// SPDX-License-Identifier: GPL-2.0

  /*
   *  gendisk handling
   */

  #include <linux/module.h>

  #include <linux/ctype.h>

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

  #include <linux/kdev_t.h>

  #include <linux/kernel.h>
  #include <linux/blkdev.h>

  #include <linux/backing-dev.h>

  #include <linux/init.h>
  #include <linux/spinlock.h>

  #include <linux/proc_fs.h>

  #include <linux/seq_file.h>
  #include <linux/slab.h>
  #include <linux/kmod.h>
  #include <linux/kobj_map.h>

  #include <linux/mutex.h>

  #include <linux/idr.h>

  #include <linux/log2.h>

  #include <linux/pm_runtime.h>

  #include <linux/badblocks.h>

  #include "blk.h"

  static DEFINE_MUTEX(block_class_lock);

  static struct kobject *block_depr;

  /* for extended dynamic devt allocation, currently only one major is used */

  #define NR_EXT_DEVT		(1 << MINORBITS)

  /* For extended devt allocation.  ext_devt_lock prevents look up

   * results from going away underneath its user.
   */

  static DEFINE_SPINLOCK(ext_devt_lock);

  static DEFINE_IDR(ext_devt_idr);

  static void disk_check_events(struct disk_events *ev,
  			      unsigned int *clearing_ptr);

  static void disk_alloc_events(struct gendisk *disk);

  static void disk_add_events(struct gendisk *disk);
  static void disk_del_events(struct gendisk *disk);
  static void disk_release_events(struct gendisk *disk);

  /*
   * Set disk capacity and notify if the size is not currently
   * zero and will not be set to zero
   */

  bool set_capacity_revalidate_and_notify(struct gendisk *disk, sector_t size,

  					bool update_bdev)

  {
  	sector_t capacity = get_capacity(disk);
  
  	set_capacity(disk, size);

  	if (update_bdev)
  		revalidate_disk_size(disk, true);

  
  	if (capacity != size && capacity != 0 && size != 0) {
  		char *envp[] = { "RESIZE=1", NULL };
  
  		kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);

  		return true;

  	}

  
  	return false;

  }
  
  EXPORT_SYMBOL_GPL(set_capacity_revalidate_and_notify);

  /*
   * Format the device name of the indicated disk into the supplied buffer and
   * return a pointer to that same buffer for convenience.
   */
  char *disk_name(struct gendisk *hd, int partno, char *buf)
  {
  	if (!partno)
  		snprintf(buf, BDEVNAME_SIZE, "%s", hd->disk_name);
  	else if (isdigit(hd->disk_name[strlen(hd->disk_name)-1]))
  		snprintf(buf, BDEVNAME_SIZE, "%sp%d", hd->disk_name, partno);
  	else
  		snprintf(buf, BDEVNAME_SIZE, "%s%d", hd->disk_name, partno);
  
  	return buf;
  }
  
  const char *bdevname(struct block_device *bdev, char *buf)
  {

  	return disk_name(bdev->bd_disk, bdev->bd_partno, buf);

  }
  EXPORT_SYMBOL(bdevname);

  static void part_stat_read_all(struct hd_struct *part, struct disk_stats *stat)
  {
  	int cpu;
  
  	memset(stat, 0, sizeof(struct disk_stats));
  	for_each_possible_cpu(cpu) {
  		struct disk_stats *ptr = per_cpu_ptr(part->dkstats, cpu);
  		int group;
  
  		for (group = 0; group < NR_STAT_GROUPS; group++) {
  			stat->nsecs[group] += ptr->nsecs[group];
  			stat->sectors[group] += ptr->sectors[group];
  			stat->ios[group] += ptr->ios[group];
  			stat->merges[group] += ptr->merges[group];
  		}
  
  		stat->io_ticks += ptr->io_ticks;

  	}
  }

  static unsigned int part_in_flight(struct hd_struct *part)

  {

  	unsigned int inflight = 0;

  	int cpu;

  	for_each_possible_cpu(cpu) {

  		inflight += part_stat_local_read_cpu(part, in_flight[0], cpu) +
  			    part_stat_local_read_cpu(part, in_flight[1], cpu);

  	}

  	if ((int)inflight < 0)
  		inflight = 0;

  	return inflight;

  }

  static void part_in_flight_rw(struct hd_struct *part, unsigned int inflight[2])

  {

  	int cpu;

  	inflight[0] = 0;
  	inflight[1] = 0;
  	for_each_possible_cpu(cpu) {
  		inflight[0] += part_stat_local_read_cpu(part, in_flight[0], cpu);
  		inflight[1] += part_stat_local_read_cpu(part, in_flight[1], cpu);
  	}
  	if ((int)inflight[0] < 0)
  		inflight[0] = 0;
  	if ((int)inflight[1] < 0)
  		inflight[1] = 0;

  }

  struct hd_struct *__disk_get_part(struct gendisk *disk, int partno)
  {
  	struct disk_part_tbl *ptbl = rcu_dereference(disk->part_tbl);
  
  	if (unlikely(partno < 0 || partno >= ptbl->len))
  		return NULL;
  	return rcu_dereference(ptbl->part[partno]);
  }

  /**
   * disk_get_part - get partition
   * @disk: disk to look partition from
   * @partno: partition number
   *
   * Look for partition @partno from @disk.  If found, increment
   * reference count and return it.
   *
   * CONTEXT:
   * Don't care.
   *
   * RETURNS:
   * Pointer to the found partition on success, NULL if not found.
   */
  struct hd_struct *disk_get_part(struct gendisk *disk, int partno)
  {

  	struct hd_struct *part;

  	rcu_read_lock();

  	part = __disk_get_part(disk, partno);
  	if (part)
  		get_device(part_to_dev(part));

  	rcu_read_unlock();
  
  	return part;
  }

  
  /**
   * disk_part_iter_init - initialize partition iterator
   * @piter: iterator to initialize
   * @disk: disk to iterate over
   * @flags: DISK_PITER_* flags
   *
   * Initialize @piter so that it iterates over partitions of @disk.
   *
   * CONTEXT:
   * Don't care.
   */
  void disk_part_iter_init(struct disk_part_iter *piter, struct gendisk *disk,
  			  unsigned int flags)
  {

  	struct disk_part_tbl *ptbl;
  
  	rcu_read_lock();
  	ptbl = rcu_dereference(disk->part_tbl);

  	piter->disk = disk;
  	piter->part = NULL;
  
  	if (flags & DISK_PITER_REVERSE)

  		piter->idx = ptbl->len - 1;

  	else if (flags & (DISK_PITER_INCL_PART0 | DISK_PITER_INCL_EMPTY_PART0))

  		piter->idx = 0;

  	else
  		piter->idx = 1;

  
  	piter->flags = flags;

  
  	rcu_read_unlock();

  }
  EXPORT_SYMBOL_GPL(disk_part_iter_init);
  
  /**
   * disk_part_iter_next - proceed iterator to the next partition and return it
   * @piter: iterator of interest
   *
   * Proceed @piter to the next partition and return it.
   *
   * CONTEXT:
   * Don't care.
   */
  struct hd_struct *disk_part_iter_next(struct disk_part_iter *piter)
  {

  	struct disk_part_tbl *ptbl;

  	int inc, end;
  
