text: /*
   *  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/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);
  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 const struct device_type disk_type;
  
  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);
  
  void part_inc_in_flight(struct request_queue *q, struct hd_struct *part, int rw)
  {
  	if (q->mq_ops)
  		return;
  
  	atomic_inc(&part->in_flight[rw]);
  	if (part->partno)
  		atomic_inc(&part_to_disk(part)->part0.in_flight[rw]);
  }
  
  void part_dec_in_flight(struct request_queue *q, struct hd_struct *part, int rw)
  {
  	if (q->mq_ops)
  		return;
  
  	atomic_dec(&part->in_flight[rw]);
  	if (part->partno)
  		atomic_dec(&part_to_disk(part)->part0.in_flight[rw]);
  }
  
  void part_in_flight(struct request_queue *q, struct hd_struct *part,
  		    unsigned int inflight[2])
  {
  	if (q->mq_ops) {
  		blk_mq_in_flight(q, part, inflight);
  		return;
  	}
  
  	inflight[0] = atomic_read(&part->in_flight[0]) +
  			atomic_read(&part->in_flight[1]);
  	if (part->partno) {
  		part = &part_to_disk(part)->part0;
  		inflight[1] = atomic_read(&part->in_flight[0]) +
  				atomic_read(&part->in_flight[1]);
  	}
  }
  
  void part_in_flight_rw(struct request_queue *q, struct hd_struct *part,
  		       unsigned int inflight[2])
  {
  	if (q->mq_ops) {
  		blk_mq_in_flight_rw(q, part, inflight);
  		return;
  	}
  
  	inflight[0] = atomic_read(&part->in_flight[0]);
  	inflight[1] = atomic_read(&part->in_flight[1]);
  }
  
  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;
  }
  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_read(part) &&
  		    !(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_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 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.
   *
   */
  #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\n", 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\n",
  			       name);
  			ret = -EBUSY;
  			goto out;
  		}
  		major = index;
  		ret = major;
  	}
  
  	if (major >= BLKDEV_MAJOR_MAX) {
  		pr_err("register_blkdev: major requested (%d) is greater than the maximum (%d) for %s\n",
  		       major, BLKDEV_MAJOR_MAX, 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 %d for %s\n",
  		       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);
  	}
  }
  
  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;
  }
  
  static void register_disk(struct device *parent, struct gendisk *disk)
  {
  	struct device *ddev = disk_to_dev(disk);
  	struct block_device *bdev;
  	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 (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);
  
  	/* No minors to use for partitions */
  	if (!disk_part_scan_enabled(disk))
  		goto exit;
  
  	/* No such device (e.g., media were just removed) */
  	if (!get_capacity(disk))
  		goto exit;
  
  	bdev = bdget_disk(disk, 0);
  	if (!bdev)
  		goto exit;
  
  	bdev->bd_invalidated = 1;
  	err = blkdev_get(bdev, FMODE_READ, NULL);
  	if (err < 0)
  		goto exit;
  	blkdev_put(bdev, FMODE_READ);
  
  exit:
  	/* 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);
  }
  
  /**
   * device_add_disk - add partitioning information to kernel list
   * @parent: parent device for the disk
   * @disk: per-device partitioning information
   *
   * This function registers the partitioning information in @disk
   * with the kernel.
   *
   * FIXME: error handling
   */
  void device_add_disk(struct device *parent, 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);
  
  	disk_alloc_events(disk);
  
  	/* Register BDI before referencing it from bdev */
  	bdi = disk->queue->backing_dev_info;
  	bdi_register_owner(bdi, disk_to_dev(disk));
  
  	blk_register_region(disk_devt(disk), disk->minors, NULL,
  			    exact_match, exact_lock, disk);
  	register_disk(parent, disk);
  	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));
  
  	retval = sysfs_create_link(&disk_to_dev(disk)->kobj, &bdi->dev->kobj,
  				   "bdi");
  	WARN_ON(retval);
  
  	disk_add_events(disk);
  	blk_integrity_add(disk);
  }
  EXPORT_SYMBOL(device_add_disk);
  
  void del_gendisk(struct gendisk *disk)
  {
  	struct disk_part_iter piter;
  	struct hd_struct *part;
  
  	blk_integrity_del(disk);
  	disk_del_events(disk);
  
