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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 1991-1998 Linus Torvalds
4 * Re-organised Feb 1998 Russell King
5 */
6#include <linux/fs.h>
7#include <linux/slab.h>
8#include <linux/ctype.h>
9#include <linux/genhd.h>
10#include <linux/vmalloc.h>
11#include <linux/blktrace_api.h>
12#include <linux/raid/detect.h>
13#include "check.h"
14
15static int (*check_part[])(struct parsed_partitions *) = {
16 /*
17 * Probe partition formats with tables at disk address 0
18 * that also have an ADFS boot block at 0xdc0.
19 */
20#ifdef CONFIG_ACORN_PARTITION_ICS
21 adfspart_check_ICS,
22#endif
23#ifdef CONFIG_ACORN_PARTITION_POWERTEC
24 adfspart_check_POWERTEC,
25#endif
26#ifdef CONFIG_ACORN_PARTITION_EESOX
27 adfspart_check_EESOX,
28#endif
29
30 /*
31 * Now move on to formats that only have partition info at
32 * disk address 0xdc0. Since these may also have stale
33 * PC/BIOS partition tables, they need to come before
34 * the msdos entry.
35 */
36#ifdef CONFIG_ACORN_PARTITION_CUMANA
37 adfspart_check_CUMANA,
38#endif
39#ifdef CONFIG_ACORN_PARTITION_ADFS
40 adfspart_check_ADFS,
41#endif
42
43#ifdef CONFIG_CMDLINE_PARTITION
44 cmdline_partition,
45#endif
46#ifdef CONFIG_EFI_PARTITION
47 efi_partition, /* this must come before msdos */
48#endif
49#ifdef CONFIG_SGI_PARTITION
50 sgi_partition,
51#endif
52#ifdef CONFIG_LDM_PARTITION
53 ldm_partition, /* this must come before msdos */
54#endif
55#ifdef CONFIG_MSDOS_PARTITION
56 msdos_partition,
57#endif
58#ifdef CONFIG_OSF_PARTITION
59 osf_partition,
60#endif
61#ifdef CONFIG_SUN_PARTITION
62 sun_partition,
63#endif
64#ifdef CONFIG_AMIGA_PARTITION
65 amiga_partition,
66#endif
67#ifdef CONFIG_ATARI_PARTITION
68 atari_partition,
69#endif
70#ifdef CONFIG_MAC_PARTITION
71 mac_partition,
72#endif
73#ifdef CONFIG_ULTRIX_PARTITION
74 ultrix_partition,
75#endif
76#ifdef CONFIG_IBM_PARTITION
77 ibm_partition,
78#endif
79#ifdef CONFIG_KARMA_PARTITION
80 karma_partition,
81#endif
82#ifdef CONFIG_SYSV68_PARTITION
83 sysv68_partition,
84#endif
85 NULL
86};
87
88static struct parsed_partitions *allocate_partitions(struct gendisk *hd)
89{
90 struct parsed_partitions *state;
91 int nr;
92
93 state = kzalloc(sizeof(*state), GFP_KERNEL);
94 if (!state)
95 return NULL;
96
97 nr = disk_max_parts(hd);
98 state->parts = vzalloc(array_size(nr, sizeof(state->parts[0])));
99 if (!state->parts) {
100 kfree(state);
101 return NULL;
102 }
103
104 state->limit = nr;
105
106 return state;
107}
108
109static void free_partitions(struct parsed_partitions *state)
110{
111 vfree(state->parts);
112 kfree(state);
113}
114
115static struct parsed_partitions *check_partition(struct gendisk *hd,
116 struct block_device *bdev)
117{
118 struct parsed_partitions *state;
119 int i, res, err;
120
121 state = allocate_partitions(hd);
122 if (!state)
123 return NULL;
124 state->pp_buf = (char *)__get_free_page(GFP_KERNEL);
125 if (!state->pp_buf) {
126 free_partitions(state);
127 return NULL;
128 }
129 state->pp_buf[0] = '\0';
130
131 state->bdev = bdev;
132 disk_name(hd, 0, state->name);
133 snprintf(state->pp_buf, PAGE_SIZE, " %s:", state->name);
134 if (isdigit(state->name[strlen(state->name)-1]))
135 sprintf(state->name, "p");
136
137 i = res = err = 0;
138 while (!res && check_part[i]) {
139 memset(state->parts, 0, state->limit * sizeof(state->parts[0]));
140 res = check_part[i++](state);
141 if (res < 0) {
142 /*
143 * We have hit an I/O error which we don't report now.
