/*
   *  gendisk handling
   */

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

  #include <linux/kdev_t.h>

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

  #include <linux/mutex.h>

  #include <linux/idr.h>

  #include "blk.h"

  static DEFINE_MUTEX(block_class_lock);
  #ifndef CONFIG_SYSFS_DEPRECATED
  struct kobject *block_depr;
  #endif

  /* for extended dynamic devt allocation, currently only one major is used */
  #define MAX_EXT_DEVT		(1 << MINORBITS)
  
  /* For extended devt allocation.  ext_devt_mutex prevents look up
   * results from going away underneath its user.
   */
  static DEFINE_MUTEX(ext_devt_mutex);
  static DEFINE_IDR(ext_devt_idr);

  static struct device_type disk_type;

  /**
   * 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 = NULL;
  	struct disk_part_tbl *ptbl;

  	if (unlikely(partno < 0))

  		return NULL;

  	rcu_read_lock();

  
  	ptbl = rcu_dereference(disk->part_tbl);
  	if (likely(partno < ptbl->len)) {
  		part = rcu_dereference(ptbl->part[partno]);
  		if (part)
  			get_device(part_to_dev(part));
  	}

  	rcu_read_unlock();
  
  	return part;
  }
  EXPORT_SYMBOL_GPL(disk_get_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;

  		if (!part->nr_sects &&
  		    !(piter->flags & DISK_PITER_INCL_EMPTY) &&
  		    !(piter->flags & DISK_PITER_INCL_EMPTY_PART0 &&
  		      piter->idx == 0))

  			continue;

  		get_device(part_to_dev(part));

  		piter->part = part;
  		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;
  }

  /**
   * 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 valid only
   * while preemption is disabled.
   *
   * RETURNS:

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

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

  	struct disk_part_tbl *ptbl;

  	struct hd_struct *part;

  	int i;

  	ptbl = rcu_dereference(disk->part_tbl);

  	part = rcu_dereference(ptbl->last_lookup);
  	if (part && sector_in_part(part, sector))
  		return part;

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

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

  		if (part && sector_in_part(part, sector)) {
  			rcu_assign_pointer(ptbl->last_lookup, part);

  			return part;

  		}

  	}

  	return &disk->part0;

  }
  EXPORT_SYMBOL_GPL(disk_map_sector_rcu);

  /*
   * Can be deleted altogether. Later.
   *
   */
  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(int 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;

  	if (offset < BLKDEV_MAJOR_HASH_SIZE) {

  		mutex_lock(&block_class_lock);

  		for (dp = major_names[offset]; dp; dp = dp->next)

  			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..255]. 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..255] 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..255] or a negative error code otherwise
   */

  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("register_blkdev: failed to get major for %s
  ",
  			       name);
  			ret = -EBUSY;
  			goto out;
  		}
  		major = index;
  		ret = major;
  	}
  
  	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 %d 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, rc;
  
  	/* in consecutive minor range? */
  	if (part->partno < disk->minors) {
  		*devt = MKDEV(disk->major, disk->first_minor + part->partno);
  		return 0;
  	}
  
  	/* allocate ext devt */
  	do {
  		if (!idr_pre_get(&ext_devt_idr, GFP_KERNEL))
  			return -ENOMEM;
  		rc = idr_get_new(&ext_devt_idr, part, &idx);
  	} while (rc == -EAGAIN);
  
  	if (rc)
  		return rc;
  
  	if (idx > MAX_EXT_DEVT) {
  		idr_remove(&ext_devt_idr, idx);
  		return -EBUSY;
  	}

  	*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)
  {
  	might_sleep();
  
  	if (devt == MKDEV(0, 0))
  		return;
  
  	if (MAJOR(devt) == BLOCK_EXT_MAJOR) {
  		mutex_lock(&ext_devt_mutex);

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

  		mutex_unlock(&ext_devt_mutex);
  	}
  }

  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(p))
  		return -1;
  	return 0;
  }
  
  /**
   * add_disk - add partitioning information to kernel list
   * @disk: per-device partitioning information
   *
   * This function registers the partitioning information in @disk
   * with the kernel.

