xref: /linux/block/partitions/core.c (revision 69050f8d6d075dc01af7a5f2f550a8067510366f) 
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/string.h>
11 #include <linux/ctype.h>
12 #include <linux/vmalloc.h>
13 #include <linux/raid/detect.h>
14 #include "check.h"
15 
16 static int (*const 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_OF_PARTITION
48 	of_partition,		/* cmdline have priority to OF */
49 #endif
50 #ifdef CONFIG_EFI_PARTITION
51 	efi_partition,		/* this must come before msdos */
52 #endif
53 #ifdef CONFIG_SGI_PARTITION
54 	sgi_partition,
55 #endif
56 #ifdef CONFIG_LDM_PARTITION
57 	ldm_partition,		/* this must come before msdos */
58 #endif
59 #ifdef CONFIG_MSDOS_PARTITION
60 	msdos_partition,
61 #endif
62 #ifdef CONFIG_OSF_PARTITION
63 	osf_partition,
64 #endif
65 #ifdef CONFIG_SUN_PARTITION
66 	sun_partition,
67 #endif
68 #ifdef CONFIG_AMIGA_PARTITION
69 	amiga_partition,
70 #endif
71 #ifdef CONFIG_ATARI_PARTITION
72 	atari_partition,
73 #endif
74 #ifdef CONFIG_MAC_PARTITION
75 	mac_partition,
76 #endif
77 #ifdef CONFIG_ULTRIX_PARTITION
78 	ultrix_partition,
79 #endif
80 #ifdef CONFIG_IBM_PARTITION
81 	ibm_partition,
82 #endif
83 #ifdef CONFIG_KARMA_PARTITION
84 	karma_partition,
85 #endif
86 #ifdef CONFIG_SYSV68_PARTITION
87 	sysv68_partition,
88 #endif
89 	NULL
90 };
91 
92 static struct parsed_partitions *allocate_partitions(struct gendisk *hd)
93 {
94 	struct parsed_partitions *state;
95 	int nr = DISK_MAX_PARTS;
96 
97 	state = kzalloc_obj(*state, GFP_KERNEL);
98 	if (!state)
99 		return NULL;
100 
101 	state->parts = vzalloc(array_size(nr, sizeof(state->parts[0])));
102 	if (!state->parts) {
103 		kfree(state);
104 		return NULL;
105 	}
106 
107 	state->limit = nr;
108 
109 	return state;
110 }
111 
112 static void free_partitions(struct parsed_partitions *state)
113 {
114 	vfree(state->parts);
115 	kfree(state);
116 }
117 
118 static struct parsed_partitions *check_partition(struct gendisk *hd)
119 {
120 	struct parsed_partitions *state;
121 	int i, res, err;
122 
123 	state = allocate_partitions(hd);
124 	if (!state)
125 		return NULL;
126 	state->pp_buf = (char *)__get_free_page(GFP_KERNEL);
127 	if (!state->pp_buf) {
128 		free_partitions(state);
129 		return NULL;
130 	}
131 	state->pp_buf[0] = '\0';
132 
133 	state->disk = hd;
134 	strscpy(state->name, hd->disk_name);
135 	snprintf(state->pp_buf, PAGE_SIZE, " %s:", state->name);
136 	if (isdigit(state->name[strlen(state->name)-1]))
137 		sprintf(state->name, "p");
138 
139 	i = res = err = 0;
140 	while (!res && check_part[i]) {
141 		memset(state->parts, 0, state->limit * sizeof(state->parts[0]));
142 		res = check_part[i++](state);
143 		if (res < 0) {
144 			/*
145 			 * We have hit an I/O error which we don't report now.
146 			 * But record it, and let the others do their job.
