state)
 131                 return NULL;
 132         state->pp_buf = (char *)__get_free_page(GFP_KERNEL);
 133         if (!state->pp_buf) {
 134                 free_partitions(state);
 135                 return NULL;
 136         }
 137         state->pp_buf[0] = '\0';
 138
 139         state->bdev = bdev;
 140         disk_name(hd, 0, state->name);
 141         snprintf(state->pp_buf, PAGE_SIZE, " %s:", state->name);
 142         if (isdigit(state->name[strlen(state->name)-1]))
 143                 sprintf(state->name, "p");
 144
 145         i = res = err = 0;
 146         while (!res && check_part[i]) {
 147                 memset(state->parts, 0, state->limit * sizeof(state->parts[0]));
 148                 res = check_part[i++](state);
 149                 if (res < 0) {
 150                         /*
 151                          * We have hit an I/O error which we don't report now.
 152                          * But record it, and let the others do their job.
 153                          */
 154                         err = res;
 155                         res = 0;
 156                 }
 157
 158         }
 159         if (res > 0) {
 160                 printk(KERN_INFO "%s", state->pp_buf);
 161
 162                 free_page((unsigned long)state->pp_buf);
 163                 return state;
 164         }
 165         if (state->access_beyond_eod)
 166                 err = -ENOSPC;
 167         /*
 168          * The partition is unrecognized. So report I/O errors if there were any
 169          */
 170         if (err)
 171                 res = err;
 172         if (res) {
 173                 strlcat(state->pp_buf,
 174                         " unable to read partition table\n", PAGE_SIZE);
 175                 printk(KERN_INFO "%s", state->pp_buf);
 176         }
 177
 178         free_page((unsigned long)state->pp_buf);
 179         free_partitions(state);
 180         return ERR_PTR(res);
 181 }
 182
 183 static ssize_t part_partition_show(struct device *dev,
 184                                    struct device_attribute *attr, char *buf)
 185 {
 186         return sprintf(buf, "%d\n", dev_to_bdev(dev)->bd_partno);
 187 }
 188
 189 static ssize_t part_start_show(struct device *dev,
 190                                struct device_attribute *attr, char *buf)
 191 {
 192         return sprintf(buf, "%llu\n", dev_to_bdev(dev)->bd_start_sect);
 193 }
 194
 195 static ssize_t part_ro_show(struct device *dev,
 196                             struct device_attribute *attr, char *buf)
 197 {
 198         return sprintf(buf, "%d\n", dev_to_bdev(dev)->bd_read_only);
 199 }
 200
 201 static ssize_t part_alignment_offset_show(struct device *dev,
 202                                           struct device_attribute *attr, char *buf)
 203 {
 204         struct block_device *bdev = dev_to_bdev(dev);
 205
 206         return sprintf(buf, "%u\n",
 207                 queue_limit_alignment_offset(&bdev->bd_disk->queue->limits,
 208                                 bdev->bd_start_sect));
 209 }
 210
 211 static ssize_t part_discard_alignment_show(struct device *dev,
 212                                            struct device_attribute *attr, char *buf)
 213 {
 214         struct block_device *bdev = dev_to_bdev(dev);
 215
 216         return sprintf(buf, "%u\n",
 217                 queue_limit_discard_alignment(&bdev->bd_disk->queue->limits,
 218                                 bdev->bd_start_sect));
 219 }
 220
 221 static DEVICE_ATTR(partition, 0444, part_partition_show, NULL);
 222 static DEVICE_ATTR(start, 0444, part_start_show, NULL);
 223 static DEVICE_ATTR(size, 0444, part_size_show, NULL);
 224 static DEVICE_ATTR(ro, 0444, part_ro_show, NULL);
 225 static DEVICE_ATTR(alignment_offset, 0444, part_alignment_offset_show, NULL);
