text: /*
   * bitmap.c two-level bitmap (C) Peter T. Breuer (ptb@ot.uc3m.es) 2003
   *
   * bitmap_create  - sets up the bitmap structure
   * bitmap_destroy - destroys the bitmap structure
   *
   * additions, Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.:
   * - added disk storage for bitmap
   * - changes to allow various bitmap chunk sizes
   */
  
  /*
   * Still to do:
   *
   * flush after percent set rather than just time based. (maybe both).
   */
  
  #include <linux/blkdev.h>
  #include <linux/module.h>
  #include <linux/errno.h>
  #include <linux/slab.h>
  #include <linux/init.h>
  #include <linux/timer.h>
  #include <linux/sched.h>
  #include <linux/list.h>
  #include <linux/file.h>
  #include <linux/mount.h>
  #include <linux/buffer_head.h>
  #include "md.h"
  #include "bitmap.h"
  
  static inline char *bmname(struct bitmap *bitmap)
  {
  	return bitmap->mddev ? mdname(bitmap->mddev) : "mdX";
  }
  
  /*
   * just a placeholder - calls kmalloc for bitmap pages
   */
  static unsigned char *bitmap_alloc_page(struct bitmap *bitmap)
  {
  	unsigned char *page;
  
  	page = kzalloc(PAGE_SIZE, GFP_NOIO);
  	if (!page)
  		printk("%s: bitmap_alloc_page FAILED\n", bmname(bitmap));
  	else
  		pr_debug("%s: bitmap_alloc_page: allocated page at %p\n",
  			 bmname(bitmap), page);
  	return page;
  }
  
  /*
   * for now just a placeholder -- just calls kfree for bitmap pages
   */
  static void bitmap_free_page(struct bitmap *bitmap, unsigned char *page)
  {
  	pr_debug("%s: bitmap_free_page: free page %p\n", bmname(bitmap), page);
  	kfree(page);
  }
  
  /*
   * check a page and, if necessary, allocate it (or hijack it if the alloc fails)
   *
   * 1) check to see if this page is allocated, if it's not then try to alloc
   * 2) if the alloc fails, set the page's hijacked flag so we'll use the
   *    page pointer directly as a counter
   *
   * if we find our page, we increment the page's refcount so that it stays
   * allocated while we're using it
   */
  static int bitmap_checkpage(struct bitmap *bitmap,
  			    unsigned long page, int create)
  __releases(bitmap->lock)
  __acquires(bitmap->lock)
  {
  	unsigned char *mappage;
  
  	if (page >= bitmap->pages) {
  		/* This can happen if bitmap_start_sync goes beyond
  		 * End-of-device while looking for a whole page.
  		 * It is harmless.
  		 */
  		return -EINVAL;
  	}
  
  	if (bitmap->bp[page].hijacked) /* it's hijacked, don't try to alloc */
  		return 0;
  
  	if (bitmap->bp[page].map) /* page is already allocated, just return */
  		return 0;
  
  	if (!create)
  		return -ENOENT;
  
  	/* this page has not been allocated yet */
  
  	spin_unlock_irq(&bitmap->lock);
  	mappage = bitmap_alloc_page(bitmap);
  	spin_lock_irq(&bitmap->lock);
  
  	if (mappage == NULL) {
  		pr_debug("%s: bitmap map page allocation failed, hijacking\n",
  			 bmname(bitmap));
  		/* failed - set the hijacked flag so that we can use the
  		 * pointer as a counter */
  		if (!bitmap->bp[page].map)
  			bitmap->bp[page].hijacked = 1;
  	} else if (bitmap->bp[page].map ||
  		   bitmap->bp[page].hijacked) {
  		/* somebody beat us to getting the page */
  		bitmap_free_page(bitmap, mappage);
  		return 0;
  	} else {
  
  		/* no page was in place and we have one, so install it */
  
  		bitmap->bp[page].map = mappage;
  		bitmap->missing_pages--;
  	}
  	return 0;
  }
  
  /* if page is completely empty, put it back on the free list, or dealloc it */
  /* if page was hijacked, unmark the flag so it might get alloced next time */
  /* Note: lock should be held when calling this */
  static void bitmap_checkfree(struct bitmap *bitmap, unsigned long page)
  {
  	char *ptr;
  
  	if (bitmap->bp[page].count) /* page is still busy */
  		return;
  
  	/* page is no longer in use, it can be released */
  
  	if (bitmap->bp[page].hijacked) { /* page was hijacked, undo this now */
  		bitmap->bp[page].hijacked = 0;
  		bitmap->bp[page].map = NULL;
  	} else {
  		/* normal case, free the page */
  		ptr = bitmap->bp[page].map;
  		bitmap->bp[page].map = NULL;
  		bitmap->missing_pages++;
  		bitmap_free_page(bitmap, ptr);
  	}
  }
  
  /*
   * bitmap file handling - read and write the bitmap file and its superblock
   */
  
  /*
   * basic page I/O operations
   */
  
  /* IO operations when bitmap is stored near all superblocks */
  static struct page *read_sb_page(struct mddev *mddev, loff_t offset,
  				 struct page *page,
  				 unsigned long index, int size)
  {
  	/* choose a good rdev and read the page from there */
  
  	struct md_rdev *rdev;
  	sector_t target;
  	int did_alloc = 0;
  
  	if (!page) {
  		page = alloc_page(GFP_KERNEL);
  		if (!page)
  			return ERR_PTR(-ENOMEM);
  		did_alloc = 1;
  	}
  
  	list_for_each_entry(rdev, &mddev->disks, same_set) {
  		if (! test_bit(In_sync, &rdev->flags)
  		    || test_bit(Faulty, &rdev->flags))
  			continue;
  
  		target = offset + index * (PAGE_SIZE/512);
  
  		if (sync_page_io(rdev, target,
  				 roundup(size, bdev_logical_block_size(rdev->bdev)),
  				 page, READ, true)) {
  			page->index = index;
  			attach_page_buffers(page, NULL); /* so that free_buffer will
  							  * quietly no-op */
  			return page;
  		}
  	}
  	if (did_alloc)
  		put_page(page);
  	return ERR_PTR(-EIO);
  
