/*
   *  linux/fs/block_dev.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *  Copyright (C) 2001  Andrea Arcangeli <andrea@suse.de> SuSE
   */

  #include <linux/init.h>
  #include <linux/mm.h>
  #include <linux/fcntl.h>
  #include <linux/slab.h>
  #include <linux/kmod.h>
  #include <linux/major.h>

  #include <linux/smp_lock.h>
  #include <linux/highmem.h>
  #include <linux/blkdev.h>
  #include <linux/module.h>
  #include <linux/blkpg.h>
  #include <linux/buffer_head.h>
  #include <linux/mpage.h>
  #include <linux/mount.h>
  #include <linux/uio.h>
  #include <linux/namei.h>
  #include <asm/uaccess.h>
  
  struct bdev_inode {
  	struct block_device bdev;
  	struct inode vfs_inode;
  };
  
  static inline struct bdev_inode *BDEV_I(struct inode *inode)
  {
  	return container_of(inode, struct bdev_inode, vfs_inode);
  }
  
  inline struct block_device *I_BDEV(struct inode *inode)
  {
  	return &BDEV_I(inode)->bdev;
  }
  
  EXPORT_SYMBOL(I_BDEV);
  
  static sector_t max_block(struct block_device *bdev)
  {
  	sector_t retval = ~((sector_t)0);
  	loff_t sz = i_size_read(bdev->bd_inode);
  
  	if (sz) {
  		unsigned int size = block_size(bdev);
  		unsigned int sizebits = blksize_bits(size);
  		retval = (sz >> sizebits);
  	}
  	return retval;
  }
  
  /* Kill _all_ buffers, dirty or not.. */
  static void kill_bdev(struct block_device *bdev)
  {
  	invalidate_bdev(bdev, 1);
  	truncate_inode_pages(bdev->bd_inode->i_mapping, 0);
  }	
  
  int set_blocksize(struct block_device *bdev, int size)
  {
  	/* Size must be a power of two, and between 512 and PAGE_SIZE */
  	if (size > PAGE_SIZE || size < 512 || (size & (size-1)))
  		return -EINVAL;
  
  	/* Size cannot be smaller than the size supported by the device */
  	if (size < bdev_hardsect_size(bdev))
  		return -EINVAL;
  
  	/* Don't change the size if it is same as current */
  	if (bdev->bd_block_size != size) {
  		sync_blockdev(bdev);
  		bdev->bd_block_size = size;
  		bdev->bd_inode->i_blkbits = blksize_bits(size);
  		kill_bdev(bdev);
  	}
  	return 0;
  }
  
  EXPORT_SYMBOL(set_blocksize);
  
  int sb_set_blocksize(struct super_block *sb, int size)
  {

  	if (set_blocksize(sb->s_bdev, size))
  		return 0;
  	/* If we get here, we know size is power of two
  	 * and it's value is between 512 and PAGE_SIZE */
  	sb->s_blocksize = size;

  	sb->s_blocksize_bits = blksize_bits(size);

  	return sb->s_blocksize;
  }
  
  EXPORT_SYMBOL(sb_set_blocksize);
  
  int sb_min_blocksize(struct super_block *sb, int size)
  {
  	int minsize = bdev_hardsect_size(sb->s_bdev);
  	if (size < minsize)
  		size = minsize;
  	return sb_set_blocksize(sb, size);
  }
  
  EXPORT_SYMBOL(sb_min_blocksize);
  
  static int
  blkdev_get_block(struct inode *inode, sector_t iblock,
  		struct buffer_head *bh, int create)
  {
  	if (iblock >= max_block(I_BDEV(inode))) {
  		if (create)
  			return -EIO;
  
  		/*
  		 * for reads, we're just trying to fill a partial page.
  		 * return a hole, they will have to call get_block again
  		 * before they can fill it, and they will get -EIO at that
  		 * time
  		 */
  		return 0;
  	}
  	bh->b_bdev = I_BDEV(inode);
  	bh->b_blocknr = iblock;
  	set_buffer_mapped(bh);
  	return 0;
  }
  
  static int
  blkdev_get_blocks(struct inode *inode, sector_t iblock,

  		struct buffer_head *bh, int create)

  {
  	sector_t end_block = max_block(I_BDEV(inode));

  	unsigned long max_blocks = bh->b_size >> inode->i_blkbits;

  
  	if ((iblock + max_blocks) > end_block) {
  		max_blocks = end_block - iblock;
  		if ((long)max_blocks <= 0) {
  			if (create)
  				return -EIO;	/* write fully beyond EOF */
  			/*
  			 * It is a read which is fully beyond EOF.  We return
  			 * a !buffer_mapped buffer
  			 */
  			max_blocks = 0;
  		}
  	}
  
  	bh->b_bdev = I_BDEV(inode);
  	bh->b_blocknr = iblock;
  	bh->b_size = max_blocks << inode->i_blkbits;
  	if (max_blocks)
  		set_buffer_mapped(bh);
  	return 0;
  }
  
  static ssize_t
  blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
  			loff_t offset, unsigned long nr_segs)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file->f_mapping->host;
  