  	/* put the last partition */
  	disk_put_part(piter->part);
  	piter->part = NULL;

  	/* get part_tbl */

  	rcu_read_lock();

  	ptbl = rcu_dereference(piter->disk->part_tbl);

  
  	/* determine iteration parameters */
  	if (piter->flags & DISK_PITER_REVERSE) {
  		inc = -1;

  		if (piter->flags & (DISK_PITER_INCL_PART0 |
  				    DISK_PITER_INCL_EMPTY_PART0))

  			end = -1;
  		else
  			end = 0;

  	} else {
  		inc = 1;

  		end = ptbl->len;

  	}
  
  	/* iterate to the next partition */
  	for (; piter->idx != end; piter->idx += inc) {
  		struct hd_struct *part;

  		part = rcu_dereference(ptbl->part[piter->idx]);

  		if (!part)
  			continue;

  		get_device(part_to_dev(part));
  		piter->part = part;

  		if (!part_nr_sects_read(part) &&

  		    !(piter->flags & DISK_PITER_INCL_EMPTY) &&
  		    !(piter->flags & DISK_PITER_INCL_EMPTY_PART0 &&

  		      piter->idx == 0)) {
  			put_device(part_to_dev(part));
  			piter->part = NULL;

  			continue;

  		}

  		piter->idx += inc;
  		break;
  	}
  
  	rcu_read_unlock();
  
  	return piter->part;
  }
  EXPORT_SYMBOL_GPL(disk_part_iter_next);
  
  /**
   * disk_part_iter_exit - finish up partition iteration
   * @piter: iter of interest
   *
   * Called when iteration is over.  Cleans up @piter.
   *
   * CONTEXT:
   * Don't care.
   */
  void disk_part_iter_exit(struct disk_part_iter *piter)
  {
  	disk_put_part(piter->part);
  	piter->part = NULL;
  }
  EXPORT_SYMBOL_GPL(disk_part_iter_exit);

  static inline int sector_in_part(struct hd_struct *part, sector_t sector)
  {
  	return part->start_sect <= sector &&

  		sector < part->start_sect + part_nr_sects_read(part);

  }

  /**
   * disk_map_sector_rcu - map sector to partition
   * @disk: gendisk of interest
   * @sector: sector to map
   *
   * Find out which partition @sector maps to on @disk.  This is
   * primarily used for stats accounting.
   *
   * CONTEXT:

   * RCU read locked.  The returned partition pointer is always valid

   * because its refcount is grabbed except for part0, which lifetime
   * is same with the disk.

   *
   * RETURNS:

   * Found partition on success, part0 is returned if no partition matches

   * or the matched partition is being deleted.

   */
  struct hd_struct *disk_map_sector_rcu(struct gendisk *disk, sector_t sector)
  {

  	struct disk_part_tbl *ptbl;

  	struct hd_struct *part;

  	int i;

  	rcu_read_lock();

  	ptbl = rcu_dereference(disk->part_tbl);

  	part = rcu_dereference(ptbl->last_lookup);

  	if (part && sector_in_part(part, sector) && hd_struct_try_get(part))

  		goto out_unlock;

  	for (i = 1; i < ptbl->len; i++) {

  		part = rcu_dereference(ptbl->part[i]);

  		if (part && sector_in_part(part, sector)) {

  			/*
  			 * only live partition can be cached for lookup,
  			 * so use-after-free on cached & deleting partition
  			 * can be avoided
  			 */
  			if (!hd_struct_try_get(part))
  				break;

  			rcu_assign_pointer(ptbl->last_lookup, part);

  			goto out_unlock;

  		}

  	}

  
  	part = &disk->part0;
  out_unlock:
  	rcu_read_unlock();
  	return part;

  }

  /**
   * disk_has_partitions
   * @disk: gendisk of interest
   *
   * Walk through the partition table and check if valid partition exists.
   *
   * CONTEXT:
   * Don't care.
   *
   * RETURNS:
   * True if the gendisk has at least one valid non-zero size partition.
   * Otherwise false.
   */
  bool disk_has_partitions(struct gendisk *disk)
  {
  	struct disk_part_tbl *ptbl;
  	int i;
  	bool ret = false;
  
  	rcu_read_lock();
  	ptbl = rcu_dereference(disk->part_tbl);
  
  	/* Iterate partitions skipping the whole device at index 0 */
  	for (i = 1; i < ptbl->len; i++) {
  		if (rcu_dereference(ptbl->part[i])) {
  			ret = true;
  			break;
  		}
  	}
  
  	rcu_read_unlock();
  
  	return ret;
  }
  EXPORT_SYMBOL_GPL(disk_has_partitions);

  /*
   * Can be deleted altogether. Later.
   *
   */

  #define BLKDEV_MAJOR_HASH_SIZE 255

  static struct blk_major_name {
  	struct blk_major_name *next;
  	int major;
  	char name[16];

  } *major_names[BLKDEV_MAJOR_HASH_SIZE];

  
  /* index in the above - for now: assume no multimajor ranges */

  static inline int major_to_index(unsigned major)

  {

  	return major % BLKDEV_MAJOR_HASH_SIZE;

  }

  #ifdef CONFIG_PROC_FS

  void blkdev_show(struct seq_file *seqf, off_t offset)

  {

  	struct blk_major_name *dp;

  	mutex_lock(&block_class_lock);
  	for (dp = major_names[major_to_index(offset)]; dp; dp = dp->next)
  		if (dp->major == offset)

  			seq_printf(seqf, "%3d %s
  ", dp->major, dp->name);

  	mutex_unlock(&block_class_lock);

  }

  #endif /* CONFIG_PROC_FS */

  /**
   * register_blkdev - register a new block device
   *

   * @major: the requested major device number [1..BLKDEV_MAJOR_MAX-1]. If
   *         @major = 0, try to allocate any unused major number.

   * @name: the name of the new block device as a zero terminated string
   *
   * The @name must be unique within the system.
   *

   * The return value depends on the @major input parameter:
   *

   *  - if a major device number was requested in range [1..BLKDEV_MAJOR_MAX-1]
   *    then the function returns zero on success, or a negative error code

   *  - if any unused major number was requested with @major = 0 parameter

   *    then the return value is the allocated major number in range

   *    [1..BLKDEV_MAJOR_MAX-1] or a negative error code otherwise
   *
   * See Documentation/admin-guide/devices.txt for the list of allocated
   * major numbers.

