xref: /linux/block/partitions/core.c (revision eb2f932100288dbb881eadfed02e1459c6b9504c) 
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_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 
88 static struct parsed_partitions *allocate_partitions(struct gendisk *hd)
89 {
90 	struct parsed_partitions *state;
91 	int nr = DISK_MAX_PARTS;
92 
93 	state = kzalloc(sizeof(*state), GFP_KERNEL);
94 	if (!state)
95 		return NULL;
96 
97 	state->parts = vzalloc(array_size(nr, sizeof(state->parts[0])));
98 	if (!state->parts) {
99 		kfree(state);
100 		return NULL;
101 	}
102 
103 	state->limit = nr;
104 
105 	return state;
106 }
107 
108 static void free_partitions(struct parsed_partitions *state)
109 {
110 	vfree(state->parts);
111 	kfree(state);
112 }
113 
114 static struct parsed_partitions *check_partition(struct gendisk *hd)
115 {
116 	struct parsed_partitions *state;
117 	int i, res, err;
118 
119 	state = allocate_partitions(hd);
120 	if (!state)
121 		return NULL;
122 	state->pp_buf = (char *)__get_free_page(GFP_KERNEL);
123 	if (!state->pp_buf) {
124 		free_partitions(state);
125 		return NULL;
126 	}
127 	state->pp_buf[0] = '\0';
128 
129 	state->disk = hd;
130 	snprintf(state->name, BDEVNAME_SIZE, "%s", hd->disk_name);
131 	snprintf(state->pp_buf, PAGE_SIZE, " %s:", state->name);
132 	if (isdigit(state->name[strlen(state->name)-1]))
133 		sprintf(state->name, "p");
134 
135 	i = res = err = 0;
136 	while (!res && check_part[i]) {
137 		memset(state->parts, 0, state->limit * sizeof(state->parts[0]));
138 		res = check_part[i++](state);
139 		if (res < 0) {
140 			/*
141 			 * We have hit an I/O error which we don't report now.
142 			 * But record it, and let the others do their job.
143 			 */
144 			err = res;
145 			res = 0;
146 		}
147 
148 	}
149 	if (res > 0) {
150 		printk(KERN_INFO "%s", state->pp_buf);
151 
152 		free_page((unsigned long)state->pp_buf);
153 		return state;
154 	}
155 	if (state->access_beyond_eod)
156 		err = -ENOSPC;
157 	/*
158 	 * The partition is unrecognized. So report I/O errors if there were any
159 	 */
160 	if (err)
161 		res = err;
162 	if (res) {
163 		strlcat(state->pp_buf,
164 			" unable to read partition table\n", PAGE_SIZE);
165 		printk(KERN_INFO "%s", state->pp_buf);
166 	}
167 
168 	free_page((unsigned long)state->pp_buf);
169 	free_partitions(state);
170 	return ERR_PTR(res);
171 }
172 
173 static ssize_t part_partition_show(struct device *dev,
174 				   struct device_attribute *attr, char *buf)
175 {
176 	return sprintf(buf, "%d\n", dev_to_bdev(dev)->bd_partno);
177 }
178 
179 static ssize_t part_start_show(struct device *dev,
180 			       struct device_attribute *attr, char *buf)
181 {
182 	return sprintf(buf, "%llu\n", dev_to_bdev(dev)->bd_start_sect);
183 }
184 
185 static ssize_t part_ro_show(struct device *dev,
186 			    struct device_attribute *attr, char *buf)
187 {
188 	return sprintf(buf, "%d\n", bdev_read_only(dev_to_bdev(dev)));
189 }
190 
191 static ssize_t part_alignment_offset_show(struct device *dev,
192 					  struct device_attribute *attr, char *buf)
193 {
194 	return sprintf(buf, "%u\n", bdev_alignment_offset(dev_to_bdev(dev)));
195 }
196 
197 static ssize_t part_discard_alignment_show(struct device *dev,
198 					   struct device_attribute *attr, char *buf)
199 {