  }
  
  static struct md_rdev *next_active_rdev(struct md_rdev *rdev, struct mddev *mddev)
  {
  	/* Iterate the disks of an mddev, using rcu to protect access to the
  	 * linked list, and raising the refcount of devices we return to ensure
  	 * they don't disappear while in use.
  	 * As devices are only added or removed when raid_disk is < 0 and
  	 * nr_pending is 0 and In_sync is clear, the entries we return will
  	 * still be in the same position on the list when we re-enter
  	 * list_for_each_continue_rcu.
  	 */
  	struct list_head *pos;
  	rcu_read_lock();
  	if (rdev == NULL)
  		/* start at the beginning */
  		pos = &mddev->disks;
  	else {
  		/* release the previous rdev and start from there. */
  		rdev_dec_pending(rdev, mddev);
  		pos = &rdev->same_set;
  	}
  	list_for_each_continue_rcu(pos, &mddev->disks) {
  		rdev = list_entry(pos, struct md_rdev, same_set);
  		if (rdev->raid_disk >= 0 &&
  		    !test_bit(Faulty, &rdev->flags)) {
  			/* this is a usable devices */
  			atomic_inc(&rdev->nr_pending);
  			rcu_read_unlock();
  			return rdev;
  		}
  	}
  	rcu_read_unlock();
  	return NULL;
  }
  
  static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
  {
  	struct md_rdev *rdev = NULL;
  	struct block_device *bdev;
  	struct mddev *mddev = bitmap->mddev;
  
  	while ((rdev = next_active_rdev(rdev, mddev)) != NULL) {
  		int size = PAGE_SIZE;
  		loff_t offset = mddev->bitmap_info.offset;
  
  		bdev = (rdev->meta_bdev) ? rdev->meta_bdev : rdev->bdev;
  
  		if (page->index == bitmap->file_pages-1)
  			size = roundup(bitmap->last_page_size,
  				       bdev_logical_block_size(bdev));
  		/* Just make sure we aren't corrupting data or
  		 * metadata
  		 */
  		if (mddev->external) {
  			/* Bitmap could be anywhere. */
  			if (rdev->sb_start + offset + (page->index
  						       * (PAGE_SIZE/512))
  			    > rdev->data_offset
  			    &&
  			    rdev->sb_start + offset
  			    < (rdev->data_offset + mddev->dev_sectors
  			     + (PAGE_SIZE/512)))
  				goto bad_alignment;
  		} else if (offset < 0) {
  			/* DATA  BITMAP METADATA  */
  			if (offset
  			    + (long)(page->index * (PAGE_SIZE/512))
  			    + size/512 > 0)
  				/* bitmap runs in to metadata */
  				goto bad_alignment;
  			if (rdev->data_offset + mddev->dev_sectors
  			    > rdev->sb_start + offset)
  				/* data runs in to bitmap */
  				goto bad_alignment;
  		} else if (rdev->sb_start < rdev->data_offset) {
  			/* METADATA BITMAP DATA */
  			if (rdev->sb_start
  			    + offset
  			    + page->index*(PAGE_SIZE/512) + size/512
  			    > rdev->data_offset)
  				/* bitmap runs in to data */
  				goto bad_alignment;
  		} else {
  			/* DATA METADATA BITMAP - no problems */
  		}
  		md_super_write(mddev, rdev,
  			       rdev->sb_start + offset
  			       + page->index * (PAGE_SIZE/512),
  			       size,
  			       page);
  	}
  
  	if (wait)
  		md_super_wait(mddev);
  	return 0;
  
   bad_alignment:
  	return -EINVAL;
  }
  
  static void bitmap_file_kick(struct bitmap *bitmap);
  /*
   * write out a page to a file
   */
  static void write_page(struct bitmap *bitmap, struct page *page, int wait)
  {
  	struct buffer_head *bh;
  
  	if (bitmap->file == NULL) {
  		switch (write_sb_page(bitmap, page, wait)) {
  		case -EINVAL:
  			bitmap->flags |= BITMAP_WRITE_ERROR;
  		}
  	} else {
  
  		bh = page_buffers(page);
  
  		while (bh && bh->b_blocknr) {
  			atomic_inc(&bitmap->pending_writes);
  			set_buffer_locked(bh);
  			set_buffer_mapped(bh);
  			submit_bh(WRITE | REQ_SYNC, bh);
  			bh = bh->b_this_page;
  		}
  
  		if (wait)
  			wait_event(bitmap->write_wait,
  				   atomic_read(&bitmap->pending_writes)==0);
  	}
  	if (bitmap->flags & BITMAP_WRITE_ERROR)
  		bitmap_file_kick(bitmap);
  }
  
  static void end_bitmap_write(struct buffer_head *bh, int uptodate)
  {
  	struct bitmap *bitmap = bh->b_private;
  	unsigned long flags;
  
  	if (!uptodate) {
  		spin_lock_irqsave(&bitmap->lock, flags);
  		bitmap->flags |= BITMAP_WRITE_ERROR;
  		spin_unlock_irqrestore(&bitmap->lock, flags);
  	}
  	if (atomic_dec_and_test(&bitmap->pending_writes))
  		wake_up(&bitmap->write_wait);
  }
  
  /* copied from buffer.c */
  static void
  __clear_page_buffers(struct page *page)
  {
  	ClearPagePrivate(page);
  	set_page_private(page, 0);
  	page_cache_release(page);
  }
  static void free_buffers(struct page *page)
  {
  	struct buffer_head *bh = page_buffers(page);
  
  	while (bh) {
  		struct buffer_head *next = bh->b_this_page;
  		free_buffer_head(bh);
  		bh = next;
  	}
  	__clear_page_buffers(page);
  	put_page(page);
  }
  
  /* read a page from a file.
   * We both read the page, and attach buffers to the page to record the
   * address of each block (using bmap).  These addresses will be used
   * to write the block later, completely bypassing the filesystem.
   * This usage is similar to how swap files are handled, and allows us
   * to write to a file with no concerns of memory allocation failing.
   */
  static struct page *read_page(struct file *file, unsigned long index,
  			      struct bitmap *bitmap,
  			      unsigned long count)
  {
  	struct page *page = NULL;
  	struct inode *inode = file->f_path.dentry->d_inode;
  	struct buffer_head *bh;
  	sector_t block;
  
  	pr_debug("read bitmap file (%dB @ %llu)\n", (int)PAGE_SIZE,
  		 (unsigned long long)index << PAGE_SHIFT);
  
  	page = alloc_page(GFP_KERNEL);
  	if (!page)
  		page = ERR_PTR(-ENOMEM);
  	if (IS_ERR(page))
  		goto out;
  
  	bh = alloc_page_buffers(page, 1<<inode->i_blkbits, 0);
  	if (!bh) {
  		put_page(page);
  		page = ERR_PTR(-ENOMEM);
  		goto out;
  	}
  	attach_page_buffers(page, bh);
  	block = index << (PAGE_SHIFT - inode->i_blkbits);
  	while (bh) {
  		if (count == 0)
  			bh->b_blocknr = 0;
  		else {
  			bh->b_blocknr = bmap(inode, block);
  			if (bh->b_blocknr == 0) {
  				/* Cannot use this file! */
  				free_buffers(page);
  				page = ERR_PTR(-EINVAL);
  				goto out;
  			}
  			bh->b_bdev = inode->i_sb->s_bdev;
  			if (count < (1<<inode->i_blkbits))
  				count = 0;
  			else
  				count -= (1<<inode->i_blkbits);
  
  			bh->b_end_io = end_bitmap_write;
  			bh->b_private = bitmap;
  			atomic_inc(&bitmap->pending_writes);
  			set_buffer_locked(bh);
  			set_buffer_mapped(bh);
  			submit_bh(READ, bh);
  		}
  		block++;
  		bh = bh->b_this_page;
  	}
  	page->index = index;
  
  	wait_event(bitmap->write_wait,
  		   atomic_read(&bitmap->pending_writes)==0);
  	if (bitmap->flags & BITMAP_WRITE_ERROR) {
  		free_buffers(page);
  		page = ERR_PTR(-EIO);
  	}
  out:
  	if (IS_ERR(page))
  		printk(KERN_ALERT "md: bitmap read error: (%dB @ %llu): %ld\n",
  			(int)PAGE_SIZE,
  			(unsigned long long)index << PAGE_SHIFT,
  			PTR_ERR(page));
  	return page;
  }
  