   */

  int register_blkdev(unsigned int major, const char *name)
  {
  	struct blk_major_name **n, *p;
  	int index, ret = 0;

  	mutex_lock(&block_class_lock);

  
  	/* temporary */
  	if (major == 0) {
  		for (index = ARRAY_SIZE(major_names)-1; index > 0; index--) {
  			if (major_names[index] == NULL)
  				break;
  		}
  
  		if (index == 0) {

  			printk("%s: failed to get major for %s
  ",
  			       __func__, name);

  			ret = -EBUSY;
  			goto out;
  		}
  		major = index;
  		ret = major;
  	}

  	if (major >= BLKDEV_MAJOR_MAX) {

  		pr_err("%s: major requested (%u) is greater than the maximum (%u) for %s
  ",
  		       __func__, major, BLKDEV_MAJOR_MAX-1, name);

  
  		ret = -EINVAL;
  		goto out;
  	}

  	p = kmalloc(sizeof(struct blk_major_name), GFP_KERNEL);
  	if (p == NULL) {
  		ret = -ENOMEM;
  		goto out;
  	}
  
  	p->major = major;
  	strlcpy(p->name, name, sizeof(p->name));
  	p->next = NULL;
  	index = major_to_index(major);
  
  	for (n = &major_names[index]; *n; n = &(*n)->next) {
  		if ((*n)->major == major)
  			break;
  	}
  	if (!*n)
  		*n = p;
  	else
  		ret = -EBUSY;
  
  	if (ret < 0) {

  		printk("register_blkdev: cannot get major %u for %s
  ",

  		       major, name);
  		kfree(p);
  	}
  out:

  	mutex_unlock(&block_class_lock);

  	return ret;
  }
  
  EXPORT_SYMBOL(register_blkdev);

  void unregister_blkdev(unsigned int major, const char *name)

  {
  	struct blk_major_name **n;
  	struct blk_major_name *p = NULL;
  	int index = major_to_index(major);

  	mutex_lock(&block_class_lock);

  	for (n = &major_names[index]; *n; n = &(*n)->next)
  		if ((*n)->major == major)
  			break;

  	if (!*n || strcmp((*n)->name, name)) {
  		WARN_ON(1);

  	} else {

  		p = *n;
  		*n = p->next;
  	}

  	mutex_unlock(&block_class_lock);

  	kfree(p);

  }
  
  EXPORT_SYMBOL(unregister_blkdev);
  
  static struct kobj_map *bdev_map;

  /**

   * blk_mangle_minor - scatter minor numbers apart
   * @minor: minor number to mangle
   *
   * Scatter consecutively allocated @minor number apart if MANGLE_DEVT
   * is enabled.  Mangling twice gives the original value.
   *
   * RETURNS:
   * Mangled value.
   *
   * CONTEXT:
   * Don't care.
   */
  static int blk_mangle_minor(int minor)
  {
  #ifdef CONFIG_DEBUG_BLOCK_EXT_DEVT
  	int i;
  
  	for (i = 0; i < MINORBITS / 2; i++) {
  		int low = minor & (1 << i);
  		int high = minor & (1 << (MINORBITS - 1 - i));
  		int distance = MINORBITS - 1 - 2 * i;
  
  		minor ^= low | high;	/* clear both bits */
  		low <<= distance;	/* swap the positions */
  		high >>= distance;
  		minor |= low | high;	/* and set */
  	}
  #endif
  	return minor;
  }
  
  /**

   * blk_alloc_devt - allocate a dev_t for a partition
   * @part: partition to allocate dev_t for

   * @devt: out parameter for resulting dev_t
   *
   * Allocate a dev_t for block device.
   *
   * RETURNS:
   * 0 on success, allocated dev_t is returned in *@devt.  -errno on
   * failure.
   *
   * CONTEXT:
   * Might sleep.
   */
  int blk_alloc_devt(struct hd_struct *part, dev_t *devt)
  {
  	struct gendisk *disk = part_to_disk(part);

  	int idx;

  
  	/* in consecutive minor range? */
  	if (part->partno < disk->minors) {
  		*devt = MKDEV(disk->major, disk->first_minor + part->partno);
  		return 0;
  	}
  
  	/* allocate ext devt */

  	idr_preload(GFP_KERNEL);

  	spin_lock_bh(&ext_devt_lock);

  	idx = idr_alloc(&ext_devt_idr, part, 0, NR_EXT_DEVT, GFP_NOWAIT);

  	spin_unlock_bh(&ext_devt_lock);

  
  	idr_preload_end();

  	if (idx < 0)
  		return idx == -ENOSPC ? -EBUSY : idx;

  	*devt = MKDEV(BLOCK_EXT_MAJOR, blk_mangle_minor(idx));

  	return 0;
  }
  
  /**
   * blk_free_devt - free a dev_t
   * @devt: dev_t to free
   *
   * Free @devt which was allocated using blk_alloc_devt().
   *
   * CONTEXT:
   * Might sleep.
   */
  void blk_free_devt(dev_t devt)
  {

  	if (devt == MKDEV(0, 0))
  		return;
  
  	if (MAJOR(devt) == BLOCK_EXT_MAJOR) {

  		spin_lock_bh(&ext_devt_lock);

  		idr_remove(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));

  		spin_unlock_bh(&ext_devt_lock);

  	}
  }

  /*
   * We invalidate devt by assigning NULL pointer for devt in idr.

   */
  void blk_invalidate_devt(dev_t devt)
  {
  	if (MAJOR(devt) == BLOCK_EXT_MAJOR) {
  		spin_lock_bh(&ext_devt_lock);
  		idr_replace(&ext_devt_idr, NULL, blk_mangle_minor(MINOR(devt)));
  		spin_unlock_bh(&ext_devt_lock);
  	}
  }

  static char *bdevt_str(dev_t devt, char *buf)
  {
  	if (MAJOR(devt) <= 0xff && MINOR(devt) <= 0xff) {
  		char tbuf[BDEVT_SIZE];
  		snprintf(tbuf, BDEVT_SIZE, "%02x%02x", MAJOR(devt), MINOR(devt));
  		snprintf(buf, BDEVT_SIZE, "%-9s", tbuf);
  	} else
  		snprintf(buf, BDEVT_SIZE, "%03x:%05x", MAJOR(devt), MINOR(devt));
  
  	return buf;
  }

  /*
   * Register device numbers dev..(dev+range-1)
   * range must be nonzero
   * The hash chain is sorted on range, so that subranges can override.
   */

  void blk_register_region(dev_t devt, unsigned long range, struct module *module,

  			 struct kobject *(*probe)(dev_t, int *, void *),
  			 int (*lock)(dev_t, void *), void *data)
  {

  	kobj_map(bdev_map, devt, range, module, probe, lock, data);

  }
  
  EXPORT_SYMBOL(blk_register_region);

  void blk_unregister_region(dev_t devt, unsigned long range)

  {

  	kobj_unmap(bdev_map, devt, range);

  }
  
  EXPORT_SYMBOL(blk_unregister_region);

  static struct kobject *exact_match(dev_t devt, int *partno, void *data)

  {
  	struct gendisk *p = data;

  	return &disk_to_dev(p)->kobj;

  }

  static int exact_lock(dev_t devt, void *data)

  {
  	struct gendisk *p = data;

  	if (!get_disk_and_module(p))

  		return -1;
  	return 0;
  }

  static void disk_scan_partitions(struct gendisk *disk)
  {
  	struct block_device *bdev;
  
  	if (!get_capacity(disk) || !disk_part_scan_enabled(disk))
  		return;
  
  	set_bit(GD_NEED_PART_SCAN, &disk->state);
  	bdev = blkdev_get_by_dev(disk_devt(disk), FMODE_READ, NULL);
  	if (!IS_ERR(bdev))
  		blkdev_put(bdev, FMODE_READ);
  }

  static void register_disk(struct device *parent, struct gendisk *disk,
  			  const struct attribute_group **groups)

  {
  	struct device *ddev = disk_to_dev(disk);

  	struct disk_part_iter piter;
  	struct hd_struct *part;
  	int err;

  	ddev->parent = parent;

  	dev_set_name(ddev, "%s", disk->disk_name);