200 	return sprintf(buf, "%u\n", bdev_discard_alignment(dev_to_bdev(dev)));
201 }
202 
203 static DEVICE_ATTR(partition, 0444, part_partition_show, NULL);
204 static DEVICE_ATTR(start, 0444, part_start_show, NULL);
205 static DEVICE_ATTR(size, 0444, part_size_show, NULL);
206 static DEVICE_ATTR(ro, 0444, part_ro_show, NULL);
207 static DEVICE_ATTR(alignment_offset, 0444, part_alignment_offset_show, NULL);
208 static DEVICE_ATTR(discard_alignment, 0444, part_discard_alignment_show, NULL);
209 static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
210 static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
211 #ifdef CONFIG_FAIL_MAKE_REQUEST
212 static struct device_attribute dev_attr_fail =
213 	__ATTR(make-it-fail, 0644, part_fail_show, part_fail_store);
214 #endif
215 
216 static struct attribute *part_attrs[] = {
217 	&dev_attr_partition.attr,
218 	&dev_attr_start.attr,
219 	&dev_attr_size.attr,
220 	&dev_attr_ro.attr,
221 	&dev_attr_alignment_offset.attr,
222 	&dev_attr_discard_alignment.attr,
223 	&dev_attr_stat.attr,
224 	&dev_attr_inflight.attr,
225 #ifdef CONFIG_FAIL_MAKE_REQUEST
226 	&dev_attr_fail.attr,
227 #endif
228 	NULL
229 };
230 
231 static const struct attribute_group part_attr_group = {
232 	.attrs = part_attrs,
233 };
234 
235 static const struct attribute_group *part_attr_groups[] = {
236 	&part_attr_group,
237 #ifdef CONFIG_BLK_DEV_IO_TRACE
238 	&blk_trace_attr_group,
239 #endif
240 	NULL
241 };
242 
243 static void part_release(struct device *dev)
244 {
245 	put_disk(dev_to_bdev(dev)->bd_disk);
246 	iput(dev_to_bdev(dev)->bd_inode);
247 }
248 
249 static int part_uevent(const struct device *dev, struct kobj_uevent_env *env)
250 {
251 	const struct block_device *part = dev_to_bdev(dev);
252 
253 	add_uevent_var(env, "PARTN=%u", part->bd_partno);
254 	if (part->bd_meta_info && part->bd_meta_info->volname[0])
255 		add_uevent_var(env, "PARTNAME=%s", part->bd_meta_info->volname);
256 	return 0;
257 }
258 
259 const struct device_type part_type = {
260 	.name		= "partition",
261 	.groups		= part_attr_groups,
262 	.release	= part_release,
263 	.uevent		= part_uevent,
264 };
265 
266 void drop_partition(struct block_device *part)
267 {
268 	lockdep_assert_held(&part->bd_disk->open_mutex);
269 
270 	xa_erase(&part->bd_disk->part_tbl, part->bd_partno);
271 	kobject_put(part->bd_holder_dir);
272 
273 	device_del(&part->bd_device);
274 	put_device(&part->bd_device);
275 }
276 
277 static ssize_t whole_disk_show(struct device *dev,
278 			       struct device_attribute *attr, char *buf)
279 {
280 	return 0;
281 }
282 static const DEVICE_ATTR(whole_disk, 0444, whole_disk_show, NULL);
283 
284 /*
285  * Must be called either with open_mutex held, before a disk can be opened or
286  * after all disk users are gone.
287  */
288 static struct block_device *add_partition(struct gendisk *disk, int partno,
289 				sector_t start, sector_t len, int flags,
290 				struct partition_meta_info *info)
291 {
292 	dev_t devt = MKDEV(0, 0);
293 	struct device *ddev = disk_to_dev(disk);
294 	struct device *pdev;
295 	struct block_device *bdev;
296 	const char *dname;
297 	int err;
298 
299 	lockdep_assert_held(&disk->open_mutex);
300 
301 	if (partno >= DISK_MAX_PARTS)
302 		return ERR_PTR(-EINVAL);
303 
304 	/*
305 	 * Partitions are not supported on zoned block devices that are used as
306 	 * such.
