block/partitions/core.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*
0003  * Copyright (C) 1991-1998  Linus Torvalds
0004  * Re-organised Feb 1998 Russell King
0005  * Copyright (C) 2020 Christoph Hellwig
0006  */
0007 #include <linux/fs.h>
0008 #include <linux/major.h>
0009 #include <linux/slab.h>
0010 #include <linux/ctype.h>
0011 #include <linux/vmalloc.h>
0012 #include <linux/raid/detect.h>
0013 #include "check.h"
0014
0015 static int (*check_part[])(struct parsed_partitions *) = {
0016     /*
0017      * Probe partition formats with tables at disk address 0
0018      * that also have an ADFS boot block at 0xdc0.
0019      */
0020 #ifdef CONFIG_ACORN_PARTITION_ICS
0021     adfspart_check_ICS,
0022 #endif
0023 #ifdef CONFIG_ACORN_PARTITION_POWERTEC
0024     adfspart_check_POWERTEC,
0025 #endif
0026 #ifdef CONFIG_ACORN_PARTITION_EESOX
0027     adfspart_check_EESOX,
0028 #endif
0029
0030     /*
0031      * Now move on to formats that only have partition info at
0032      * disk address 0xdc0.  Since these may also have stale
0033      * PC/BIOS partition tables, they need to come before
0034      * the msdos entry.
0035      */
0036 #ifdef CONFIG_ACORN_PARTITION_CUMANA
0037     adfspart_check_CUMANA,
0038 #endif
0039 #ifdef CONFIG_ACORN_PARTITION_ADFS
0040     adfspart_check_ADFS,
0041 #endif
0042
0043 #ifdef CONFIG_CMDLINE_PARTITION
0044     cmdline_partition,
0045 #endif
0046 #ifdef CONFIG_EFI_PARTITION
0047     efi_partition,      /* this must come before msdos */
0048 #endif
0049 #ifdef CONFIG_SGI_PARTITION
0050     sgi_partition,
0051 #endif
0052 #ifdef CONFIG_LDM_PARTITION
0053     ldm_partition,      /* this must come before msdos */
0054 #endif
0055 #ifdef CONFIG_MSDOS_PARTITION
0056     msdos_partition,
0057 #endif
0058 #ifdef CONFIG_OSF_PARTITION
0059     osf_partition,
0060 #endif
0061 #ifdef CONFIG_SUN_PARTITION
0062     sun_partition,
0063 #endif
0064 #ifdef CONFIG_AMIGA_PARTITION
0065     amiga_partition,
0066 #endif
0067 #ifdef CONFIG_ATARI_PARTITION
0068     atari_partition,
0069 #endif
0070 #ifdef CONFIG_MAC_PARTITION
0071     mac_partition,
0072 #endif
0073 #ifdef CONFIG_ULTRIX_PARTITION
0074     ultrix_partition,
0075 #endif
0076 #ifdef CONFIG_IBM_PARTITION
0077     ibm_partition,
0078 #endif
0079 #ifdef CONFIG_KARMA_PARTITION
0080     karma_partition,
0081 #endif
0082 #ifdef CONFIG_SYSV68_PARTITION
0083     sysv68_partition,
0084 #endif
0085     NULL
0086 };
0087
0088 static void bdev_set_nr_sectors(struct block_device *bdev, sector_t sectors)
0089 {
0090     spin_lock(&bdev->bd_size_lock);
0091     i_size_write(bdev->bd_inode, (loff_t)sectors << SECTOR_SHIFT);
0092     bdev->bd_nr_sectors = sectors;
0093     spin_unlock(&bdev->bd_size_lock);
0094 }
0095
0096 static struct parsed_partitions *allocate_partitions(struct gendisk *hd)
0097 {
0098     struct parsed_partitions *state;
0099     int nr = DISK_MAX_PARTS;
0100
0101     state = kzalloc(sizeof(*state), GFP_KERNEL);
0102     if (!state)
0103         return NULL;
0104
0105     state->parts = vzalloc(array_size(nr, sizeof(state->parts[0])));
0106     if (!state->parts) {
0107         kfree(state);
0108         return NULL;
0109     }
0110
0111     state->limit = nr;
0112
0113     return state;
0114 }
0115
0116 static void free_partitions(struct parsed_partitions *state)
0117 {
0118     vfree(state->parts);
0119     kfree(state);
0120 }
0121
0122 static struct parsed_partitions *check_partition(struct gendisk *hd)
0123 {
0124     struct parsed_partitions *state;
0125     int i, res, err;
0126
0127     state = allocate_partitions(hd);
0128     if (!state)
0129         return NULL;
0130     state->pp_buf = (char *)__get_free_page(GFP_KERNEL);
0131     if (!state->pp_buf) {
0132         free_partitions(state);
0133         return NULL;
0134     }
0135     state->pp_buf[0] = '\0';
0136
0137     state->disk = hd;
0138     snprintf(state->name, BDEVNAME_SIZE, "%s", hd->disk_name);
0139     snprintf(state->pp_buf, PAGE_SIZE, " %s:", state->name);
0140     if (isdigit(state->name[strlen(state->name)-1]))
0141         sprintf(state->name, "p");
0142
0143     i = res = err = 0;
0144     while (!res && check_part[i]) {
0145         memset(state->parts, 0, state->limit * sizeof(state->parts[0]));
0146         res = check_part[i++](state);
0147         if (res < 0) {
0148             /*
0149              * We have hit an I/O error which we don't report now.