  	/* 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);
  		bdev_unhash_inode(part_devt(part));
  		delete_partition(disk, part->partno);
  	}
  	disk_part_iter_exit(&piter);
  
  	invalidate_partition(disk, 0);
  	bdev_unhash_inode(disk_devt(disk));
  	set_capacity(disk, 0);
  	disk->flags &= ~GENHD_FL_UP;
  
  	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).
  		 */
  		bdi_unregister(disk->queue->backing_dev_info);
  		blk_unregister_queue(disk);
  	} else {
  		WARN_ON(1);
  	}
  	blk_unregister_region(disk_devt(disk), disk->minors);
  
  	part_stat_set_all(&disk->part0, 0);
  	disk->part0.stamp = 0;
  
  	kobject_put(disk->part0.holder_dir);
  	kobject_put(disk->slave_dir);
  	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, "\n");
  
  	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.
   */
  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;
  
  		spin_lock_bh(&ext_devt_lock);
  		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);
  		}
  		spin_unlock_bh(&ext_devt_lock);
  	}
  
  	return disk;
  }
  EXPORT_SYMBOL(get_gendisk);
  
  /**
   * 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
  		 * 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\n",
  					      dev->parent->driver->name);
  				else
  					printk(" (driver?)\n");
  			} else
  				printk("\n");
  		}
  		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\n\n");
  	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\n",
  			   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
  };
  
  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");
  
  	/* 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\n", 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\n", 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\n",
  		       (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\n", 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\n", 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\n", 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\n", queue_discard_alignment(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(discard_alignment, S_IRUGO, disk_discard_alignment_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);
  static DEVICE_ATTR(badblocks, S_IRUGO | S_IWUSR, disk_badblocks_show,
  		disk_badblocks_store);
  #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_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;
  	size_t size;
  
  	/*
  	 * 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;
  
  	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;
  
  	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);
  
  	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->devnode)
  		return disk->devnode(disk, mode);
  	return NULL;
  }
  
  static 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[2];
  	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"
  				"\n\n");
  	*/
  
  	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(gp->queue, cpu, hd);
  		part_stat_unlock();
  		part_in_flight(gp->queue, hd, inflight);
  		seq_printf(seqf, "%4d %7d %s %lu %lu %lu "
  			   "%u %lu %lu %lu %u %u %u %u\n",
  			   MAJOR(part_devt(hd)), MINOR(part_devt(hd)),
  			   disk_name(gp, hd->partno, buf),
  			   part_stat_read(hd, ios[READ]),
  			   part_stat_read(hd, merges[READ]),
  			   part_stat_read(hd, sectors[READ]),
  			   jiffies_to_msecs(part_stat_read(hd, ticks[READ])),
  			   part_stat_read(hd, ios[WRITE]),
  			   part_stat_read(hd, merges[WRITE]),
  			   part_stat_read(hd, sectors[WRITE]),
  			   jiffies_to_msecs(part_stat_read(hd, ticks[WRITE])),
  			   inflight[0],
  			   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 */
  
  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, NUMA_NO_NODE);
  }
  EXPORT_SYMBOL(alloc_disk);
  
  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 allocated more than %d partitions\n",
  			DISK_MAX_PARTS);
  		minors = DISK_MAX_PARTS;
  	}
  
  	disk = kzalloc_node(sizeof(struct gendisk), GFP_KERNEL, 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;
  		}
  		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.
  		 */
  		seqcount_init(&disk->part0.nr_sects_seq);
  		if (hd_ref_init(&disk->part0)) {
  			hd_free_part(&disk->part0);
  			kfree(disk);
  			return NULL;
  		}
  