  /*
   * bitmap file superblock operations
   */
  
  /* update the event counter and sync the superblock to disk */
  void bitmap_update_sb(struct bitmap *bitmap)
  {
  	bitmap_super_t *sb;
  	unsigned long flags;
  
  	if (!bitmap || !bitmap->mddev) /* no bitmap for this array */
  		return;
  	if (bitmap->mddev->bitmap_info.external)
  		return;
  	spin_lock_irqsave(&bitmap->lock, flags);
  	if (!bitmap->sb_page) { /* no superblock */
  		spin_unlock_irqrestore(&bitmap->lock, flags);
  		return;
  	}
  	spin_unlock_irqrestore(&bitmap->lock, flags);
  	sb = kmap_atomic(bitmap->sb_page, KM_USER0);
  	sb->events = cpu_to_le64(bitmap->mddev->events);
  	if (bitmap->mddev->events < bitmap->events_cleared)
  		/* rocking back to read-only */
  		bitmap->events_cleared = bitmap->mddev->events;
  	sb->events_cleared = cpu_to_le64(bitmap->events_cleared);
  	sb->state = cpu_to_le32(bitmap->flags);
  	/* Just in case these have been changed via sysfs: */
  	sb->daemon_sleep = cpu_to_le32(bitmap->mddev->bitmap_info.daemon_sleep/HZ);
  	sb->write_behind = cpu_to_le32(bitmap->mddev->bitmap_info.max_write_behind);
  	kunmap_atomic(sb, KM_USER0);
  	write_page(bitmap, bitmap->sb_page, 1);
  }
  
  /* print out the bitmap file superblock */
  void bitmap_print_sb(struct bitmap *bitmap)
  {
  	bitmap_super_t *sb;
  
  	if (!bitmap || !bitmap->sb_page)
  		return;
  	sb = kmap_atomic(bitmap->sb_page, KM_USER0);
  	printk(KERN_DEBUG "%s: bitmap file superblock:\n", bmname(bitmap));
  	printk(KERN_DEBUG "         magic: %08x\n", le32_to_cpu(sb->magic));
  	printk(KERN_DEBUG "       version: %d\n", le32_to_cpu(sb->version));
  	printk(KERN_DEBUG "          uuid: %08x.%08x.%08x.%08x\n",
  					*(__u32 *)(sb->uuid+0),
  					*(__u32 *)(sb->uuid+4),
  					*(__u32 *)(sb->uuid+8),
  					*(__u32 *)(sb->uuid+12));
  	printk(KERN_DEBUG "        events: %llu\n",
  			(unsigned long long) le64_to_cpu(sb->events));
  	printk(KERN_DEBUG "events cleared: %llu\n",
  			(unsigned long long) le64_to_cpu(sb->events_cleared));
  	printk(KERN_DEBUG "         state: %08x\n", le32_to_cpu(sb->state));
  	printk(KERN_DEBUG "     chunksize: %d B\n", le32_to_cpu(sb->chunksize));
  	printk(KERN_DEBUG "  daemon sleep: %ds\n", le32_to_cpu(sb->daemon_sleep));
  	printk(KERN_DEBUG "     sync size: %llu KB\n",
  			(unsigned long long)le64_to_cpu(sb->sync_size)/2);
  	printk(KERN_DEBUG "max write behind: %d\n", le32_to_cpu(sb->write_behind));
  	kunmap_atomic(sb, KM_USER0);
  }
  
  /*
   * bitmap_new_disk_sb
   * @bitmap
   *
   * This function is somewhat the reverse of bitmap_read_sb.  bitmap_read_sb
   * reads and verifies the on-disk bitmap superblock and populates bitmap_info.
   * This function verifies 'bitmap_info' and populates the on-disk bitmap
   * structure, which is to be written to disk.
   *
   * Returns: 0 on success, -Exxx on error
   */
  static int bitmap_new_disk_sb(struct bitmap *bitmap)
  {
  	bitmap_super_t *sb;
  	unsigned long chunksize, daemon_sleep, write_behind;
  	int err = -EINVAL;
  
  	bitmap->sb_page = alloc_page(GFP_KERNEL);
  	if (IS_ERR(bitmap->sb_page)) {
  		err = PTR_ERR(bitmap->sb_page);
  		bitmap->sb_page = NULL;
  		return err;
  	}
  	bitmap->sb_page->index = 0;
  
  	sb = kmap_atomic(bitmap->sb_page, KM_USER0);
  
  	sb->magic = cpu_to_le32(BITMAP_MAGIC);
  	sb->version = cpu_to_le32(BITMAP_MAJOR_HI);
  
  	chunksize = bitmap->mddev->bitmap_info.chunksize;
  	BUG_ON(!chunksize);
  	if (!is_power_of_2(chunksize)) {
  		kunmap_atomic(sb, KM_USER0);
  		printk(KERN_ERR "bitmap chunksize not a power of 2\n");
  		return -EINVAL;
  	}
  	sb->chunksize = cpu_to_le32(chunksize);
  
  	daemon_sleep = bitmap->mddev->bitmap_info.daemon_sleep;
  	if (!daemon_sleep ||
  	    (daemon_sleep < 1) || (daemon_sleep > MAX_SCHEDULE_TIMEOUT)) {
  		printk(KERN_INFO "Choosing daemon_sleep default (5 sec)\n");
  		daemon_sleep = 5 * HZ;
  	}
  	sb->daemon_sleep = cpu_to_le32(daemon_sleep);
  	bitmap->mddev->bitmap_info.daemon_sleep = daemon_sleep;
  
  	/*
  	 * FIXME: write_behind for RAID1.  If not specified, what
  	 * is a good choice?  We choose COUNTER_MAX / 2 arbitrarily.
  	 */
  	write_behind = bitmap->mddev->bitmap_info.max_write_behind;
  	if (write_behind > COUNTER_MAX)
  		write_behind = COUNTER_MAX / 2;
  	sb->write_behind = cpu_to_le32(write_behind);
  	bitmap->mddev->bitmap_info.max_write_behind = write_behind;
  
