개념 설명 전체 · v6.6 / 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_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 void delete_partition(struct block_device *part)
  278 {
  279 	/*
  280 	 * Remove the block device from the inode hash, so that it cannot be
  281 	 * looked up any more even when openers still hold references.
  282 	 */
  283 	remove_inode_hash(part->bd_inode);
  284 	bdev_mark_dead(part, false);
  285 	drop_partition(part);
  286 }
  287 
  288 static ssize_t whole_disk_show(struct device *dev,
  289 			       struct device_attribute *attr, char *buf)
  290 {
  291 	return 0;
  292 }
  293 static const DEVICE_ATTR(whole_disk, 0444, whole_disk_show, NULL);
  294 
  295 /*
  296  * Must be called either with open_mutex held, before a disk can be opened or
  297  * after all disk users are gone.
  298  */
  299 static struct block_device *add_partition(struct gendisk *disk, int partno,
  300 				sector_t start, sector_t len, int flags,
  301 				struct partition_meta_info *info)
  302 {
  303 	dev_t devt = MKDEV(0, 0);
  304 	struct device *ddev = disk_to_dev(disk);
  305 	struct device *pdev;
  306 	struct block_device *bdev;
  307 	const char *dname;
  308 	int err;
  309 
  310 	lockdep_assert_held(&disk->open_mutex);
  311 
  312 	if (partno >= DISK_MAX_PARTS)
  313 		return ERR_PTR(-EINVAL);
  314 
  315 	/*
  316 	 * Partitions are not supported on zoned block devices that are used as
  317 	 * such.
  318 	 */
  319 	switch (disk->queue->limits.zoned) {
  320 	case BLK_ZONED_HM:
  321 		pr_warn("%s: partitions not supported on host managed zoned block device\n",
  322 			disk->disk_name);
  323 		return ERR_PTR(-ENXIO);
  324 	case BLK_ZONED_HA:
  325 		pr_info("%s: disabling host aware zoned block device support due to partitions\n",
  326 			disk->disk_name);
  327 		disk_set_zoned(disk, BLK_ZONED_NONE);
  328 		break;
  329 	case BLK_ZONED_NONE:
  330 		break;
  331 	}
  332 
  333 	if (xa_load(&disk->part_tbl, partno))
  334 		return ERR_PTR(-EBUSY);
  335 
  336 	/* ensure we always have a reference to the whole disk */
  337 	get_device(disk_to_dev(disk));
  338 
  339 	err = -ENOMEM;
  340 	bdev = bdev_alloc(disk, partno);
  341 	if (!bdev)
  342 		goto out_put_disk;
  343 
  344 	bdev->bd_start_sect = start;
  345 	bdev_set_nr_sectors(bdev, len);
  346 
  347 	pdev = &bdev->bd_device;
  348 	dname = dev_name(ddev);
  349 	if (isdigit(dname[strlen(dname) - 1]))
  350 		dev_set_name(pdev, "%sp%d", dname, partno);
  351 	else
  352 		dev_set_name(pdev, "%s%d", dname, partno);
  353 
  354 	device_initialize(pdev);
  355 	pdev->class = &block_class;
  356 	pdev->type = &part_type;
  357 	pdev->parent = ddev;
  358 
  359 	/* in consecutive minor range? */
  360 	if (bdev->bd_partno < disk->minors) {
  361 		devt = MKDEV(disk->major, disk->first_minor + bdev->bd_partno);
  362 	} else {
  363 		err = blk_alloc_ext_minor();
  364 		if (err < 0)
  365 			goto out_put;
  366 		devt = MKDEV(BLOCK_EXT_MAJOR, err);
  367 	}
  368 	pdev->devt = devt;
  369 
  370 	if (info) {
  371 		err = -ENOMEM;
  372 		bdev->bd_meta_info = kmemdup(info, sizeof(*info), GFP_KERNEL);
  373 		if (!bdev->bd_meta_info)
  374 			goto out_put;
  375 	}
  376 
  377 	/* delay uevent until 'holders' subdir is created */
  378 	dev_set_uevent_suppress(pdev, 1);