  	return blockdev_direct_IO_no_locking(rw, iocb, inode, I_BDEV(inode),
  				iov, offset, nr_segs, blkdev_get_blocks, NULL);
  }
  
  static int blkdev_writepage(struct page *page, struct writeback_control *wbc)
  {
  	return block_write_full_page(page, blkdev_get_block, wbc);
  }
  
  static int blkdev_readpage(struct file * file, struct page * page)
  {
  	return block_read_full_page(page, blkdev_get_block);
  }
  
  static int blkdev_prepare_write(struct file *file, struct page *page, unsigned from, unsigned to)
  {
  	return block_prepare_write(page, from, to, blkdev_get_block);
  }
  
  static int blkdev_commit_write(struct file *file, struct page *page, unsigned from, unsigned to)
  {
  	return block_commit_write(page, from, to);
  }
  
  /*
   * private llseek:
   * for a block special file file->f_dentry->d_inode->i_size is zero
   * so we compute the size by hand (just as in block_read/write above)
   */
  static loff_t block_llseek(struct file *file, loff_t offset, int origin)
  {
  	struct inode *bd_inode = file->f_mapping->host;
  	loff_t size;
  	loff_t retval;

  	mutex_lock(&bd_inode->i_mutex);

  	size = i_size_read(bd_inode);
  
  	switch (origin) {
  		case 2:
  			offset += size;
  			break;
  		case 1:
  			offset += file->f_pos;
  	}
  	retval = -EINVAL;
  	if (offset >= 0 && offset <= size) {
  		if (offset != file->f_pos) {
  			file->f_pos = offset;
  		}
  		retval = offset;
  	}

  	mutex_unlock(&bd_inode->i_mutex);

  	return retval;
  }
  	
  /*
   *	Filp is never NULL; the only case when ->fsync() is called with
   *	NULL first argument is nfsd_sync_dir() and that's not a directory.
   */
   
  static int block_fsync(struct file *filp, struct dentry *dentry, int datasync)
  {
  	return sync_blockdev(I_BDEV(filp->f_mapping->host));
  }
  
  /*
   * pseudo-fs
   */
  
  static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(bdev_lock);

  static kmem_cache_t * bdev_cachep __read_mostly;

  
  static struct inode *bdev_alloc_inode(struct super_block *sb)
  {
  	struct bdev_inode *ei = kmem_cache_alloc(bdev_cachep, SLAB_KERNEL);
  	if (!ei)
  		return NULL;
  	return &ei->vfs_inode;
  }
  
  static void bdev_destroy_inode(struct inode *inode)
  {
  	struct bdev_inode *bdi = BDEV_I(inode);
  
  	bdi->bdev.bd_inode_backing_dev_info = NULL;
  	kmem_cache_free(bdev_cachep, bdi);
  }
  
  static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags)
  {
  	struct bdev_inode *ei = (struct bdev_inode *) foo;
  	struct block_device *bdev = &ei->bdev;
  
  	if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
  	    SLAB_CTOR_CONSTRUCTOR)
  	{
  		memset(bdev, 0, sizeof(*bdev));

  		mutex_init(&bdev->bd_mutex);
  		mutex_init(&bdev->bd_mount_mutex);

  		INIT_LIST_HEAD(&bdev->bd_inodes);
  		INIT_LIST_HEAD(&bdev->bd_list);

  #ifdef CONFIG_SYSFS
  		INIT_LIST_HEAD(&bdev->bd_holder_list);
  #endif

  		inode_init_once(&ei->vfs_inode);
  	}
  }
  
  static inline void __bd_forget(struct inode *inode)
  {
  	list_del_init(&inode->i_devices);
  	inode->i_bdev = NULL;
  	inode->i_mapping = &inode->i_data;
  }
  
  static void bdev_clear_inode(struct inode *inode)
  {
  	struct block_device *bdev = &BDEV_I(inode)->bdev;
  	struct list_head *p;
  	spin_lock(&bdev_lock);
  	while ( (p = bdev->bd_inodes.next) != &bdev->bd_inodes ) {
  		__bd_forget(list_entry(p, struct inode, i_devices));
  	}
  	list_del_init(&bdev->bd_list);
  	spin_unlock(&bdev_lock);
  }
  
  static struct super_operations bdev_sops = {
  	.statfs = simple_statfs,
  	.alloc_inode = bdev_alloc_inode,
  	.destroy_inode = bdev_destroy_inode,
  	.drop_inode = generic_delete_inode,
  	.clear_inode = bdev_clear_inode,
  };

  static int bd_get_sb(struct file_system_type *fs_type,
  	int flags, const char *dev_name, void *data, struct vfsmount *mnt)

  {

  	return get_sb_pseudo(fs_type, "bdev:", &bdev_sops, 0x62646576, mnt);

  }
  
  static struct file_system_type bd_type = {
  	.name		= "bdev",
  	.get_sb		= bd_get_sb,
  	.kill_sb	= kill_anon_super,
  };

  static struct vfsmount *bd_mnt __read_mostly;

  struct super_block *blockdev_superblock;
  
  void __init bdev_cache_init(void)
  {
  	int err;
  	bdev_cachep = kmem_cache_create("bdev_cache", sizeof(struct bdev_inode),