  	/* keep the array size field of the bitmap superblock up to date */
  	sb->sync_size = cpu_to_le64(bitmap->mddev->resync_max_sectors);
  
  	memcpy(sb->uuid, bitmap->mddev->uuid, 16);
  
  	bitmap->flags |= BITMAP_STALE;
  	sb->state |= cpu_to_le32(BITMAP_STALE);
  	bitmap->events_cleared = bitmap->mddev->events;
  	sb->events_cleared = cpu_to_le64(bitmap->mddev->events);
  
  	bitmap->flags |= BITMAP_HOSTENDIAN;
  	sb->version = cpu_to_le32(BITMAP_MAJOR_HOSTENDIAN);
  
  	kunmap_atomic(sb, KM_USER0);
  
  	return 0;
  }
  
  /* read the superblock from the bitmap file and initialize some bitmap fields */
  static int bitmap_read_sb(struct bitmap *bitmap)
  {
  	char *reason = NULL;
  	bitmap_super_t *sb;
  	unsigned long chunksize, daemon_sleep, write_behind;
  	unsigned long long events;
  	int err = -EINVAL;
  
  	/* page 0 is the superblock, read it... */
  	if (bitmap->file) {
  		loff_t isize = i_size_read(bitmap->file->f_mapping->host);
  		int bytes = isize > PAGE_SIZE ? PAGE_SIZE : isize;
  
  		bitmap->sb_page = read_page(bitmap->file, 0, bitmap, bytes);
  	} else {
  		bitmap->sb_page = read_sb_page(bitmap->mddev,
  					       bitmap->mddev->bitmap_info.offset,
  					       NULL,
  					       0, sizeof(bitmap_super_t));
  	}
  	if (IS_ERR(bitmap->sb_page)) {
  		err = PTR_ERR(bitmap->sb_page);
  		bitmap->sb_page = NULL;
  		return err;
  	}
  
  	sb = kmap_atomic(bitmap->sb_page, KM_USER0);
  
  	chunksize = le32_to_cpu(sb->chunksize);
  	daemon_sleep = le32_to_cpu(sb->daemon_sleep) * HZ;
  	write_behind = le32_to_cpu(sb->write_behind);
  
  	/* verify that the bitmap-specific fields are valid */
  	if (sb->magic != cpu_to_le32(BITMAP_MAGIC))
  		reason = "bad magic";
  	else if (le32_to_cpu(sb->version) < BITMAP_MAJOR_LO ||
  		 le32_to_cpu(sb->version) > BITMAP_MAJOR_HI)
  		reason = "unrecognized superblock version";
  	else if (chunksize < 512)
  		reason = "bitmap chunksize too small";
  	else if (!is_power_of_2(chunksize))
  		reason = "bitmap chunksize not a power of 2";
  	else if (daemon_sleep < 1 || daemon_sleep > MAX_SCHEDULE_TIMEOUT)
  		reason = "daemon sleep period out of range";
  	else if (write_behind > COUNTER_MAX)
  		reason = "write-behind limit out of range (0 - 16383)";
  	if (reason) {
  		printk(KERN_INFO "%s: invalid bitmap file superblock: %s\n",
  			bmname(bitmap), reason);
  		goto out;
  	}
  
  	/* keep the array size field of the bitmap superblock up to date */
  	sb->sync_size = cpu_to_le64(bitmap->mddev->resync_max_sectors);
  
  	if (!bitmap->mddev->persistent)
  		goto success;
  
  	/*
  	 * if we have a persistent array superblock, compare the
  	 * bitmap's UUID and event counter to the mddev's
  	 */
  	if (memcmp(sb->uuid, bitmap->mddev->uuid, 16)) {
  		printk(KERN_INFO "%s: bitmap superblock UUID mismatch\n",
  			bmname(bitmap));
  		goto out;
  	}
  	events = le64_to_cpu(sb->events);
  	if (events < bitmap->mddev->events) {
  		printk(KERN_INFO "%s: bitmap file is out of date (%llu < %llu) "
  			"-- forcing full recovery\n", bmname(bitmap), events,
  			(unsigned long long) bitmap->mddev->events);
  		sb->state |= cpu_to_le32(BITMAP_STALE);
  	}
  success:
  	/* assign fields using values from superblock */
  	bitmap->mddev->bitmap_info.chunksize = chunksize;
  	bitmap->mddev->bitmap_info.daemon_sleep = daemon_sleep;
  	bitmap->mddev->bitmap_info.max_write_behind = write_behind;
  	bitmap->flags |= le32_to_cpu(sb->state);
  	if (le32_to_cpu(sb->version) == BITMAP_MAJOR_HOSTENDIAN)
  		bitmap->flags |= BITMAP_HOSTENDIAN;
  	bitmap->events_cleared = le64_to_cpu(sb->events_cleared);
  	if (bitmap->flags & BITMAP_STALE)
  		bitmap->events_cleared = bitmap->mddev->events;
  	err = 0;
  out:
  	kunmap_atomic(sb, KM_USER0);
  	if (err)
  		bitmap_print_sb(bitmap);
  	return err;
  }
  
  enum bitmap_mask_op {
  	MASK_SET,
  	MASK_UNSET
  };
  
  /* record the state of the bitmap in the superblock.  Return the old value */
  static int bitmap_mask_state(struct bitmap *bitmap, enum bitmap_state bits,
  			     enum bitmap_mask_op op)
  {
  	bitmap_super_t *sb;
  	unsigned long flags;
  	int old;
  
  	spin_lock_irqsave(&bitmap->lock, flags);
  	if (!bitmap->sb_page) { /* can't set the state */
  		spin_unlock_irqrestore(&bitmap->lock, flags);
  		return 0;
  	}
  	spin_unlock_irqrestore(&bitmap->lock, flags);
  	sb = kmap_atomic(bitmap->sb_page, KM_USER0);
  	old = le32_to_cpu(sb->state) & bits;
  	switch (op) {
  	case MASK_SET:
  		sb->state |= cpu_to_le32(bits);
  		bitmap->flags |= bits;
  		break;
  	case MASK_UNSET:
  		sb->state &= cpu_to_le32(~bits);
  		bitmap->flags &= ~bits;
  		break;
  	default:
  		BUG();
  	}
  	kunmap_atomic(sb, KM_USER0);
  	return old;
  }
  
  /*
   * general bitmap file operations
   */
  
  /*
   * on-disk bitmap:
   *
   * Use one bit per "chunk" (block set). We do the disk I/O on the bitmap
   * file a page at a time. There's a superblock at the start of the file.
   */
  /* calculate the index of the page that contains this bit */
  static inline unsigned long file_page_index(struct bitmap *bitmap, unsigned long chunk)
  {
  	if (!bitmap->mddev->bitmap_info.external)
  		chunk += sizeof(bitmap_super_t) << 3;
  	return chunk >> PAGE_BIT_SHIFT;
  }
  
  /* calculate the (bit) offset of this bit within a page */
  static inline unsigned long file_page_offset(struct bitmap *bitmap, unsigned long chunk)
  {
  	if (!bitmap->mddev->bitmap_info.external)
  		chunk += sizeof(bitmap_super_t) << 3;
  	return chunk & (PAGE_BITS - 1);
  }
  