  379 	err = device_add(pdev);
  380 	if (err)
  381 		goto out_put;
  382 
  383 	err = -ENOMEM;
  384 	bdev->bd_holder_dir = kobject_create_and_add("holders", &pdev->kobj);
  385 	if (!bdev->bd_holder_dir)
  386 		goto out_del;
  387 
  388 	dev_set_uevent_suppress(pdev, 0);
  389 	if (flags & ADDPART_FLAG_WHOLEDISK) {
  390 		err = device_create_file(pdev, &dev_attr_whole_disk);
  391 		if (err)
  392 			goto out_del;
  393 	}
  394 
  395 	/* everything is up and running, commence */
  396 	err = xa_insert(&disk->part_tbl, partno, bdev, GFP_KERNEL);
  397 	if (err)
  398 		goto out_del;
  399 	bdev_add(bdev, devt);
  400 
  401 	/* suppress uevent if the disk suppresses it */
  402 	if (!dev_get_uevent_suppress(ddev))
  403 		kobject_uevent(&pdev->kobj, KOBJ_ADD);
  404 	return bdev;
  405 
  406 out_del:
  407 	kobject_put(bdev->bd_holder_dir);
  408 	device_del(pdev);
  409 out_put:
  410 	put_device(pdev);
  411 	return ERR_PTR(err);
  412 out_put_disk:
  413 	put_disk(disk);
  414 	return ERR_PTR(err);
  415 }
  416 
  417 static bool partition_overlaps(struct gendisk *disk, sector_t start,
  418 		sector_t length, int skip_partno)
  419 {
  420 	struct block_device *part;
  421 	bool overlap = false;
  422 	unsigned long idx;
  423 
  424 	rcu_read_lock();
  425 	xa_for_each_start(&disk->part_tbl, idx, part, 1) {
  426 		if (part->bd_partno != skip_partno &&
  427 		    start < part->bd_start_sect + bdev_nr_sectors(part) &&
  428 		    start + length > part->bd_start_sect) {
  429 			overlap = true;
  430 			break;
  431 		}
  432 	}
  433 	rcu_read_unlock();
  434 
  435 	return overlap;
  436 }
  437 
  438 int bdev_add_partition(struct gendisk *disk, int partno, sector_t start,
  439 		sector_t length)
  440 {
  441 	sector_t capacity = get_capacity(disk), end;
  442 	struct block_device *part;
  443 	int ret;
  444 
  445 	mutex_lock(&disk->open_mutex);
  446 	if (check_add_overflow(start, length, &end)) {
  447 		ret = -EINVAL;
  448 		goto out;
  449 	}
  450 
  451 	if (start >= capacity || end > capacity) {
  452 		ret = -EINVAL;
  453 		goto out;
  454 	}
  455 
  456 	if (!disk_live(disk)) {
  457 		ret = -ENXIO;
  458 		goto out;
  459 	}
  460 
  461 	if (partition_overlaps(disk, start, length, -1)) {
  462 		ret = -EBUSY;
  463 		goto out;
  464 	}
  465 
  466 	part = add_partition(disk, partno, start, length,
  467 			ADDPART_FLAG_NONE, NULL);
  468 	ret = PTR_ERR_OR_ZERO(part);
  469 out:
  470 	mutex_unlock(&disk->open_mutex);
  471 	return ret;
  472 }
  473 
  474 int bdev_del_partition(struct gendisk *disk, int partno)
  475 {
  476 	struct block_device *part = NULL;
  477 	int ret = -ENXIO;
  478 
  479 	mutex_lock(&disk->open_mutex);
  480 	part = xa_load(&disk->part_tbl, partno);
  481 	if (!part)
  482 		goto out_unlock;
  483 
  484 	ret = -EBUSY;
  485 	if (atomic_read(&part->bd_openers))
  486 		goto out_unlock;
  487 
  488 	delete_partition(part);
  489 	ret = 0;
  490 out_unlock:
  491 	mutex_unlock(&disk->open_mutex);
  492 	return ret;
  493 }
  494 
  495 int bdev_resize_partition(struct gendisk *disk, int partno, sector_t start,
  496 		sector_t length)
  497 {
  498 	struct block_device *part = NULL;
  499 	int ret = -ENXIO;
  500 
  501 	mutex_lock(&disk->open_mutex);
  502 	part = xa_load(&disk->part_tbl, partno);
  503 	if (!part)