  			0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
  				SLAB_MEM_SPREAD|SLAB_PANIC),

  			init_once, NULL);
  	err = register_filesystem(&bd_type);
  	if (err)
  		panic("Cannot register bdev pseudo-fs");
  	bd_mnt = kern_mount(&bd_type);
  	err = PTR_ERR(bd_mnt);
  	if (IS_ERR(bd_mnt))
  		panic("Cannot create bdev pseudo-fs");
  	blockdev_superblock = bd_mnt->mnt_sb;	/* For writeback */
  }
  
  /*
   * Most likely _very_ bad one - but then it's hardly critical for small
   * /dev and can be fixed when somebody will need really large one.
   * Keep in mind that it will be fed through icache hash function too.
   */
  static inline unsigned long hash(dev_t dev)
  {
  	return MAJOR(dev)+MINOR(dev);
  }
  
  static int bdev_test(struct inode *inode, void *data)
  {
  	return BDEV_I(inode)->bdev.bd_dev == *(dev_t *)data;
  }
  
  static int bdev_set(struct inode *inode, void *data)
  {
  	BDEV_I(inode)->bdev.bd_dev = *(dev_t *)data;
  	return 0;
  }
  
  static LIST_HEAD(all_bdevs);
  
  struct block_device *bdget(dev_t dev)
  {
  	struct block_device *bdev;
  	struct inode *inode;
  
  	inode = iget5_locked(bd_mnt->mnt_sb, hash(dev),
  			bdev_test, bdev_set, &dev);
  
  	if (!inode)
  		return NULL;
  
  	bdev = &BDEV_I(inode)->bdev;
  
  	if (inode->i_state & I_NEW) {
  		bdev->bd_contains = NULL;
  		bdev->bd_inode = inode;
  		bdev->bd_block_size = (1 << inode->i_blkbits);
  		bdev->bd_part_count = 0;
  		bdev->bd_invalidated = 0;
  		inode->i_mode = S_IFBLK;
  		inode->i_rdev = dev;
  		inode->i_bdev = bdev;
  		inode->i_data.a_ops = &def_blk_aops;
  		mapping_set_gfp_mask(&inode->i_data, GFP_USER);
  		inode->i_data.backing_dev_info = &default_backing_dev_info;
  		spin_lock(&bdev_lock);
  		list_add(&bdev->bd_list, &all_bdevs);
  		spin_unlock(&bdev_lock);
  		unlock_new_inode(inode);
  	}
  	return bdev;
  }
  
  EXPORT_SYMBOL(bdget);
  
  long nr_blockdev_pages(void)
  {
  	struct list_head *p;
  	long ret = 0;
  	spin_lock(&bdev_lock);
  	list_for_each(p, &all_bdevs) {
  		struct block_device *bdev;
  		bdev = list_entry(p, struct block_device, bd_list);
  		ret += bdev->bd_inode->i_mapping->nrpages;
  	}
  	spin_unlock(&bdev_lock);
  	return ret;
  }
  
  void bdput(struct block_device *bdev)
  {
  	iput(bdev->bd_inode);
  }
  
  EXPORT_SYMBOL(bdput);
   
  static struct block_device *bd_acquire(struct inode *inode)
  {
  	struct block_device *bdev;

  	spin_lock(&bdev_lock);
  	bdev = inode->i_bdev;

  	if (bdev) {
  		atomic_inc(&bdev->bd_inode->i_count);

  		spin_unlock(&bdev_lock);
  		return bdev;
  	}
  	spin_unlock(&bdev_lock);

  	bdev = bdget(inode->i_rdev);
  	if (bdev) {
  		spin_lock(&bdev_lock);

  		if (!inode->i_bdev) {
  			/*
  			 * We take an additional bd_inode->i_count for inode,
  			 * and it's released in clear_inode() of inode.
  			 * So, we can access it via ->i_mapping always
  			 * without igrab().
  			 */
  			atomic_inc(&bdev->bd_inode->i_count);
  			inode->i_bdev = bdev;
  			inode->i_mapping = bdev->bd_inode->i_mapping;
  			list_add(&inode->i_devices, &bdev->bd_inodes);
  		}

  		spin_unlock(&bdev_lock);
  	}
  	return bdev;
  }
  
  /* Call when you free inode */
  
  void bd_forget(struct inode *inode)
  {

  	struct block_device *bdev = NULL;

  	spin_lock(&bdev_lock);

  	if (inode->i_bdev) {
  		if (inode->i_sb != blockdev_superblock)
  			bdev = inode->i_bdev;

  		__bd_forget(inode);

  	}

  	spin_unlock(&bdev_lock);

  
  	if (bdev)
  		iput(bdev->bd_inode);

  }
  
  int bd_claim(struct block_device *bdev, void *holder)
  {
  	int res;
  	spin_lock(&bdev_lock);
  
