// SPDX-License-Identifier: GPL-2.0

  /*

   * Copyright (C) 1991-1998  Linus Torvalds
   * Re-organised Feb 1998 Russell King

   */

  #include <linux/fs.h>
  #include <linux/slab.h>

  #include <linux/ctype.h>
  #include <linux/genhd.h>

  #include <linux/vmalloc.h>

  #include <linux/blktrace_api.h>

  #include <linux/raid/detect.h>

  #include "check.h"
  
  static int (*check_part[])(struct parsed_partitions *) = {
  	/*
  	 * Probe partition formats with tables at disk address 0
  	 * that also have an ADFS boot block at 0xdc0.
  	 */
  #ifdef CONFIG_ACORN_PARTITION_ICS
  	adfspart_check_ICS,
  #endif
  #ifdef CONFIG_ACORN_PARTITION_POWERTEC
  	adfspart_check_POWERTEC,
  #endif
  #ifdef CONFIG_ACORN_PARTITION_EESOX
  	adfspart_check_EESOX,
  #endif
  
  	/*
  	 * Now move on to formats that only have partition info at
  	 * disk address 0xdc0.  Since these may also have stale
  	 * PC/BIOS partition tables, they need to come before
  	 * the msdos entry.
  	 */
  #ifdef CONFIG_ACORN_PARTITION_CUMANA
  	adfspart_check_CUMANA,
  #endif
  #ifdef CONFIG_ACORN_PARTITION_ADFS
  	adfspart_check_ADFS,
  #endif
  
  #ifdef CONFIG_CMDLINE_PARTITION
  	cmdline_partition,
  #endif
  #ifdef CONFIG_EFI_PARTITION
  	efi_partition,		/* this must come before msdos */
  #endif
  #ifdef CONFIG_SGI_PARTITION
  	sgi_partition,
  #endif
  #ifdef CONFIG_LDM_PARTITION
  	ldm_partition,		/* this must come before msdos */
  #endif
  #ifdef CONFIG_MSDOS_PARTITION
  	msdos_partition,
  #endif
  #ifdef CONFIG_OSF_PARTITION
  	osf_partition,
  #endif
  #ifdef CONFIG_SUN_PARTITION
  	sun_partition,
  #endif
  #ifdef CONFIG_AMIGA_PARTITION
  	amiga_partition,
  #endif
  #ifdef CONFIG_ATARI_PARTITION
  	atari_partition,
  #endif
  #ifdef CONFIG_MAC_PARTITION
  	mac_partition,
  #endif
  #ifdef CONFIG_ULTRIX_PARTITION
  	ultrix_partition,
  #endif
  #ifdef CONFIG_IBM_PARTITION
  	ibm_partition,
  #endif
  #ifdef CONFIG_KARMA_PARTITION
  	karma_partition,
  #endif
  #ifdef CONFIG_SYSV68_PARTITION
  	sysv68_partition,
  #endif
  	NULL
  };
  
  static struct parsed_partitions *allocate_partitions(struct gendisk *hd)
  {
  	struct parsed_partitions *state;
  	int nr;
  
  	state = kzalloc(sizeof(*state), GFP_KERNEL);
  	if (!state)
  		return NULL;
  
  	nr = disk_max_parts(hd);
  	state->parts = vzalloc(array_size(nr, sizeof(state->parts[0])));
  	if (!state->parts) {
  		kfree(state);
  		return NULL;
  	}
  
  	state->limit = nr;
  
  	return state;
  }
  
  static void free_partitions(struct parsed_partitions *state)
  {
  	vfree(state->parts);
  	kfree(state);
  }
  
  static struct parsed_partitions *check_partition(struct gendisk *hd,
  		struct block_device *bdev)
  {
  	struct parsed_partitions *state;
  	int i, res, err;
  
  	state = allocate_partitions(hd);
  	if (!state)
  		return NULL;
  	state->pp_buf = (char *)__get_free_page(GFP_KERNEL);
  	if (!state->pp_buf) {
  		free_partitions(state);
  		return NULL;
  	}
  	state->pp_buf[0] = '\0';
  
  	state->bdev = bdev;
  	disk_name(hd, 0, state->name);
  	snprintf(state->pp_buf, PAGE_SIZE, " %s:", state->name);
  	if (isdigit(state->name[strlen(state->name)-1]))
  		sprintf(state->name, "p");
  
  	i = res = err = 0;
  	while (!res && check_part[i]) {
  		memset(state->parts, 0, state->limit * sizeof(state->parts[0]));
  		res = check_part[i++](state);
  		if (res < 0) {
  			/*
  			 * We have hit an I/O error which we don't report now.
  			 * But record it, and let the others do their job.
  			 */
  			err = res;
  			res = 0;
  		}
  