144 * But record it, and let the others do their job.
145 */
146 err = res;
147 res = 0;
148 }
149
150 }
151 if (res > 0) {
152 printk(KERN_INFO "%s", state->pp_buf);
153
154 free_page((unsigned long)state->pp_buf);
155 return state;
156 }
157 if (state->access_beyond_eod)
158 err = -ENOSPC;
159 /*
160 * The partition is unrecognized. So report I/O errors if there were any
161 */
162 if (err)
163 res = err;
164 if (res) {
165 strlcat(state->pp_buf,
166 " unable to read partition table\n", PAGE_SIZE);
167 printk(KERN_INFO "%s", state->pp_buf);
168 }
169
170 free_page((unsigned long)state->pp_buf);
171 free_partitions(state);
172 return ERR_PTR(res);
173}
174
175static ssize_t part_partition_show(struct device *dev,
176 struct device_attribute *attr, char *buf)
177{
178 struct hd_struct *p = dev_to_part(dev);
179
180 return sprintf(buf, "%d\n", p->partno);
181}
182
183static ssize_t part_start_show(struct device *dev,
184 struct device_attribute *attr, char *buf)
185{
186 struct hd_struct *p = dev_to_part(dev);
187
188 return sprintf(buf, "%llu\n",(unsigned long long)p->start_sect);
189}
190
191static ssize_t part_ro_show(struct device *dev,
192 struct device_attribute *attr, char *buf)
193{
194 struct hd_struct *p = dev_to_part(dev);
195 return sprintf(buf, "%d\n", p->policy ? 1 : 0);
196}
197
198static ssize_t part_alignment_offset_show(struct device *dev,
199 struct device_attribute *attr, char *buf)
200{
201 struct hd_struct *p = dev_to_part(dev);
202 return sprintf(buf, "%llu\n", (unsigned long long)p->alignment_offset);
203}
204
205static ssize_t part_discard_alignment_show(struct device *dev,
206 struct device_attribute *attr, char *buf)
207{
208 struct hd_struct *p = dev_to_part(dev);
209 return sprintf(buf, "%u\n", p->discard_alignment);
210}
211
212static DEVICE_ATTR(partition, 0444, part_partition_show, NULL);
213static DEVICE_ATTR(start, 0444, part_start_show, NULL);
214static DEVICE_ATTR(size, 0444, part_size_show, NULL);
215static DEVICE_ATTR(ro, 0444, part_ro_show, NULL);
216static DEVICE_ATTR(alignment_offset, 0444, part_alignment_offset_show, NULL);
217static DEVICE_ATTR(discard_alignment, 0444, part_discard_alignment_show, NULL);
218static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
219static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
220#ifdef CONFIG_FAIL_MAKE_REQUEST
221static struct device_attribute dev_attr_fail =
222 __ATTR(make-it-fail, 0644, part_fail_show, part_fail_store);
223#endif
224
225static struct attribute *part_attrs[] = {
226 &dev_attr_partition.attr,
227 &dev_attr_start.attr,
228 &dev_attr_size.attr,
229 &dev_attr_ro.attr,
230 &dev_attr_alignment_offset.attr,
231 &dev_attr_discard_alignment.attr,
232 &dev_attr_stat.attr,
233 &dev_attr_inflight.attr,
234#ifdef CONFIG_FAIL_MAKE_REQUEST
235 &dev_attr_fail.attr,
236#endif
237 NULL
238};
239
240static struct attribute_group part_attr_group = {
241 .attrs = part_attrs,
242};
243
244static const struct attribute_group *part_attr_groups[] = {
245 &part_attr_group,
246#ifdef CONFIG_BLK_DEV_IO_TRACE
247 &blk_trace_attr_group,
248#endif
249 NULL
250};
251
252static void part_release(struct device *dev)
253{
254 struct hd_struct *p = dev_to_part(dev);
255 blk_free_devt(dev->devt);
256 hd_free_part(p);
257 kfree(p);
258}
259
260static int part_uevent(struct device *dev, struct kobj_uevent_env *env)
261{
262 struct hd_struct *part = dev_to_part(dev);
263
264 add_uevent_var(env, "PARTN=%u", part->partno);
265 if (part->info && part->info->volname[0])
266 add_uevent_var(env, "PARTNAME=%s", part->info->volname);
267 return 0;
268}
269
270struct device_type part_type = {
271 .name = "partition",
272 .groups = part_attr_groups,
273 .release = part_release,
274 .uevent = part_uevent,
275};
276
277static void hd_struct_free_work(struct work_struct *work)
278{
279 struct hd_struct *part =
280 container_of(to_rcu_work(work), struct hd_struct, rcu_work);
281 struct gendisk *disk = part_to_disk(part);
282
283 /*
284 * Release the disk reference acquired in delete_partition here.