  	/* first decide result */
  	if (bdev->bd_holder == holder)
  		res = 0;	 /* already a holder */
  	else if (bdev->bd_holder != NULL)
  		res = -EBUSY; 	 /* held by someone else */
  	else if (bdev->bd_contains == bdev)
  		res = 0;  	 /* is a whole device which isn't held */
  
  	else if (bdev->bd_contains->bd_holder == bd_claim)
  		res = 0; 	 /* is a partition of a device that is being partitioned */
  	else if (bdev->bd_contains->bd_holder != NULL)
  		res = -EBUSY;	 /* is a partition of a held device */
  	else
  		res = 0;	 /* is a partition of an un-held device */
  
  	/* now impose change */
  	if (res==0) {
  		/* note that for a whole device bd_holders
  		 * will be incremented twice, and bd_holder will
  		 * be set to bd_claim before being set to holder
  		 */
  		bdev->bd_contains->bd_holders ++;
  		bdev->bd_contains->bd_holder = bd_claim;
  		bdev->bd_holders++;
  		bdev->bd_holder = holder;
  	}
  	spin_unlock(&bdev_lock);
  	return res;
  }
  
  EXPORT_SYMBOL(bd_claim);
  
  void bd_release(struct block_device *bdev)
  {
  	spin_lock(&bdev_lock);
  	if (!--bdev->bd_contains->bd_holders)
  		bdev->bd_contains->bd_holder = NULL;
  	if (!--bdev->bd_holders)
  		bdev->bd_holder = NULL;
  	spin_unlock(&bdev_lock);
  }
  
  EXPORT_SYMBOL(bd_release);

  #ifdef CONFIG_SYSFS
  /*
   * Functions for bd_claim_by_kobject / bd_release_from_kobject
   *
   *     If a kobject is passed to bd_claim_by_kobject()
   *     and the kobject has a parent directory,
   *     following symlinks are created:
   *        o from the kobject to the claimed bdev
   *        o from "holders" directory of the bdev to the parent of the kobject
   *     bd_release_from_kobject() removes these symlinks.
   *
   *     Example:
   *        If /dev/dm-0 maps to /dev/sda, kobject corresponding to
   *        /sys/block/dm-0/slaves is passed to bd_claim_by_kobject(), then:
   *           /sys/block/dm-0/slaves/sda --> /sys/block/sda
   *           /sys/block/sda/holders/dm-0 --> /sys/block/dm-0
   */
  
  static struct kobject *bdev_get_kobj(struct block_device *bdev)
  {
  	if (bdev->bd_contains != bdev)
  		return kobject_get(&bdev->bd_part->kobj);
  	else
  		return kobject_get(&bdev->bd_disk->kobj);
  }
  
  static struct kobject *bdev_get_holder(struct block_device *bdev)
  {
  	if (bdev->bd_contains != bdev)
  		return kobject_get(bdev->bd_part->holder_dir);
  	else
  		return kobject_get(bdev->bd_disk->holder_dir);
  }
  
  static void add_symlink(struct kobject *from, struct kobject *to)
  {
  	if (!from || !to)
  		return;
  	sysfs_create_link(from, to, kobject_name(to));
  }
  
  static void del_symlink(struct kobject *from, struct kobject *to)
  {
  	if (!from || !to)
  		return;
  	sysfs_remove_link(from, kobject_name(to));
  }
  
  /*
   * 'struct bd_holder' contains pointers to kobjects symlinked by
   * bd_claim_by_kobject.
   * It's connected to bd_holder_list which is protected by bdev->bd_sem.
   */
  struct bd_holder {
  	struct list_head list;	/* chain of holders of the bdev */
  	int count;		/* references from the holder */
  	struct kobject *sdir;	/* holder object, e.g. "/block/dm-0/slaves" */
  	struct kobject *hdev;	/* e.g. "/block/dm-0" */
  	struct kobject *hdir;	/* e.g. "/block/sda/holders" */
  	struct kobject *sdev;	/* e.g. "/block/sda" */
  };
  
  /*
   * Get references of related kobjects at once.
   * Returns 1 on success. 0 on failure.
   *
   * Should call bd_holder_release_dirs() after successful use.
   */
  static int bd_holder_grab_dirs(struct block_device *bdev,
  			struct bd_holder *bo)
  {
  	if (!bdev || !bo)
  		return 0;
  
  	bo->sdir = kobject_get(bo->sdir);
  	if (!bo->sdir)
  		return 0;
  
  	bo->hdev = kobject_get(bo->sdir->parent);
  	if (!bo->hdev)
  		goto fail_put_sdir;
  
  	bo->sdev = bdev_get_kobj(bdev);
  	if (!bo->sdev)
  		goto fail_put_hdev;
  
  	bo->hdir = bdev_get_holder(bdev);
  	if (!bo->hdir)
  		goto fail_put_sdev;
  
  	return 1;
  
  fail_put_sdev:
  	kobject_put(bo->sdev);
  fail_put_hdev:
  	kobject_put(bo->hdev);
  fail_put_sdir:
  	kobject_put(bo->sdir);
  
  	return 0;
  }
  
  /* Put references of related kobjects at once. */
  static void bd_holder_release_dirs(struct bd_holder *bo)
  {
  	kobject_put(bo->hdir);
  	kobject_put(bo->sdev);
  	kobject_put(bo->hdev);
  	kobject_put(bo->sdir);
  }
  