  /*
   * return a pointer to the page in the filemap that contains the given bit
   *
   * this lookup is complicated by the fact that the bitmap sb might be exactly
   * 1 page (e.g., x86) or less than 1 page -- so the bitmap might start on page
   * 0 or page 1
   */
  static inline struct page *filemap_get_page(struct bitmap *bitmap,
  					    unsigned long chunk)
  {
  	if (file_page_index(bitmap, chunk) >= bitmap->file_pages)
  		return NULL;
  	return bitmap->filemap[file_page_index(bitmap, chunk)
  			       - file_page_index(bitmap, 0)];
  }
  
  static void bitmap_file_unmap(struct bitmap *bitmap)
  {
  	struct page **map, *sb_page;
  	unsigned long *attr;
  	int pages;
  	unsigned long flags;
  
  	spin_lock_irqsave(&bitmap->lock, flags);
  	map = bitmap->filemap;
  	bitmap->filemap = NULL;
  	attr = bitmap->filemap_attr;
  	bitmap->filemap_attr = NULL;
  	pages = bitmap->file_pages;
  	bitmap->file_pages = 0;
  	sb_page = bitmap->sb_page;
  	bitmap->sb_page = NULL;
  	spin_unlock_irqrestore(&bitmap->lock, flags);
  
  	while (pages--)
  		if (map[pages] != sb_page) /* 0 is sb_page, release it below */
  			free_buffers(map[pages]);
  	kfree(map);
  	kfree(attr);
  
  	if (sb_page)
  		free_buffers(sb_page);
  }
  
  static void bitmap_file_put(struct bitmap *bitmap)
  {
  	struct file *file;
  	unsigned long flags;
  
  	spin_lock_irqsave(&bitmap->lock, flags);
  	file = bitmap->file;
  	bitmap->file = NULL;
  	spin_unlock_irqrestore(&bitmap->lock, flags);
  
  	if (file)
  		wait_event(bitmap->write_wait,
  			   atomic_read(&bitmap->pending_writes)==0);
  	bitmap_file_unmap(bitmap);
  
  	if (file) {
  		struct inode *inode = file->f_path.dentry->d_inode;
  		invalidate_mapping_pages(inode->i_mapping, 0, -1);
  		fput(file);
  	}
  }
  
  /*
   * bitmap_file_kick - if an error occurs while manipulating the bitmap file
   * then it is no longer reliable, so we stop using it and we mark the file
   * as failed in the superblock
   */
  static void bitmap_file_kick(struct bitmap *bitmap)
  {
  	char *path, *ptr = NULL;
  
  	if (bitmap_mask_state(bitmap, BITMAP_STALE, MASK_SET) == 0) {
  		bitmap_update_sb(bitmap);
  
  		if (bitmap->file) {
  			path = kmalloc(PAGE_SIZE, GFP_KERNEL);
  			if (path)
  				ptr = d_path(&bitmap->file->f_path, path,
  					     PAGE_SIZE);
  
  			printk(KERN_ALERT
  			      "%s: kicking failed bitmap file %s from array!\n",
  			      bmname(bitmap), IS_ERR(ptr) ? "" : ptr);
  
  			kfree(path);
  		} else
  			printk(KERN_ALERT
  			       "%s: disabling internal bitmap due to errors\n",
  			       bmname(bitmap));
  	}
  
  	bitmap_file_put(bitmap);
  
  	return;
  }
  
  enum bitmap_page_attr {
  	BITMAP_PAGE_DIRTY = 0,     /* there are set bits that need to be synced */
  	BITMAP_PAGE_PENDING = 1,   /* there are bits that are being cleaned.
  				    * i.e. counter is 1 or 2. */
  	BITMAP_PAGE_NEEDWRITE = 2, /* there are cleared bits that need to be synced */
  };
  
  static inline void set_page_attr(struct bitmap *bitmap, struct page *page,
  				enum bitmap_page_attr attr)
  {
  	__set_bit((page->index<<2) + attr, bitmap->filemap_attr);
  }
  
  static inline void clear_page_attr(struct bitmap *bitmap, struct page *page,
  				enum bitmap_page_attr attr)
  {
  	__clear_bit((page->index<<2) + attr, bitmap->filemap_attr);
  }
  
  static inline unsigned long test_page_attr(struct bitmap *bitmap, struct page *page,
  					   enum bitmap_page_attr attr)
  {
  	return test_bit((page->index<<2) + attr, bitmap->filemap_attr);
  }
  
  /*
   * bitmap_file_set_bit -- called before performing a write to the md device
   * to set (and eventually sync) a particular bit in the bitmap file
   *
   * we set the bit immediately, then we record the page number so that
   * when an unplug occurs, we can flush the dirty pages out to disk
   */
  static void bitmap_file_set_bit(struct bitmap *bitmap, sector_t block)
  {
  	unsigned long bit;
  	struct page *page;
  	void *kaddr;
  	unsigned long chunk = block >> CHUNK_BLOCK_SHIFT(bitmap);
  
  	if (!bitmap->filemap)
  		return;
  
  	page = filemap_get_page(bitmap, chunk);
  	if (!page)
  		return;
  	bit = file_page_offset(bitmap, chunk);
  
  	/* set the bit */
  	kaddr = kmap_atomic(page, KM_USER0);
  	if (bitmap->flags & BITMAP_HOSTENDIAN)
  		set_bit(bit, kaddr);
  	else
  		__set_bit_le(bit, kaddr);
  	kunmap_atomic(kaddr, KM_USER0);
  	pr_debug("set file bit %lu page %lu\n", bit, page->index);
  	/* record page number so it gets flushed to disk when unplug occurs */
  	set_page_attr(bitmap, page, BITMAP_PAGE_DIRTY);
  }
  
  /* this gets called when the md device is ready to unplug its underlying
   * (slave) device queues -- before we let any writes go down, we need to
   * sync the dirty pages of the bitmap file to disk */
  void bitmap_unplug(struct bitmap *bitmap)
  {
  	unsigned long i, flags;
  	int dirty, need_write;
  	struct page *page;
  	int wait = 0;
  
  	if (!bitmap)
  		return;
  