 226 static DEVICE_ATTR(discard_alignment, 0444, part_discard_alignment_show, NULL);
 227 static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
 228 static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
 229 #ifdef CONFIG_FAIL_MAKE_REQUEST
 230 static struct device_attribute dev_attr_fail =
 231         __ATTR(make-it-fail, 0644, part_fail_show, part_fail_store);
 232 #endif
 233
 234 static struct attribute *part_attrs[] = {
 235         &dev_attr_partition.attr,
 236         &dev_attr_start.attr,
 237         &dev_attr_size.attr,
 238         &dev_attr_ro.attr,
 239         &dev_attr_alignment_offset.attr,
 240         &dev_attr_discard_alignment.attr,
 241         &dev_attr_stat.attr,
 242         &dev_attr_inflight.attr,
 243 #ifdef CONFIG_FAIL_MAKE_REQUEST
 244         &dev_attr_fail.attr,
 245 #endif
 246         NULL
 247 };
 248
 249 static struct attribute_group part_attr_group = {
 250         .attrs = part_attrs,
 251 };
 252
 253 static const struct attribute_group *part_attr_groups[] = {
 254         &part_attr_group,
 255 #ifdef CONFIG_BLK_DEV_IO_TRACE
 256         &blk_trace_attr_group,
 257 #endif
 258         NULL
 259 };
 260
 261 static void part_release(struct device *dev)
 262 {
 263         blk_free_devt(dev->devt);
 264         bdput(dev_to_bdev(dev));
 265 }
 266
 267 static int part_uevent(struct device *dev, struct kobj_uevent_env *env)
 268 {
 269         struct block_device *part = dev_to_bdev(dev);
 270
 271         add_uevent_var(env, "PARTN=%u", part->bd_partno);
 272         if (part->bd_meta_info && part->bd_meta_info->volname[0])
 273                 add_uevent_var(env, "PARTNAME=%s", part->bd_meta_info->volname);
 274         return 0;
 275 }
 276
 277 struct device_type part_type = {
 278         .name           = "partition",
 279         .groups         = part_attr_groups,
 280         .release        = part_release,
 281         .uevent         = part_uevent,
 282 };
 283
 284 /*
 285  * Must be called either with bd_mutex held, before a disk can be opened or
 286  * after all disk users are gone.
 287  */
 288 void delete_partition(struct block_device *part)
 289 {
 290         struct gendisk *disk = part->bd_disk;
 291         struct disk_part_tbl *ptbl =
 292                 rcu_dereference_protected(disk->part_tbl, 1);
 293
 294         rcu_assign_pointer(ptbl->part[part->bd_partno], NULL);
 295         rcu_assign_pointer(ptbl->last_lookup, NULL);
 296
 297         kobject_put(part->bd_holder_dir);
 298         device_del(&part->bd_device);
 299
 300         /*
 301          * Remove the block device from the inode hash, so that it cannot be
 302          * looked up any more even when openers still hold references.
 303          */
 304         remove_inode_hash(part->bd_inode);
 305
 306         put_device(&part->bd_device);
 307 }
 308
 309 static ssize_t whole_disk_show(struct device *dev,
 310                                struct device_attribute *attr, char *buf)
 311 {
 312         return 0;
 313 }
 314 static DEVICE_ATTR(whole_disk, 0444, whole_disk_show, NULL);
 315
 316 /*
 317  * Must be called either with bd_mutex held, before a disk can be opened or
 318  * after all disk users are gone.
 319  */
 320 static struct block_device *add_partition(struct gendisk *disk, int partno,
 321                                 sector_t start, sector_t len, int flags,
 322                                 struct partition_meta_info *info)
 323 {
 324         dev_t devt = MKDEV(0, 0);
 325         struct device *ddev = disk_to_dev(disk);
 326         struct device *pdev;
 327         struct block_device *bdev;
 328         struct disk_part_tbl *ptbl;
 329         const char *dname;
 330         int err;
 331
 332         /*
 333          * Partitions are not supported on zoned block devices that are used as
 334          * such.
