xref: /linux/block/partitions/core.c (revision cdd30ebb1b9f36159d66f088b61aee264e649d7a) 
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/major.h>
9 #include <linux/slab.h>
10 #include <linux/ctype.h>
11 #include <linux/vmalloc.h>
12 #include <linux/raid/detect.h>
13 #include "check.h"
14 
15 static int (*const 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_OF_PARTITION
47 	of_partition,		/* cmdline have priority to OF */
48 #endif
49 #ifdef CONFIG_EFI_PARTITION
50 	efi_partition,		/* this must come before msdos */
51 #endif
52 #ifdef CONFIG_SGI_PARTITION
53 	sgi_partition,
54 #endif
55 #ifdef CONFIG_LDM_PARTITION
56 	ldm_partition,		/* this must come before msdos */
57 #endif
58 #ifdef CONFIG_MSDOS_PARTITION
59 	msdos_partition,
60 #endif
61 #ifdef CONFIG_OSF_PARTITION
62 	osf_partition,
63 #endif
64 #ifdef CONFIG_SUN_PARTITION
65 	sun_partition,
66 #endif
67 #ifdef CONFIG_AMIGA_PARTITION
68 	amiga_partition,
69 #endif
70 #ifdef CONFIG_ATARI_PARTITION
71 	atari_partition,
72 #endif
73 #ifdef CONFIG_MAC_PARTITION
74 	mac_partition,
75 #endif
76 #ifdef CONFIG_ULTRIX_PARTITION
77 	ultrix_partition,
78 #endif
79 #ifdef CONFIG_IBM_PARTITION
80 	ibm_partition,
81 #endif
82 #ifdef CONFIG_KARMA_PARTITION
83 	karma_partition,
84 #endif
85 #ifdef CONFIG_SYSV68_PARTITION
86 	sysv68_partition,
87 #endif
88 	NULL
89 };
90 
91 static struct parsed_partitions *allocate_partitions(struct gendisk *hd)
92 {
93 	struct parsed_partitions *state;
94 	int nr = DISK_MAX_PARTS;
95 
96 	state = kzalloc(sizeof(*state), GFP_KERNEL);
97 	if (!state)
98 		return NULL;
99 
100 	state->parts = vzalloc(array_size(nr, sizeof(state->parts[0])));
101 	if (!state->parts) {
102 		kfree(state);
103 		return NULL;
104 	}
105 
106 	state->limit = nr;
107 
108 	return state;
109 }
110 
111 static void free_partitions(struct parsed_partitions *state)
112 {
113 	vfree(state->parts);
114 	kfree(state);
115 }
116 
117 static struct parsed_partitions *check_partition(struct gendisk *hd)
118 {
119 	struct parsed_partitions *state;
120 	int i, res, err;
121 
122 	state = allocate_partitions(hd);
123 	if (!state)
124 		return NULL;
125 	state->pp_buf = (char *)__get_free_page(GFP_KERNEL);
126 	if (!state->pp_buf) {
127 		free_partitions(state);
128 		return NULL;
129 	}
130 	state->pp_buf[0] = '\0';
131 
132 	state->disk = hd;
133 	snprintf(state->name, BDEVNAME_SIZE, "%s", hd->disk_name);
134 	snprintf(state->pp_buf, PAGE_SIZE, " %s:", state->name);
135 	if (isdigit(state->name[strlen(state->name)-1]))
136 		sprintf(state->name, "p");
137 
138 	i = res = err = 0;
139 	while (!res && check_part[i]) {
140 		memset(state->parts, 0, state->limit * sizeof(state->parts[0]));
141 		res = check_part[i++](state);
142 		if (res < 0) {
143 			/*
144 			 * We have hit an I/O error which we don't report now.
145 			 * But record it, and let the others do their job.