307 	 */
308 	if (bdev_is_zoned(disk->part0)) {
309 		pr_warn("%s: partitions not supported on host managed zoned block device\n",
310 			disk->disk_name);
311 		return ERR_PTR(-ENXIO);
312 	}
313 
314 	if (xa_load(&disk->part_tbl, partno))
315 		return ERR_PTR(-EBUSY);
316 
317 	/* ensure we always have a reference to the whole disk */
318 	get_device(disk_to_dev(disk));
319 
320 	err = -ENOMEM;
321 	bdev = bdev_alloc(disk, partno);
322 	if (!bdev)
323 		goto out_put_disk;
324 
325 	bdev->bd_start_sect = start;
326 	bdev_set_nr_sectors(bdev, len);
327 
328 	pdev = &bdev->bd_device;
329 	dname = dev_name(ddev);
330 	if (isdigit(dname[strlen(dname) - 1]))
331 		dev_set_name(pdev, "%sp%d", dname, partno);
332 	else
333 		dev_set_name(pdev, "%s%d", dname, partno);
334 
335 	device_initialize(pdev);
336 	pdev->class = &block_class;
337 	pdev->type = &part_type;
338 	pdev->parent = ddev;
339 
340 	/* in consecutive minor range? */
341 	if (bdev->bd_partno < disk->minors) {
342 		devt = MKDEV(disk->major, disk->first_minor + bdev->bd_partno);
343 	} else {
344 		err = blk_alloc_ext_minor();
345 		if (err < 0)
346 			goto out_put;
347 		devt = MKDEV(BLOCK_EXT_MAJOR, err);
348 	}
349 	pdev->devt = devt;
350 
351 	if (info) {
352 		err = -ENOMEM;
353 		bdev->bd_meta_info = kmemdup(info, sizeof(*info), GFP_KERNEL);
354 		if (!bdev->bd_meta_info)
355 			goto out_put;
356 	}
357 
358 	/* delay uevent until 'holders' subdir is created */
359 	dev_set_uevent_suppress(pdev, 1);
360 	err = device_add(pdev);
361 	if (err)
362 		goto out_put;
363 
364 	err = -ENOMEM;
365 	bdev->bd_holder_dir = kobject_create_and_add("holders", &pdev->kobj);
366 	if (!bdev->bd_holder_dir)
367 		goto out_del;
368 
369 	dev_set_uevent_suppress(pdev, 0);
370 	if (flags & ADDPART_FLAG_WHOLEDISK) {
371 		err = device_create_file(pdev, &dev_attr_whole_disk);
372 		if (err)
373 			goto out_del;
374 	}
375 
376 	/* everything is up and running, commence */
377 	err = xa_insert(&disk->part_tbl, partno, bdev, GFP_KERNEL);
378 	if (err)
379 		goto out_del;
380 	bdev_add(bdev, devt);
381 
382 	/* suppress uevent if the disk suppresses it */
383 	if (!dev_get_uevent_suppress(ddev))
384 		kobject_uevent(&pdev->kobj, KOBJ_ADD);
385 	return bdev;
386 
387 out_del:
388 	kobject_put(bdev->bd_holder_dir);
389 	device_del(pdev);
390 out_put:
391 	put_device(pdev);
392 	return ERR_PTR(err);
393 out_put_disk:
394 	put_disk(disk);
395 	return ERR_PTR(err);
396 }
397 
398 static bool partition_overlaps(struct gendisk *disk, sector_t start,
399 		sector_t length, int skip_partno)
400 {
401 	struct block_device *part;
402 	bool overlap = false;
403 	unsigned long idx;
404 
405 	rcu_read_lock();
406 	xa_for_each_start(&disk->part_tbl, idx, part, 1) {
407 		if (part->bd_partno != skip_partno &&
408 		    start < part->bd_start_sect + bdev_nr_sectors(part) &&
409 		    start + length > part->bd_start_sect) {
410 			overlap = true;
411 			break;
412 		}
413 	}
414 	rcu_read_unlock();
415 
416 	return overlap;
417 }
418 
419 int bdev_add_partition(struct gendisk *disk, int partno, sector_t start,
420 		sector_t length)
421 {
422 	sector_t capacity = get_capacity(disk), end;
423 	struct block_device *part;
424 	int ret;
425 
426 	mutex_lock(&disk->open_mutex);
427 	if (check_add_overflow(start, length, &end)) {
428 		ret = -EINVAL;
429 		goto out;
430 	}
431 
432 	if (start >= capacity || end > capacity) {
433 		ret = -EINVAL;
434 		goto out;
435 	}
436 
437 	if (!disk_live(disk)) {
438 		ret = -ENXIO;
439 		goto out;
440 	}
441 
442 	if (disk->flags & GENHD_FL_NO_PART) {
443 		ret = -EINVAL;
444 		goto out;
445 	}
446 
447 	if (partition_overlaps(disk, start, length, -1)) {
448 		ret = -EBUSY;
449 		goto out;
450 	}
451 
452 	part = add_partition(disk, partno, start, length,
453 			ADDPART_FLAG_NONE, NULL);
454 	ret = PTR_ERR_OR_ZERO(part);
455 out:
456 	mutex_unlock(&disk->open_mutex);
457 	return ret;
458 }
459 
460 int bdev_del_partition(struct gendisk *disk, int partno)
461 {
462 	struct block_device *part = NULL;
463 	int ret = -ENXIO;
464 
465 	mutex_lock(&disk->open_mutex);
466 	part = xa_load(&disk->part_tbl, partno);
467 	if (!part)
468 		goto out_unlock;
469 
470 	ret = -EBUSY;
471 	if (atomic_read(&part->bd_openers))
472 		goto out_unlock;
473 
474 	/*
475 	 * We verified that @part->bd_openers is zero above and so
476 	 * @part->bd_holder{_ops} can't be set. And since we hold
477 	 * @disk->open_mutex the device can't be claimed by anyone.