  	}
  	if (res > 0) {
  		printk(KERN_INFO "%s", state->pp_buf);
  
  		free_page((unsigned long)state->pp_buf);
  		return state;
  	}
  	if (state->access_beyond_eod)
  		err = -ENOSPC;
  	/*
  	 * The partition is unrecognized. So report I/O errors if there were any
  	 */
  	if (err)
  		res = err;
  	if (res) {
  		strlcat(state->pp_buf,
  			" unable to read partition table
  ", PAGE_SIZE);
  		printk(KERN_INFO "%s", state->pp_buf);
  	}

  	free_page((unsigned long)state->pp_buf);
  	free_partitions(state);
  	return ERR_PTR(res);
  }

  static ssize_t part_partition_show(struct device *dev,
  				   struct device_attribute *attr, char *buf)
  {
  	struct hd_struct *p = dev_to_part(dev);
  
  	return sprintf(buf, "%d
  ", p->partno);
  }
  
  static ssize_t part_start_show(struct device *dev,
  			       struct device_attribute *attr, char *buf)
  {
  	struct hd_struct *p = dev_to_part(dev);
  
  	return sprintf(buf, "%llu
  ",(unsigned long long)p->start_sect);
  }

  static ssize_t part_ro_show(struct device *dev,
  			    struct device_attribute *attr, char *buf)
  {
  	struct hd_struct *p = dev_to_part(dev);
  	return sprintf(buf, "%d
  ", p->policy ? 1 : 0);
  }
  
  static ssize_t part_alignment_offset_show(struct device *dev,
  					  struct device_attribute *attr, char *buf)
  {
  	struct hd_struct *p = dev_to_part(dev);

  
  	return sprintf(buf, "%u
  ",
  		queue_limit_alignment_offset(&part_to_disk(p)->queue->limits,
  				p->start_sect));

  }
  
  static ssize_t part_discard_alignment_show(struct device *dev,
  					   struct device_attribute *attr, char *buf)
  {
  	struct hd_struct *p = dev_to_part(dev);

  
  	return sprintf(buf, "%u
  ",
  		queue_limit_discard_alignment(&part_to_disk(p)->queue->limits,
  				p->start_sect));

  }

  static DEVICE_ATTR(partition, 0444, part_partition_show, NULL);
  static DEVICE_ATTR(start, 0444, part_start_show, NULL);
  static DEVICE_ATTR(size, 0444, part_size_show, NULL);
  static DEVICE_ATTR(ro, 0444, part_ro_show, NULL);
  static DEVICE_ATTR(alignment_offset, 0444, part_alignment_offset_show, NULL);
  static DEVICE_ATTR(discard_alignment, 0444, part_discard_alignment_show, NULL);
  static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
  static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);

  #ifdef CONFIG_FAIL_MAKE_REQUEST
  static struct device_attribute dev_attr_fail =

  	__ATTR(make-it-fail, 0644, part_fail_show, part_fail_store);

  #endif
  
  static struct attribute *part_attrs[] = {
  	&dev_attr_partition.attr,
  	&dev_attr_start.attr,
  	&dev_attr_size.attr,
  	&dev_attr_ro.attr,
  	&dev_attr_alignment_offset.attr,
  	&dev_attr_discard_alignment.attr,
  	&dev_attr_stat.attr,
  	&dev_attr_inflight.attr,
  #ifdef CONFIG_FAIL_MAKE_REQUEST
  	&dev_attr_fail.attr,
  #endif
  	NULL
  };
  
  static struct attribute_group part_attr_group = {
  	.attrs = part_attrs,
  };
  
  static const struct attribute_group *part_attr_groups[] = {
  	&part_attr_group,
  #ifdef CONFIG_BLK_DEV_IO_TRACE
  	&blk_trace_attr_group,
  #endif
  	NULL
  };
  
  static void part_release(struct device *dev)
  {
  	struct hd_struct *p = dev_to_part(dev);

  	blk_free_devt(dev->devt);

  	hd_free_part(p);

  	kfree(p);
  }

  static int part_uevent(struct device *dev, struct kobj_uevent_env *env)
  {
  	struct hd_struct *part = dev_to_part(dev);
  
  	add_uevent_var(env, "PARTN=%u", part->partno);
  	if (part->info && part->info->volname[0])
  		add_uevent_var(env, "PARTNAME=%s", part->info->volname);
  	return 0;
  }

  struct device_type part_type = {
  	.name		= "partition",
  	.groups		= part_attr_groups,
  	.release	= part_release,