  static struct bd_holder *alloc_bd_holder(struct kobject *kobj)
  {
  	struct bd_holder *bo;
  
  	bo = kzalloc(sizeof(*bo), GFP_KERNEL);
  	if (!bo)
  		return NULL;
  
  	bo->count = 1;
  	bo->sdir = kobj;
  
  	return bo;
  }
  
  static void free_bd_holder(struct bd_holder *bo)
  {
  	kfree(bo);
  }
  
  /**
   * add_bd_holder - create sysfs symlinks for bd_claim() relationship
   *
   * @bdev:	block device to be bd_claimed
   * @bo:		preallocated and initialized by alloc_bd_holder()
   *
   * If there is no matching entry with @bo in @bdev->bd_holder_list,
   * add @bo to the list, create symlinks.
   *
   * Returns 1 if @bo was added to the list.
   * Returns 0 if @bo wasn't used by any reason and should be freed.
   */
  static int add_bd_holder(struct block_device *bdev, struct bd_holder *bo)
  {
  	struct bd_holder *tmp;
  
  	if (!bo)
  		return 0;
  
  	list_for_each_entry(tmp, &bdev->bd_holder_list, list) {
  		if (tmp->sdir == bo->sdir) {
  			tmp->count++;
  			return 0;
  		}
  	}
  
  	if (!bd_holder_grab_dirs(bdev, bo))
  		return 0;
  
  	add_symlink(bo->sdir, bo->sdev);
  	add_symlink(bo->hdir, bo->hdev);
  	list_add_tail(&bo->list, &bdev->bd_holder_list);
  	return 1;
  }
  
  /**
   * del_bd_holder - delete sysfs symlinks for bd_claim() relationship
   *
   * @bdev:	block device to be bd_claimed
   * @kobj:	holder's kobject
   *
   * If there is matching entry with @kobj in @bdev->bd_holder_list
   * and no other bd_claim() from the same kobject,
   * remove the struct bd_holder from the list, delete symlinks for it.
   *
   * Returns a pointer to the struct bd_holder when it's removed from the list
   * and ready to be freed.
   * Returns NULL if matching claim isn't found or there is other bd_claim()
   * by the same kobject.
   */
  static struct bd_holder *del_bd_holder(struct block_device *bdev,
  					struct kobject *kobj)
  {
  	struct bd_holder *bo;
  
  	list_for_each_entry(bo, &bdev->bd_holder_list, list) {
  		if (bo->sdir == kobj) {
  			bo->count--;
  			BUG_ON(bo->count < 0);
  			if (!bo->count) {
  				list_del(&bo->list);
  				del_symlink(bo->sdir, bo->sdev);
  				del_symlink(bo->hdir, bo->hdev);
  				bd_holder_release_dirs(bo);
  				return bo;
  			}
  			break;
  		}
  	}
  
  	return NULL;
  }
  
  /**
   * bd_claim_by_kobject - bd_claim() with additional kobject signature
   *
   * @bdev:	block device to be claimed
   * @holder:	holder's signature
   * @kobj:	holder's kobject
   *
   * Do bd_claim() and if it succeeds, create sysfs symlinks between
   * the bdev and the holder's kobject.
   * Use bd_release_from_kobject() when relesing the claimed bdev.
   *
   * Returns 0 on success. (same as bd_claim())
   * Returns errno on failure.
   */
  static int bd_claim_by_kobject(struct block_device *bdev, void *holder,
  				struct kobject *kobj)
  {
  	int res;
  	struct bd_holder *bo;
  
  	if (!kobj)
  		return -EINVAL;
  
  	bo = alloc_bd_holder(kobj);
  	if (!bo)
  		return -ENOMEM;

  	mutex_lock(&bdev->bd_mutex);

  	res = bd_claim(bdev, holder);
  	if (res || !add_bd_holder(bdev, bo))
  		free_bd_holder(bo);

  	mutex_unlock(&bdev->bd_mutex);

  
  	return res;
  }
  
  /**
   * bd_release_from_kobject - bd_release() with additional kobject signature
   *
   * @bdev:	block device to be released
   * @kobj:	holder's kobject
   *
   * Do bd_release() and remove sysfs symlinks created by bd_claim_by_kobject().
   */
  static void bd_release_from_kobject(struct block_device *bdev,
  					struct kobject *kobj)
  {
  	struct bd_holder *bo;
  
  	if (!kobj)
  		return;

  	mutex_lock(&bdev->bd_mutex);

  	bd_release(bdev);
  	if ((bo = del_bd_holder(bdev, kobj)))
  		free_bd_holder(bo);

  	mutex_unlock(&bdev->bd_mutex);

  }
  
  /**
   * bd_claim_by_disk - wrapper function for bd_claim_by_kobject()
   *
   * @bdev:	block device to be claimed
   * @holder:	holder's signature
   * @disk:	holder's gendisk
   *
   * Call bd_claim_by_kobject() with getting @disk->slave_dir.
   */
  int bd_claim_by_disk(struct block_device *bdev, void *holder,
  			struct gendisk *disk)
  {
  	return bd_claim_by_kobject(bdev, holder, kobject_get(disk->slave_dir));
  }
  EXPORT_SYMBOL_GPL(bd_claim_by_disk);
  