 335          */
 336         switch (disk->queue->limits.zoned) {
 337         case BLK_ZONED_HM:
 338                 pr_warn("%s: partitions not supported on host managed zoned block device\n",
 339                         disk->disk_name);
 340                 return ERR_PTR(-ENXIO);
 341         case BLK_ZONED_HA:
 342                 pr_info("%s: disabling host aware zoned block device support due to partitions\n",
 343                         disk->disk_name);
 344                 disk->queue->limits.zoned = BLK_ZONED_NONE;
 345                 break;
 346         case BLK_ZONED_NONE:
 347                 break;
 348         }
 349
 350         err = disk_expand_part_tbl(disk, partno);
 351         if (err)
 352                 return ERR_PTR(err);
 353         ptbl = rcu_dereference_protected(disk->part_tbl, 1);
 354
 355         if (ptbl->part[partno])
 356                 return ERR_PTR(-EBUSY);
 357
 358         bdev = bdev_alloc(disk, partno);
 359         if (!bdev)
 360                 return ERR_PTR(-ENOMEM);
 361
 362         bdev->bd_start_sect = start;
 363         bdev_set_nr_sectors(bdev, len);
 364         bdev->bd_read_only = get_disk_ro(disk);
 365
 366         if (info) {
 367                 err = -ENOMEM;
 368                 bdev->bd_meta_info = kmemdup(info, sizeof(*info), GFP_KERNEL);
 369                 if (!bdev->bd_meta_info)
 370                         goto out_bdput;
 371         }
 372
 373         pdev = &bdev->bd_device;
 374         dname = dev_name(ddev);
 375         if (isdigit(dname[strlen(dname) - 1]))
 376                 dev_set_name(pdev, "%sp%d", dname, partno);
 377         else
 378                 dev_set_name(pdev, "%s%d", dname, partno);
 379
 380         device_initialize(pdev);
 381         pdev->class = &block_class;
 382         pdev->type = &part_type;
 383         pdev->parent = ddev;
 384
 385         err = blk_alloc_devt(bdev, &devt);
 386         if (err)
 387                 goto out_bdput;
 388         pdev->devt = devt;
 389
 390         /* delay uevent until 'holders' subdir is created */
 391         dev_set_uevent_suppress(pdev, 1);
 392         err = device_add(pdev);
 393         if (err)
 394                 goto out_put;
 395
 396         err = -ENOMEM;
 397         bdev->bd_holder_dir = kobject_create_and_add("holders", &pdev->kobj);
 398         if (!bdev->bd_holder_dir)
 399                 goto out_del;
 400
 401         dev_set_uevent_suppress(pdev, 0);
 402         if (flags & ADDPART_FLAG_WHOLEDISK) {
 403                 err = device_create_file(pdev, &dev_attr_whole_disk);
 404                 if (err)
 405                         goto out_del;
 406         }
 407
 408         /* everything is up and running, commence */
 409         bdev_add(bdev, devt);
 410         rcu_assign_pointer(ptbl->part[partno], bdev);
 411
 412         /* suppress uevent if the disk suppresses it */
 413         if (!dev_get_uevent_suppress(ddev))
 414                 kobject_uevent(&pdev->kobj, KOBJ_ADD);
 415         return bdev;
 416
 417 out_bdput:
 418         bdput(bdev);
 419         return ERR_PTR(err);
 420 out_del:
 421         kobject_put(bdev->bd_holder_dir);
 422         device_del(pdev);
 423 out_put:
 424         put_device(pdev);
 425         return ERR_PTR(err);
 426 }
 427
 428 static bool partition_overlaps(struct gendisk *disk, sector_t start,
 429                 sector_t length, int skip_partno)
 430 {
 431         struct disk_part_iter piter;
 432         struct block_device *part;
 433         bool overlap = false;
 434
 435         disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
 436         while ((part = disk_part_iter_next(&piter))) {
 437                 if (part->bd_partno == skip_partno ||
 438                     start >= part->bd_start_sect + bdev_nr_sectors(part) ||
 439                     start + length <= part->bd_start_sect)
 440                         continue;
 441                 overlap = true;
 442                 break;
 443         }
 444
 445         disk_part_iter_exit(&piter);
 446         return overlap;
 447 }
 448
 449 int bdev_add_partition(struct block_device *bdev, int partno,
 450                 sector_t start, sector_t length)
 451 {
 452         struct block_device *part;
 453
 454         mutex_lock(&bdev->bd_mutex);
 455         if (partition_overlaps(bdev->bd_disk, start, length, -1)) {
 456                 mutex_unlock(&bdev->bd_mutex);
 457                 return -EBUSY;
 458         }
 459
 460         part = add_partition(bdev->bd_disk, partno, start, length,