0150              * But record it, and let the others do their job.
0151              */
0152             err = res;
0153             res = 0;
0154         }
0155
0156     }
0157     if (res > 0) {
0158         printk(KERN_INFO "%s", state->pp_buf);
0159
0160         free_page((unsigned long)state->pp_buf);
0161         return state;
0162     }
0163     if (state->access_beyond_eod)
0164         err = -ENOSPC;
0165     /*
0166      * The partition is unrecognized. So report I/O errors if there were any
0167      */
0168     if (err)
0169         res = err;
0170     if (res) {
0171         strlcat(state->pp_buf,
0172             " unable to read partition table\n", PAGE_SIZE);
0173         printk(KERN_INFO "%s", state->pp_buf);
0174     }
0175
0176     free_page((unsigned long)state->pp_buf);
0177     free_partitions(state);
0178     return ERR_PTR(res);
0179 }
0180
0181 static ssize_t part_partition_show(struct device *dev,
0182                    struct device_attribute *attr, char *buf)
0183 {
0184     return sprintf(buf, "%d\n", dev_to_bdev(dev)->bd_partno);
0185 }
0186
0187 static ssize_t part_start_show(struct device *dev,
0188                    struct device_attribute *attr, char *buf)
0189 {
0190     return sprintf(buf, "%llu\n", dev_to_bdev(dev)->bd_start_sect);
0191 }
0192
0193 static ssize_t part_ro_show(struct device *dev,
0194                 struct device_attribute *attr, char *buf)
0195 {
0196     return sprintf(buf, "%d\n", bdev_read_only(dev_to_bdev(dev)));
0197 }
0198
0199 static ssize_t part_alignment_offset_show(struct device *dev,
0200                       struct device_attribute *attr, char *buf)
0201 {
0202     return sprintf(buf, "%u\n", bdev_alignment_offset(dev_to_bdev(dev)));
0203 }
0204
0205 static ssize_t part_discard_alignment_show(struct device *dev,
0206                        struct device_attribute *attr, char *buf)
0207 {
0208     return sprintf(buf, "%u\n", bdev_discard_alignment(dev_to_bdev(dev)));
0209 }
0210
0211 static DEVICE_ATTR(partition, 0444, part_partition_show, NULL);
0212 static DEVICE_ATTR(start, 0444, part_start_show, NULL);
0213 static DEVICE_ATTR(size, 0444, part_size_show, NULL);
0214 static DEVICE_ATTR(ro, 0444, part_ro_show, NULL);
0215 static DEVICE_ATTR(alignment_offset, 0444, part_alignment_offset_show, NULL);
0216 static DEVICE_ATTR(discard_alignment, 0444, part_discard_alignment_show, NULL);
0217 static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
0218 static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
0219 #ifdef CONFIG_FAIL_MAKE_REQUEST
0220 static struct device_attribute dev_attr_fail =
0221     __ATTR(make-it-fail, 0644, part_fail_show, part_fail_store);
0222 #endif
0223
0224 static struct attribute *part_attrs[] = {
0225     &dev_attr_partition.attr,
0226     &dev_attr_start.attr,
0227     &dev_attr_size.attr,
0228     &dev_attr_ro.attr,
0229     &dev_attr_alignment_offset.attr,