  504 		goto out_unlock;
  505 
  506 	ret = -EINVAL;
  507 	if (start != part->bd_start_sect)
  508 		goto out_unlock;
  509 
  510 	ret = -EBUSY;
  511 	if (partition_overlaps(disk, start, length, partno))
  512 		goto out_unlock;
  513 
  514 	bdev_set_nr_sectors(part, length);
  515 
  516 	ret = 0;
  517 out_unlock:
  518 	mutex_unlock(&disk->open_mutex);
  519 	return ret;
  520 }
  521 
  522 static bool disk_unlock_native_capacity(struct gendisk *disk)
  523 {
  524 	if (!disk->fops->unlock_native_capacity ||
  525 	    test_and_set_bit(GD_NATIVE_CAPACITY, &disk->state)) {
  526 		printk(KERN_CONT "truncated\n");
  527 		return false;
  528 	}
  529 
  530 	printk(KERN_CONT "enabling native capacity\n");
  531 	disk->fops->unlock_native_capacity(disk);
  532 	return true;
  533 }
  534 
  535 static bool blk_add_partition(struct gendisk *disk,
  536 		struct parsed_partitions *state, int p)
  537 {
  538 	sector_t size = state->parts[p].size;
  539 	sector_t from = state->parts[p].from;
  540 	struct block_device *part;
  541 
  542 	if (!size)
  543 		return true;
  544 
  545 	if (from >= get_capacity(disk)) {
  546 		printk(KERN_WARNING
  547 		       "%s: p%d start %llu is beyond EOD, ",
  548 		       disk->disk_name, p, (unsigned long long) from);
  549 		if (disk_unlock_native_capacity(disk))
  550 			return false;
  551 		return true;
  552 	}
  553 
  554 	if (from + size > get_capacity(disk)) {
  555 		printk(KERN_WARNING
  556 		       "%s: p%d size %llu extends beyond EOD, ",
  557 		       disk->disk_name, p, (unsigned long long) size);
  558 
  559 		if (disk_unlock_native_capacity(disk))
  560 			return false;
  561 
  562 		/*
  563 		 * We can not ignore partitions of broken tables created by for
  564 		 * example camera firmware, but we limit them to the end of the
  565 		 * disk to avoid creating invalid block devices.
  566 		 */
  567 		size = get_capacity(disk) - from;
  568 	}
  569 
  570 	part = add_partition(disk, p, from, size, state->parts[p].flags,
  571 			     &state->parts[p].info);
  572 	if (IS_ERR(part) && PTR_ERR(part) != -ENXIO) {
  573 		printk(KERN_ERR " %s: p%d could not be added: %ld\n",
  574 		       disk->disk_name, p, -PTR_ERR(part));
  575 		return true;
  576 	}
  577 
  578 	if (IS_BUILTIN(CONFIG_BLK_DEV_MD) &&
  579 	    (state->parts[p].flags & ADDPART_FLAG_RAID))
  580 		md_autodetect_dev(part->bd_dev);
  581 
  582 	return true;
  583 }
  584 
  585 static int blk_add_partitions(struct gendisk *disk)
  586 {
  587 	struct parsed_partitions *state;
  588 	int ret = -EAGAIN, p;
  589 
  590 	if (disk->flags & GENHD_FL_NO_PART)
  591 		return 0;
  592 
  593 	if (test_bit(GD_SUPPRESS_PART_SCAN, &disk->state))
  594 		return 0;
  595 
  596 	state = check_partition(disk);
  597 	if (!state)
  598 		return 0;
  599 	if (IS_ERR(state)) {
  600 		/*
  601 		 * I/O error reading the partition table.  If we tried to read
  602 		 * beyond EOD, retry after unlocking the native capacity.
  603 		 */
  604 		if (PTR_ERR(state) == -ENOSPC) {
  605 			printk(KERN_WARNING "%s: partition table beyond EOD, ",
  606 			       disk->disk_name);
  607 			if (disk_unlock_native_capacity(disk))
  608 				return -EAGAIN;
  609 		}
  610 		return -EIO;
  611 	}
  612 
  613 	/*
  614 	 * Partitions are not supported on host managed zoned block devices.