  
  	/* delay uevents, until we scanned partition table */
  	dev_set_uevent_suppress(ddev, 1);

  	if (groups) {
  		WARN_ON(ddev->groups);
  		ddev->groups = groups;
  	}

  	if (device_add(ddev))
  		return;
  	if (!sysfs_deprecated) {
  		err = sysfs_create_link(block_depr, &ddev->kobj,
  					kobject_name(&ddev->kobj));
  		if (err) {
  			device_del(ddev);
  			return;
  		}
  	}

  
  	/*
  	 * avoid probable deadlock caused by allocating memory with
  	 * GFP_KERNEL in runtime_resume callback of its all ancestor
  	 * devices
  	 */
  	pm_runtime_set_memalloc_noio(ddev, true);

  	disk->part0.holder_dir = kobject_create_and_add("holders", &ddev->kobj);
  	disk->slave_dir = kobject_create_and_add("slaves", &ddev->kobj);

  	if (disk->flags & GENHD_FL_HIDDEN) {
  		dev_set_uevent_suppress(ddev, 0);
  		return;
  	}

  	disk_scan_partitions(disk);

  	/* announce disk after possible partitions are created */
  	dev_set_uevent_suppress(ddev, 0);
  	kobject_uevent(&ddev->kobj, KOBJ_ADD);
  
  	/* announce possible partitions */
  	disk_part_iter_init(&piter, disk, 0);
  	while ((part = disk_part_iter_next(&piter)))
  		kobject_uevent(&part_to_dev(part)->kobj, KOBJ_ADD);
  	disk_part_iter_exit(&piter);

  	if (disk->queue->backing_dev_info->dev) {
  		err = sysfs_create_link(&ddev->kobj,
  			  &disk->queue->backing_dev_info->dev->kobj,
  			  "bdi");
  		WARN_ON(err);
  	}

  }

  /**

   * __device_add_disk - add disk information to kernel list

   * @parent: parent device for the disk

   * @disk: per-device partitioning information

   * @groups: Additional per-device sysfs groups

   * @register_queue: register the queue if set to true

   *
   * This function registers the partitioning information in @disk
   * with the kernel.

   *
   * FIXME: error handling

   */

  static void __device_add_disk(struct device *parent, struct gendisk *disk,

  			      const struct attribute_group **groups,

  			      bool register_queue)

  {

  	dev_t devt;

  	int retval;

  	/*
  	 * The disk queue should now be all set with enough information about
  	 * the device for the elevator code to pick an adequate default
  	 * elevator if one is needed, that is, for devices requesting queue
  	 * registration.
  	 */
  	if (register_queue)
  		elevator_init_mq(disk->queue);

  	/* minors == 0 indicates to use ext devt from part0 and should
  	 * be accompanied with EXT_DEVT flag.  Make sure all
  	 * parameters make sense.
  	 */
  	WARN_ON(disk->minors && !(disk->major || disk->first_minor));

  	WARN_ON(!disk->minors &&
  		!(disk->flags & (GENHD_FL_EXT_DEVT | GENHD_FL_HIDDEN)));

  	disk->flags |= GENHD_FL_UP;

  
  	retval = blk_alloc_devt(&disk->part0, &devt);
  	if (retval) {
  		WARN_ON(1);
  		return;
  	}

  	disk->major = MAJOR(devt);
  	disk->first_minor = MINOR(devt);

  	disk_alloc_events(disk);

  	if (disk->flags & GENHD_FL_HIDDEN) {
  		/*
  		 * Don't let hidden disks show up in /proc/partitions,
  		 * and don't bother scanning for partitions either.
  		 */
  		disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO;
  		disk->flags |= GENHD_FL_NO_PART_SCAN;
  	} else {

  		struct backing_dev_info *bdi = disk->queue->backing_dev_info;
  		struct device *dev = disk_to_dev(disk);

  		int ret;

  		/* Register BDI before referencing it from bdev */

  		dev->devt = devt;
  		ret = bdi_register(bdi, "%u:%u", MAJOR(devt), MINOR(devt));

  		WARN_ON(ret);

  		bdi_set_owner(bdi, dev);

  		blk_register_region(disk_devt(disk), disk->minors, NULL,
  				    exact_match, exact_lock, disk);
  	}

  	register_disk(parent, disk, groups);

  	if (register_queue)
  		blk_register_queue(disk);

  	/*
  	 * Take an extra ref on queue which will be put on disk_release()
  	 * so that it sticks around as long as @disk is there.
  	 */

  	WARN_ON_ONCE(!blk_get_queue(disk->queue));

  	disk_add_events(disk);

  	blk_integrity_add(disk);

  }

  void device_add_disk(struct device *parent, struct gendisk *disk,
  		     const struct attribute_group **groups)

  {

  	__device_add_disk(parent, disk, groups, true);

  }

  EXPORT_SYMBOL(device_add_disk);

  void device_add_disk_no_queue_reg(struct device *parent, struct gendisk *disk)
  {

  	__device_add_disk(parent, disk, NULL, false);

  }
  EXPORT_SYMBOL(device_add_disk_no_queue_reg);

  static void invalidate_partition(struct gendisk *disk, int partno)
  {
  	struct block_device *bdev;
  
  	bdev = bdget_disk(disk, partno);
  	if (!bdev)
  		return;
  
  	fsync_bdev(bdev);
  	__invalidate_device(bdev, true);

  
  	/*
  	 * Unhash the bdev inode for this device so that it gets evicted as soon
  	 * as last inode reference is dropped.
  	 */
  	remove_inode_hash(bdev->bd_inode);

  	bdput(bdev);
  }

  /**
   * del_gendisk - remove the gendisk
   * @disk: the struct gendisk to remove
   *
   * Removes the gendisk and all its associated resources. This deletes the
   * partitions associated with the gendisk, and unregisters the associated
   * request_queue.
   *
   * This is the counter to the respective __device_add_disk() call.
   *
   * The final removal of the struct gendisk happens when its refcount reaches 0
   * with put_disk(), which should be called after del_gendisk(), if
   * __device_add_disk() was used.

   *
   * Drivers exist which depend on the release of the gendisk to be synchronous,
   * it should not be deferred.
   *
   * Context: can sleep

   */

  void del_gendisk(struct gendisk *disk)

  {

  	struct disk_part_iter piter;
  	struct hd_struct *part;

  	might_sleep();

  	blk_integrity_del(disk);

  	disk_del_events(disk);

  	/*
  	 * Block lookups of the disk until all bdevs are unhashed and the
  	 * disk is marked as dead (GENHD_FL_UP cleared).
  	 */
  	down_write(&disk->lookup_sem);

  	/* invalidate stuff */
  	disk_part_iter_init(&piter, disk,
  			     DISK_PITER_INCL_EMPTY | DISK_PITER_REVERSE);
  	while ((part = disk_part_iter_next(&piter))) {
  		invalidate_partition(disk, part->partno);

  		delete_partition(part);