  /**
   * bd_release_from_disk - wrapper function for bd_release_from_kobject()
   *
   * @bdev:	block device to be claimed
   * @disk:	holder's gendisk
   *
   * Call bd_release_from_kobject() and put @disk->slave_dir.
   */
  void bd_release_from_disk(struct block_device *bdev, struct gendisk *disk)
  {
  	bd_release_from_kobject(bdev, disk->slave_dir);
  	kobject_put(disk->slave_dir);
  }
  EXPORT_SYMBOL_GPL(bd_release_from_disk);
  #endif

  /*
   * Tries to open block device by device number.  Use it ONLY if you
   * really do not have anything better - i.e. when you are behind a
   * truly sucky interface and all you are given is a device number.  _Never_
   * to be used for internal purposes.  If you ever need it - reconsider
   * your API.
   */
  struct block_device *open_by_devnum(dev_t dev, unsigned mode)
  {
  	struct block_device *bdev = bdget(dev);
  	int err = -ENOMEM;
  	int flags = mode & FMODE_WRITE ? O_RDWR : O_RDONLY;
  	if (bdev)
  		err = blkdev_get(bdev, mode, flags);
  	return err ? ERR_PTR(err) : bdev;
  }
  
  EXPORT_SYMBOL(open_by_devnum);
  
  /*
   * This routine checks whether a removable media has been changed,
   * and invalidates all buffer-cache-entries in that case. This
   * is a relatively slow routine, so we have to try to minimize using
   * it. Thus it is called only upon a 'mount' or 'open'. This
   * is the best way of combining speed and utility, I think.
   * People changing diskettes in the middle of an operation deserve
   * to lose :-)
   */
  int check_disk_change(struct block_device *bdev)
  {
  	struct gendisk *disk = bdev->bd_disk;
  	struct block_device_operations * bdops = disk->fops;
  
  	if (!bdops->media_changed)
  		return 0;
  	if (!bdops->media_changed(bdev->bd_disk))
  		return 0;

  	if (__invalidate_device(bdev))

  		printk("VFS: busy inodes on changed media.
  ");
  
  	if (bdops->revalidate_disk)
  		bdops->revalidate_disk(bdev->bd_disk);
  	if (bdev->bd_disk->minors > 1)
  		bdev->bd_invalidated = 1;
  	return 1;
  }
  
  EXPORT_SYMBOL(check_disk_change);
  
  void bd_set_size(struct block_device *bdev, loff_t size)
  {
  	unsigned bsize = bdev_hardsect_size(bdev);
  
  	bdev->bd_inode->i_size = size;
  	while (bsize < PAGE_CACHE_SIZE) {
  		if (size & bsize)
  			break;
  		bsize <<= 1;
  	}
  	bdev->bd_block_size = bsize;
  	bdev->bd_inode->i_blkbits = blksize_bits(bsize);
  }
  EXPORT_SYMBOL(bd_set_size);
  
  static int do_open(struct block_device *bdev, struct file *file)
  {
  	struct module *owner = NULL;
  	struct gendisk *disk;
  	int ret = -ENXIO;
  	int part;
  
  	file->f_mapping = bdev->bd_inode->i_mapping;
  	lock_kernel();
  	disk = get_gendisk(bdev->bd_dev, &part);
  	if (!disk) {
  		unlock_kernel();
  		bdput(bdev);
  		return ret;
  	}
  	owner = disk->fops->owner;

  	mutex_lock(&bdev->bd_mutex);

  	if (!bdev->bd_openers) {
  		bdev->bd_disk = disk;
  		bdev->bd_contains = bdev;
  		if (!part) {
  			struct backing_dev_info *bdi;
  			if (disk->fops->open) {
  				ret = disk->fops->open(bdev->bd_inode, file);
  				if (ret)
  					goto out_first;
  			}
  			if (!bdev->bd_openers) {
  				bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
  				bdi = blk_get_backing_dev_info(bdev);
  				if (bdi == NULL)
  					bdi = &default_backing_dev_info;
  				bdev->bd_inode->i_data.backing_dev_info = bdi;
  			}
  			if (bdev->bd_invalidated)
  				rescan_partitions(disk, bdev);
  		} else {
  			struct hd_struct *p;
  			struct block_device *whole;
  			whole = bdget_disk(disk, 0);
  			ret = -ENOMEM;
  			if (!whole)
  				goto out_first;
  			ret = blkdev_get(whole, file->f_mode, file->f_flags);
  			if (ret)
  				goto out_first;
  			bdev->bd_contains = whole;

  			mutex_lock(&whole->bd_mutex);

  			whole->bd_part_count++;
  			p = disk->part[part - 1];
  			bdev->bd_inode->i_data.backing_dev_info =
  			   whole->bd_inode->i_data.backing_dev_info;
  			if (!(disk->flags & GENHD_FL_UP) || !p || !p->nr_sects) {
  				whole->bd_part_count--;

  				mutex_unlock(&whole->bd_mutex);

  				ret = -ENXIO;
  				goto out_first;
  			}
  			kobject_get(&p->kobj);
  			bdev->bd_part = p;
  			bd_set_size(bdev, (loff_t) p->nr_sects << 9);

  			mutex_unlock(&whole->bd_mutex);