0230     &dev_attr_discard_alignment.attr,
0231     &dev_attr_stat.attr,
0232     &dev_attr_inflight.attr,
0233 #ifdef CONFIG_FAIL_MAKE_REQUEST
0234     &dev_attr_fail.attr,
0235 #endif
0236     NULL
0237 };
0238
0239 static struct attribute_group part_attr_group = {
0240     .attrs = part_attrs,
0241 };
0242
0243 static const struct attribute_group *part_attr_groups[] = {
0244     &part_attr_group,
0245 #ifdef CONFIG_BLK_DEV_IO_TRACE
0246     &blk_trace_attr_group,
0247 #endif
0248     NULL
0249 };
0250
0251 static void part_release(struct device *dev)
0252 {
0253     put_disk(dev_to_bdev(dev)->bd_disk);
0254     iput(dev_to_bdev(dev)->bd_inode);
0255 }
0256
0257 static int part_uevent(struct device *dev, struct kobj_uevent_env *env)
0258 {
0259     struct block_device *part = dev_to_bdev(dev);
0260
0261     add_uevent_var(env, "PARTN=%u", part->bd_partno);
0262     if (part->bd_meta_info && part->bd_meta_info->volname[0])
0263         add_uevent_var(env, "PARTNAME=%s", part->bd_meta_info->volname);
0264     return 0;
0265 }
0266
0267 struct device_type part_type = {
0268     .name       = "partition",
0269     .groups     = part_attr_groups,
0270     .release    = part_release,
0271     .uevent     = part_uevent,
0272 };
0273
0274 static void delete_partition(struct block_device *part)
0275 {
0276     lockdep_assert_held(&part->bd_disk->open_mutex);
0277
0278     fsync_bdev(part);
0279     __invalidate_device(part, true);
0280
0281     xa_erase(&part->bd_disk->part_tbl, part->bd_partno);
0282     kobject_put(part->bd_holder_dir);
0283     device_del(&part->bd_device);
0284
0285     /*
0286      * Remove the block device from the inode hash, so that it cannot be
0287      * looked up any more even when openers still hold references.
0288      */
0289     remove_inode_hash(part->bd_inode);
0290
0291     put_device(&part->bd_device);
0292 }
0293
0294 static ssize_t whole_disk_show(struct device *dev,
0295                    struct device_attribute *attr, char *buf)
0296 {
0297     return 0;
0298 }
0299 static DEVICE_ATTR(whole_disk, 0444, whole_disk_show, NULL);
0300
0301 /*
0302  * Must be called either with open_mutex held, before a disk can be opened or
0303  * after all disk users are gone.
0304  */
0305 static struct block_device *add_partition(struct gendisk *disk, int partno,
0306                 sector_t start, sector_t len, int flags,
0307                 struct partition_meta_info *info)
0308 {
0309     dev_t devt = MKDEV(0, 0);
0310     struct device *ddev = disk_to_dev(disk);
0311     struct device *pdev;
0312     struct block_device *bdev;
0313     const char *dname;
0314     int err;
0315
0316     lockdep_assert_held(&disk->open_mutex);
0317
0318     if (partno >= DISK_MAX_PARTS)
0319         return ERR_PTR(-EINVAL);
0320
0321     /*
0322      * Partitions are not supported on zoned block devices that are used as
0323      * such.