  	}
  	disk_part_iter_exit(&piter);
  
  	invalidate_partition(disk, 0);

  	set_capacity(disk, 0);
  	disk->flags &= ~GENHD_FL_UP;

  	up_write(&disk->lookup_sem);

  	if (!(disk->flags & GENHD_FL_HIDDEN))
  		sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");

  	if (disk->queue) {
  		/*
  		 * Unregister bdi before releasing device numbers (as they can
  		 * get reused and we'd get clashes in sysfs).
  		 */

  		if (!(disk->flags & GENHD_FL_HIDDEN))
  			bdi_unregister(disk->queue->backing_dev_info);

  		blk_unregister_queue(disk);
  	} else {
  		WARN_ON(1);
  	}

  	if (!(disk->flags & GENHD_FL_HIDDEN))

  		blk_unregister_region(disk_devt(disk), disk->minors);

  	/*
  	 * 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(disk_devt(disk));

  
  	kobject_put(disk->part0.holder_dir);
  	kobject_put(disk->slave_dir);

  
  	part_stat_set_all(&disk->part0, 0);
  	disk->part0.stamp = 0;

  	if (!sysfs_deprecated)
  		sysfs_remove_link(block_depr, dev_name(disk_to_dev(disk)));

  	pm_runtime_set_memalloc_noio(disk_to_dev(disk), false);

  	device_del(disk_to_dev(disk));

  }

  EXPORT_SYMBOL(del_gendisk);

  /* sysfs access to bad-blocks list. */
  static ssize_t disk_badblocks_show(struct device *dev,
  					struct device_attribute *attr,
  					char *page)
  {
  	struct gendisk *disk = dev_to_disk(dev);
  
  	if (!disk->bb)
  		return sprintf(page, "
  ");
  
  	return badblocks_show(disk->bb, page, 0);
  }
  
  static ssize_t disk_badblocks_store(struct device *dev,
  					struct device_attribute *attr,
  					const char *page, size_t len)
  {
  	struct gendisk *disk = dev_to_disk(dev);
  
  	if (!disk->bb)
  		return -ENXIO;
  
  	return badblocks_store(disk->bb, page, len, 0);
  }

  /**
   * get_gendisk - get partitioning information for a given device

   * @devt: device to get partitioning information for

   * @partno: returned partition index

   *
   * This function gets the structure containing partitioning

   * information for the given device @devt.

   *
   * Context: can sleep

   */

  struct gendisk *get_gendisk(dev_t devt, int *partno)

  {

  	struct gendisk *disk = NULL;

  	might_sleep();

  	if (MAJOR(devt) != BLOCK_EXT_MAJOR) {
  		struct kobject *kobj;
  
  		kobj = kobj_lookup(bdev_map, devt, partno);
  		if (kobj)
  			disk = dev_to_disk(kobj_to_dev(kobj));
  	} else {
  		struct hd_struct *part;

  		spin_lock_bh(&ext_devt_lock);

  		part = idr_find(&ext_devt_idr, blk_mangle_minor(MINOR(devt)));

  		if (part && get_disk_and_module(part_to_disk(part))) {

  			*partno = part->partno;
  			disk = part_to_disk(part);
  		}

  		spin_unlock_bh(&ext_devt_lock);

  	}

  	if (!disk)
  		return NULL;
  
  	/*
  	 * Synchronize with del_gendisk() to not return disk that is being
  	 * destroyed.
  	 */
  	down_read(&disk->lookup_sem);
  	if (unlikely((disk->flags & GENHD_FL_HIDDEN) ||
  		     !(disk->flags & GENHD_FL_UP))) {
  		up_read(&disk->lookup_sem);

  		put_disk_and_module(disk);

  		disk = NULL;

  	} else {
  		up_read(&disk->lookup_sem);

  	}

  	return disk;

  }

  /**
   * bdget_disk - do bdget() by gendisk and partition number
   * @disk: gendisk of interest
   * @partno: partition number
   *
   * Find partition @partno from @disk, do bdget() on it.
   *
   * CONTEXT:
   * Don't care.
   *
   * RETURNS:
   * Resulting block_device on success, NULL on failure.
   */

  struct block_device *bdget_disk(struct gendisk *disk, int partno)

  {

  	struct hd_struct *part;
  	struct block_device *bdev = NULL;

  	part = disk_get_part(disk, partno);

  	if (part)

  		bdev = bdget_part(part);

  	disk_put_part(part);

  	return bdev;

  }
  EXPORT_SYMBOL(bdget_disk);

  /*

   * print a full list of all partitions - intended for places where the root
   * filesystem can't be mounted and thus to give the victim some idea of what
   * went wrong
   */
  void __init printk_all_partitions(void)
  {

  	struct class_dev_iter iter;
  	struct device *dev;
  
  	class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
  	while ((dev = class_dev_iter_next(&iter))) {
  		struct gendisk *disk = dev_to_disk(dev);

  		struct disk_part_iter piter;
  		struct hd_struct *part;

  		char name_buf[BDEVNAME_SIZE];
  		char devt_buf[BDEVT_SIZE];

  
  		/*
  		 * Don't show empty devices or things that have been

  		 * suppressed

  		 */
  		if (get_capacity(disk) == 0 ||
  		    (disk->flags & GENHD_FL_SUPPRESS_PARTITION_INFO))
  			continue;
  
  		/*
  		 * Note, unlike /proc/partitions, I am showing the
  		 * numbers in hex - the same format as the root=
  		 * option takes.
  		 */

  		disk_part_iter_init(&piter, disk, DISK_PITER_INCL_PART0);
  		while ((part = disk_part_iter_next(&piter))) {
  			bool is_part0 = part == &disk->part0;

  			printk("%s%s %10llu %s %s", is_part0 ? "" : "  ",

  			       bdevt_str(part_devt(part), devt_buf),

  			       (unsigned long long)part_nr_sects_read(part) >> 1
  			       , disk_name(disk, part->partno, name_buf),

  			       part->info ? part->info->uuid : "");

  			if (is_part0) {

  				if (dev->parent && dev->parent->driver)

  					printk(" driver: %s
  ",

  					      dev->parent->driver->name);

  				else
  					printk(" (driver?)
  ");
  			} else
  				printk("
  ");
  		}

  		disk_part_iter_exit(&piter);

  	}
  	class_dev_iter_exit(&iter);

  }

  #ifdef CONFIG_PROC_FS
  /* iterator */

  static void *disk_seqf_start(struct seq_file *seqf, loff_t *pos)

  {

  	loff_t skip = *pos;
  	struct class_dev_iter *iter;
  	struct device *dev;

  	iter = kmalloc(sizeof(*iter), GFP_KERNEL);

  	if (!iter)
  		return ERR_PTR(-ENOMEM);
  
  	seqf->private = iter;
  	class_dev_iter_init(iter, &block_class, NULL, &disk_type);
  	do {
  		dev = class_dev_iter_next(iter);
  		if (!dev)
  			return NULL;
  	} while (skip--);
  
  	return dev_to_disk(dev);

  }

  static void *disk_seqf_next(struct seq_file *seqf, void *v, loff_t *pos)

  {

  	struct device *dev;

  	(*pos)++;
  	dev = class_dev_iter_next(seqf->private);

  	if (dev)

  		return dev_to_disk(dev);

  	return NULL;
  }

  static void disk_seqf_stop(struct seq_file *seqf, void *v)

  {

  	struct class_dev_iter *iter = seqf->private;