 461                         ADDPART_FLAG_NONE, NULL);
 462         mutex_unlock(&bdev->bd_mutex);
 463         return PTR_ERR_OR_ZERO(part);
 464 }
 465
 466 int bdev_del_partition(struct block_device *bdev, int partno)
 467 {
 468         struct block_device *part;
 469         int ret;
 470
 471         part = bdget_disk(bdev->bd_disk, partno);
 472         if (!part)
 473                 return -ENXIO;
 474
 475         mutex_lock(&part->bd_mutex);
 476         mutex_lock_nested(&bdev->bd_mutex, 1);
 477
 478         ret = -EBUSY;
 479         if (part->bd_openers)
 480                 goto out_unlock;
 481
 482         sync_blockdev(part);
 483         invalidate_bdev(part);
 484
 485         delete_partition(part);
 486         ret = 0;
 487 out_unlock:
 488         mutex_unlock(&bdev->bd_mutex);
 489         mutex_unlock(&part->bd_mutex);
 490         bdput(part);
 491         return ret;
 492 }
 493
 494 int bdev_resize_partition(struct block_device *bdev, int partno,
 495                 sector_t start, sector_t length)
 496 {
 497         struct block_device *part;
 498         int ret = 0;
 499
 500         part = bdget_disk(bdev->bd_disk, partno);
 501         if (!part)
 502                 return -ENXIO;
 503
 504         mutex_lock(&part->bd_mutex);
 505         mutex_lock_nested(&bdev->bd_mutex, 1);
 506         ret = -EINVAL;
 507         if (start != part->bd_start_sect)
 508                 goto out_unlock;
 509
 510         ret = -EBUSY;
 511         if (partition_overlaps(bdev->bd_disk, start, length, partno))
 512                 goto out_unlock;
 513
 514         bdev_set_nr_sectors(part, length);
 515
 516         ret = 0;
 517 out_unlock:
 518         mutex_unlock(&part->bd_mutex);
 519         mutex_unlock(&bdev->bd_mutex);
 520         bdput(part);
 521         return ret;
 522 }
 523
 524 static bool disk_unlock_native_capacity(struct gendisk *disk)
 525 {
 526         const struct block_device_operations *bdops = disk->fops;
 527
 528         if (bdops->unlock_native_capacity &&
 529             !(disk->flags & GENHD_FL_NATIVE_CAPACITY)) {
 530                 printk(KERN_CONT "enabling native capacity\n");
 531                 bdops->unlock_native_capacity(disk);
 532                 disk->flags |= GENHD_FL_NATIVE_CAPACITY;
 533                 return true;
 534         } else {
 535                 printk(KERN_CONT "truncated\n");
 536                 return false;
 537         }
 538 }
 539
 540 int blk_drop_partitions(struct block_device *bdev)
 541 {
 542         struct disk_part_iter piter;
 543         struct block_device *part;
 544
 545         if (bdev->bd_part_count)
 546                 return -EBUSY;
 547
 548         sync_blockdev(bdev);
 549         invalidate_bdev(bdev);
 550
 551         disk_part_iter_init(&piter, bdev->bd_disk, DISK_PITER_INCL_EMPTY);
 552         while ((part = disk_part_iter_next(&piter)))
 553                 delete_partition(part);
 554         disk_part_iter_exit(&piter);
 555
 556         return 0;
 557 }
 558 #ifdef CONFIG_S390
 559 /* for historic reasons in the DASD driver */
 560 EXPORT_SYMBOL_GPL(blk_drop_partitions);
 561 #endif
 562
 563 static bool blk_add_partition(struct gendisk *disk, struct block_device *bdev,
 564                 struct parsed_partitions *state, int p)
 565 {
 566         sector_t size = state->parts[p].size;
 567         sector_t from = state->parts[p].from;
 568         struct block_device *part;
 569
 570         if (!size)
 571                 return true;
 572
 573         if (from >= get_capacity(disk)) {
 574                 printk(KERN_WARNING
 575                        "%s: p%d start %llu is beyond EOD, ",
 576                        disk->disk_name, p, (unsigned long long) from);
 577                 if (disk_unlock_native_capacity(disk))
 578                         return false;
 579                 return true;
 580         }
 581
 582         if (from + size > get_capacity(disk)) {
 583                 printk(KERN_WARNING
 584                        "%s: p%d size %llu extends beyond EOD, ",
 585                        disk->disk_name, p, (unsigned long long) size);
 586
 587                 if (disk_unlock_native_capacity(disk))
 588                         return false;
 589
 590                 /*
 591                  * We can not ignore partitions of broken tables created by for
 592                  * example camera firmware, but we limit them to the end of the
 593                  * disk to avoid creating invalid block devices.