  		}
  	} else {
  		put_disk(disk);
  		module_put(owner);
  		if (bdev->bd_contains == bdev) {
  			if (bdev->bd_disk->fops->open) {
  				ret = bdev->bd_disk->fops->open(bdev->bd_inode, file);
  				if (ret)
  					goto out;
  			}
  			if (bdev->bd_invalidated)
  				rescan_partitions(bdev->bd_disk, bdev);
  		} else {

  			mutex_lock(&bdev->bd_contains->bd_mutex);

  			bdev->bd_contains->bd_part_count++;

  			mutex_unlock(&bdev->bd_contains->bd_mutex);

  		}
  	}
  	bdev->bd_openers++;

  	mutex_unlock(&bdev->bd_mutex);

  	unlock_kernel();
  	return 0;
  
  out_first:
  	bdev->bd_disk = NULL;
  	bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info;
  	if (bdev != bdev->bd_contains)
  		blkdev_put(bdev->bd_contains);
  	bdev->bd_contains = NULL;
  	put_disk(disk);
  	module_put(owner);
  out:

  	mutex_unlock(&bdev->bd_mutex);

  	unlock_kernel();
  	if (ret)
  		bdput(bdev);
  	return ret;
  }
  
  int blkdev_get(struct block_device *bdev, mode_t mode, unsigned flags)
  {
  	/*
  	 * This crockload is due to bad choice of ->open() type.
  	 * It will go away.
  	 * For now, block device ->open() routine must _not_
  	 * examine anything in 'inode' argument except ->i_rdev.
  	 */
  	struct file fake_file = {};
  	struct dentry fake_dentry = {};
  	fake_file.f_mode = mode;
  	fake_file.f_flags = flags;
  	fake_file.f_dentry = &fake_dentry;
  	fake_dentry.d_inode = bdev->bd_inode;
  
  	return do_open(bdev, &fake_file);
  }
  
  EXPORT_SYMBOL(blkdev_get);
  
  static int blkdev_open(struct inode * inode, struct file * filp)
  {
  	struct block_device *bdev;
  	int res;
  
  	/*
  	 * Preserve backwards compatibility and allow large file access
  	 * even if userspace doesn't ask for it explicitly. Some mkfs
  	 * binary needs it. We might want to drop this workaround
  	 * during an unstable branch.
  	 */
  	filp->f_flags |= O_LARGEFILE;
  
  	bdev = bd_acquire(inode);
  
  	res = do_open(bdev, filp);
  	if (res)
  		return res;
  
  	if (!(filp->f_flags & O_EXCL) )
  		return 0;
  
  	if (!(res = bd_claim(bdev, filp)))
  		return 0;
  
  	blkdev_put(bdev);
  	return res;
  }
  
  int blkdev_put(struct block_device *bdev)
  {
  	int ret = 0;
  	struct inode *bd_inode = bdev->bd_inode;
  	struct gendisk *disk = bdev->bd_disk;

  	mutex_lock(&bdev->bd_mutex);

  	lock_kernel();
  	if (!--bdev->bd_openers) {
  		sync_blockdev(bdev);
  		kill_bdev(bdev);
  	}
  	if (bdev->bd_contains == bdev) {
  		if (disk->fops->release)
  			ret = disk->fops->release(bd_inode, NULL);
  	} else {

  		mutex_lock(&bdev->bd_contains->bd_mutex);

  		bdev->bd_contains->bd_part_count--;

  		mutex_unlock(&bdev->bd_contains->bd_mutex);

  	}
  	if (!bdev->bd_openers) {
  		struct module *owner = disk->fops->owner;
  
  		put_disk(disk);
  		module_put(owner);
  
  		if (bdev->bd_contains != bdev) {
  			kobject_put(&bdev->bd_part->kobj);
  			bdev->bd_part = NULL;
  		}
  		bdev->bd_disk = NULL;
  		bdev->bd_inode->i_data.backing_dev_info = &default_backing_dev_info;
  		if (bdev != bdev->bd_contains) {
  			blkdev_put(bdev->bd_contains);
  		}
  		bdev->bd_contains = NULL;
  	}
  	unlock_kernel();

  	mutex_unlock(&bdev->bd_mutex);

  	bdput(bdev);
  	return ret;
  }
  
  EXPORT_SYMBOL(blkdev_put);
  
  static int blkdev_close(struct inode * inode, struct file * filp)
  {
  	struct block_device *bdev = I_BDEV(filp->f_mapping->host);
  	if (bdev->bd_holder == filp)
  		bd_release(bdev);
  	return blkdev_put(bdev);
  }
  
  static ssize_t blkdev_file_write(struct file *file, const char __user *buf,
  				   size_t count, loff_t *ppos)
  {
  	struct iovec local_iov = { .iov_base = (void __user *)buf, .iov_len = count };
  
  	return generic_file_write_nolock(file, &local_iov, 1, ppos);
  }
  
  static ssize_t blkdev_file_aio_write(struct kiocb *iocb, const char __user *buf,
  				   size_t count, loff_t pos)
  {
  	struct iovec local_iov = { .iov_base = (void __user *)buf, .iov_len = count };
  
  	return generic_file_aio_write_nolock(iocb, &local_iov, 1, &iocb->ki_pos);
  }

  static long block_ioctl(struct file *file, unsigned cmd, unsigned long arg)