  	/* stop is called even after start failed :-( */
  	if (iter) {
  		class_dev_iter_exit(iter);
  		kfree(iter);

  		seqf->private = NULL;

  	}

  }

  static void *show_partition_start(struct seq_file *seqf, loff_t *pos)

  {

  	void *p;

  
  	p = disk_seqf_start(seqf, pos);

  	if (!IS_ERR_OR_NULL(p) && !*pos)

  		seq_puts(seqf, "major minor  #blocks  name
  
  ");
  	return p;

  }

  static int show_partition(struct seq_file *seqf, void *v)

  {
  	struct gendisk *sgp = v;

  	struct disk_part_iter piter;
  	struct hd_struct *part;

  	char buf[BDEVNAME_SIZE];

  	/* Don't show non-partitionable removeable devices or empty devices */

  	if (!get_capacity(sgp) || (!disk_max_parts(sgp) &&

  				   (sgp->flags & GENHD_FL_REMOVABLE)))

  		return 0;
  	if (sgp->flags & GENHD_FL_SUPPRESS_PARTITION_INFO)
  		return 0;
  
  	/* show the full disk and all non-0 size partitions of it */

  	disk_part_iter_init(&piter, sgp, DISK_PITER_INCL_PART0);

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

  		seq_printf(seqf, "%4d  %7d %10llu %s
  ",

  			   MAJOR(part_devt(part)), MINOR(part_devt(part)),

  			   (unsigned long long)part_nr_sects_read(part) >> 1,

  			   disk_name(sgp, part->partno, buf));

  	disk_part_iter_exit(&piter);

  
  	return 0;
  }

  static const struct seq_operations partitions_op = {

  	.start	= show_partition_start,
  	.next	= disk_seqf_next,
  	.stop	= disk_seqf_stop,

  	.show	= show_partition

  };
  #endif

  static struct kobject *base_probe(dev_t devt, int *partno, void *data)

  {

  	if (request_module("block-major-%d-%d", MAJOR(devt), MINOR(devt)) > 0)

  		/* Make old-style 2.4 aliases work */

  		request_module("block-major-%d", MAJOR(devt));

  	return NULL;
  }
  
  static int __init genhd_device_init(void)
  {

  	int error;
  
  	block_class.dev_kobj = sysfs_dev_block_kobj;
  	error = class_register(&block_class);

  	if (unlikely(error))
  		return error;

  	bdev_map = kobj_map_init(base_probe, &block_class_lock);

  	blk_dev_init();

  	register_blkdev(BLOCK_EXT_MAJOR, "blkext");

  	/* create top-level block dir */

  	if (!sysfs_deprecated)
  		block_depr = kobject_create_and_add("block", NULL);

  	return 0;

  }
  
  subsys_initcall(genhd_device_init);

  static ssize_t disk_range_show(struct device *dev,
  			       struct device_attribute *attr, char *buf)

  {

  	struct gendisk *disk = dev_to_disk(dev);

  	return sprintf(buf, "%d
  ", disk->minors);

  }

  static ssize_t disk_ext_range_show(struct device *dev,
  				   struct device_attribute *attr, char *buf)
  {
  	struct gendisk *disk = dev_to_disk(dev);

  	return sprintf(buf, "%d
  ", disk_max_parts(disk));

  }

  static ssize_t disk_removable_show(struct device *dev,
  				   struct device_attribute *attr, char *buf)

  {

  	struct gendisk *disk = dev_to_disk(dev);

  	return sprintf(buf, "%d
  ",
  		       (disk->flags & GENHD_FL_REMOVABLE ? 1 : 0));

  }

  static ssize_t disk_hidden_show(struct device *dev,
  				   struct device_attribute *attr, char *buf)
  {
  	struct gendisk *disk = dev_to_disk(dev);
  
  	return sprintf(buf, "%d
  ",
  		       (disk->flags & GENHD_FL_HIDDEN ? 1 : 0));
  }

  static ssize_t disk_ro_show(struct device *dev,
  				   struct device_attribute *attr, char *buf)
  {
  	struct gendisk *disk = dev_to_disk(dev);

  	return sprintf(buf, "%d
  ", get_disk_ro(disk) ? 1 : 0);

  }

  ssize_t part_size_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)part_nr_sects_read(p));
  }
  
  ssize_t part_stat_show(struct device *dev,
  		       struct device_attribute *attr, char *buf)
  {
  	struct hd_struct *p = dev_to_part(dev);
  	struct request_queue *q = part_to_disk(p)->queue;

  	struct disk_stats stat;

  	unsigned int inflight;

  	part_stat_read_all(p, &stat);

  	if (queue_is_mq(q))
  		inflight = blk_mq_in_flight(q, p);
  	else

  		inflight = part_in_flight(p);

  	return sprintf(buf,
  		"%8lu %8lu %8llu %8u "
  		"%8lu %8lu %8llu %8u "
  		"%8u %8u %8u "
  		"%8lu %8lu %8llu %8u "
  		"%8lu %8u"
  		"
  ",

  		stat.ios[STAT_READ],
  		stat.merges[STAT_READ],
  		(unsigned long long)stat.sectors[STAT_READ],
  		(unsigned int)div_u64(stat.nsecs[STAT_READ], NSEC_PER_MSEC),
  		stat.ios[STAT_WRITE],
  		stat.merges[STAT_WRITE],
  		(unsigned long long)stat.sectors[STAT_WRITE],
  		(unsigned int)div_u64(stat.nsecs[STAT_WRITE], NSEC_PER_MSEC),

  		inflight,

  		jiffies_to_msecs(stat.io_ticks),

  		(unsigned int)div_u64(stat.nsecs[STAT_READ] +
  				      stat.nsecs[STAT_WRITE] +
  				      stat.nsecs[STAT_DISCARD] +
  				      stat.nsecs[STAT_FLUSH],
  						NSEC_PER_MSEC),

  		stat.ios[STAT_DISCARD],
  		stat.merges[STAT_DISCARD],
  		(unsigned long long)stat.sectors[STAT_DISCARD],
  		(unsigned int)div_u64(stat.nsecs[STAT_DISCARD], NSEC_PER_MSEC),
  		stat.ios[STAT_FLUSH],
  		(unsigned int)div_u64(stat.nsecs[STAT_FLUSH], NSEC_PER_MSEC));

  }
  
  ssize_t part_inflight_show(struct device *dev, struct device_attribute *attr,
  			   char *buf)
  {
  	struct hd_struct *p = dev_to_part(dev);
  	struct request_queue *q = part_to_disk(p)->queue;
  	unsigned int inflight[2];

  	if (queue_is_mq(q))
  		blk_mq_in_flight_rw(q, p, inflight);
  	else

  		part_in_flight_rw(p, inflight);

  	return sprintf(buf, "%8u %8u
  ", inflight[0], inflight[1]);
  }

  static ssize_t disk_capability_show(struct device *dev,
  				    struct device_attribute *attr, char *buf)

  {

  	struct gendisk *disk = dev_to_disk(dev);
  
  	return sprintf(buf, "%x
  ", disk->flags);