146 			 */
147 			err = res;
148 			res = 0;
149 		}
150 
151 	}
152 	if (res > 0) {
153 		printk(KERN_INFO "%s", state->pp_buf);
154 
155 		free_page((unsigned long)state->pp_buf);
156 		return state;
157 	}
158 	if (state->access_beyond_eod)
159 		err = -ENOSPC;
160 	/*
161 	 * The partition is unrecognized. So report I/O errors if there were any
162 	 */
163 	if (err)
164 		res = err;
165 	if (res) {
166 		strlcat(state->pp_buf,
167 			" unable to read partition table\n", PAGE_SIZE);
168 		printk(KERN_INFO "%s", state->pp_buf);
169 	}
170 
171 	free_page((unsigned long)state->pp_buf);
172 	free_partitions(state);
173 	return ERR_PTR(res);
174 }
175 
176 static ssize_t part_partition_show(struct device *dev,
177 				   struct device_attribute *attr, char *buf)
178 {
179 	return sprintf(buf, "%d\n", bdev_partno(dev_to_bdev(dev)));
180 }
181 
182 static ssize_t part_start_show(struct device *dev,
183 			       struct device_attribute *attr, char *buf)
184 {
185 	return sprintf(buf, "%llu\n", dev_to_bdev(dev)->bd_start_sect);
186 }
187 
188 static ssize_t part_ro_show(struct device *dev,
189 			    struct device_attribute *attr, char *buf)
190 {
191 	return sprintf(buf, "%d\n", bdev_read_only(dev_to_bdev(dev)));
192 }
193 
194 static ssize_t part_alignment_offset_show(struct device *dev,
195 					  struct device_attribute *attr, char *buf)
196 {
197 	return sprintf(buf, "%u\n", bdev_alignment_offset(dev_to_bdev(dev)));
198 }
199 
200 static ssize_t part_discard_alignment_show(struct device *dev,
201 					   struct device_attribute *attr, char *buf)
202 {
203 	return sprintf(buf, "%u\n", bdev_discard_alignment(dev_to_bdev(dev)));
204 }
205 
206 static DEVICE_ATTR(partition, 0444, part_partition_show, NULL);
207 static DEVICE_ATTR(start, 0444, part_start_show, NULL);
208 static DEVICE_ATTR(size, 0444, part_size_show, NULL);
209 static DEVICE_ATTR(ro, 0444, part_ro_show, NULL);
210 static DEVICE_ATTR(alignment_offset, 0444, part_alignment_offset_show, NULL);
211 static DEVICE_ATTR(discard_alignment, 0444, part_discard_alignment_show, NULL);
212 static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
213 static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
214 #ifdef CONFIG_FAIL_MAKE_REQUEST
215 static struct device_attribute dev_attr_fail =
216 	__ATTR(make-it-fail, 0644, part_fail_show, part_fail_store);
217 #endif
218 
219 static struct attribute *part_attrs[] = {
220 	&dev_attr_partition.attr,
221 	&dev_attr_start.attr,
222 	&dev_attr_size.attr,
223 	&dev_attr_ro.attr,
224 	&dev_attr_alignment_offset.attr,
225 	&dev_attr_discard_alignment.attr,
226 	&dev_attr_stat.attr,
227 	&dev_attr_inflight.attr,
228 #ifdef CONFIG_FAIL_MAKE_REQUEST
229 	&dev_attr_fail.attr,
230 #endif
231 	NULL
232 };
233 
234 static const struct attribute_group part_attr_group = {
235 	.attrs = part_attrs,
236 };
237 
238 static const struct attribute_group *part_attr_groups[] = {
239 	&part_attr_group,
240 #ifdef CONFIG_BLK_DEV_IO_TRACE
241 	&blk_trace_attr_group,
242 #endif
243 	NULL
244 };
245 
246 static void part_release(struct device *dev)
247 {
248 	put_disk(dev_to_bdev(dev)->bd_disk);
249 	bdev_drop(dev_to_bdev(dev));
250 }
251 
252 static int part_uevent(const struct device *dev, struct kobj_uevent_env *env)
253 {
254 	const struct block_device *part = dev_to_bdev(dev);
255 
256 	add_uevent_var(env, "PARTN=%u", bdev_partno(part));
257 	if (part->bd_meta_info && part->bd_meta_info->volname[0])
258 		add_uevent_var(env, "PARTNAME=%s", part->bd_meta_info->volname);
259 	if (part->bd_meta_info && part->bd_meta_info->uuid[0])
260 		add_uevent_var(env, "PARTUUID=%s", part->bd_meta_info->uuid);
261 	return 0;
262 }
263 
264 const struct device_type part_type = {
265 	.name		= "partition",
266 	.groups		= part_attr_groups,
267 	.release	= part_release,
268 	.uevent		= part_uevent,
269 };
270 
271 void drop_partition(struct block_device *part)
272 {
273 	lockdep_assert_held(&part->bd_disk->open_mutex);
274 
275 	xa_erase(&part->bd_disk->part_tbl, bdev_partno(part));
276 	kobject_put(part->bd_holder_dir);
277 
278 	device_del(&part->bd_device);
279 	put_device(&part->bd_device);
280 }
281 
282 static ssize_t whole_disk_show(struct device *dev,
283 			       struct device_attribute *attr, char *buf)
284 {
285 	return 0;
286 }
287 static const DEVICE_ATTR(whole_disk, 0444, whole_disk_show, NULL);
288 
289 /*
290  * Must be called either with open_mutex held, before a disk can be opened or
291  * after all disk users are gone.