285 * We can't release it in hd_struct_free because the final put_device
286 * needs process context and thus can't be run directly from a
287 * percpu_ref ->release handler.
288 */
289 put_device(disk_to_dev(disk));
290
291 part->start_sect = 0;
292 part->nr_sects = 0;
293 part_stat_set_all(part, 0);
294 put_device(part_to_dev(part));
295}
296
297static void hd_struct_free(struct percpu_ref *ref)
298{
299 struct hd_struct *part = container_of(ref, struct hd_struct, ref);
300 struct gendisk *disk = part_to_disk(part);
301 struct disk_part_tbl *ptbl =
302 rcu_dereference_protected(disk->part_tbl, 1);
303
304 rcu_assign_pointer(ptbl->last_lookup, NULL);
305
306 INIT_RCU_WORK(&part->rcu_work, hd_struct_free_work);
307 queue_rcu_work(system_wq, &part->rcu_work);
308}
309
310int hd_ref_init(struct hd_struct *part)
311{
312 if (percpu_ref_init(&part->ref, hd_struct_free, 0, GFP_KERNEL))
313 return -ENOMEM;
314 return 0;
315}
316
317/*
318 * Must be called either with bd_mutex held, before a disk can be opened or
319 * after all disk users are gone.
320 */
321void delete_partition(struct gendisk *disk, struct hd_struct *part)
322{
323 struct disk_part_tbl *ptbl =
324 rcu_dereference_protected(disk->part_tbl, 1);
325
326 /*
327 * ->part_tbl is referenced in this part's release handler, so
328 * we have to hold the disk device
329 */
330 get_device(disk_to_dev(part_to_disk(part)));
331 rcu_assign_pointer(ptbl->part[part->partno], NULL);
332 kobject_put(part->holder_dir);
333 device_del(part_to_dev(part));
334
335 /*
336 * Remove gendisk pointer from idr so that it cannot be looked up
337 * while RCU period before freeing gendisk is running to prevent
338 * use-after-free issues. Note that the device number stays
339 * "in-use" until we really free the gendisk.
340 */
341 blk_invalidate_devt(part_devt(part));
342 percpu_ref_kill(&part->ref);
343}
344
345static ssize_t whole_disk_show(struct device *dev,
346 struct device_attribute *attr, char *buf)
347{
348 return 0;
349}
350static DEVICE_ATTR(whole_disk, 0444, whole_disk_show, NULL);
351
352/*
353 * Must be called either with bd_mutex held, before a disk can be opened or
354 * after all disk users are gone.
355 */
356static struct hd_struct *add_partition(struct gendisk *disk, int partno,
357 sector_t start, sector_t len, int flags,
358 struct partition_meta_info *info)
359{
360 struct hd_struct *p;
361 dev_t devt = MKDEV(0, 0);
362 struct device *ddev = disk_to_dev(disk);
363 struct device *pdev;
364 struct disk_part_tbl *ptbl;
365 const char *dname;
366 int err;
367
368 /*
369 * Partitions are not supported on zoned block devices that are used as
370 * such.