   *
   * FIXME: error handling

   */
  void add_disk(struct gendisk *disk)
  {

  	struct backing_dev_info *bdi;

  	dev_t devt;

  	int retval;

  	/* 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));

  	disk->flags |= GENHD_FL_UP;

  
  	retval = blk_alloc_devt(&disk->part0, &devt);
  	if (retval) {
  		WARN_ON(1);
  		return;
  	}
  	disk_to_dev(disk)->devt = devt;
  
  	/* ->major and ->first_minor aren't supposed to be
  	 * dereferenced from here on, but set them just in case.
  	 */
  	disk->major = MAJOR(devt);
  	disk->first_minor = MINOR(devt);

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

  	register_disk(disk);
  	blk_register_queue(disk);

  
  	bdi = &disk->queue->backing_dev_info;

  	bdi_register_dev(bdi, disk_devt(disk));

  	retval = sysfs_create_link(&disk_to_dev(disk)->kobj, &bdi->dev->kobj,
  				   "bdi");

  	WARN_ON(retval);

  }
  
  EXPORT_SYMBOL(add_disk);
  EXPORT_SYMBOL(del_gendisk);	/* in partitions/check.c */
  
  void unlink_gendisk(struct gendisk *disk)
  {

  	sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");

  	bdi_unregister(&disk->queue->backing_dev_info);

  	blk_unregister_queue(disk);

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

  }

  /**
   * 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.

   */

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

  {

  	struct gendisk *disk = NULL;
  
  	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;
  
  		mutex_lock(&ext_devt_mutex);

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

  		if (part && get_disk(part_to_disk(part))) {
  			*partno = part->partno;
  			disk = part_to_disk(part);
  		}
  		mutex_unlock(&ext_devt_mutex);
  	}

  	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_devt(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
  		 * surpressed
  		 */
  		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", is_part0 ? "" : "  ",

  			       bdevt_str(part_devt(part), devt_buf),

  			       (unsigned long long)part->nr_sects >> 1,

  			       disk_name(disk, part->partno, name_buf));

  			if (is_part0) {
  				if (disk->driverfs_dev != NULL &&
  				    disk->driverfs_dev->driver != NULL)
  					printk(" driver: %s
  ",
  					      disk->driverfs_dev->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);

  	}

  }

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

  {

  	static void *p;
  
  	p = disk_seqf_start(seqf, pos);

  	if (!IS_ERR(p) && 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_partitionable(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 >> 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

  };

  
  static int partitions_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &partitions_op);
  }
  
  static const struct file_operations proc_partitions_operations = {
  	.open		= partitions_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release,
  };

  #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");

  #ifndef CONFIG_SYSFS_DEPRECATED
  	/* create top-level block dir */
  	block_depr = kobject_create_and_add("block", NULL);
  #endif

  	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_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);

  }

  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 DEVICE_ATTR(range, S_IRUGO, disk_range_show, NULL);

  static DEVICE_ATTR(ext_range, S_IRUGO, disk_ext_range_show, NULL);

  static DEVICE_ATTR(removable, S_IRUGO, disk_removable_show, NULL);

  static DEVICE_ATTR(ro, S_IRUGO, disk_ro_show, NULL);

  static DEVICE_ATTR(size, S_IRUGO, part_size_show, NULL);

  static DEVICE_ATTR(alignment_offset, S_IRUGO, disk_alignment_offset_show, NULL);

  static DEVICE_ATTR(capability, S_IRUGO, disk_capability_show, NULL);

  static DEVICE_ATTR(stat, S_IRUGO, part_stat_show, NULL);

  static DEVICE_ATTR(inflight, S_IRUGO, part_inflight_show, NULL);

  #ifdef CONFIG_FAIL_MAKE_REQUEST

  static struct device_attribute dev_attr_fail =

  	__ATTR(make-it-fail, S_IRUGO|S_IWUSR, part_fail_show, part_fail_store);

  #endif

  #ifdef CONFIG_FAIL_IO_TIMEOUT
  static struct device_attribute dev_attr_fail_timeout =
  	__ATTR(io-timeout-fail,  S_IRUGO|S_IWUSR, 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_ro.attr,