  }

  static ssize_t disk_alignment_offset_show(struct device *dev,
  					  struct device_attribute *attr,
  					  char *buf)
  {
  	struct gendisk *disk = dev_to_disk(dev);
  
  	return sprintf(buf, "%d
  ", queue_alignment_offset(disk->queue));
  }

  static ssize_t disk_discard_alignment_show(struct device *dev,
  					   struct device_attribute *attr,
  					   char *buf)
  {
  	struct gendisk *disk = dev_to_disk(dev);

  	return sprintf(buf, "%d
  ", queue_discard_alignment(disk->queue));

  }

  static DEVICE_ATTR(range, 0444, disk_range_show, NULL);
  static DEVICE_ATTR(ext_range, 0444, disk_ext_range_show, NULL);
  static DEVICE_ATTR(removable, 0444, disk_removable_show, NULL);
  static DEVICE_ATTR(hidden, 0444, disk_hidden_show, NULL);
  static DEVICE_ATTR(ro, 0444, disk_ro_show, NULL);
  static DEVICE_ATTR(size, 0444, part_size_show, NULL);
  static DEVICE_ATTR(alignment_offset, 0444, disk_alignment_offset_show, NULL);
  static DEVICE_ATTR(discard_alignment, 0444, disk_discard_alignment_show, NULL);
  static DEVICE_ATTR(capability, 0444, disk_capability_show, NULL);
  static DEVICE_ATTR(stat, 0444, part_stat_show, NULL);
  static DEVICE_ATTR(inflight, 0444, part_inflight_show, NULL);
  static DEVICE_ATTR(badblocks, 0644, disk_badblocks_show, disk_badblocks_store);

  #ifdef CONFIG_FAIL_MAKE_REQUEST

  ssize_t part_fail_show(struct device *dev,
  		       struct device_attribute *attr, char *buf)
  {
  	struct hd_struct *p = dev_to_part(dev);
  
  	return sprintf(buf, "%d
  ", p->make_it_fail);
  }
  
  ssize_t part_fail_store(struct device *dev,
  			struct device_attribute *attr,
  			const char *buf, size_t count)
  {
  	struct hd_struct *p = dev_to_part(dev);
  	int i;
  
  	if (count > 0 && sscanf(buf, "%d", &i) > 0)
  		p->make_it_fail = (i == 0) ? 0 : 1;
  
  	return count;
  }

  static struct device_attribute dev_attr_fail =

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

  #endif /* CONFIG_FAIL_MAKE_REQUEST */

  #ifdef CONFIG_FAIL_IO_TIMEOUT
  static struct device_attribute dev_attr_fail_timeout =

  	__ATTR(io-timeout-fail, 0644, part_timeout_show, part_timeout_store);

  #endif

  
  static struct attribute *disk_attrs[] = {
  	&dev_attr_range.attr,

  	&dev_attr_ext_range.attr,

  	&dev_attr_removable.attr,

  	&dev_attr_hidden.attr,

  	&dev_attr_ro.attr,

  	&dev_attr_size.attr,

  	&dev_attr_alignment_offset.attr,

  	&dev_attr_discard_alignment.attr,

  	&dev_attr_capability.attr,
  	&dev_attr_stat.attr,

  	&dev_attr_inflight.attr,

  	&dev_attr_badblocks.attr,

  #ifdef CONFIG_FAIL_MAKE_REQUEST
  	&dev_attr_fail.attr,
  #endif

  #ifdef CONFIG_FAIL_IO_TIMEOUT
  	&dev_attr_fail_timeout.attr,
  #endif

  	NULL
  };

  static umode_t disk_visible(struct kobject *kobj, struct attribute *a, int n)
  {
  	struct device *dev = container_of(kobj, typeof(*dev), kobj);
  	struct gendisk *disk = dev_to_disk(dev);
  
  	if (a == &dev_attr_badblocks.attr && !disk->bb)
  		return 0;
  	return a->mode;
  }

  static struct attribute_group disk_attr_group = {
  	.attrs = disk_attrs,

  	.is_visible = disk_visible,

  };

  static const struct attribute_group *disk_attr_groups[] = {

  	&disk_attr_group,
  	NULL

  };

  /**
   * disk_replace_part_tbl - replace disk->part_tbl in RCU-safe way
   * @disk: disk to replace part_tbl for
   * @new_ptbl: new part_tbl to install
   *
   * Replace disk->part_tbl with @new_ptbl in RCU-safe way.  The
   * original ptbl is freed using RCU callback.
   *
   * LOCKING:

   * Matching bd_mutex locked or the caller is the only user of @disk.

   */
  static void disk_replace_part_tbl(struct gendisk *disk,
  				  struct disk_part_tbl *new_ptbl)
  {

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

  
  	rcu_assign_pointer(disk->part_tbl, new_ptbl);

  
  	if (old_ptbl) {
  		rcu_assign_pointer(old_ptbl->last_lookup, NULL);

  		kfree_rcu(old_ptbl, rcu_head);

  	}

  }
  
  /**
   * disk_expand_part_tbl - expand disk->part_tbl
   * @disk: disk to expand part_tbl for
   * @partno: expand such that this partno can fit in
   *
   * Expand disk->part_tbl such that @partno can fit in.  disk->part_tbl
   * uses RCU to allow unlocked dereferencing for stats and other stuff.
   *
   * LOCKING:

   * Matching bd_mutex locked or the caller is the only user of @disk.
   * Might sleep.

   *
   * RETURNS:
   * 0 on success, -errno on failure.
   */
  int disk_expand_part_tbl(struct gendisk *disk, int partno)
  {

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

  	struct disk_part_tbl *new_ptbl;
  	int len = old_ptbl ? old_ptbl->len : 0;

  	int i, target;

  
  	/*
  	 * check for int overflow, since we can get here from blkpg_ioctl()
  	 * with a user passed 'partno'.
  	 */
  	target = partno + 1;
  	if (target < 0)
  		return -EINVAL;

  
  	/* disk_max_parts() is zero during initialization, ignore if so */
  	if (disk_max_parts(disk) && target > disk_max_parts(disk))
  		return -EINVAL;
  
  	if (target <= len)
  		return 0;

  	new_ptbl = kzalloc_node(struct_size(new_ptbl, part, target), GFP_KERNEL,
  				disk->node_id);

  	if (!new_ptbl)
  		return -ENOMEM;

  	new_ptbl->len = target;
  
  	for (i = 0; i < len; i++)
  		rcu_assign_pointer(new_ptbl->part[i], old_ptbl->part[i]);
  
  	disk_replace_part_tbl(disk, new_ptbl);
  	return 0;
  }

  /**
   * disk_release - releases all allocated resources of the gendisk
   * @dev: the device representing this disk
   *
   * This function releases all allocated resources of the gendisk.
   *
   * The struct gendisk refcount is incremented with get_gendisk() or
   * get_disk_and_module(), and its refcount is decremented with
   * put_disk_and_module() or put_disk(). Once the refcount reaches 0 this
   * function is called.
   *
   * Drivers which used __device_add_disk() have a gendisk with a request_queue
   * assigned. Since the request_queue sits on top of the gendisk for these
   * drivers we also call blk_put_queue() for them, and we expect the
   * request_queue refcount to reach 0 at this point, and so the request_queue
   * will also be freed prior to the disk.