  		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;
  }
  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_unless_zero(&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, true);
  		bdput(bdev);
  	}
  	return res;
  }
  
  EXPORT_SYMBOL(invalidate_partition);
  
  /*
   * Disk events - monitor disk events like media change and eject request.
   */
  struct disk_events {
  	struct list_head	node;		/* all disk_event's */
  	struct gendisk		*disk;		/* the associated disk */
  	spinlock_t		lock;
  
  	struct mutex		block_mutex;	/* protects blocking */
  	int			block;		/* event blocking depth */
  	unsigned int		pending;	/* events already sent out */
  	unsigned int		clearing;	/* events being cleared */
  
  	long			poll_msecs;	/* interval, -1 for default */
  	struct delayed_work	dwork;
  };
  
  static const char *disk_events_strs[] = {
  	[ilog2(DISK_EVENT_MEDIA_CHANGE)]	= "media_change",
  	[ilog2(DISK_EVENT_EJECT_REQUEST)]	= "eject_request",
  };
  
  static char *disk_uevents[] = {
  	[ilog2(DISK_EVENT_MEDIA_CHANGE)]	= "DISK_MEDIA_CHANGE=1",
  	[ilog2(DISK_EVENT_EJECT_REQUEST)]	= "DISK_EJECT_REQUEST=1",
  };
  
  /* list of all disk_events */
  static DEFINE_MUTEX(disk_events_mutex);
  static LIST_HEAD(disk_events);
  
  /* disable in-kernel polling by default */
  static unsigned long disk_events_dfl_poll_msecs;
  
  static unsigned long disk_events_poll_jiffies(struct gendisk *disk)
  {
  	struct disk_events *ev = disk->ev;
  	long intv_msecs = 0;
  
  	/*
  	 * If device-specific poll interval is set, always use it.  If
  	 * the default is being used, poll iff there are events which
  	 * can't be monitored asynchronously.
  	 */
  	if (ev->poll_msecs >= 0)
  		intv_msecs = ev->poll_msecs;
  	else if (disk->events & ~disk->async_events)
  		intv_msecs = disk_events_dfl_poll_msecs;
  
  	return msecs_to_jiffies(intv_msecs);
  }
  
  /**
   * disk_block_events - block and flush disk event checking
   * @disk: disk to block events for
   *
   * On return from this function, it is guaranteed that event checking
   * isn't in progress and won't happen until unblocked by
   * disk_unblock_events().  Events blocking is counted and the actual
   * unblocking happens after the matching number of unblocks are done.
   *
   * Note that this intentionally does not block event checking from
   * disk_clear_events().
   *
   * CONTEXT:
   * Might sleep.
   */
  void disk_block_events(struct gendisk *disk)
  {
  	struct disk_events *ev = disk->ev;
  	unsigned long flags;
  	bool cancel;
  
  	if (!ev)
  		return;
  
  	/*
  	 * Outer mutex ensures that the first blocker completes canceling
  	 * the event work before further blockers are allowed to finish.
  	 */
  	mutex_lock(&ev->block_mutex);
  
  	spin_lock_irqsave(&ev->lock, flags);
  	cancel = !ev->block++;
  	spin_unlock_irqrestore(&ev->lock, flags);
  
  	if (cancel)
  		cancel_delayed_work_sync(&disk->ev->dwork);
  
  	mutex_unlock(&ev->block_mutex);
  }
  
  static void __disk_unblock_events(struct gendisk *disk, bool check_now)
  {
  	struct disk_events *ev = disk->ev;
  	unsigned long intv;
  	unsigned long flags;
  
  	spin_lock_irqsave(&ev->lock, flags);
  
  	if (WARN_ON_ONCE(ev->block <= 0))
  		goto out_unlock;
  
  	if (--ev->block)
  		goto out_unlock;
  
  	intv = disk_events_poll_jiffies(disk);
  	if (check_now)
  		queue_delayed_work(system_freezable_power_efficient_wq,
  				&ev->dwork, 0);
  	else if (intv)
  		queue_delayed_work(system_freezable_power_efficient_wq,
  				&ev->dwork, intv);
  out_unlock:
  	spin_unlock_irqrestore(&ev->lock, flags);
  }
  