  615 	 */
  616 	if (disk->queue->limits.zoned == BLK_ZONED_HM) {
  617 		pr_warn("%s: ignoring partition table on host managed zoned block device\n",
  618 			disk->disk_name);
  619 		ret = 0;
  620 		goto out_free_state;
  621 	}
  622 
  623 	/*
  624 	 * If we read beyond EOD, try unlocking native capacity even if the
  625 	 * partition table was successfully read as we could be missing some
  626 	 * partitions.
  627 	 */
  628 	if (state->access_beyond_eod) {
  629 		printk(KERN_WARNING
  630 		       "%s: partition table partially beyond EOD, ",
  631 		       disk->disk_name);
  632 		if (disk_unlock_native_capacity(disk))
  633 			goto out_free_state;
  634 	}
  635 
  636 	/* tell userspace that the media / partition table may have changed */
  637 	kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
  638 
  639 	for (p = 1; p < state->limit; p++)
  640 		if (!blk_add_partition(disk, state, p))
  641 			goto out_free_state;
  642 
  643 	ret = 0;
  644 out_free_state:
  645 	free_partitions(state);
  646 	return ret;
  647 }
  648 
  649 int bdev_disk_changed(struct gendisk *disk, bool invalidate)
  650 {
  651 	struct block_device *part;
  652 	unsigned long idx;
  653 	int ret = 0;
  654 
  655 	lockdep_assert_held(&disk->open_mutex);
  656 
  657 	if (!disk_live(disk))
  658 		return -ENXIO;
  659 
  660 rescan:
  661 	if (disk->open_partitions)
  662 		return -EBUSY;
  663 	sync_blockdev(disk->part0);
  664 	invalidate_bdev(disk->part0);
  665 
  666 	xa_for_each_start(&disk->part_tbl, idx, part, 1)
  667 		delete_partition(part);
  668 	clear_bit(GD_NEED_PART_SCAN, &disk->state);
  669 
  670 	/*
  671 	 * Historically we only set the capacity to zero for devices that
  672 	 * support partitions (independ of actually having partitions created).
  673 	 * Doing that is rather inconsistent, but changing it broke legacy
  674 	 * udisks polling for legacy ide-cdrom devices.  Use the crude check
  675 	 * below to get the sane behavior for most device while not breaking
  676 	 * userspace for this particular setup.
  677 	 */
  678 	if (invalidate) {
  679 		if (!(disk->flags & GENHD_FL_NO_PART) ||
  680 		    !(disk->flags & GENHD_FL_REMOVABLE))
  681 			set_capacity(disk, 0);
  682 	}
  683 
  684 	if (get_capacity(disk)) {
  685 		ret = blk_add_partitions(disk);
  686 		if (ret == -EAGAIN)
  687 			goto rescan;
  688 	} else if (invalidate) {
  689 		/*
  690 		 * Tell userspace that the media / partition table may have
  691 		 * changed.
  692 		 */
  693 		kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
  694 	}
  695 
  696 	return ret;
  697 }
  698 /*
  699  * Only exported for loop and dasd for historic reasons.  Don't use in new
  700  * code!
  701  */
  702 EXPORT_SYMBOL_GPL(bdev_disk_changed);
  703 
  704 void *read_part_sector(struct parsed_partitions *state, sector_t n, Sector *p)
  705 {
  706 	struct address_space *mapping = state->disk->part0->bd_inode->i_mapping;
  707 	struct folio *folio;
  708 
  709 	if (n >= get_capacity(state->disk)) {
  710 		state->access_beyond_eod = true;
  711 		goto out;
  712 	}
  713 
  714 	folio = read_mapping_folio(mapping, n >> PAGE_SECTORS_SHIFT, NULL);
  715 	if (IS_ERR(folio))
  716 		goto out;
  717 
  718 	p->v = folio;
  719 	return folio_address(folio) + offset_in_folio(folio, n * SECTOR_SIZE);
  720 out:
  721 	p->v = NULL;
  722 	return NULL;
  723 }