147 			 */
148 			err = res;
149 			res = 0;
150 		}
151 
152 	}
153 	if (res > 0) {
154 		printk(KERN_INFO "%s", state->pp_buf);
155 
156 		free_page((unsigned long)state->pp_buf);
157 		return state;
158 	}
159 	if (state->access_beyond_eod)
160 		err = -ENOSPC;
161 	/*
162 	 * The partition is unrecognized. So report I/O errors if there were any
163 	 */
164 	if (err)
165 		res = err;
166 	if (res) {
167 		strlcat(state->pp_buf,
168 			" unable to read partition table\n", PAGE_SIZE);
169 		printk(KERN_INFO "%s", state->pp_buf);
170 	}
171 
172 	free_page((unsigned long)state->pp_buf);
173 	free_partitions(state);
174 	return ERR_PTR(res);
175 }
176 
177 static ssize_t part_partition_show(struct device *dev,
178 				   struct device_attribute *attr, char *buf)
179 {
180 	return sprintf(buf, "%d\n", bdev_partno(dev_to_bdev(dev)));
181 }
182 
183 static ssize_t part_start_show(struct device *dev,
184 			       struct device_attribute *attr, char *buf)
185 {
186 	return sprintf(buf, "%llu\n", dev_to_bdev(dev)->bd_start_sect);
187 }
188 
189 static ssize_t part_ro_show(struct device *dev,
190 			    struct device_attribute *attr, char *buf)
191 {
192 	return sprintf(buf, "%d\n", bdev_read_only(dev_to_bdev(dev)));
193 }
194 
195 static ssize_t part_alignment_offset_show(struct device *dev,
196 					  struct device_attribute *attr, char *buf)
197 {
198 	return sprintf(buf, "%u\n", bdev_alignment_offset(dev_to_bdev(dev)));
199 }
200 
201 static ssize_t part_discard_alignment_show(struct device *dev,
202 					   struct device_attribute *attr, char *buf)
203 {
204 	return sprintf(buf, "%u\n", bdev_discard_alignment(dev_to_bdev(dev)));
205 }
206 
207 static DEVICE_ATTR(partition, 0444, part_partition_show, NULL);
208 static DEVICE_ATTR(start, 0444, part_start_show, NULL);
209 static DEVICE_ATTR(size, 0444, part_size_show, NULL);
210 static DEVICE_ATTR(ro, 0444, part_ro_show, NULL);
211 static DEVICE_ATTR(alignment_offset, 0444, part_alignment_offset_show, NULL);
212 static DEVICE_ATTR(discard_alignment, 0444, part_discard_alignment_show, NULL);
213 static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
214 static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
215 #ifdef CONFIG_FAIL_MAKE_REQUEST
216 static struct device_attribute dev_attr_fail =
217 	__ATTR(make-it-fail, 0644, part_fail_show, part_fail_store);
218 #endif
219 
220 static struct attribute *part_attrs[] = {
221 	&dev_attr_partition.attr,
222 	&dev_attr_start.attr,
223 	&dev_attr_size.attr,
224 	&dev_attr_ro.attr,
225 	&dev_attr_alignment_offset.attr,
226 	&dev_attr_discard_alignment.attr,
227 	&dev_attr_stat.attr,
228 	&dev_attr_inflight.attr,
229 #ifdef CONFIG_FAIL_MAKE_REQUEST
230 	&dev_attr_fail.attr,
231 #endif
232 	NULL
233 };
234 
235 static const struct attribute_group part_attr_group = {
236 	.attrs = part_attrs,
237 };
238 
239 static const struct attribute_group *part_attr_groups[] = {
240 	&part_attr_group,
241 #ifdef CONFIG_BLK_DEV_IO_TRACE
242 	&blk_trace_attr_group,
243 #endif
244 	NULL
245 };
246 
247 static void part_release(struct device *dev)
248 {
249 	put_disk(dev_to_bdev(dev)->bd_disk);
250 	bdev_drop(dev_to_bdev(dev));
251 }
252 
253 static int part_uevent(const struct device *dev, struct kobj_uevent_env *env)
254 {
255 	const struct block_device *part = dev_to_bdev(dev);
256 
257 	add_uevent_var(env, "PARTN=%u", bdev_partno(part));
258 	if (part->bd_meta_info && part->bd_meta_info->volname[0])
259 		add_uevent_var(env, "PARTNAME=%s", part->bd_meta_info->volname);
260 	if (part->bd_meta_info && part->bd_meta_info->uuid[0])
261 		add_uevent_var(env, "PARTUUID=%s", part->bd_meta_info->uuid);
262 	return 0;
263 }
264 
265 const struct device_type part_type = {
266 	.name		= "partition",
267 	.groups		= part_attr_groups,
268 	.release	= part_release,
269 	.uevent		= part_uevent,
270 };
271 
272 void drop_partition(struct block_device *part)
273 {
274 	lockdep_assert_held(&part->bd_disk->open_mutex);
275 
276 	xa_erase(&part->bd_disk->part_tbl, bdev_partno(part));
277 	kobject_put(part->bd_holder_dir);
278 
279 	device_del(&part->bd_device);
280 	put_device(&part->bd_device);
281 }
282 
283 static ssize_t whole_disk_show(struct device *dev,
284 			       struct device_attribute *attr, char *buf)
285 {
286 	return 0;
287 }
288 static const DEVICE_ATTR(whole_disk, 0444, whole_disk_show, NULL);
289 
290 /*
291  * Must be called either with open_mutex held, before a disk can be opened or
292  * after all disk users are gone.