  /**
   * disk_unblock_events - unblock disk event checking
   * @disk: disk to unblock events for
   *
   * Undo disk_block_events().  When the block count reaches zero, it
   * starts events polling if configured.
   *
   * CONTEXT:
   * Don't care.  Safe to call from irq context.
   */
  void disk_unblock_events(struct gendisk *disk)
  {
  	if (disk->ev)
  		__disk_unblock_events(disk, false);
  }
  
  /**
   * disk_flush_events - schedule immediate event checking and flushing
   * @disk: disk to check and flush events for
   * @mask: events to flush
   *
   * Schedule immediate event checking on @disk if not blocked.  Events in
   * @mask are scheduled to be cleared from the driver.  Note that this
   * doesn't clear the events from @disk->ev.
   *
   * CONTEXT:
   * If @mask is non-zero must be called with bdev->bd_mutex held.
   */
  void disk_flush_events(struct gendisk *disk, unsigned int mask)
  {
  	struct disk_events *ev = disk->ev;
  
  	if (!ev)
  		return;
  
  	spin_lock_irq(&ev->lock);
  	ev->clearing |= mask;
  	if (!ev->block)
  		mod_delayed_work(system_freezable_power_efficient_wq,
  				&ev->dwork, 0);
  	spin_unlock_irq(&ev->lock);
  }
  
  /**
   * disk_clear_events - synchronously check, clear and return pending events
   * @disk: disk to fetch and clear events from
   * @mask: mask of events to be fetched and cleared
   *
   * Disk events are synchronously checked and pending events in @mask
   * are cleared and returned.  This ignores the block count.
   *
   * CONTEXT:
   * Might sleep.
   */
  unsigned int disk_clear_events(struct gendisk *disk, unsigned int mask)
  {
  	const struct block_device_operations *bdops = disk->fops;
  	struct disk_events *ev = disk->ev;
  	unsigned int pending;
  	unsigned int clearing = mask;
  
  	if (!ev) {
  		/* for drivers still using the old ->media_changed method */
  		if ((mask & DISK_EVENT_MEDIA_CHANGE) &&
  		    bdops->media_changed && bdops->media_changed(disk))
  			return DISK_EVENT_MEDIA_CHANGE;
  		return 0;
  	}
  
  	disk_block_events(disk);
  
  	/*
  	 * store the union of mask and ev->clearing on the stack so that the
  	 * race with disk_flush_events does not cause ambiguity (ev->clearing
  	 * can still be modified even if events are blocked).
  	 */
  	spin_lock_irq(&ev->lock);
  	clearing |= ev->clearing;
  	ev->clearing = 0;
  	spin_unlock_irq(&ev->lock);
  
  	disk_check_events(ev, &clearing);
  	/*
  	 * if ev->clearing is not 0, the disk_flush_events got called in the
  	 * middle of this function, so we want to run the workfn without delay.
  	 */
  	__disk_unblock_events(disk, ev->clearing ? true : false);
  
  	/* then, fetch and clear pending events */
  	spin_lock_irq(&ev->lock);
  	pending = ev->pending & mask;
  	ev->pending &= ~mask;
  	spin_unlock_irq(&ev->lock);
  	WARN_ON_ONCE(clearing & mask);
  
  	return pending;
  }
  
  /*
   * Separate this part out so that a different pointer for clearing_ptr can be
   * passed in for disk_clear_events.
   */
  static void disk_events_workfn(struct work_struct *work)
  {
  	struct delayed_work *dwork = to_delayed_work(work);
  	struct disk_events *ev = container_of(dwork, struct disk_events, dwork);
  
  	disk_check_events(ev, &ev->clearing);
  }
  
  static void disk_check_events(struct disk_events *ev,
  			      unsigned int *clearing_ptr)
  {
  	struct gendisk *disk = ev->disk;
  	char *envp[ARRAY_SIZE(disk_uevents) + 1] = { };
  	unsigned int clearing = *clearing_ptr;
  	unsigned int events;
  	unsigned long intv;
  	int nr_events = 0, i;
  