478 	 *
479 	 * So no need to call @part->bd_holder_ops->mark_dead() here.
480 	 * Just delete the partition and invalidate it.
481 	 */
482 
483 	remove_inode_hash(part->bd_inode);
484 	invalidate_bdev(part);
485 	drop_partition(part);
486 	ret = 0;
487 out_unlock:
488 	mutex_unlock(&disk->open_mutex);
489 	return ret;
490 }
491 
492 int bdev_resize_partition(struct gendisk *disk, int partno, sector_t start,
493 		sector_t length)
494 {
495 	struct block_device *part = NULL;
496 	int ret = -ENXIO;
497 
498 	mutex_lock(&disk->open_mutex);
499 	part = xa_load(&disk->part_tbl, partno);
500 	if (!part)
501 		goto out_unlock;
502 
503 	ret = -EINVAL;
504 	if (start != part->bd_start_sect)
505 		goto out_unlock;
506 
507 	ret = -EBUSY;
508 	if (partition_overlaps(disk, start, length, partno))
509 		goto out_unlock;
510 
511 	bdev_set_nr_sectors(part, length);
512 
513 	ret = 0;
514 out_unlock:
515 	mutex_unlock(&disk->open_mutex);
516 	return ret;
517 }
518 
519 static bool disk_unlock_native_capacity(struct gendisk *disk)
520 {
521 	if (!disk->fops->unlock_native_capacity ||
522 	    test_and_set_bit(GD_NATIVE_CAPACITY, &disk->state)) {
523 		printk(KERN_CONT "truncated\n");
524 		return false;
525 	}
526 
527 	printk(KERN_CONT "enabling native capacity\n");
528 	disk->fops->unlock_native_capacity(disk);
529 	return true;
530 }
531 
532 static bool blk_add_partition(struct gendisk *disk,
533 		struct parsed_partitions *state, int p)
534 {
535 	sector_t size = state->parts[p].size;
536 	sector_t from = state->parts[p].from;
537 	struct block_device *part;
538 
539 	if (!size)
540 		return true;
541 
542 	if (from >= get_capacity(disk)) {
543 		printk(KERN_WARNING
544 		       "%s: p%d start %llu is beyond EOD, ",
545 		       disk->disk_name, p, (unsigned long long) from);
546 		if (disk_unlock_native_capacity(disk))
547 			return false;
548 		return true;
549 	}
550 
551 	if (from + size > get_capacity(disk)) {
552 		printk(KERN_WARNING
553 		       "%s: p%d size %llu extends beyond EOD, ",
554 		       disk->disk_name, p, (unsigned long long) size);
555 
556 		if (disk_unlock_native_capacity(disk))
557 			return false;
558 
559 		/*
560 		 * We can not ignore partitions of broken tables created by for
561 		 * example camera firmware, but we limit them to the end of the
562 		 * disk to avoid creating invalid block devices.
563 		 */
564 		size = get_capacity(disk) - from;
565 	}
566 
567 	part = add_partition(disk, p, from, size, state->parts[p].flags,
568 			     &state->parts[p].info);
569 	if (IS_ERR(part) && PTR_ERR(part) != -ENXIO) {
570 		printk(KERN_ERR " %s: p%d could not be added: %pe\n",
571 		       disk->disk_name, p, part);
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->flags & GENHD_FL_NO_PART)
588 		return 0;
589 
590 	if (test_bit(GD_SUPPRESS_PART_SCAN, &disk->state))
591 		return 0;
592 
593 	state = check_partition(disk);
594 	if (!state)
595 		return 0;
596 	if (IS_ERR(state)) {
597 		/*
598 		 * I/O error reading the partition table.  If we tried to read
599 		 * beyond EOD, retry after unlocking the native capacity.