371 */
372 switch (disk->queue->limits.zoned) {
373 case BLK_ZONED_HM:
374 pr_warn("%s: partitions not supported on host managed zoned block device\n",
375 disk->disk_name);
376 return ERR_PTR(-ENXIO);
377 case BLK_ZONED_HA:
378 pr_info("%s: disabling host aware zoned block device support due to partitions\n",
379 disk->disk_name);
380 disk->queue->limits.zoned = BLK_ZONED_NONE;
381 break;
382 case BLK_ZONED_NONE:
383 break;
384 }
385
386 err = disk_expand_part_tbl(disk, partno);
387 if (err)
388 return ERR_PTR(err);
389 ptbl = rcu_dereference_protected(disk->part_tbl, 1);
390
391 if (ptbl->part[partno])
392 return ERR_PTR(-EBUSY);
393
394 p = kzalloc(sizeof(*p), GFP_KERNEL);
395 if (!p)
396 return ERR_PTR(-EBUSY);
397
398 p->dkstats = alloc_percpu(struct disk_stats);
399 if (!p->dkstats) {
400 err = -ENOMEM;
401 goto out_free;
402 }
403
404 hd_sects_seq_init(p);
405 pdev = part_to_dev(p);
406
407 p->start_sect = start;
408 p->alignment_offset =
409 queue_limit_alignment_offset(&disk->queue->limits, start);
410 p->discard_alignment =
411 queue_limit_discard_alignment(&disk->queue->limits, start);
412 p->nr_sects = len;
413 p->partno = partno;
414 p->policy = get_disk_ro(disk);
415
416 if (info) {
417 struct partition_meta_info *pinfo;
418
419 pinfo = kzalloc_node(sizeof(*pinfo), GFP_KERNEL, disk->node_id);
420 if (!pinfo) {
421 err = -ENOMEM;
422 goto out_free_stats;
423 }
424 memcpy(pinfo, info, sizeof(*info));
425 p->info = pinfo;
426 }
427
428 dname = dev_name(ddev);
429 if (isdigit(dname[strlen(dname) - 1]))
430 dev_set_name(pdev, "%sp%d", dname, partno);
431 else
432 dev_set_name(pdev, "%s%d", dname, partno);
433
434 device_initialize(pdev);
435 pdev->class = &block_class;
436 pdev->type = &part_type;
437 pdev->parent = ddev;
438
439 err = blk_alloc_devt(p, &devt);
440 if (err)
441 goto out_free_info;
442 pdev->devt = devt;
443
444 /* delay uevent until 'holders' subdir is created */
445 dev_set_uevent_suppress(pdev, 1);
446 err = device_add(pdev);
447 if (err)
448 goto out_put;
449
450 err = -ENOMEM;
451 p->holder_dir = kobject_create_and_add("holders", &pdev->kobj);
452 if (!p->holder_dir)
453 goto out_del;
454
455 dev_set_uevent_suppress(pdev, 0);
456 if (flags & ADDPART_FLAG_WHOLEDISK) {
457 err = device_create_file(pdev, &dev_attr_whole_disk);
458 if (err)
459 goto out_del;
460 }
461
462 err = hd_ref_init(p);
463 if (err) {
464 if (flags & ADDPART_FLAG_WHOLEDISK)
465 goto out_remove_file;
466 goto out_del;
467 }
468
469 /* everything is up and running, commence */
470 rcu_assign_pointer(ptbl->part[partno], p);
471
472 /* suppress uevent if the disk suppresses it */
473 if (!dev_get_uevent_suppress(ddev))
474 kobject_uevent(&pdev->kobj, KOBJ_ADD);
475 return p;
476
477out_free_info:
478 kfree(p->info);
479out_free_stats:
480 free_percpu(p->dkstats);
481out_free:
482 kfree(p);
483 return ERR_PTR(err);
484out_remove_file:
485 device_remove_file(pdev, &dev_attr_whole_disk);
486out_del:
487 kobject_put(p->holder_dir);
488 device_del(pdev);
489out_put:
490 put_device(pdev);
491 return ERR_PTR(err);
492}
493
494static bool partition_overlaps(struct gendisk *disk, sector_t start,
495 sector_t length, int skip_partno)
496{
497 struct disk_part_iter piter;
498 struct hd_struct *part;
499 bool overlap = false;
500
501 disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
502 while ((part = disk_part_iter_next(&piter))) {
503 if (part->partno == skip_partno ||
504 start >= part->start_sect + part->nr_sects ||
505 start + length <= part->start_sect)
506 continue;
507 overlap = true;
508 break;
509 }
510
511 disk_part_iter_exit(&piter);
512 return overlap;
513}
514
515int bdev_add_partition(struct block_device *bdev, int partno,
516 sector_t start, sector_t length)
517{
518 struct hd_struct *part;
519
520 mutex_lock(&bdev->bd_mutex);
521 if (partition_overlaps(bdev->bd_disk, start, length, -1)) {
522 mutex_unlock(&bdev->bd_mutex);