292  */
293 static struct block_device *add_partition(struct gendisk *disk, int partno,
294 				sector_t start, sector_t len, int flags,
295 				struct partition_meta_info *info)
296 {
297 	dev_t devt = MKDEV(0, 0);
298 	struct device *ddev = disk_to_dev(disk);
299 	struct device *pdev;
300 	struct block_device *bdev;
301 	const char *dname;
302 	int err;
303 
304 	lockdep_assert_held(&disk->open_mutex);
305 
306 	if (partno >= DISK_MAX_PARTS)
307 		return ERR_PTR(-EINVAL);
308 
309 	/*
310 	 * Partitions are not supported on zoned block devices that are used as
311 	 * such.
312 	 */
313 	if (bdev_is_zoned(disk->part0)) {
314 		pr_warn("%s: partitions not supported on host managed zoned block device\n",
315 			disk->disk_name);
316 		return ERR_PTR(-ENXIO);
317 	}
318 
319 	if (xa_load(&disk->part_tbl, partno))
320 		return ERR_PTR(-EBUSY);
321 
322 	/* ensure we always have a reference to the whole disk */
323 	get_device(disk_to_dev(disk));
324 
325 	err = -ENOMEM;
326 	bdev = bdev_alloc(disk, partno);
327 	if (!bdev)
328 		goto out_put_disk;
329 
330 	bdev->bd_start_sect = start;
331 	bdev_set_nr_sectors(bdev, len);
332 
333 	pdev = &bdev->bd_device;
334 	dname = dev_name(ddev);
335 	if (isdigit(dname[strlen(dname) - 1]))
336 		dev_set_name(pdev, "%sp%d", dname, partno);
337 	else
338 		dev_set_name(pdev, "%s%d", dname, partno);
339 
340 	device_initialize(pdev);
341 	pdev->class = &block_class;
342 	pdev->type = &part_type;
343 	pdev->parent = ddev;
344 
345 	/* in consecutive minor range? */
346 	if (bdev_partno(bdev) < disk->minors) {
347 		devt = MKDEV(disk->major, disk->first_minor + bdev_partno(bdev));
348 	} else {
349 		err = blk_alloc_ext_minor();
350 		if (err < 0)
351 			goto out_put;
352 		devt = MKDEV(BLOCK_EXT_MAJOR, err);
353 	}
354 	pdev->devt = devt;
355 
356 	if (info) {
357 		err = -ENOMEM;
358 		bdev->bd_meta_info = kmemdup(info, sizeof(*info), GFP_KERNEL);
359 		if (!bdev->bd_meta_info)
360 			goto out_put;
361 	}
362 
363 	/* delay uevent until 'holders' subdir is created */
364 	dev_set_uevent_suppress(pdev, 1);
365 	err = device_add(pdev);
366 	if (err)
367 		goto out_put;
368 
369 	err = -ENOMEM;
370 	bdev->bd_holder_dir = kobject_create_and_add("holders", &pdev->kobj);
371 	if (!bdev->bd_holder_dir)
372 		goto out_del;
373 
374 	dev_set_uevent_suppress(pdev, 0);
375 	if (flags & ADDPART_FLAG_WHOLEDISK) {
376 		err = device_create_file(pdev, &dev_attr_whole_disk);
377 		if (err)
378 			goto out_del;
379 	}
380 
381 	if (flags & ADDPART_FLAG_READONLY)