  	/* look at each page to see if there are any set bits that need to be
  	 * flushed out to disk */
  	for (i = 0; i < bitmap->file_pages; i++) {
  		spin_lock_irqsave(&bitmap->lock, flags);
  		if (!bitmap->filemap) {
  			spin_unlock_irqrestore(&bitmap->lock, flags);
  			return;
  		}
  		page = bitmap->filemap[i];
  		dirty = test_page_attr(bitmap, page, BITMAP_PAGE_DIRTY);
  		need_write = test_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
  		clear_page_attr(bitmap, page, BITMAP_PAGE_DIRTY);
  		clear_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
  		if (dirty)
  			wait = 1;
  		spin_unlock_irqrestore(&bitmap->lock, flags);
  
  		if (dirty || need_write)
  			write_page(bitmap, page, 0);
  	}
  	if (wait) { /* if any writes were performed, we need to wait on them */
  		if (bitmap->file)
  			wait_event(bitmap->write_wait,
  				   atomic_read(&bitmap->pending_writes)==0);
  		else
  			md_super_wait(bitmap->mddev);
  	}
  	if (bitmap->flags & BITMAP_WRITE_ERROR)
  		bitmap_file_kick(bitmap);
  }
  EXPORT_SYMBOL(bitmap_unplug);
  
  static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int needed);
  /* * bitmap_init_from_disk -- called at bitmap_create time to initialize
   * the in-memory bitmap from the on-disk bitmap -- also, sets up the
   * memory mapping of the bitmap file
   * Special cases:
   *   if there's no bitmap file, or if the bitmap file had been
   *   previously kicked from the array, we mark all the bits as
   *   1's in order to cause a full resync.
   *
   * We ignore all bits for sectors that end earlier than 'start'.
   * This is used when reading an out-of-date bitmap...
   */
  static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
  {
  	unsigned long i, chunks, index, oldindex, bit;
  	struct page *page = NULL, *oldpage = NULL;
  	unsigned long num_pages, bit_cnt = 0;
  	struct file *file;
  	unsigned long bytes, offset;
  	int outofdate;
  	int ret = -ENOSPC;
  	void *paddr;
  
  	chunks = bitmap->chunks;
  	file = bitmap->file;
  
  	BUG_ON(!file && !bitmap->mddev->bitmap_info.offset);
  
  	outofdate = bitmap->flags & BITMAP_STALE;
  	if (outofdate)
  		printk(KERN_INFO "%s: bitmap file is out of date, doing full "
  			"recovery\n", bmname(bitmap));
  
  	bytes = DIV_ROUND_UP(bitmap->chunks, 8);
  	if (!bitmap->mddev->bitmap_info.external)
  		bytes += sizeof(bitmap_super_t);
  
  	num_pages = DIV_ROUND_UP(bytes, PAGE_SIZE);
  
  	if (file && i_size_read(file->f_mapping->host) < bytes) {
  		printk(KERN_INFO "%s: bitmap file too short %lu < %lu\n",
  			bmname(bitmap),
  			(unsigned long) i_size_read(file->f_mapping->host),
  			bytes);
  		goto err;
  	}
  
  	ret = -ENOMEM;
  
  	bitmap->filemap = kmalloc(sizeof(struct page *) * num_pages, GFP_KERNEL);
  	if (!bitmap->filemap)
  		goto err;
  
  	/* We need 4 bits per page, rounded up to a multiple of sizeof(unsigned long) */
  	bitmap->filemap_attr = kzalloc(
  		roundup(DIV_ROUND_UP(num_pages*4, 8), sizeof(unsigned long)),
  		GFP_KERNEL);
  	if (!bitmap->filemap_attr)
  		goto err;
  
  	oldindex = ~0L;
  
  	for (i = 0; i < chunks; i++) {
  		int b;
  		index = file_page_index(bitmap, i);
  		bit = file_page_offset(bitmap, i);
  		if (index != oldindex) { /* this is a new page, read it in */
  			int count;
  			/* unmap the old page, we're done with it */
  			if (index == num_pages-1)
  				count = bytes - index * PAGE_SIZE;
  			else
  				count = PAGE_SIZE;
  			if (index == 0 && bitmap->sb_page) {
  				/*
  				 * if we're here then the superblock page
  				 * contains some bits (PAGE_SIZE != sizeof sb)
  				 * we've already read it in, so just use it
  				 */
  				page = bitmap->sb_page;
  				offset = sizeof(bitmap_super_t);
  				if (!file)
  					page = read_sb_page(
  						bitmap->mddev,
  						bitmap->mddev->bitmap_info.offset,
  						page,
  						index, count);
  			} else if (file) {
  				page = read_page(file, index, bitmap, count);
  				offset = 0;
  			} else {
  				page = read_sb_page(bitmap->mddev,
  						    bitmap->mddev->bitmap_info.offset,
  						    NULL,
  						    index, count);
  				offset = 0;
  			}
  			if (IS_ERR(page)) { /* read error */
  				ret = PTR_ERR(page);
  				goto err;
  			}
  
  			oldindex = index;
  			oldpage = page;
  
  			bitmap->filemap[bitmap->file_pages++] = page;
  			bitmap->last_page_size = count;
  
  			if (outofdate) {
  				/*
  				 * if bitmap is out of date, dirty the
  				 * whole page and write it out
  				 */
  				paddr = kmap_atomic(page, KM_USER0);
  				memset(paddr + offset, 0xff,
  				       PAGE_SIZE - offset);
  				kunmap_atomic(paddr, KM_USER0);
  				write_page(bitmap, page, 1);
  
  				ret = -EIO;
  				if (bitmap->flags & BITMAP_WRITE_ERROR)
  					goto err;
  			}
  		}
  		paddr = kmap_atomic(page, KM_USER0);
  		if (bitmap->flags & BITMAP_HOSTENDIAN)
  			b = test_bit(bit, paddr);
  		else
  			b = test_bit_le(bit, paddr);
  		kunmap_atomic(paddr, KM_USER0);
  		if (b) {
  			/* if the disk bit is set, set the memory bit */
  			int needed = ((sector_t)(i+1) << (CHUNK_BLOCK_SHIFT(bitmap))
  				      >= start);
  			bitmap_set_memory_bits(bitmap,
  					       (sector_t)i << CHUNK_BLOCK_SHIFT(bitmap),
  					       needed);
  			bit_cnt++;
  		}
  	}
  
  	/* everything went OK */
  	ret = 0;
  	bitmap_mask_state(bitmap, BITMAP_STALE, MASK_UNSET);
  
  	if (bit_cnt) { /* Kick recovery if any bits were set */
  		set_bit(MD_RECOVERY_NEEDED, &bitmap->mddev->recovery);
  		md_wakeup_thread(bitmap->mddev->thread);
  	}
  
  	printk(KERN_INFO "%s: bitmap initialized from disk: "
  	       "read %lu/%lu pages, set %lu of %lu bits\n",
  	       bmname(bitmap), bitmap->file_pages, num_pages, bit_cnt, chunks);
  
  	return 0;
  
   err:
  	printk(KERN_INFO "%s: bitmap initialisation failed: %d\n",
  	       bmname(bitmap), ret);
  	return ret;
  }
  
  void bitmap_write_all(struct bitmap *bitmap)
  {
  	/* We don't actually write all bitmap blocks here,
  	 * just flag them as needing to be written
  	 */
  	int i;
  
  	spin_lock_irq(&bitmap->lock);
  	for (i = 0; i < bitmap->file_pages; i++)
  		set_page_attr(bitmap, bitmap->filemap[i],
  			      BITMAP_PAGE_NEEDWRITE);
  	bitmap->allclean = 0;
  	spin_unlock_irq(&bitmap->lock);
  }
  
  static void bitmap_count_page(struct bitmap *bitmap, sector_t offset, int inc)
  {
  	sector_t chunk = offset >> CHUNK_BLOCK_SHIFT(bitmap);
  	unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
  	bitmap->bp[page].count += inc;
  	bitmap_checkfree(bitmap, page);
  }
  static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
  					    sector_t offset, sector_t *blocks,
  					    int create);
  