  	.uevent		= part_uevent,

  };

  static void hd_struct_free_work(struct work_struct *work)

  {

  	struct hd_struct *part =
  		container_of(to_rcu_work(work), struct hd_struct, rcu_work);

  	struct gendisk *disk = part_to_disk(part);
  
  	/*
  	 * Release the disk reference acquired in delete_partition here.
  	 * We can't release it in hd_struct_free because the final put_device
  	 * needs process context and thus can't be run directly from a
  	 * percpu_ref ->release handler.
  	 */
  	put_device(disk_to_dev(disk));

  
  	part->start_sect = 0;
  	part->nr_sects = 0;
  	part_stat_set_all(part, 0);
  	put_device(part_to_dev(part));
  }

  static void hd_struct_free(struct percpu_ref *ref)

  {

  	struct hd_struct *part = container_of(ref, struct hd_struct, ref);

  	struct gendisk *disk = part_to_disk(part);
  	struct disk_part_tbl *ptbl =
  		rcu_dereference_protected(disk->part_tbl, 1);
  
  	rcu_assign_pointer(ptbl->last_lookup, NULL);

  
  	INIT_RCU_WORK(&part->rcu_work, hd_struct_free_work);

  	queue_rcu_work(system_wq, &part->rcu_work);

  }

  int hd_ref_init(struct hd_struct *part)
  {
  	if (percpu_ref_init(&part->ref, hd_struct_free, 0, GFP_KERNEL))
  		return -ENOMEM;
  	return 0;
  }

  /*
   * Must be called either with bd_mutex held, before a disk can be opened or
   * after all disk users are gone.
   */

  void delete_partition(struct hd_struct *part)

  {

  	struct gendisk *disk = part_to_disk(part);

  	struct disk_part_tbl *ptbl =
  		rcu_dereference_protected(disk->part_tbl, 1);

  	/*
  	 * ->part_tbl is referenced in this part's release handler, so
  	 *  we have to hold the disk device
  	 */

  	get_device(disk_to_dev(disk));

  	rcu_assign_pointer(ptbl->part[part->partno], NULL);

  	kobject_put(part->holder_dir);
  	device_del(part_to_dev(part));

  	/*
  	 * Remove gendisk pointer from idr so that it cannot be looked up
  	 * while RCU period before freeing gendisk is running to prevent
  	 * use-after-free issues. Note that the device number stays
  	 * "in-use" until we really free the gendisk.
  	 */
  	blk_invalidate_devt(part_devt(part));

  	percpu_ref_kill(&part->ref);

  }
  
  static ssize_t whole_disk_show(struct device *dev,
  			       struct device_attribute *attr, char *buf)
  {
  	return 0;
  }

  static DEVICE_ATTR(whole_disk, 0444, whole_disk_show, NULL);

  /*
   * Must be called either with bd_mutex held, before a disk can be opened or
   * after all disk users are gone.
   */

  static struct hd_struct *add_partition(struct gendisk *disk, int partno,

  				sector_t start, sector_t len, int flags,
  				struct partition_meta_info *info)
  {
  	struct hd_struct *p;
  	dev_t devt = MKDEV(0, 0);
  	struct device *ddev = disk_to_dev(disk);
  	struct device *pdev;
  	struct disk_part_tbl *ptbl;
  	const char *dname;
  	int err;