382 		bdev_set_flag(bdev, BD_READ_ONLY);
383 
384 	/* everything is up and running, commence */
385 	err = xa_insert(&disk->part_tbl, partno, bdev, GFP_KERNEL);
386 	if (err)
387 		goto out_del;
388 	bdev_add(bdev, devt);
389 
390 	/* suppress uevent if the disk suppresses it */
391 	if (!dev_get_uevent_suppress(ddev))
392 		kobject_uevent(&pdev->kobj, KOBJ_ADD);
393 	return bdev;
394 
395 out_del:
396 	kobject_put(bdev->bd_holder_dir);
397 	device_del(pdev);
398 out_put:
399 	put_device(pdev);
400 	return ERR_PTR(err);
401 out_put_disk:
402 	put_disk(disk);
403 	return ERR_PTR(err);
404 }
405 
406 static bool partition_overlaps(struct gendisk *disk, sector_t start,
407 		sector_t length, int skip_partno)
408 {
409 	struct block_device *part;
410 	bool overlap = false;
411 	unsigned long idx;
412 
413 	rcu_read_lock();
414 	xa_for_each_start(&disk->part_tbl, idx, part, 1) {
415 		if (bdev_partno(part) != skip_partno &&
416 		    start < part->bd_start_sect + bdev_nr_sectors(part) &&
417 		    start + length > part->bd_start_sect) {
418 			overlap = true;
419 			break;
420 		}
421 	}
422 	rcu_read_unlock();
423 
424 	return overlap;
425 }
426 
427 int bdev_add_partition(struct gendisk *disk, int partno, sector_t start,
428 		sector_t length)
429 {
430 	struct block_device *part;
431 	int ret;
432 
433 	mutex_lock(&disk->open_mutex);
434 	if (!disk_live(disk)) {
435 		ret = -ENXIO;
436 		goto out;
437 	}
438 
439 	if (disk->flags & GENHD_FL_NO_PART) {
440 		ret = -EINVAL;
441 		goto out;
442 	}
443 
444 	if (partition_overlaps(disk, start, length, -1)) {
445 		ret = -EBUSY;
446 		goto out;
447 	}
448 
449 	part = add_partition(disk, partno, start, length,
450 			ADDPART_FLAG_NONE, NULL);
451 	ret = PTR_ERR_OR_ZERO(part);
452 out:
453 	mutex_unlock(&disk->open_mutex);
454 	return ret;
455 }
456 
457 int bdev_del_partition(struct gendisk *disk, int partno)
458 {
459 	struct block_device *part = NULL;
460 	int ret = -ENXIO;
461 
462 	mutex_lock(&disk->open_mutex);
463 	part = xa_load(&disk->part_tbl, partno);
464 	if (!part)
465 		goto out_unlock;
466 
467 	ret = -EBUSY;
468 	if (atomic_read(&part->bd_openers))
469 		goto out_unlock;
470 
471 	/*
472 	 * We verified that @part->bd_openers is zero above and so
473 	 * @part->bd_holder{_ops} can't be set. And since we hold
474 	 * @disk->open_mutex the device can't be claimed by anyone.
475 	 *
476 	 * So no need to call @part->bd_holder_ops->mark_dead() here.
477 	 * Just delete the partition and invalidate it.