523 return -EBUSY;
524 }
525
526 part = add_partition(bdev->bd_disk, partno, start, length,
527 ADDPART_FLAG_NONE, NULL);
528 mutex_unlock(&bdev->bd_mutex);
529 return PTR_ERR_OR_ZERO(part);
530}
531
532int bdev_del_partition(struct block_device *bdev, int partno)
533{
534 struct block_device *bdevp;
535 struct hd_struct *part = NULL;
536 int ret;
537
538 bdevp = bdget_disk(bdev->bd_disk, partno);
539 if (!bdevp)
540 return -ENXIO;
541
542 mutex_lock(&bdevp->bd_mutex);
543 mutex_lock_nested(&bdev->bd_mutex, 1);
544
545 ret = -ENXIO;
546 part = disk_get_part(bdev->bd_disk, partno);
547 if (!part)
548 goto out_unlock;
549
550 ret = -EBUSY;
551 if (bdevp->bd_openers)
552 goto out_unlock;
553
554 sync_blockdev(bdevp);
555 invalidate_bdev(bdevp);
556
557 delete_partition(bdev->bd_disk, part);
558 ret = 0;
559out_unlock:
560 mutex_unlock(&bdev->bd_mutex);
561 mutex_unlock(&bdevp->bd_mutex);
562 bdput(bdevp);
563 if (part)
564 disk_put_part(part);
565 return ret;
566}
567
568int bdev_resize_partition(struct block_device *bdev, int partno,
569 sector_t start, sector_t length)
570{
571 struct block_device *bdevp;
572 struct hd_struct *part;
573 int ret = 0;
574
575 part = disk_get_part(bdev->bd_disk, partno);
576 if (!part)
577 return -ENXIO;
578
579 ret = -ENOMEM;
580 bdevp = bdget(part_devt(part));
581 if (!bdevp)
582 goto out_put_part;
583
584 mutex_lock(&bdevp->bd_mutex);
585 mutex_lock_nested(&bdev->bd_mutex, 1);
586
587 ret = -EINVAL;
588 if (start != part->start_sect)
589 goto out_unlock;
590
591 ret = -EBUSY;
592 if (partition_overlaps(bdev->bd_disk, start, length, partno))
593 goto out_unlock;
594
595 part_nr_sects_write(part, (sector_t)length);
596 i_size_write(bdevp->bd_inode, length << SECTOR_SHIFT);
597
598 ret = 0;
599out_unlock:
600 mutex_unlock(&bdevp->bd_mutex);
601 mutex_unlock(&bdev->bd_mutex);
602 bdput(bdevp);
603out_put_part:
604 disk_put_part(part);
605 return ret;
606}
607
608static bool disk_unlock_native_capacity(struct gendisk *disk)
609{
610 const struct block_device_operations *bdops = disk->fops;
611
612 if (bdops->unlock_native_capacity &&
613 !(disk->flags & GENHD_FL_NATIVE_CAPACITY)) {
614 printk(KERN_CONT "enabling native capacity\n");
615 bdops->unlock_native_capacity(disk);
616 disk->flags |= GENHD_FL_NATIVE_CAPACITY;
617 return true;
618 } else {
619 printk(KERN_CONT "truncated\n");
620 return false;
621 }
622}
623
624int blk_drop_partitions(struct block_device *bdev)
625{
626 struct disk_part_iter piter;
627 struct hd_struct *part;
628
629 if (bdev->bd_part_count)
630 return -EBUSY;
631
632 sync_blockdev(bdev);
633 invalidate_bdev(bdev);
634
635 disk_part_iter_init(&piter, bdev->bd_disk, DISK_PITER_INCL_EMPTY);
636 while ((part = disk_part_iter_next(&piter)))
637 delete_partition(bdev->bd_disk, part);
638 disk_part_iter_exit(&piter);
639
640 return 0;
641}
642#ifdef CONFIG_S390
643/* for historic reasons in the DASD driver */
644EXPORT_SYMBOL_GPL(blk_drop_partitions);
645#endif
646
647static bool blk_add_partition(struct gendisk *disk, struct block_device *bdev,
648 struct parsed_partitions *state, int p)
649{
650 sector_t size = state->parts[p].size;
651 sector_t from = state->parts[p].from;
652 struct hd_struct *part;
653
654 if (!size)
655 return true;
656
657 if (from >= get_capacity(disk)) {
658 printk(KERN_WARNING
659 "%s: p%d start %llu is beyond EOD, ",
660 disk->disk_name, p, (unsigned long long) from);
661 if (disk_unlock_native_capacity(disk))
662 return false;
663 return true;
664 }
665
666 if (from + size > get_capacity(disk)) {
667 printk(KERN_WARNING
668 "%s: p%d size %llu extends beyond EOD, ",
669 disk->disk_name, p, (unsigned long long) size);
670
671 if (disk_unlock_native_capacity(disk))
672 return false;
673
674 /*
675 * We can not ignore partitions of broken tables created by for
676 * example camera firmware, but we limit them to the end of the
677 * disk to avoid creating invalid block devices.