293  */
294 static struct block_device *add_partition(struct gendisk *disk, int partno,
295 				sector_t start, sector_t len, int flags,
296 				struct partition_meta_info *info)
297 {
298 	dev_t devt = MKDEV(0, 0);
299 	struct device *ddev = disk_to_dev(disk);
300 	struct device *pdev;
301 	struct block_device *bdev;
302 	const char *dname;
303 	int err;
304 
305 	lockdep_assert_held(&disk->open_mutex);
306 
307 	if (partno >= DISK_MAX_PARTS)
308 		return ERR_PTR(-EINVAL);
309 
310 	/*
311 	 * Partitions are not supported on zoned block devices that are used as
312 	 * such.
313 	 */
314 	if (bdev_is_zoned(disk->part0)) {
315 		pr_warn("%s: partitions not supported on host managed zoned block device\n",
316 			disk->disk_name);
317 		return ERR_PTR(-ENXIO);
318 	}
319 
320 	if (xa_load(&disk->part_tbl, partno))
321 		return ERR_PTR(-EBUSY);
322 
323 	/* ensure we always have a reference to the whole disk */
324 	get_device(disk_to_dev(disk));
325 
326 	err = -ENOMEM;
327 	bdev = bdev_alloc(disk, partno);
328 	if (!bdev)
329 		goto out_put_disk;
330 
331 	bdev->bd_start_sect = start;
332 	bdev_set_nr_sectors(bdev, len);
333 
334 	pdev = &bdev->bd_device;
335 	dname = dev_name(ddev);
336 	if (isdigit(dname[strlen(dname) - 1]))
337 		dev_set_name(pdev, "%sp%d", dname, partno);
338 	else
339 		dev_set_name(pdev, "%s%d", dname, partno);
340 
341 	device_initialize(pdev);
342 	pdev->class = &block_class;
343 	pdev->type = &part_type;
344 	pdev->parent = ddev;
345 
346 	/* in consecutive minor range? */
347 	if (bdev_partno(bdev) < disk->minors) {
348 		devt = MKDEV(disk->major, disk->first_minor + bdev_partno(bdev));
349 	} else {
350 		err = blk_alloc_ext_minor();
351 		if (err < 0)
352 			goto out_put;
353 		devt = MKDEV(BLOCK_EXT_MAJOR, err);
354 	}
355 	pdev->devt = devt;
356 
357 	if (info) {
358 		err = -ENOMEM;
359 		bdev->bd_meta_info = kmemdup(info, sizeof(*info), GFP_KERNEL);
360 		if (!bdev->bd_meta_info)
361 			goto out_put;
362 	}
363 
364 	/* delay uevent until 'holders' subdir is created */
365 	dev_set_uevent_suppress(pdev, 1);
366 	err = device_add(pdev);
367 	if (err)
368 		goto out_put;
369 
370 	err = -ENOMEM;
371 	bdev->bd_holder_dir = kobject_create_and_add("holders", &pdev->kobj);
372 	if (!bdev->bd_holder_dir)
373 		goto out_del;
374 
375 	dev_set_uevent_suppress(pdev, 0);
376 	if (flags & ADDPART_FLAG_WHOLEDISK) {
377 		err = device_create_file(pdev, &dev_attr_whole_disk);
378 		if (err)
379 			goto out_del;
380 	}
381 
382 	if (flags & ADDPART_FLAG_READONLY)