478 	 */
479 
480 	bdev_unhash(part);
481 	invalidate_bdev(part);
482 	drop_partition(part);
483 	ret = 0;
484 out_unlock:
485 	mutex_unlock(&disk->open_mutex);
486 	return ret;
487 }
488 
489 int bdev_resize_partition(struct gendisk *disk, int partno, sector_t start,
490 		sector_t length)
491 {
492 	struct block_device *part = NULL;
493 	int ret = -ENXIO;
494 
495 	mutex_lock(&disk->open_mutex);
496 	part = xa_load(&disk->part_tbl, partno);
497 	if (!part)
498 		goto out_unlock;
499 
500 	ret = -EINVAL;
501 	if (start != part->bd_start_sect)
502 		goto out_unlock;
503 
504 	ret = -EBUSY;
505 	if (partition_overlaps(disk, start, length, partno))
506 		goto out_unlock;
507 
508 	bdev_set_nr_sectors(part, length);
509 
510 	ret = 0;
511 out_unlock:
512 	mutex_unlock(&disk->open_mutex);
513 	return ret;
514 }
515 
516 static bool disk_unlock_native_capacity(struct gendisk *disk)
517 {
518 	if (!disk->fops->unlock_native_capacity ||
519 	    test_and_set_bit(GD_NATIVE_CAPACITY, &disk->state)) {
520 		printk(KERN_CONT "truncated\n");
521 		return false;
522 	}
523 
524 	printk(KERN_CONT "enabling native capacity\n");
525 	disk->fops->unlock_native_capacity(disk);
526 	return true;
527 }
528 
529 static bool blk_add_partition(struct gendisk *disk,
530 		struct parsed_partitions *state, int p)
531 {
532 	sector_t size = state->parts[p].size;
533 	sector_t from = state->parts[p].from;
534 	struct block_device *part;
535 
536 	if (!size)
537 		return true;
538 
539 	if (from >= get_capacity(disk)) {
540 		printk(KERN_WARNING
541 		       "%s: p%d start %llu is beyond EOD, ",
542 		       disk->disk_name, p, (unsigned long long) from);
543 		if (disk_unlock_native_capacity(disk))
544 			return false;
545 		return true;
546 	}
547 
548 	if (from + size > get_capacity(disk)) {
549 		printk(KERN_WARNING
550 		       "%s: p%d size %llu extends beyond EOD, ",
551 		       disk->disk_name, p, (unsigned long long) size);
552 
553 		if (disk_unlock_native_capacity(disk))
554 			return false;
555 
556 		/*
557 		 * We can not ignore partitions of broken tables created by for
558 		 * example camera firmware, but we limit them to the end of the
559 		 * disk to avoid creating invalid block devices.
560 		 */
561 		size = get_capacity(disk) - from;
562 	}
563 
564 	part = add_partition(disk, p, from, size, state->parts[p].flags,
565 			     &state->parts[p].info);
566 	if (IS_ERR(part)) {
567 		if (PTR_ERR(part) != -ENXIO) {
568 			printk(KERN_ERR " %s: p%d could not be added: %pe\n",
569 			       disk->disk_name, p, part);
570 		}
571 		return true;
572 	}
573 
574 	if (IS_BUILTIN(CONFIG_BLK_DEV_MD) &&
575 	    (state->parts[p].flags & ADDPART_FLAG_RAID))
576 		md_autodetect_dev(part->bd_dev);
577 
578 	return true;
579 }
580 
581 static int blk_add_partitions(struct gendisk *disk)
582 {
583 	struct parsed_partitions *state;
584 	int ret = -EAGAIN, p;
585 
586 	if (!disk_has_partscan(disk))
587 		return 0;
588 
589 	state = check_partition(disk);
590 	if (!state)
591 		return 0;
592 	if (IS_ERR(state)) {
593 		/*
594 		 * I/O error reading the partition table.  If we tried to read
595 		 * beyond EOD, retry after unlocking the native capacity.
596 		 */
597 		if (PTR_ERR(state) == -ENOSPC) {
598 			printk(KERN_WARNING "%s: partition table beyond EOD, ",
599 			       disk->disk_name);
600 			if (disk_unlock_native_capacity(disk))
601 				return -EAGAIN;
602 		}
603 		return -EIO;
604 	}
605 
606 	/*
607 	 * Partitions are not supported on host managed zoned block devices.