  /*
   * bitmap daemon -- periodically wakes up to clean bits and flush pages
   *			out to disk
   */
  
  void bitmap_daemon_work(struct mddev *mddev)
  {
  	struct bitmap *bitmap;
  	unsigned long j;
  	unsigned long flags;
  	struct page *page = NULL, *lastpage = NULL;
  	sector_t blocks;
  	void *paddr;
  
  	/* Use a mutex to guard daemon_work against
  	 * bitmap_destroy.
  	 */
  	mutex_lock(&mddev->bitmap_info.mutex);
  	bitmap = mddev->bitmap;
  	if (bitmap == NULL) {
  		mutex_unlock(&mddev->bitmap_info.mutex);
  		return;
  	}
  	if (time_before(jiffies, bitmap->daemon_lastrun
  			+ mddev->bitmap_info.daemon_sleep))
  		goto done;
  
  	bitmap->daemon_lastrun = jiffies;
  	if (bitmap->allclean) {
  		mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;
  		goto done;
  	}
  	bitmap->allclean = 1;
  
  	spin_lock_irqsave(&bitmap->lock, flags);
  	for (j = 0; j < bitmap->chunks; j++) {
  		bitmap_counter_t *bmc;
  		if (!bitmap->filemap)
  			/* error or shutdown */
  			break;
  
  		page = filemap_get_page(bitmap, j);
  
  		if (page != lastpage) {
  			/* skip this page unless it's marked as needing cleaning */
  			if (!test_page_attr(bitmap, page, BITMAP_PAGE_PENDING)) {
  				int need_write = test_page_attr(bitmap, page,
  								BITMAP_PAGE_NEEDWRITE);
  				if (need_write)
  					clear_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
  
  				spin_unlock_irqrestore(&bitmap->lock, flags);
  				if (need_write)
  					write_page(bitmap, page, 0);
  				spin_lock_irqsave(&bitmap->lock, flags);
  				j |= (PAGE_BITS - 1);
  				continue;
  			}
  
  			/* grab the new page, sync and release the old */
  			if (lastpage != NULL) {
  				if (test_page_attr(bitmap, lastpage,
  						   BITMAP_PAGE_NEEDWRITE)) {
  					clear_page_attr(bitmap, lastpage,
  							BITMAP_PAGE_NEEDWRITE);
  					spin_unlock_irqrestore(&bitmap->lock, flags);
  					write_page(bitmap, lastpage, 0);
  				} else {
  					set_page_attr(bitmap, lastpage,
  						      BITMAP_PAGE_NEEDWRITE);
  					bitmap->allclean = 0;
  					spin_unlock_irqrestore(&bitmap->lock, flags);
  				}
  			} else
  				spin_unlock_irqrestore(&bitmap->lock, flags);
  			lastpage = page;
  
  			/* We are possibly going to clear some bits, so make
  			 * sure that events_cleared is up-to-date.
  			 */
  			if (bitmap->need_sync &&
  			    mddev->bitmap_info.external == 0) {
  				bitmap_super_t *sb;
  				bitmap->need_sync = 0;
  				sb = kmap_atomic(bitmap->sb_page, KM_USER0);
  				sb->events_cleared =
  					cpu_to_le64(bitmap->events_cleared);
  				kunmap_atomic(sb, KM_USER0);
  				write_page(bitmap, bitmap->sb_page, 1);
  			}
  			spin_lock_irqsave(&bitmap->lock, flags);
  			if (!bitmap->need_sync)
  				clear_page_attr(bitmap, page, BITMAP_PAGE_PENDING);
  			else
  				bitmap->allclean = 0;
  		}
  		bmc = bitmap_get_counter(bitmap,
  					 (sector_t)j << CHUNK_BLOCK_SHIFT(bitmap),
  					 &blocks, 0);
  		if (!bmc)
  			j |= PAGE_COUNTER_MASK;
  		else if (*bmc) {
  			if (*bmc == 1 && !bitmap->need_sync) {
  				/* we can clear the bit */
  				*bmc = 0;
  				bitmap_count_page(bitmap,
  						  (sector_t)j << CHUNK_BLOCK_SHIFT(bitmap),
  						  -1);
  
  				/* clear the bit */
  				paddr = kmap_atomic(page, KM_USER0);
  				if (bitmap->flags & BITMAP_HOSTENDIAN)
  					clear_bit(file_page_offset(bitmap, j),
  						  paddr);
  				else
  					__clear_bit_le(
  						file_page_offset(bitmap,
  								 j),
  						paddr);
  				kunmap_atomic(paddr, KM_USER0);
  			} else if (*bmc <= 2) {
  				*bmc = 1; /* maybe clear the bit next time */
  				set_page_attr(bitmap, page, BITMAP_PAGE_PENDING);
  				bitmap->allclean = 0;
  			}
  		}
  	}
  	spin_unlock_irqrestore(&bitmap->lock, flags);
  
  	/* now sync the final page */
  	if (lastpage != NULL) {
  		spin_lock_irqsave(&bitmap->lock, flags);
  		if (test_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE)) {
  			clear_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
  			spin_unlock_irqrestore(&bitmap->lock, flags);
  			write_page(bitmap, lastpage, 0);
  		} else {
  			set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
  			bitmap->allclean = 0;
  			spin_unlock_irqrestore(&bitmap->lock, flags);
  		}
  	}
  
   done:
  	if (bitmap->allclean == 0)
  		mddev->thread->timeout =
  			mddev->bitmap_info.daemon_sleep;
  	mutex_unlock(&mddev->bitmap_info.mutex);
  }
  
  static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
  					    sector_t offset, sector_t *blocks,
  					    int create)
  __releases(bitmap->lock)
  __acquires(bitmap->lock)
  {
  	/* If 'create', we might release the lock and reclaim it.
  	 * The lock must have been taken with interrupts enabled.
  	 * If !create, we don't release the lock.
  	 */
  	sector_t chunk = offset >> CHUNK_BLOCK_SHIFT(bitmap);
  	unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
  	unsigned long pageoff = (chunk & PAGE_COUNTER_MASK) << COUNTER_BYTE_SHIFT;
  	sector_t csize;
  	int err;
  
  	err = bitmap_checkpage(bitmap, page, create);
  
  	if (bitmap->bp[page].hijacked ||
  	    bitmap->bp[page].map == NULL)
  		csize = ((sector_t)1) << (CHUNK_BLOCK_SHIFT(bitmap) +
  					  PAGE_COUNTER_SHIFT - 1);
  	else
  		csize = ((sector_t)1) << (CHUNK_BLOCK_SHIFT(bitmap));
  	*blocks = csize - (offset & (csize - 1));
  
  	if (err < 0)
  		return NULL;
  