  {
  	return blkdev_ioctl(file->f_mapping->host, file, cmd, arg);
  }

  const struct address_space_operations def_blk_aops = {

  	.readpage	= blkdev_readpage,
  	.writepage	= blkdev_writepage,
  	.sync_page	= block_sync_page,
  	.prepare_write	= blkdev_prepare_write,
  	.commit_write	= blkdev_commit_write,
  	.writepages	= generic_writepages,
  	.direct_IO	= blkdev_direct_IO,
  };

  const struct file_operations def_blk_fops = {

  	.open		= blkdev_open,
  	.release	= blkdev_close,
  	.llseek		= block_llseek,
  	.read		= generic_file_read,
  	.write		= blkdev_file_write,
    	.aio_read	= generic_file_aio_read,
    	.aio_write	= blkdev_file_aio_write, 
  	.mmap		= generic_file_mmap,
  	.fsync		= block_fsync,

  	.unlocked_ioctl	= block_ioctl,

  #ifdef CONFIG_COMPAT
  	.compat_ioctl	= compat_blkdev_ioctl,
  #endif
  	.readv		= generic_file_readv,
  	.writev		= generic_file_write_nolock,
  	.sendfile	= generic_file_sendfile,

  	.splice_read	= generic_file_splice_read,
  	.splice_write	= generic_file_splice_write,

  };
  
  int ioctl_by_bdev(struct block_device *bdev, unsigned cmd, unsigned long arg)
  {
  	int res;
  	mm_segment_t old_fs = get_fs();
  	set_fs(KERNEL_DS);
  	res = blkdev_ioctl(bdev->bd_inode, NULL, cmd, arg);
  	set_fs(old_fs);
  	return res;
  }
  
  EXPORT_SYMBOL(ioctl_by_bdev);
  
  /**
   * lookup_bdev  - lookup a struct block_device by name
   *
   * @path:	special file representing the block device
   *
   * Get a reference to the blockdevice at @path in the current
   * namespace if possible and return it.  Return ERR_PTR(error)
   * otherwise.
   */
  struct block_device *lookup_bdev(const char *path)
  {
  	struct block_device *bdev;
  	struct inode *inode;
  	struct nameidata nd;
  	int error;
  
  	if (!path || !*path)
  		return ERR_PTR(-EINVAL);
  
  	error = path_lookup(path, LOOKUP_FOLLOW, &nd);
  	if (error)
  		return ERR_PTR(error);
  
  	inode = nd.dentry->d_inode;
  	error = -ENOTBLK;
  	if (!S_ISBLK(inode->i_mode))
  		goto fail;
  	error = -EACCES;
  	if (nd.mnt->mnt_flags & MNT_NODEV)
  		goto fail;
  	error = -ENOMEM;
  	bdev = bd_acquire(inode);
  	if (!bdev)
  		goto fail;
  out:
  	path_release(&nd);
  	return bdev;
  fail:
  	bdev = ERR_PTR(error);
  	goto out;
  }
  
  /**
   * open_bdev_excl  -  open a block device by name and set it up for use
   *
   * @path:	special file representing the block device
   * @flags:	%MS_RDONLY for opening read-only
   * @holder:	owner for exclusion
   *
   * Open the blockdevice described by the special file at @path, claim it
   * for the @holder.
   */
  struct block_device *open_bdev_excl(const char *path, int flags, void *holder)
  {
  	struct block_device *bdev;
  	mode_t mode = FMODE_READ;
  	int error = 0;
  
  	bdev = lookup_bdev(path);
  	if (IS_ERR(bdev))
  		return bdev;
  
  	if (!(flags & MS_RDONLY))
  		mode |= FMODE_WRITE;
  	error = blkdev_get(bdev, mode, 0);
  	if (error)
  		return ERR_PTR(error);
  	error = -EACCES;
  	if (!(flags & MS_RDONLY) && bdev_read_only(bdev))
  		goto blkdev_put;
  	error = bd_claim(bdev, holder);
  	if (error)
  		goto blkdev_put;
  
  	return bdev;
  	
  blkdev_put:
  	blkdev_put(bdev);
  	return ERR_PTR(error);
  }
  
  EXPORT_SYMBOL(open_bdev_excl);
  
  /**
   * close_bdev_excl  -  release a blockdevice openen by open_bdev_excl()
   *
   * @bdev:	blockdevice to close
   *
   * This is the counterpart to open_bdev_excl().
   */
  void close_bdev_excl(struct block_device *bdev)
  {
  	bd_release(bdev);
  	blkdev_put(bdev);
  }
  
  EXPORT_SYMBOL(close_bdev_excl);