0324      */
0325     switch (disk->queue->limits.zoned) {
0326     case BLK_ZONED_HM:
0327         pr_warn("%s: partitions not supported on host managed zoned block device\n",
0328             disk->disk_name);
0329         return ERR_PTR(-ENXIO);
0330     case BLK_ZONED_HA:
0331         pr_info("%s: disabling host aware zoned block device support due to partitions\n",
0332             disk->disk_name);
0333         disk_set_zoned(disk, BLK_ZONED_NONE);
0334         break;
0335     case BLK_ZONED_NONE:
0336         break;
0337     }
0338
0339     if (xa_load(&disk->part_tbl, partno))
0340         return ERR_PTR(-EBUSY);
0341
0342     /* ensure we always have a reference to the whole disk */
0343     get_device(disk_to_dev(disk));
0344
0345     err = -ENOMEM;
0346     bdev = bdev_alloc(disk, partno);
0347     if (!bdev)
0348         goto out_put_disk;
0349
0350     bdev->bd_start_sect = start;
0351     bdev_set_nr_sectors(bdev, len);
0352
0353     pdev = &bdev->bd_device;
0354     dname = dev_name(ddev);
0355     if (isdigit(dname[strlen(dname) - 1]))
0356         dev_set_name(pdev, "%sp%d", dname, partno);
0357     else
0358         dev_set_name(pdev, "%s%d", dname, partno);
0359
0360     device_initialize(pdev);
0361     pdev->class = &block_class;
0362     pdev->type = &part_type;
0363     pdev->parent = ddev;
0364
0365     /* in consecutive minor range? */
0366     if (bdev->bd_partno < disk->minors) {
0367         devt = MKDEV(disk->major, disk->first_minor + bdev->bd_partno);
0368     } else {
0369         err = blk_alloc_ext_minor();
0370         if (err < 0)
0371             goto out_put;
0372         devt = MKDEV(BLOCK_EXT_MAJOR, err);
0373     }
0374     pdev->devt = devt;
0375
0376     if (info) {
0377         err = -ENOMEM;
0378         bdev->bd_meta_info = kmemdup(info, sizeof(*info), GFP_KERNEL);
0379         if (!bdev->bd_meta_info)
0380             goto out_put;
0381     }
0382
0383     /* delay uevent until 'holders' subdir is created */
0384     dev_set_uevent_suppress(pdev, 1);
0385     err = device_add(pdev);
0386     if (err)
0387         goto out_put;
0388
0389     err = -ENOMEM;
0390     bdev->bd_holder_dir = kobject_create_and_add("holders", &pdev->kobj);
0391     if (!bdev->bd_holder_dir)
0392         goto out_del;
0393
0394     dev_set_uevent_suppress(pdev, 0);
0395     if (flags & ADDPART_FLAG_WHOLEDISK) {
0396         err = device_create_file(pdev, &dev_attr_whole_disk);
0397         if (err)
0398             goto out_del;
0399     }
0400
0401     /* everything is up and running, commence */
0402     err = xa_insert(&disk->part_tbl, partno, bdev, GFP_KERNEL);
0403     if (err)
0404         goto out_del;
0405     bdev_add(bdev, devt);
0406
0407     /* suppress uevent if the disk suppresses it */
0408     if (!dev_get_uevent_suppress(ddev))
0409         kobject_uevent(&pdev->kobj, KOBJ_ADD);
0410     return bdev;
0411
0412 out_del:
0413     kobject_put(bdev->bd_holder_dir);
0414     device_del(pdev);
0415 out_put:
0416     put_device(pdev);
0417     return ERR_PTR(err);
0418 out_put_disk:
0419     put_disk(disk);
0420     return ERR_PTR(err);
0421 }
0422
0423 static bool partition_overlaps(struct gendisk *disk, sector_t start,
0424         sector_t length, int skip_partno)
0425 {
0426     struct block_device *part;
0427     bool overlap = false;
0428     unsigned long idx;
0429
0430     rcu_read_lock();
0431     xa_for_each_start(&disk->part_tbl, idx, part, 1) {
0432         if (part->bd_partno != skip_partno &&
0433             start < part->bd_start_sect + bdev_nr_sectors(part) &&
0434             start + length > part->bd_start_sect) {
0435             overlap = true;
0436             break;
0437         }
0438     }
0439     rcu_read_unlock();
0440
0441     return overlap;
0442 }
0443
0444 int bdev_add_partition(struct gendisk *disk, int partno, sector_t start,
0445         sector_t length)
0446 {
0447     struct block_device *part;
0448     int ret;
0449
0450     mutex_lock(&disk->open_mutex);
0451     if (!disk_live(disk)) {
0452         ret = -ENXIO;
0453         goto out;
0454     }
0455
0456     if (partition_overlaps(disk, start, length, -1)) {
0457         ret = -EBUSY;
0458         goto out;
0459     }
0460
0461     part = add_partition(disk, partno, start, length,
0462             ADDPART_FLAG_NONE, NULL);
0463     ret = PTR_ERR_OR_ZERO(part);
0464 out:
