개념 설명 전체 · v6.18.37 / 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/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 }