383 		bdev_set_flag(bdev, BD_READ_ONLY);
384 
385 	/* everything is up and running, commence */
386 	err = xa_insert(&disk->part_tbl, partno, bdev, GFP_KERNEL);
387 	if (err)
388 		goto out_del;
389 	bdev_add(bdev, devt);
390 
391 	/* suppress uevent if the disk suppresses it */
392 	if (!dev_get_uevent_suppress(ddev))
393 		kobject_uevent(&pdev->kobj, KOBJ_ADD);
394 	return bdev;
395 
396 out_del:
397 	kobject_put(bdev->bd_holder_dir);
398 	device_del(pdev);
399 out_put:
400 	put_device(pdev);
401 	return ERR_PTR(err);
402 out_put_disk:
403 	put_disk(disk);
404 	return ERR_PTR(err);
405 }
406 
407 static bool partition_overlaps(struct gendisk *disk, sector_t start,
408 		sector_t length, int skip_partno)
409 {
410 	struct block_device *part;
411 	bool overlap = false;
412 	unsigned long idx;
413 
414 	rcu_read_lock();
415 	xa_for_each_start(&disk->part_tbl, idx, part, 1) {
416 		if (bdev_partno(part) != skip_partno &&
417 		    start < part->bd_start_sect + bdev_nr_sectors(part) &&
418 		    start + length > part->bd_start_sect) {
419 			overlap = true;
420 			break;
421 		}
422 	}
423 	rcu_read_unlock();
424 
425 	return overlap;
426 }
427 
428 int bdev_add_partition(struct gendisk *disk, int partno, sector_t start,
429 		sector_t length)
430 {
431 	struct block_device *part;
432 	int ret;
433 
434 	mutex_lock(&disk->open_mutex);
435 	if (!disk_live(disk)) {
436 		ret = -ENXIO;
437 		goto out;
438 	}
439 
440 	if (disk->flags & GENHD_FL_NO_PART) {
441 		ret = -EINVAL;
442 		goto out;
443 	}
444 
445 	if (partition_overlaps(disk, start, length, -1)) {
446 		ret = -EBUSY;
447 		goto out;
448 	}
449 
450 	part = add_partition(disk, partno, start, length,
451 			ADDPART_FLAG_NONE, NULL);
452 	ret = PTR_ERR_OR_ZERO(part);
453 out:
454 	mutex_unlock(&disk->open_mutex);
455 	return ret;
456 }
457 
458 int bdev_del_partition(struct gendisk *disk, int partno)
459 {
460 	struct block_device *part = NULL;
461 	int ret = -ENXIO;
462 
463 	mutex_lock(&disk->open_mutex);
464 	part = xa_load(&disk->part_tbl, partno);
465 	if (!part)
466 		goto out_unlock;
467 
468 	ret = -EBUSY;
469 	if (atomic_read(&part->bd_openers))
470 		goto out_unlock;
471 
472 	/*
473 	 * We verified that @part->bd_openers is zero above and so
474 	 * @part->bd_holder{_ops} can't be set. And since we hold
475 	 * @disk->open_mutex the device can't be claimed by anyone.
476 	 *
477 	 * So no need to call @part->bd_holder_ops->mark_dead() here.
478 	 * Just delete the partition and invalidate it.