  	/*
  	 * Partitions are not supported on zoned block devices that are used as
  	 * such.
  	 */
  	switch (disk->queue->limits.zoned) {
  	case BLK_ZONED_HM:
  		pr_warn("%s: partitions not supported on host managed zoned block device
  ",
  			disk->disk_name);
  		return ERR_PTR(-ENXIO);
  	case BLK_ZONED_HA:
  		pr_info("%s: disabling host aware zoned block device support due to partitions
  ",
  			disk->disk_name);
  		disk->queue->limits.zoned = BLK_ZONED_NONE;
  		break;
  	case BLK_ZONED_NONE:
  		break;
  	}

  	err = disk_expand_part_tbl(disk, partno);
  	if (err)
  		return ERR_PTR(err);

  	ptbl = rcu_dereference_protected(disk->part_tbl, 1);

  
  	if (ptbl->part[partno])
  		return ERR_PTR(-EBUSY);
  
  	p = kzalloc(sizeof(*p), GFP_KERNEL);
  	if (!p)
  		return ERR_PTR(-EBUSY);

  	p->dkstats = alloc_percpu(struct disk_stats);
  	if (!p->dkstats) {

  		err = -ENOMEM;
  		goto out_free;
  	}

  	hd_sects_seq_init(p);

  	pdev = part_to_dev(p);
  
  	p->start_sect = start;

  	p->nr_sects = len;
  	p->partno = partno;
  	p->policy = get_disk_ro(disk);
  
  	if (info) {

  		struct partition_meta_info *pinfo;
  
  		pinfo = kzalloc_node(sizeof(*pinfo), GFP_KERNEL, disk->node_id);

  		if (!pinfo) {
  			err = -ENOMEM;

  			goto out_free_stats;

  		}

  		memcpy(pinfo, info, sizeof(*info));
  		p->info = pinfo;
  	}
  
  	dname = dev_name(ddev);
  	if (isdigit(dname[strlen(dname) - 1]))
  		dev_set_name(pdev, "%sp%d", dname, partno);
  	else
  		dev_set_name(pdev, "%s%d", dname, partno);
  
  	device_initialize(pdev);
  	pdev->class = &block_class;
  	pdev->type = &part_type;
  	pdev->parent = ddev;
  
  	err = blk_alloc_devt(p, &devt);
  	if (err)
  		goto out_free_info;
  	pdev->devt = devt;
  
  	/* delay uevent until 'holders' subdir is created */
  	dev_set_uevent_suppress(pdev, 1);
  	err = device_add(pdev);
  	if (err)
  		goto out_put;
  
  	err = -ENOMEM;
  	p->holder_dir = kobject_create_and_add("holders", &pdev->kobj);
  	if (!p->holder_dir)
  		goto out_del;
  
  	dev_set_uevent_suppress(pdev, 0);
  	if (flags & ADDPART_FLAG_WHOLEDISK) {
  		err = device_create_file(pdev, &dev_attr_whole_disk);
  		if (err)
  			goto out_del;
  	}

  	err = hd_ref_init(p);
  	if (err) {
  		if (flags & ADDPART_FLAG_WHOLEDISK)
  			goto out_remove_file;
  		goto out_del;
  	}

  	/* everything is up and running, commence */
  	rcu_assign_pointer(ptbl->part[partno], p);
  
  	/* suppress uevent if the disk suppresses it */
  	if (!dev_get_uevent_suppress(ddev))
  		kobject_uevent(&pdev->kobj, KOBJ_ADD);

  	return p;

  
  out_free_info:

  	kfree(p->info);

  out_free_stats:

  	free_percpu(p->dkstats);

  out_free:
  	kfree(p);
  	return ERR_PTR(err);

  out_remove_file:
  	device_remove_file(pdev, &dev_attr_whole_disk);

  out_del:
  	kobject_put(p->holder_dir);
  	device_del(pdev);
  out_put:
  	put_device(pdev);

  	return ERR_PTR(err);
  }

  static bool partition_overlaps(struct gendisk *disk, sector_t start,
  		sector_t length, int skip_partno)
  {
  	struct disk_part_iter piter;
  	struct hd_struct *part;
  	bool overlap = false;
  
  	disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
  	while ((part = disk_part_iter_next(&piter))) {
  		if (part->partno == skip_partno ||
  		    start >= part->start_sect + part->nr_sects ||
  		    start + length <= part->start_sect)
  			continue;
  		overlap = true;
  		break;
  	}
  
  	disk_part_iter_exit(&piter);
  	return overlap;
  }
  
  int bdev_add_partition(struct block_device *bdev, int partno,
  		sector_t start, sector_t length)
  {
  	struct hd_struct *part;
  
  	mutex_lock(&bdev->bd_mutex);
  	if (partition_overlaps(bdev->bd_disk, start, length, -1)) {
  		mutex_unlock(&bdev->bd_mutex);
  		return -EBUSY;
  	}
  