678 */
679 size = get_capacity(disk) - from;
680 }
681
682 part = add_partition(disk, p, from, size, state->parts[p].flags,
683 &state->parts[p].info);
684 if (IS_ERR(part) && PTR_ERR(part) != -ENXIO) {
685 printk(KERN_ERR " %s: p%d could not be added: %ld\n",
686 disk->disk_name, p, -PTR_ERR(part));
687 return true;
688 }
689
690 if (IS_BUILTIN(CONFIG_BLK_DEV_MD) &&
691 (state->parts[p].flags & ADDPART_FLAG_RAID))
692 md_autodetect_dev(part_to_dev(part)->devt);
693
694 return true;
695}
696
697int blk_add_partitions(struct gendisk *disk, struct block_device *bdev)
698{
699 struct parsed_partitions *state;
700 int ret = -EAGAIN, p, highest;
701
702 if (!disk_part_scan_enabled(disk))
703 return 0;
704
705 state = check_partition(disk, bdev);
706 if (!state)
707 return 0;
708 if (IS_ERR(state)) {
709 /*
710 * I/O error reading the partition table. If we tried to read
711 * beyond EOD, retry after unlocking the native capacity.
712 */
713 if (PTR_ERR(state) == -ENOSPC) {
714 printk(KERN_WARNING "%s: partition table beyond EOD, ",
715 disk->disk_name);
716 if (disk_unlock_native_capacity(disk))
717 return -EAGAIN;
718 }
719 return -EIO;
720 }
721
722 /*
723 * Partitions are not supported on host managed zoned block devices.
724 */
725 if (disk->queue->limits.zoned == BLK_ZONED_HM) {
726 pr_warn("%s: ignoring partition table on host managed zoned block device\n",
727 disk->disk_name);
728 ret = 0;
729 goto out_free_state;
730 }
731
732 /*
733 * If we read beyond EOD, try unlocking native capacity even if the
734 * partition table was successfully read as we could be missing some
735 * partitions.
736 */
737 if (state->access_beyond_eod) {
738 printk(KERN_WARNING
739 "%s: partition table partially beyond EOD, ",
740 disk->disk_name);
741 if (disk_unlock_native_capacity(disk))
742 goto out_free_state;
743 }
744
745 /* tell userspace that the media / partition table may have changed */
746 kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
747
748 /*
749 * Detect the highest partition number and preallocate disk->part_tbl.
750 * This is an optimization and not strictly necessary.
751 */
752 for (p = 1, highest = 0; p < state->limit; p++)
753 if (state->parts[p].size)
754 highest = p;
755 disk_expand_part_tbl(disk, highest);
756
757 for (p = 1; p < state->limit; p++)
758 if (!blk_add_partition(disk, bdev, state, p))
759 goto out_free_state;
760
761 ret = 0;
762out_free_state:
763 free_partitions(state);
764 return ret;
765}
766
767void *read_part_sector(struct parsed_partitions *state, sector_t n, Sector *p)
768{
769 struct address_space *mapping = state->bdev->bd_inode->i_mapping;
770 struct page *page;
771
772 if (n >= get_capacity(state->bdev->bd_disk)) {
773 state->access_beyond_eod = true;
774 return NULL;
775 }
776
777 page = read_mapping_page(mapping,
778 (pgoff_t)(n >> (PAGE_SHIFT - 9)), NULL);
779 if (IS_ERR(page))
780 goto out;
781 if (PageError(page))
782 goto out_put_page;
783
784 p->v = page;
785 return (unsigned char *)page_address(page) +
786 ((n & ((1 << (PAGE_SHIFT - 9)) - 1)) << SECTOR_SHIFT);
787out_put_page:
788 put_page(page);
789out:
790 p->v = NULL;
791 return NULL;
792}