0465     mutex_unlock(&disk->open_mutex);
0466     return ret;
0467 }
0468
0469 int bdev_del_partition(struct gendisk *disk, int partno)
0470 {
0471     struct block_device *part = NULL;
0472     int ret = -ENXIO;
0473
0474     mutex_lock(&disk->open_mutex);
0475     part = xa_load(&disk->part_tbl, partno);
0476     if (!part)
0477         goto out_unlock;
0478
0479     ret = -EBUSY;
0480     if (atomic_read(&part->bd_openers))
0481         goto out_unlock;
0482
0483     delete_partition(part);
0484     ret = 0;
0485 out_unlock:
0486     mutex_unlock(&disk->open_mutex);
0487     return ret;
0488 }
0489
0490 int bdev_resize_partition(struct gendisk *disk, int partno, sector_t start,
0491         sector_t length)
0492 {
0493     struct block_device *part = NULL;
0494     int ret = -ENXIO;
0495
0496     mutex_lock(&disk->open_mutex);
0497     part = xa_load(&disk->part_tbl, partno);
0498     if (!part)
0499         goto out_unlock;
0500
0501     ret = -EINVAL;
0502     if (start != part->bd_start_sect)
0503         goto out_unlock;
0504
0505     ret = -EBUSY;
0506     if (partition_overlaps(disk, start, length, partno))
0507         goto out_unlock;
0508
0509     bdev_set_nr_sectors(part, length);
0510
0511     ret = 0;
0512 out_unlock:
0513     mutex_unlock(&disk->open_mutex);
0514     return ret;
0515 }
0516
0517 static bool disk_unlock_native_capacity(struct gendisk *disk)
0518 {
0519     if (!disk->fops->unlock_native_capacity ||
0520         test_and_set_bit(GD_NATIVE_CAPACITY, &disk->state)) {
0521         printk(KERN_CONT "truncated\n");
0522         return false;
0523     }
0524
0525     printk(KERN_CONT "enabling native capacity\n");
0526     disk->fops->unlock_native_capacity(disk);
0527     return true;
0528 }
0529
0530 void blk_drop_partitions(struct gendisk *disk)
0531 {
0532     struct block_device *part;
0533     unsigned long idx;
0534
0535     lockdep_assert_held(&disk->open_mutex);
0536
0537     xa_for_each_start(&disk->part_tbl, idx, part, 1)
0538         delete_partition(part);
0539 }
0540
0541 static bool blk_add_partition(struct gendisk *disk,
0542         struct parsed_partitions *state, int p)
0543 {
0544     sector_t size = state->parts[p].size;
0545     sector_t from = state->parts[p].from;
0546     struct block_device *part;
0547
0548     if (!size)
0549         return true;
0550
0551     if (from >= get_capacity(disk)) {
0552         printk(KERN_WARNING
0553                "%s: p%d start %llu is beyond EOD, ",
0554                disk->disk_name, p, (unsigned long long) from);
0555         if (disk_unlock_native_capacity(disk))
0556             return false;
0557         return true;
0558     }
0559
0560     if (from + size > get_capacity(disk)) {
0561         printk(KERN_WARNING
0562                "%s: p%d size %llu extends beyond EOD, ",
0563                disk->disk_name, p, (unsigned long long) size);
0564
0565         if (disk_unlock_native_capacity(disk))
0566             return false;
0567
0568         /*
0569          * We can not ignore partitions of broken tables created by for
0570          * example camera firmware, but we limit them to the end of the
0571          * disk to avoid creating invalid block devices.
0572          */
0573         size = get_capacity(disk) - from;
0574     }
0575
0576     part = add_partition(disk, p, from, size, state->parts[p].flags,
0577                  &state->parts[p].info);
0578     if (IS_ERR(part) && PTR_ERR(part) != -ENXIO) {
0579         printk(KERN_ERR " %s: p%d could not be added: %ld\n",
0580                disk->disk_name, p, -PTR_ERR(part));
0581         return true;
0582     }
0583
0584     if (IS_BUILTIN(CONFIG_BLK_DEV_MD) &&
0585         (state->parts[p].flags & ADDPART_FLAG_RAID))
0586         md_autodetect_dev(part->bd_dev);
0587
0588     return true;
0589 }
0590
0591 static int blk_add_partitions(struct gendisk *disk)
0592 {
0593     struct parsed_partitions *state;
0594     int ret = -EAGAIN, p;
0595
0596     if (disk->flags & GENHD_FL_NO_PART)
0597         return 0;
0598
0599     if (test_bit(GD_SUPPRESS_PART_SCAN, &disk->state))
0600         return 0;
0601
0602     state = check_partition(disk);
0603     if (!state)
0604         return 0;
0605     if (IS_ERR(state)) {
0606         /*
0607          * I/O error reading the partition table.  If we tried to read
0608          * beyond EOD, retry after unlocking the native capacity.