  	part = add_partition(bdev->bd_disk, partno, start, length,
  			ADDPART_FLAG_NONE, NULL);
  	mutex_unlock(&bdev->bd_mutex);
  	return PTR_ERR_OR_ZERO(part);
  }
  
  int bdev_del_partition(struct block_device *bdev, int partno)
  {
  	struct block_device *bdevp;

  	struct hd_struct *part = NULL;
  	int ret;

  	bdevp = bdget_disk(bdev->bd_disk, partno);

  	if (!bdevp)

  		return -ENXIO;

  
  	mutex_lock(&bdevp->bd_mutex);

  	mutex_lock_nested(&bdev->bd_mutex, 1);
  
  	ret = -ENXIO;
  	part = disk_get_part(bdev->bd_disk, partno);
  	if (!part)
  		goto out_unlock;

  
  	ret = -EBUSY;
  	if (bdevp->bd_openers)
  		goto out_unlock;

  	sync_blockdev(bdevp);

  	invalidate_bdev(bdevp);

  	delete_partition(part);

  	ret = 0;
  out_unlock:

  	mutex_unlock(&bdev->bd_mutex);

  	mutex_unlock(&bdevp->bd_mutex);
  	bdput(bdevp);

  	if (part)
  		disk_put_part(part);

  	return ret;
  }
  
  int bdev_resize_partition(struct block_device *bdev, int partno,
  		sector_t start, sector_t length)
  {
  	struct block_device *bdevp;
  	struct hd_struct *part;
  	int ret = 0;
  
  	part = disk_get_part(bdev->bd_disk, partno);
  	if (!part)
  		return -ENXIO;
  
  	ret = -ENOMEM;

  	bdevp = bdget_part(part);

  	if (!bdevp)
  		goto out_put_part;
  
  	mutex_lock(&bdevp->bd_mutex);
  	mutex_lock_nested(&bdev->bd_mutex, 1);
  
  	ret = -EINVAL;
  	if (start != part->start_sect)
  		goto out_unlock;
  
  	ret = -EBUSY;
  	if (partition_overlaps(bdev->bd_disk, start, length, partno))
  		goto out_unlock;

  	part_nr_sects_write(part, length);
  	bd_set_nr_sectors(bdevp, length);

  
  	ret = 0;
  out_unlock:
  	mutex_unlock(&bdevp->bd_mutex);
  	mutex_unlock(&bdev->bd_mutex);
  	bdput(bdevp);
  out_put_part:
  	disk_put_part(part);
  	return ret;
  }

  static bool disk_unlock_native_capacity(struct gendisk *disk)
  {
  	const struct block_device_operations *bdops = disk->fops;
  
  	if (bdops->unlock_native_capacity &&
  	    !(disk->flags & GENHD_FL_NATIVE_CAPACITY)) {
  		printk(KERN_CONT "enabling native capacity
  ");
  		bdops->unlock_native_capacity(disk);
  		disk->flags |= GENHD_FL_NATIVE_CAPACITY;
  		return true;
  	} else {
  		printk(KERN_CONT "truncated
  ");
  		return false;
  	}
  }

  int blk_drop_partitions(struct block_device *bdev)

  {

  	struct disk_part_iter piter;
  	struct hd_struct *part;

  	if (bdev->bd_part_count)

  		return -EBUSY;

  
  	sync_blockdev(bdev);
  	invalidate_bdev(bdev);

  	disk_part_iter_init(&piter, bdev->bd_disk, DISK_PITER_INCL_EMPTY);

  	while ((part = disk_part_iter_next(&piter)))

  		delete_partition(part);

  	disk_part_iter_exit(&piter);

  	return 0;
  }

  #ifdef CONFIG_S390
  /* for historic reasons in the DASD driver */
  EXPORT_SYMBOL_GPL(blk_drop_partitions);
  #endif

  static bool blk_add_partition(struct gendisk *disk, struct block_device *bdev,
  		struct parsed_partitions *state, int p)

  {

  	sector_t size = state->parts[p].size;
  	sector_t from = state->parts[p].from;

  	struct hd_struct *part;

  
  	if (!size)
  		return true;
  
  	if (from >= get_capacity(disk)) {
  		printk(KERN_WARNING
  		       "%s: p%d start %llu is beyond EOD, ",
  		       disk->disk_name, p, (unsigned long long) from);
  		if (disk_unlock_native_capacity(disk))
  			return false;
  		return true;