479 	 */
480 
481 	bdev_unhash(part);
482 	invalidate_bdev(part);
483 	drop_partition(part);
484 	ret = 0;
485 out_unlock:
486 	mutex_unlock(&disk->open_mutex);
487 	return ret;
488 }
489 
490 int bdev_resize_partition(struct gendisk *disk, int partno, sector_t start,
491 		sector_t length)
492 {
493 	struct block_device *part = NULL;
494 	int ret = -ENXIO;
495 
496 	mutex_lock(&disk->open_mutex);
497 	part = xa_load(&disk->part_tbl, partno);
498 	if (!part)
499 		goto out_unlock;
500 
501 	ret = -EINVAL;
502 	if (start != part->bd_start_sect)
503 		goto out_unlock;
504 
505 	ret = -EBUSY;
506 	if (partition_overlaps(disk, start, length, partno))
507 		goto out_unlock;
508 
509 	bdev_set_nr_sectors(part, length);
510 
511 	ret = 0;
512 out_unlock:
513 	mutex_unlock(&disk->open_mutex);
514 	return ret;
515 }
516 
517 static bool disk_unlock_native_capacity(struct gendisk *disk)
518 {
519 	if (!disk->fops->unlock_native_capacity ||
520 	    test_and_set_bit(GD_NATIVE_CAPACITY, &disk->state)) {
521 		printk(KERN_CONT "truncated\n");
522 		return false;
523 	}
524 
525 	printk(KERN_CONT "enabling native capacity\n");
526 	disk->fops->unlock_native_capacity(disk);
527 	return true;
528 }
529 
530 static bool blk_add_partition(struct gendisk *disk,
531 		struct parsed_partitions *state, int p)
532 {
533 	sector_t size = state->parts[p].size;
534 	sector_t from = state->parts[p].from;
535 	struct block_device *part;
536 
537 	if (!size)
538 		return true;
539 
540 	if (from >= get_capacity(disk)) {
541 		printk(KERN_WARNING
542 		       "%s: p%d start %llu is beyond EOD, ",
543 		       disk->disk_name, p, (unsigned long long) from);
544 		if (disk_unlock_native_capacity(disk))
545 			return false;
546 		return true;
547 	}
548 
549 	if (from + size > get_capacity(disk)) {
550 		printk(KERN_WARNING
551 		       "%s: p%d size %llu extends beyond EOD, ",
552 		       disk->disk_name, p, (unsigned long long) size);
553 
554 		if (disk_unlock_native_capacity(disk))
555 			return false;
556 
557 		/*
558 		 * We can not ignore partitions of broken tables created by for
559 		 * example camera firmware, but we limit them to the end of the
560 		 * disk to avoid creating invalid block devices.
561 		 */
562 		size = get_capacity(disk) - from;
563 	}
564 
565 	part = add_partition(disk, p, from, size, state->parts[p].flags,
566 			     &state->parts[p].info);
567 	if (IS_ERR(part)) {
568 		if (PTR_ERR(part) != -ENXIO) {
569 			printk(KERN_ERR " %s: p%d could not be added: %pe\n",
570 			       disk->disk_name, p, part);
571 		}
572 		return true;
573 	}
574 
575 	if (IS_BUILTIN(CONFIG_BLK_DEV_MD) &&
576 	    (state->parts[p].flags & ADDPART_FLAG_RAID))
577 		md_autodetect_dev(part->bd_dev);
578 
579 	return true;
580 }
581 
582 static int blk_add_partitions(struct gendisk *disk)
583 {
584 	struct parsed_partitions *state;
585 	int ret = -EAGAIN, p;
586 
587 	if (!disk_has_partscan(disk))
588 		return 0;
589 
590 	state = check_partition(disk);
591 	if (!state)
592 		return 0;
593 	if (IS_ERR(state)) {
594 		/*
595 		 * I/O error reading the partition table.  If we tried to read
596 		 * beyond EOD, retry after unlocking the native capacity.
597 		 */
598 		if (PTR_ERR(state) == -ENOSPC) {
599 			printk(KERN_WARNING "%s: partition table beyond EOD, ",
600 			       disk->disk_name);
601 			if (disk_unlock_native_capacity(disk))
602 				return -EAGAIN;
603 		}
604 		return -EIO;
605 	}
606 
607 	/*
608 	 * Partitions are not supported on host managed zoned block devices.