  	&dev_attr_size.attr,

  	&dev_attr_alignment_offset.attr,

  	&dev_attr_capability.attr,
  	&dev_attr_stat.attr,

  	&dev_attr_inflight.attr,

  #ifdef CONFIG_FAIL_MAKE_REQUEST
  	&dev_attr_fail.attr,
  #endif

  #ifdef CONFIG_FAIL_IO_TIMEOUT
  	&dev_attr_fail_timeout.attr,
  #endif

  	NULL
  };
  
  static struct attribute_group disk_attr_group = {
  	.attrs = disk_attrs,
  };

  static const struct attribute_group *disk_attr_groups[] = {

  	&disk_attr_group,
  	NULL

  };

  static void disk_free_ptbl_rcu_cb(struct rcu_head *head)
  {
  	struct disk_part_tbl *ptbl =
  		container_of(head, struct disk_part_tbl, rcu_head);
  
  	kfree(ptbl);
  }
  
  /**
   * 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_mutx locked.
   */
  static void disk_replace_part_tbl(struct gendisk *disk,
  				  struct disk_part_tbl *new_ptbl)
  {
  	struct disk_part_tbl *old_ptbl = disk->part_tbl;
  
  	rcu_assign_pointer(disk->part_tbl, new_ptbl);

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

  		call_rcu(&old_ptbl->rcu_head, disk_free_ptbl_rcu_cb);

  	}

  }
  
  /**
   * 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, 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 = disk->part_tbl;
  	struct disk_part_tbl *new_ptbl;
  	int len = old_ptbl ? old_ptbl->len : 0;
  	int target = partno + 1;
  	size_t size;
  	int i;
  
  	/* 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;
  
  	size = sizeof(*new_ptbl) + target * sizeof(new_ptbl->part[0]);
  	new_ptbl = kzalloc_node(size, GFP_KERNEL, disk->node_id);
  	if (!new_ptbl)
  		return -ENOMEM;
  
  	INIT_RCU_HEAD(&new_ptbl->rcu_head);
  	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;
  }

  static void disk_release(struct device *dev)

  {

  	struct gendisk *disk = dev_to_disk(dev);

  	kfree(disk->random);

  	disk_replace_part_tbl(disk, NULL);

  	free_part_stats(&disk->part0);

  	kfree(disk);
  }

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

  };

  static char *block_devnode(struct device *dev, mode_t *mode)

  {
  	struct gendisk *disk = dev_to_disk(dev);

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

  	return NULL;
  }

  static 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];

  	int cpu;

  
  	/*

  	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))) {

  		cpu = part_stat_lock();

  		part_round_stats(cpu, hd);

  		part_stat_unlock();

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

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

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

  			   part_stat_read(hd, ios[0]),
  			   part_stat_read(hd, merges[0]),
  			   (unsigned long long)part_stat_read(hd, sectors[0]),
  			   jiffies_to_msecs(part_stat_read(hd, ticks[0])),
  			   part_stat_read(hd, ios[1]),
  			   part_stat_read(hd, merges[1]),
  			   (unsigned long long)part_stat_read(hd, sectors[1]),
  			   jiffies_to_msecs(part_stat_read(hd, ticks[1])),

  			   part_in_flight(hd),

  			   jiffies_to_msecs(part_stat_read(hd, io_ticks)),
  			   jiffies_to_msecs(part_stat_read(hd, time_in_queue))
  			);

  	}

  	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 diskstats_open(struct inode *inode, struct file *file)
  {
  	return seq_open(file, &diskstats_op);
  }
  
  static const struct file_operations proc_diskstats_operations = {
  	.open		= diskstats_open,
  	.read		= seq_read,
  	.llseek		= seq_lseek,
  	.release	= seq_release,
  };

  static int __init proc_genhd_init(void)
  {

  	proc_create("diskstats", 0, NULL, &proc_diskstats_operations);

  	proc_create("partitions", 0, NULL, &proc_partitions_operations);
  	return 0;
  }
  module_init(proc_genhd_init);

  #endif /* CONFIG_PROC_FS */

  static void media_change_notify_thread(struct work_struct *work)
  {
  	struct gendisk *gd = container_of(work, struct gendisk, async_notify);
  	char event[] = "MEDIA_CHANGE=1";
  	char *envp[] = { event, NULL };
  