  	}

  	if (from + size > get_capacity(disk)) {
  		printk(KERN_WARNING
  		       "%s: p%d size %llu extends beyond EOD, ",
  		       disk->disk_name, p, (unsigned long long) size);

  		if (disk_unlock_native_capacity(disk))
  			return false;
  
  		/*
  		 * We can not ignore partitions of broken tables created by for
  		 * example camera firmware, but we limit them to the end of the
  		 * disk to avoid creating invalid block devices.
  		 */
  		size = get_capacity(disk) - from;
  	}
  
  	part = add_partition(disk, p, from, size, state->parts[p].flags,
  			     &state->parts[p].info);

  	if (IS_ERR(part) && PTR_ERR(part) != -ENXIO) {

  		printk(KERN_ERR " %s: p%d could not be added: %ld
  ",
  		       disk->disk_name, p, -PTR_ERR(part));
  		return true;
  	}

  	if (IS_BUILTIN(CONFIG_BLK_DEV_MD) &&
  	    (state->parts[p].flags & ADDPART_FLAG_RAID))

  		md_autodetect_dev(part_to_dev(part)->devt);

  	return true;
  }

  int blk_add_partitions(struct gendisk *disk, struct block_device *bdev)

  {
  	struct parsed_partitions *state;
  	int ret = -EAGAIN, p, highest;

  	if (!disk_part_scan_enabled(disk))
  		return 0;

  	state = check_partition(disk, bdev);
  	if (!state)

  		return 0;
  	if (IS_ERR(state)) {
  		/*

  		 * I/O error reading the partition table.  If we tried to read
  		 * beyond EOD, retry after unlocking the native capacity.

  		 */
  		if (PTR_ERR(state) == -ENOSPC) {
  			printk(KERN_WARNING "%s: partition table beyond EOD, ",
  			       disk->disk_name);
  			if (disk_unlock_native_capacity(disk))

  				return -EAGAIN;

  		}
  		return -EIO;
  	}

  	/*

  	 * Partitions are not supported on host managed zoned block devices.

  	 */

  	if (disk->queue->limits.zoned == BLK_ZONED_HM) {
  		pr_warn("%s: ignoring partition table on host managed zoned block device
  ",

  			disk->disk_name);

  		ret = 0;
  		goto out_free_state;

  	}

  	/*

  	 * If we read beyond EOD, try unlocking native capacity even if the
  	 * partition table was successfully read as we could be missing some
  	 * partitions.

  	 */
  	if (state->access_beyond_eod) {
  		printk(KERN_WARNING
  		       "%s: partition table partially beyond EOD, ",
  		       disk->disk_name);
  		if (disk_unlock_native_capacity(disk))

  			goto out_free_state;

  	}
  
  	/* tell userspace that the media / partition table may have changed */
  	kobject_uevent(&disk_to_dev(disk)->kobj, KOBJ_CHANGE);

  	/*
  	 * Detect the highest partition number and preallocate disk->part_tbl.
  	 * This is an optimization and not strictly necessary.

  	 */
  	for (p = 1, highest = 0; p < state->limit; p++)
  		if (state->parts[p].size)
  			highest = p;

  	disk_expand_part_tbl(disk, highest);

  	for (p = 1; p < state->limit; p++)
  		if (!blk_add_partition(disk, bdev, state, p))
  			goto out_free_state;

  	ret = 0;
  out_free_state:

  	free_partitions(state);

  	return ret;

  }

  void *read_part_sector(struct parsed_partitions *state, sector_t n, Sector *p)

  {

  	struct address_space *mapping = state->bdev->bd_inode->i_mapping;

  	struct page *page;

  	if (n >= get_capacity(state->bdev->bd_disk)) {
  		state->access_beyond_eod = true;
  		return NULL;

  	}

  
  	page = read_mapping_page(mapping,
  			(pgoff_t)(n >> (PAGE_SHIFT - 9)), NULL);
  	if (IS_ERR(page))
  		goto out;
  	if (PageError(page))
  		goto out_put_page;
  
  	p->v = page;
  	return (unsigned char *)page_address(page) +
  			((n & ((1 << (PAGE_SHIFT - 9)) - 1)) << SECTOR_SHIFT);
  out_put_page:
  	put_page(page);
  out:

  	p->v = NULL;
  	return NULL;
  }