609 	 */
610 	if (bdev_is_zoned(disk->part0)) {
611 		pr_warn("%s: ignoring partition table on host managed zoned block device\n",
612 			disk->disk_name);
613 		ret = 0;
614 		goto out_free_state;
615 	}
616 
617 	/*
618 	 * If we read beyond EOD, try unlocking native capacity even if the
619 	 * partition table was successfully read as we could be missing some
620 	 * partitions.
621 	 */
622 	if (state->access_beyond_eod) {
623 		printk(KERN_WARNING
624 		       "%s: partition table partially beyond EOD, ",
625 		       disk->disk_name);
626 		if (disk_unlock_native_capacity(disk))
627 			goto out_free_state;
628 	}
629 
630 	/* tell userspace that the media / partition table may have changed */
631 	kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
632 
633 	for (p = 1; p < state->limit; p++)
634 		if (!blk_add_partition(disk, state, p))
635 			goto out_free_state;
636 
637 	ret = 0;
638 out_free_state:
639 	free_partitions(state);
640 	return ret;
641 }
642 
643 int bdev_disk_changed(struct gendisk *disk, bool invalidate)
644 {
645 	struct block_device *part;
646 	unsigned long idx;
647 	int ret = 0;
648 
649 	lockdep_assert_held(&disk->open_mutex);
650 
651 	if (!disk_live(disk))
652 		return -ENXIO;
653 
654 rescan:
655 	if (disk->open_partitions)
656 		return -EBUSY;
657 	sync_blockdev(disk->part0);
658 	invalidate_bdev(disk->part0);
659 
660 	xa_for_each_start(&disk->part_tbl, idx, part, 1) {
661 		/*
662 		 * Remove the block device from the inode hash, so that
663 		 * it cannot be looked up any more even when openers
664 		 * still hold references.
665 		 */
666 		bdev_unhash(part);
667 
668 		/*
669 		 * If @disk->open_partitions isn't elevated but there's
670 		 * still an active holder of that block device things
671 		 * are broken.
672 		 */
673 		WARN_ON_ONCE(atomic_read(&part->bd_openers));
674 		invalidate_bdev(part);
675 		drop_partition(part);
676 	}
677 	clear_bit(GD_NEED_PART_SCAN, &disk->state);
678 
679 	/*
680 	 * Historically we only set the capacity to zero for devices that
681 	 * support partitions (independ of actually having partitions created).
682 	 * Doing that is rather inconsistent, but changing it broke legacy
683 	 * udisks polling for legacy ide-cdrom devices.  Use the crude check
684 	 * below to get the sane behavior for most device while not breaking
685 	 * userspace for this particular setup.
686 	 */
687 	if (invalidate) {
688 		if (!(disk->flags & GENHD_FL_NO_PART) ||
689 		    !(disk->flags & GENHD_FL_REMOVABLE))
690 			set_capacity(disk, 0);
691 	}
692 
693 	if (get_capacity(disk)) {
694 		ret = blk_add_partitions(disk);
695 		if (ret == -EAGAIN)
696 			goto rescan;
697 	} else if (invalidate) {
698 		/*
699 		 * Tell userspace that the media / partition table may have
700 		 * changed.
701 		 */
702 		kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
703 	}
704 
705 	return ret;
706 }
707 /*
708  * Only exported for loop and dasd for historic reasons.  Don't use in new
709  * code!
710  */
711 EXPORT_SYMBOL_GPL(bdev_disk_changed);
712 
713 void *read_part_sector(struct parsed_partitions *state, sector_t n, Sector *p)
714 {
715 	struct address_space *mapping = state->disk->part0->bd_mapping;
716 	struct folio *folio;
717 
718 	if (n >= get_capacity(state->disk)) {
719 		state->access_beyond_eod = true;
720 		goto out;
721 	}
722 
723 	folio = read_mapping_folio(mapping, n >> PAGE_SECTORS_SHIFT, NULL);
724 	if (IS_ERR(folio))
725 		goto out;
726 
727 	p->v = folio;
728 	return folio_address(folio) + offset_in_folio(folio, n * SECTOR_SIZE);
729 out:
730 	p->v = NULL;
731 	return NULL;
732 }
733