608 	 */
609 	if (bdev_is_zoned(disk->part0)) {
610 		pr_warn("%s: ignoring partition table on host managed zoned block device\n",
611 			disk->disk_name);
612 		ret = 0;
613 		goto out_free_state;
614 	}
615 
616 	/*
617 	 * If we read beyond EOD, try unlocking native capacity even if the
618 	 * partition table was successfully read as we could be missing some
619 	 * partitions.
620 	 */
621 	if (state->access_beyond_eod) {
622 		printk(KERN_WARNING
623 		       "%s: partition table partially beyond EOD, ",
624 		       disk->disk_name);
625 		if (disk_unlock_native_capacity(disk))
626 			goto out_free_state;
627 	}
628 
629 	/* tell userspace that the media / partition table may have changed */
630 	kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
631 
632 	for (p = 1; p < state->limit; p++)
633 		if (!blk_add_partition(disk, state, p))
634 			goto out_free_state;
635 
636 	ret = 0;
637 out_free_state:
638 	free_partitions(state);
639 	return ret;
640 }
641 
642 int bdev_disk_changed(struct gendisk *disk, bool invalidate)
643 {
644 	struct block_device *part;
645 	unsigned long idx;
646 	int ret = 0;
647 
648 	lockdep_assert_held(&disk->open_mutex);
649 
650 	if (!disk_live(disk))
651 		return -ENXIO;
652 
653 rescan:
654 	if (disk->open_partitions)
655 		return -EBUSY;
656 	sync_blockdev(disk->part0);
657 	invalidate_bdev(disk->part0);
658 
659 	xa_for_each_start(&disk->part_tbl, idx, part, 1) {
660 		/*
661 		 * Remove the block device from the inode hash, so that
662 		 * it cannot be looked up any more even when openers
663 		 * still hold references.
664 		 */
665 		bdev_unhash(part);
666 
667 		/*
668 		 * If @disk->open_partitions isn't elevated but there's
669 		 * still an active holder of that block device things
670 		 * are broken.
671 		 */
672 		WARN_ON_ONCE(atomic_read(&part->bd_openers));
673 		invalidate_bdev(part);
674 		drop_partition(part);
675 	}
676 	clear_bit(GD_NEED_PART_SCAN, &disk->state);
677 
678 	/*
679 	 * Historically we only set the capacity to zero for devices that
680 	 * support partitions (independ of actually having partitions created).
681 	 * Doing that is rather inconsistent, but changing it broke legacy
682 	 * udisks polling for legacy ide-cdrom devices.  Use the crude check
683 	 * below to get the sane behavior for most device while not breaking
684 	 * userspace for this particular setup.
685 	 */
686 	if (invalidate) {
687 		if (!(disk->flags & GENHD_FL_NO_PART) ||
688 		    !(disk->flags & GENHD_FL_REMOVABLE))
689 			set_capacity(disk, 0);
690 	}
691 
692 	if (get_capacity(disk)) {
693 		ret = blk_add_partitions(disk);
694 		if (ret == -EAGAIN)
695 			goto rescan;
696 	} else if (invalidate) {
697 		/*
698 		 * Tell userspace that the media / partition table may have
699 		 * changed.
700 		 */
701 		kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
702 	}
703 
704 	return ret;
705 }
706 /*
707  * Only exported for loop and dasd for historic reasons.  Don't use in new
708  * code!
709  */
710 EXPORT_SYMBOL_GPL(bdev_disk_changed);
711 
712 void *read_part_sector(struct parsed_partitions *state, sector_t n, Sector *p)
713 {
714 	struct address_space *mapping = state->disk->part0->bd_mapping;
715 	struct folio *folio;
716 
717 	if (n >= get_capacity(state->disk)) {
718 		state->access_beyond_eod = true;
719 		goto out;
720 	}
721 
722 	folio = read_mapping_folio(mapping, n >> PAGE_SECTORS_SHIFT, NULL);
723 	if (IS_ERR(folio))
724 		goto out;
725 
726 	p->v = folio;
727 	return folio_address(folio) + offset_in_folio(folio, n * SECTOR_SIZE);
728 out:
729 	p->v = NULL;
730 	return NULL;
731 }
732