   *
   * Context: can sleep

   */

  static void disk_release(struct device *dev)

  {

  	struct gendisk *disk = dev_to_disk(dev);

  	might_sleep();

  	blk_free_devt(dev->devt);

  	disk_release_events(disk);

  	kfree(disk->random);

  	disk_replace_part_tbl(disk, NULL);

  	hd_free_part(&disk->part0);

  	if (disk->queue)
  		blk_put_queue(disk->queue);

  	kfree(disk);
  }

  struct class block_class = {
  	.name		= "block",

  };

  static char *block_devnode(struct device *dev, umode_t *mode,

  			   kuid_t *uid, kgid_t *gid)

  {
  	struct gendisk *disk = dev_to_disk(dev);

  	if (disk->fops->devnode)
  		return disk->fops->devnode(disk, mode);

  	return NULL;
  }

  const struct device_type disk_type = {

  	.name		= "disk",
  	.groups		= disk_attr_groups,
  	.release	= disk_release,

  	.devnode	= block_devnode,

  };

  #ifdef CONFIG_PROC_FS

  /*
   * aggregate disk stat collector.  Uses the same stats that the sysfs
   * entries do, above, but makes them available through one seq_file.
   *
   * The output looks suspiciously like /proc/partitions with a bunch of
   * extra fields.
   */
  static int diskstats_show(struct seq_file *seqf, void *v)

  {
  	struct gendisk *gp = v;

  	struct disk_part_iter piter;
  	struct hd_struct *hd;

  	char buf[BDEVNAME_SIZE];

  	unsigned int inflight;

  	struct disk_stats stat;

  
  	/*

  	if (&disk_to_dev(gp)->kobj.entry == block_class.devices.next)

  		seq_puts(seqf,	"major minor name"

  				"     rio rmerge rsect ruse wio wmerge "
  				"wsect wuse running use aveq"
  				"
  
  ");
  	*/

  	disk_part_iter_init(&piter, gp, DISK_PITER_INCL_EMPTY_PART0);

  	while ((hd = disk_part_iter_next(&piter))) {

  		part_stat_read_all(hd, &stat);

  		if (queue_is_mq(gp->queue))
  			inflight = blk_mq_in_flight(gp->queue, hd);
  		else

  			inflight = part_in_flight(hd);

  		seq_printf(seqf, "%4d %7d %s "
  			   "%lu %lu %lu %u "
  			   "%lu %lu %lu %u "
  			   "%u %u %u "

  			   "%lu %lu %lu %u "
  			   "%lu %u"
  			   "
  ",

  			   MAJOR(part_devt(hd)), MINOR(part_devt(hd)),
  			   disk_name(gp, hd->partno, buf),

  			   stat.ios[STAT_READ],
  			   stat.merges[STAT_READ],
  			   stat.sectors[STAT_READ],
  			   (unsigned int)div_u64(stat.nsecs[STAT_READ],
  							NSEC_PER_MSEC),
  			   stat.ios[STAT_WRITE],
  			   stat.merges[STAT_WRITE],
  			   stat.sectors[STAT_WRITE],
  			   (unsigned int)div_u64(stat.nsecs[STAT_WRITE],
  							NSEC_PER_MSEC),

  			   inflight,

  			   jiffies_to_msecs(stat.io_ticks),

  			   (unsigned int)div_u64(stat.nsecs[STAT_READ] +
  						 stat.nsecs[STAT_WRITE] +
  						 stat.nsecs[STAT_DISCARD] +
  						 stat.nsecs[STAT_FLUSH],
  							NSEC_PER_MSEC),

  			   stat.ios[STAT_DISCARD],
  			   stat.merges[STAT_DISCARD],
  			   stat.sectors[STAT_DISCARD],
  			   (unsigned int)div_u64(stat.nsecs[STAT_DISCARD],
  						 NSEC_PER_MSEC),
  			   stat.ios[STAT_FLUSH],
  			   (unsigned int)div_u64(stat.nsecs[STAT_FLUSH],
  						 NSEC_PER_MSEC)

  			);

  	}

  	disk_part_iter_exit(&piter);

  	return 0;
  }

  static const struct seq_operations diskstats_op = {

  	.start	= disk_seqf_start,
  	.next	= disk_seqf_next,
  	.stop	= disk_seqf_stop,

  	.show	= diskstats_show
  };

  
  static int __init proc_genhd_init(void)
  {

  	proc_create_seq("diskstats", 0, NULL, &diskstats_op);
  	proc_create_seq("partitions", 0, NULL, &partitions_op);

  	return 0;
  }
  module_init(proc_genhd_init);

  #endif /* CONFIG_PROC_FS */

  dev_t blk_lookup_devt(const char *name, int partno)

  {

  	dev_t devt = MKDEV(0, 0);
  	struct class_dev_iter iter;
  	struct device *dev;

  	class_dev_iter_init(&iter, &block_class, NULL, &disk_type);
  	while ((dev = class_dev_iter_next(&iter))) {

  		struct gendisk *disk = dev_to_disk(dev);

  		struct hd_struct *part;

  		if (strcmp(dev_name(dev), name))

  			continue;

  		if (partno < disk->minors) {
  			/* We need to return the right devno, even
  			 * if the partition doesn't exist yet.
  			 */
  			devt = MKDEV(MAJOR(dev->devt),
  				     MINOR(dev->devt) + partno);
  			break;
  		}

  		part = disk_get_part(disk, partno);

  		if (part) {

  			devt = part_devt(part);

  			disk_put_part(part);

  			break;

  		}

  		disk_put_part(part);

  	}

  	class_dev_iter_exit(&iter);

  	return devt;
  }

  struct gendisk *__alloc_disk_node(int minors, int node_id)

  {
  	struct gendisk *disk;

  	struct disk_part_tbl *ptbl;

  	if (minors > DISK_MAX_PARTS) {
  		printk(KERN_ERR

  			"block: can't allocate more than %d partitions
  ",

  			DISK_MAX_PARTS);
  		minors = DISK_MAX_PARTS;
  	}

  	disk = kzalloc_node(sizeof(struct gendisk), GFP_KERNEL, node_id);

  	if (!disk)
  		return NULL;

  	disk->part0.dkstats = alloc_percpu(struct disk_stats);
  	if (!disk->part0.dkstats)
  		goto out_free_disk;

  	init_rwsem(&disk->lookup_sem);
  	disk->node_id = node_id;
  	if (disk_expand_part_tbl(disk, 0)) {
  		free_percpu(disk->part0.dkstats);
  		goto out_free_disk;

  	}

  
  	ptbl = rcu_dereference_protected(disk->part_tbl, 1);
  	rcu_assign_pointer(ptbl->part[0], &disk->part0);
  
  	/*
  	 * set_capacity() and get_capacity() currently don't use
  	 * seqcounter to read/update the part0->nr_sects. Still init
  	 * the counter as we can read the sectors in IO submission
  	 * patch using seqence counters.
  	 *
  	 * TODO: Ideally set_capacity() and get_capacity() should be
  	 * converted to make use of bd_mutex and sequence counters.
  	 */
  	hd_sects_seq_init(&disk->part0);
  	if (hd_ref_init(&disk->part0))
  		goto out_free_part0;
  
  	disk->minors = minors;
  	rand_initialize_disk(disk);
  	disk_to_dev(disk)->class = &block_class;
  	disk_to_dev(disk)->type = &disk_type;
  	device_initialize(disk_to_dev(disk));

  	return disk;