600 		 */
601 		if (PTR_ERR(state) == -ENOSPC) {
602 			printk(KERN_WARNING "%s: partition table beyond EOD, ",
603 			       disk->disk_name);
604 			if (disk_unlock_native_capacity(disk))
605 				return -EAGAIN;
606 		}
607 		return -EIO;
608 	}
609 
610 	/*
611 	 * Partitions are not supported on host managed zoned block devices.
612 	 */
613 	if (bdev_is_zoned(disk->part0)) {
614 		pr_warn("%s: ignoring partition table on host managed zoned block device\n",
615 			disk->disk_name);
616 		ret = 0;
617 		goto out_free_state;
618 	}
619 
620 	/*
621 	 * If we read beyond EOD, try unlocking native capacity even if the
622 	 * partition table was successfully read as we could be missing some
623 	 * partitions.
624 	 */
625 	if (state->access_beyond_eod) {
626 		printk(KERN_WARNING
627 		       "%s: partition table partially beyond EOD, ",
628 		       disk->disk_name);
629 		if (disk_unlock_native_capacity(disk))
630 			goto out_free_state;
631 	}
632 
633 	/* tell userspace that the media / partition table may have changed */
634 	kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
635 
636 	for (p = 1; p < state->limit; p++)
637 		if (!blk_add_partition(disk, state, p))
638 			goto out_free_state;
639 
640 	ret = 0;
641 out_free_state:
642 	free_partitions(state);
643 	return ret;
644 }
645 
646 int bdev_disk_changed(struct gendisk *disk, bool invalidate)
647 {
648 	struct block_device *part;
649 	unsigned long idx;
650 	int ret = 0;
651 
652 	lockdep_assert_held(&disk->open_mutex);
653 
654 	if (!disk_live(disk))
655 		return -ENXIO;
656 
657 rescan:
658 	if (disk->open_partitions)
659 		return -EBUSY;
660 	sync_blockdev(disk->part0);
661 	invalidate_bdev(disk->part0);
662 
663 	xa_for_each_start(&disk->part_tbl, idx, part, 1) {
664 		/*
665 		 * Remove the block device from the inode hash, so that
666 		 * it cannot be looked up any more even when openers
667 		 * still hold references.
668 		 */
669 		remove_inode_hash(part->bd_inode);
670 
671 		/*
672 		 * If @disk->open_partitions isn't elevated but there's
673 		 * still an active holder of that block device things
674 		 * are broken.
675 		 */
676 		WARN_ON_ONCE(atomic_read(&part->bd_openers));
677 		invalidate_bdev(part);
678 		drop_partition(part);
679 	}
680 	clear_bit(GD_NEED_PART_SCAN, &disk->state);
681 
682 	/*
683 	 * Historically we only set the capacity to zero for devices that
684 	 * support partitions (independ of actually having partitions created).
685 	 * Doing that is rather inconsistent, but changing it broke legacy
686 	 * udisks polling for legacy ide-cdrom devices.  Use the crude check
687 	 * below to get the sane behavior for most device while not breaking
688 	 * userspace for this particular setup.
689 	 */
690 	if (invalidate) {
691 		if (!(disk->flags & GENHD_FL_NO_PART) ||
692 		    !(disk->flags & GENHD_FL_REMOVABLE))
693 			set_capacity(disk, 0);
694 	}
695 
696 	if (get_capacity(disk)) {
697 		ret = blk_add_partitions(disk);
698 		if (ret == -EAGAIN)
699 			goto rescan;
700 	} else if (invalidate) {
701 		/*
702 		 * Tell userspace that the media / partition table may have
703 		 * changed.
704 		 */
705 		kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
706 	}
707 
708 	return ret;
709 }
710 /*
711  * Only exported for loop and dasd for historic reasons.  Don't use in new
712  * code!
713  */
714 EXPORT_SYMBOL_GPL(bdev_disk_changed);
715 
716 void *read_part_sector(struct parsed_partitions *state, sector_t n, Sector *p)
717 {
718 	struct address_space *mapping = state->disk->part0->bd_inode->i_mapping;
719 	struct folio *folio;
720 
721 	if (n >= get_capacity(state->disk)) {
722 		state->access_beyond_eod = true;
723 		goto out;
724 	}
725 
726 	folio = read_mapping_folio(mapping, n >> PAGE_SECTORS_SHIFT, NULL);
727 	if (IS_ERR(folio))
728 		goto out;
729 
730 	p->v = folio;
731 	return folio_address(folio) + offset_in_folio(folio, n * SECTOR_SIZE);
732 out:
733 	p->v = NULL;
734 	return NULL;
735 }
736