 594                  */
 595                 size = get_capacity(disk) - from;
 596         }
 597
 598         part = add_partition(disk, p, from, size, state->parts[p].flags,
 599                              &state->parts[p].info);
 600         if (IS_ERR(part) && PTR_ERR(part) != -ENXIO) {
 601                 printk(KERN_ERR " %s: p%d could not be added: %ld\n",
 602                        disk->disk_name, p, -PTR_ERR(part));
 603                 return true;
 604         }
 605
 606         if (IS_BUILTIN(CONFIG_BLK_DEV_MD) &&
 607             (state->parts[p].flags & ADDPART_FLAG_RAID))
 608                 md_autodetect_dev(part->bd_dev);
 609
 610         return true;
 611 }
 612
 613 int blk_add_partitions(struct gendisk *disk, struct block_device *bdev)
 614 {
 615         struct parsed_partitions *state;
 616         int ret = -EAGAIN, p, highest;
 617
 618         if (!disk_part_scan_enabled(disk))
 619                 return 0;
 620
 621         state = check_partition(disk, bdev);
 622         if (!state)
 623                 return 0;
 624         if (IS_ERR(state)) {
 625                 /*
 626                  * I/O error reading the partition table.  If we tried to read
 627                  * beyond EOD, retry after unlocking the native capacity.
 628                  */
 629                 if (PTR_ERR(state) == -ENOSPC) {
 630                         printk(KERN_WARNING "%s: partition table beyond EOD, ",
 631                                disk->disk_name);
 632                         if (disk_unlock_native_capacity(disk))
 633                                 return -EAGAIN;
 634                 }
 635                 return -EIO;
 636         }
 637
 638         /*
 639          * Partitions are not supported on host managed zoned block devices.
 640          */
 641         if (disk->queue->limits.zoned == BLK_ZONED_HM) {
 642                 pr_warn("%s: ignoring partition table on host managed zoned block device\n",
 643                         disk->disk_name);
 644                 ret = 0;
 645                 goto out_free_state;
 646         }
 647
 648         /*
 649          * If we read beyond EOD, try unlocking native capacity even if the
 650          * partition table was successfully read as we could be missing some
 651          * partitions.
 652          */
 653         if (state->access_beyond_eod) {
 654                 printk(KERN_WARNING
 655                        "%s: partition table partially beyond EOD, ",
 656                        disk->disk_name);
 657                 if (disk_unlock_native_capacity(disk))
 658                         goto out_free_state;
 659         }
 660
 661         /* tell userspace that the media / partition table may have changed */
 662         kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
 663
 664         /*
 665          * Detect the highest partition number and preallocate disk->part_tbl.
 666          * This is an optimization and not strictly necessary.
 667          */
 668         for (p = 1, highest = 0; p < state->limit; p++)
 669                 if (state->parts[p].size)
 670                         highest = p;
 671         disk_expand_part_tbl(disk, highest);
 672
 673         for (p = 1; p < state->limit; p++)
 674                 if (!blk_add_partition(disk, bdev, state, p))
 675                         goto out_free_state;
 676
 677         ret = 0;
 678 out_free_state:
 679         free_partitions(state);
 680         return ret;
 681 }
 682
 683 void *read_part_sector(struct parsed_partitions *state, sector_t n, Sector *p)
 684 {
 685         struct address_space *mapping = state->bdev->bd_inode->i_mapping;
 686         struct page *page;
 687
 688         if (n >= get_capacity(state->bdev->bd_disk)) {
 689                 state->access_beyond_eod = true;
 690                 return NULL;
 691         }
 692
 693         page = read_mapping_page(mapping,
 694                         (pgoff_t)(n >> (PAGE_SHIFT - 9)), NULL);
 695         if (IS_ERR(page))
 696                 goto out;
 697         if (PageError(page))
 698                 goto out_put_page;
 699
 700         p->v = page;
 701         return (unsigned char *)page_address(page) +
 702                         ((n & ((1 << (PAGE_SHIFT - 9)) - 1)) << SECTOR_SHIFT);
 703 out_put_page:
 704         put_page(page);
 705 out:
 706         p->v = NULL;
 707         return NULL;
 708 }