  	/* check events */
  	events = disk->fops->check_events(disk, clearing);
  
  	/* accumulate pending events and schedule next poll if necessary */
  	spin_lock_irq(&ev->lock);
  
  	events &= ~ev->pending;
  	ev->pending |= events;
  	*clearing_ptr &= ~clearing;
  
  	intv = disk_events_poll_jiffies(disk);
  	if (!ev->block && intv)
  		queue_delayed_work(system_freezable_power_efficient_wq,
  				&ev->dwork, intv);
  
  	spin_unlock_irq(&ev->lock);
  
  	/*
  	 * Tell userland about new events.  Only the events listed in
  	 * @disk->events are reported.  Unlisted events are processed the
  	 * same internally but never get reported to userland.
  	 */
  	for (i = 0; i < ARRAY_SIZE(disk_uevents); i++)
  		if (events & disk->events & (1 << i))
  			envp[nr_events++] = disk_uevents[i];
  
  	if (nr_events)
  		kobject_uevent_env(&disk_to_dev(disk)->kobj, KOBJ_CHANGE, envp);
  }
  
  /*
   * A disk events enabled device has the following sysfs nodes under
   * its /sys/block/X/ directory.
   *
   * events		: list of all supported events
   * events_async		: list of events which can be detected w/o polling
   * events_poll_msecs	: polling interval, 0: disable, -1: system default
   */
  static ssize_t __disk_events_show(unsigned int events, char *buf)
  {
  	const char *delim = "";
  	ssize_t pos = 0;
  	int i;
  
  	for (i = 0; i < ARRAY_SIZE(disk_events_strs); i++)
  		if (events & (1 << i)) {
  			pos += sprintf(buf + pos, "%s%s",
  				       delim, disk_events_strs[i]);
  			delim = " ";
  		}
  	if (pos)
  		pos += sprintf(buf + pos, "\n");
  	return pos;
  }
  
  static ssize_t disk_events_show(struct device *dev,
  				struct device_attribute *attr, char *buf)
  {
  	struct gendisk *disk = dev_to_disk(dev);
  
  	return __disk_events_show(disk->events, buf);
  }
  
  static ssize_t disk_events_async_show(struct device *dev,
  				      struct device_attribute *attr, char *buf)
  {
  	struct gendisk *disk = dev_to_disk(dev);
  
  	return __disk_events_show(disk->async_events, buf);
  }
  
  static ssize_t disk_events_poll_msecs_show(struct device *dev,
  					   struct device_attribute *attr,
  					   char *buf)
  {
  	struct gendisk *disk = dev_to_disk(dev);
  
  	return sprintf(buf, "%ld\n", disk->ev->poll_msecs);
  }
  
  static ssize_t disk_events_poll_msecs_store(struct device *dev,
  					    struct device_attribute *attr,
  					    const char *buf, size_t count)
  {
  	struct gendisk *disk = dev_to_disk(dev);
  	long intv;
  
  	if (!count || !sscanf(buf, "%ld", &intv))
  		return -EINVAL;
  
  	if (intv < 0 && intv != -1)
  		return -EINVAL;
  
  	disk_block_events(disk);
  	disk->ev->poll_msecs = intv;
  	__disk_unblock_events(disk, true);
  
  	return count;
  }
  
  static const DEVICE_ATTR(events, S_IRUGO, disk_events_show, NULL);
  static const DEVICE_ATTR(events_async, S_IRUGO, disk_events_async_show, NULL);
  static const DEVICE_ATTR(events_poll_msecs, S_IRUGO|S_IWUSR,
  			 disk_events_poll_msecs_show,
  			 disk_events_poll_msecs_store);
  
  static const struct attribute *disk_events_attrs[] = {
  	&dev_attr_events.attr,
  	&dev_attr_events_async.attr,
  	&dev_attr_events_poll_msecs.attr,
  	NULL,
  };
  