0609          */
0610         if (PTR_ERR(state) == -ENOSPC) {
0611             printk(KERN_WARNING "%s: partition table beyond EOD, ",
0612                    disk->disk_name);
0613             if (disk_unlock_native_capacity(disk))
0614                 return -EAGAIN;
0615         }
0616         return -EIO;
0617     }
0618
0619     /*
0620      * Partitions are not supported on host managed zoned block devices.
0621      */
0622     if (disk->queue->limits.zoned == BLK_ZONED_HM) {
0623         pr_warn("%s: ignoring partition table on host managed zoned block device\n",
0624             disk->disk_name);
0625         ret = 0;
0626         goto out_free_state;
0627     }
0628
0629     /*
0630      * If we read beyond EOD, try unlocking native capacity even if the
0631      * partition table was successfully read as we could be missing some
0632      * partitions.
0633      */
0634     if (state->access_beyond_eod) {
0635         printk(KERN_WARNING
0636                "%s: partition table partially beyond EOD, ",
0637                disk->disk_name);
0638         if (disk_unlock_native_capacity(disk))
0639             goto out_free_state;
0640     }
0641
0642     /* tell userspace that the media / partition table may have changed */
0643     kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
0644
0645     for (p = 1; p < state->limit; p++)
0646         if (!blk_add_partition(disk, state, p))
0647             goto out_free_state;
0648
0649     ret = 0;
0650 out_free_state:
0651     free_partitions(state);
0652     return ret;
0653 }
0654
0655 int bdev_disk_changed(struct gendisk *disk, bool invalidate)
0656 {
0657     int ret = 0;
0658
0659     lockdep_assert_held(&disk->open_mutex);
0660
0661     if (!disk_live(disk))
0662         return -ENXIO;
0663
0664 rescan:
0665     if (disk->open_partitions)
0666         return -EBUSY;
0667     sync_blockdev(disk->part0);
0668     invalidate_bdev(disk->part0);
0669     blk_drop_partitions(disk);
0670
0671     clear_bit(GD_NEED_PART_SCAN, &disk->state);
0672
0673     /*
0674      * Historically we only set the capacity to zero for devices that
0675      * support partitions (independ of actually having partitions created).
0676      * Doing that is rather inconsistent, but changing it broke legacy
0677      * udisks polling for legacy ide-cdrom devices.  Use the crude check
0678      * below to get the sane behavior for most device while not breaking
0679      * userspace for this particular setup.
0680      */
0681     if (invalidate) {
0682         if (!(disk->flags & GENHD_FL_NO_PART) ||
0683             !(disk->flags & GENHD_FL_REMOVABLE))
0684             set_capacity(disk, 0);
0685     }
0686
0687     if (get_capacity(disk)) {
0688         ret = blk_add_partitions(disk);
0689         if (ret == -EAGAIN)
0690             goto rescan;
0691     } else if (invalidate) {
0692         /*
0693          * Tell userspace that the media / partition table may have
0694          * changed.
0695          */
0696         kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);
0697     }
0698
0699     return ret;
0700 }
0701 /*
0702  * Only exported for loop and dasd for historic reasons.  Don't use in new
0703  * code!
0704  */
0705 EXPORT_SYMBOL_GPL(bdev_disk_changed);
0706
0707 void *read_part_sector(struct parsed_partitions *state, sector_t n, Sector *p)
0708 {
0709     struct address_space *mapping = state->disk->part0->bd_inode->i_mapping;
0710     struct folio *folio;
0711
0712     if (n >= get_capacity(state->disk)) {
0713         state->access_beyond_eod = true;
0714         goto out;
0715     }
0716
0717     folio = read_mapping_folio(mapping, n >> PAGE_SECTORS_SHIFT, NULL);
0718     if (IS_ERR(folio))
0719         goto out;
0720
0721     p->v = folio;
0722     return folio_address(folio) + offset_in_folio(folio, n * SECTOR_SIZE);
0723 out:
0724     p->v = NULL;
0725     return NULL;
0726 }