  	/*
  	 * set enviroment vars to indicate which event this is for
  	 * so that user space will know to go check the media status.
  	 */

  	kobject_uevent_env(&disk_to_dev(gd)->kobj, KOBJ_CHANGE, envp);

  	put_device(gd->driverfs_dev);
  }

  #if 0

  void genhd_media_change_notify(struct gendisk *disk)
  {
  	get_device(disk->driverfs_dev);
  	schedule_work(&disk->async_notify);
  }
  EXPORT_SYMBOL_GPL(genhd_media_change_notify);

  #endif  /*  0  */

  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;
  }

  EXPORT_SYMBOL(blk_lookup_devt);

  struct gendisk *alloc_disk(int minors)
  {

  	return alloc_disk_node(minors, -1);
  }

  EXPORT_SYMBOL(alloc_disk);

  
  struct gendisk *alloc_disk_node(int minors, int node_id)
  {
  	struct gendisk *disk;

  	disk = kmalloc_node(sizeof(struct gendisk),
  				GFP_KERNEL | __GFP_ZERO, node_id);

  	if (disk) {

  		if (!init_part_stats(&disk->part0)) {

  			kfree(disk);
  			return NULL;
  		}

  		disk->node_id = node_id;

  		if (disk_expand_part_tbl(disk, 0)) {
  			free_part_stats(&disk->part0);

  			kfree(disk);
  			return NULL;

  		}

  		disk->part_tbl->part[0] = &disk->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));

  		INIT_WORK(&disk->async_notify,
  			media_change_notify_thread);

  	}
  	return disk;
  }

  EXPORT_SYMBOL(alloc_disk_node);

  
  struct kobject *get_disk(struct gendisk *disk)
  {
  	struct module *owner;
  	struct kobject *kobj;
  
  	if (!disk->fops)
  		return NULL;
  	owner = disk->fops->owner;
  	if (owner && !try_module_get(owner))
  		return NULL;

  	kobj = kobject_get(&disk_to_dev(disk)->kobj);

  	if (kobj == NULL) {
  		module_put(owner);
  		return NULL;
  	}
  	return kobj;
  
  }
  
  EXPORT_SYMBOL(get_disk);
  
  void put_disk(struct gendisk *disk)
  {
  	if (disk)

  		kobject_put(&disk_to_dev(disk)->kobj);

  }
  
  EXPORT_SYMBOL(put_disk);

  static void set_disk_ro_uevent(struct gendisk *gd, int ro)
  {
  	char event[] = "DISK_RO=1";
  	char *envp[] = { event, NULL };
  
  	if (!ro)
  		event[8] = '0';
  	kobject_uevent_env(&disk_to_dev(gd)->kobj, KOBJ_CHANGE, envp);
  }

  void set_device_ro(struct block_device *bdev, int flag)
  {

  	bdev->bd_part->policy = flag;

  }
  
  EXPORT_SYMBOL(set_device_ro);
  
  void set_disk_ro(struct gendisk *disk, int flag)
  {

  	struct disk_part_iter piter;
  	struct hd_struct *part;

  	if (disk->part0.policy != flag) {
  		set_disk_ro_uevent(disk, flag);
  		disk->part0.policy = flag;
  	}
  
  	disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);

  	while ((part = disk_part_iter_next(&piter)))
  		part->policy = flag;
  	disk_part_iter_exit(&piter);

  }
  
  EXPORT_SYMBOL(set_disk_ro);
  
  int bdev_read_only(struct block_device *bdev)
  {
  	if (!bdev)
  		return 0;

  	return bdev->bd_part->policy;

  }
  
  EXPORT_SYMBOL(bdev_read_only);

  int invalidate_partition(struct gendisk *disk, int partno)

  {
  	int res = 0;

  	struct block_device *bdev = bdget_disk(disk, partno);

  	if (bdev) {

  		fsync_bdev(bdev);
  		res = __invalidate_device(bdev);

  		bdput(bdev);
  	}
  	return res;
  }
  
  EXPORT_SYMBOL(invalidate_partition);