  /*
   * The default polling interval can be specified by the kernel
   * parameter block.events_dfl_poll_msecs which defaults to 0
   * (disable).  This can also be modified runtime by writing to
   * /sys/module/block/events_dfl_poll_msecs.
   */
  static int disk_events_set_dfl_poll_msecs(const char *val,
  					  const struct kernel_param *kp)
  {
  	struct disk_events *ev;
  	int ret;
  
  	ret = param_set_ulong(val, kp);
  	if (ret < 0)
  		return ret;
  
  	mutex_lock(&disk_events_mutex);
  
  	list_for_each_entry(ev, &disk_events, node)
  		disk_flush_events(ev->disk, 0);
  
  	mutex_unlock(&disk_events_mutex);
  
  	return 0;
  }
  
  static const struct kernel_param_ops disk_events_dfl_poll_msecs_param_ops = {
  	.set	= disk_events_set_dfl_poll_msecs,
  	.get	= param_get_ulong,
  };
  
  #undef MODULE_PARAM_PREFIX
  #define MODULE_PARAM_PREFIX	"block."
  
  module_param_cb(events_dfl_poll_msecs, &disk_events_dfl_poll_msecs_param_ops,
  		&disk_events_dfl_poll_msecs, 0644);
  
  /*
   * disk_{alloc|add|del|release}_events - initialize and destroy disk_events.
   */
  static void disk_alloc_events(struct gendisk *disk)
  {
  	struct disk_events *ev;
  
  	if (!disk->fops->check_events)
  		return;
  
  	ev = kzalloc(sizeof(*ev), GFP_KERNEL);
  	if (!ev) {
  		pr_warn("%s: failed to initialize events\n", disk->disk_name);
  		return;
  	}
  
  	INIT_LIST_HEAD(&ev->node);
  	ev->disk = disk;
  	spin_lock_init(&ev->lock);
  	mutex_init(&ev->block_mutex);
  	ev->block = 1;
  	ev->poll_msecs = -1;
  	INIT_DELAYED_WORK(&ev->dwork, disk_events_workfn);
  
  	disk->ev = ev;
  }
  
  static void disk_add_events(struct gendisk *disk)
  {
  	if (!disk->ev)
  		return;
  
  	/* FIXME: error handling */
  	if (sysfs_create_files(&disk_to_dev(disk)->kobj, disk_events_attrs) < 0)
  		pr_warn("%s: failed to create sysfs files for events\n",
  			disk->disk_name);
  
  	mutex_lock(&disk_events_mutex);
  	list_add_tail(&disk->ev->node, &disk_events);
  	mutex_unlock(&disk_events_mutex);
  
  	/*
  	 * Block count is initialized to 1 and the following initial
  	 * unblock kicks it into action.
  	 */
  	__disk_unblock_events(disk, true);
  }
  
  static void disk_del_events(struct gendisk *disk)
  {
  	if (!disk->ev)
  		return;
  
  	disk_block_events(disk);
  
  	mutex_lock(&disk_events_mutex);
  	list_del_init(&disk->ev->node);
  	mutex_unlock(&disk_events_mutex);
  
  	sysfs_remove_files(&disk_to_dev(disk)->kobj, disk_events_attrs);
  }
  
  static void disk_release_events(struct gendisk *disk)
  {
  	/* the block count should be 1 from disk_del_events() */
  	WARN_ON_ONCE(disk->ev && disk->ev->block != 1);
  	kfree(disk->ev);
  }
  