  	/* now locked ... */
  
  	if (bitmap->bp[page].hijacked) { /* hijacked pointer */
  		/* should we use the first or second counter field
  		 * of the hijacked pointer? */
  		int hi = (pageoff > PAGE_COUNTER_MASK);
  		return  &((bitmap_counter_t *)
  			  &bitmap->bp[page].map)[hi];
  	} else /* page is allocated */
  		return (bitmap_counter_t *)
  			&(bitmap->bp[page].map[pageoff]);
  }
  
  int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors, int behind)
  {
  	if (!bitmap)
  		return 0;
  
  	if (behind) {
  		int bw;
  		atomic_inc(&bitmap->behind_writes);
  		bw = atomic_read(&bitmap->behind_writes);
  		if (bw > bitmap->behind_writes_used)
  			bitmap->behind_writes_used = bw;
  
  		pr_debug("inc write-behind count %d/%lu\n",
  			 bw, bitmap->mddev->bitmap_info.max_write_behind);
  	}
  
  	while (sectors) {
  		sector_t blocks;
  		bitmap_counter_t *bmc;
  
  		spin_lock_irq(&bitmap->lock);
  		bmc = bitmap_get_counter(bitmap, offset, &blocks, 1);
  		if (!bmc) {
  			spin_unlock_irq(&bitmap->lock);
  			return 0;
  		}
  
  		if (unlikely(COUNTER(*bmc) == COUNTER_MAX)) {
  			DEFINE_WAIT(__wait);
  			/* note that it is safe to do the prepare_to_wait
  			 * after the test as long as we do it before dropping
  			 * the spinlock.
  			 */
  			prepare_to_wait(&bitmap->overflow_wait, &__wait,
  					TASK_UNINTERRUPTIBLE);
  			spin_unlock_irq(&bitmap->lock);
  			io_schedule();
  			finish_wait(&bitmap->overflow_wait, &__wait);
  			continue;
  		}
  
  		switch (*bmc) {
  		case 0:
  			bitmap_file_set_bit(bitmap, offset);
  			bitmap_count_page(bitmap, offset, 1);
  			/* fall through */
  		case 1:
  			*bmc = 2;
  		}
  
  		(*bmc)++;
  
  		spin_unlock_irq(&bitmap->lock);
  
  		offset += blocks;
  		if (sectors > blocks)
  			sectors -= blocks;
  		else
  			sectors = 0;
  	}
  	return 0;
  }
  EXPORT_SYMBOL(bitmap_startwrite);
  
  void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors,
  		     int success, int behind)
  {
  	if (!bitmap)
  		return;
  	if (behind) {
  		if (atomic_dec_and_test(&bitmap->behind_writes))
  			wake_up(&bitmap->behind_wait);
  		pr_debug("dec write-behind count %d/%lu\n",
  			 atomic_read(&bitmap->behind_writes),
  			 bitmap->mddev->bitmap_info.max_write_behind);
  	}
  
  	while (sectors) {
  		sector_t blocks;
  		unsigned long flags;
  		bitmap_counter_t *bmc;
  
  		spin_lock_irqsave(&bitmap->lock, flags);
  		bmc = bitmap_get_counter(bitmap, offset, &blocks, 0);
  		if (!bmc) {
  			spin_unlock_irqrestore(&bitmap->lock, flags);
  			return;
  		}
  
  		if (success && !bitmap->mddev->degraded &&
  		    bitmap->events_cleared < bitmap->mddev->events) {
  			bitmap->events_cleared = bitmap->mddev->events;
  			bitmap->need_sync = 1;
  			sysfs_notify_dirent_safe(bitmap->sysfs_can_clear);
  		}
  
  		if (!success && !NEEDED(*bmc))
  			*bmc |= NEEDED_MASK;
  
  		if (COUNTER(*bmc) == COUNTER_MAX)
  			wake_up(&bitmap->overflow_wait);
  
  		(*bmc)--;
  		if (*bmc <= 2) {
  			set_page_attr(bitmap,
  				      filemap_get_page(
  					      bitmap,
  					      offset >> CHUNK_BLOCK_SHIFT(bitmap)),
  				      BITMAP_PAGE_PENDING);
  			bitmap->allclean = 0;
  		}
  		spin_unlock_irqrestore(&bitmap->lock, flags);
  		offset += blocks;
  		if (sectors > blocks)
  			sectors -= blocks;
  		else
  			sectors = 0;
  	}
  }
  EXPORT_SYMBOL(bitmap_endwrite);
  
  static int __bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks,
  			       int degraded)
  {
  	bitmap_counter_t *bmc;
  	int rv;
  	if (bitmap == NULL) {/* FIXME or bitmap set as 'failed' */
  		*blocks = 1024;
  		return 1; /* always resync if no bitmap */
  	}
  	spin_lock_irq(&bitmap->lock);
  	bmc = bitmap_get_counter(bitmap, offset, blocks, 0);
  	rv = 0;
  	if (bmc) {
  		/* locked */
  		if (RESYNC(*bmc))
  			rv = 1;
  		else if (NEEDED(*bmc)) {
  			rv = 1;
  			if (!degraded) { /* don't set/clear bits if degraded */
  				*bmc |= RESYNC_MASK;
  				*bmc &= ~NEEDED_MASK;
  			}
  		}
  	}
  	spin_unlock_irq(&bitmap->lock);
  	return rv;
  }
  
  int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks,
  		      int degraded)
  {
  	/* bitmap_start_sync must always report on multiples of whole
  	 * pages, otherwise resync (which is very PAGE_SIZE based) will
  	 * get confused.
  	 * So call __bitmap_start_sync repeatedly (if needed) until
  	 * At least PAGE_SIZE>>9 blocks are covered.
  	 * Return the 'or' of the result.
  	 */
  	int rv = 0;
  	sector_t blocks1;
  
  	*blocks = 0;
  	while (*blocks < (PAGE_SIZE>>9)) {
  		rv |= __bitmap_start_sync(bitmap, offset,
  					  &blocks1, degraded);
  		offset += blocks1;
  		*blocks += blocks1;
  	}
  	return rv;
  }
  EXPORT_SYMBOL(bitmap_start_sync);
  
  void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int aborted)
  {
  	bitmap_counter_t *bmc;
  	unsigned long flags;
  
  	if (bitmap == NULL) {
  		*blocks = 1024;
  		return;
  	}
  	spin_lock_irqsave(&bitmap->lock, flags);
  	bmc = bitmap_get_counter(bitmap, offset, blocks, 0);
  	if (bmc == NULL)
  		goto unlock;
  	/* locked */
  	if (RESYNC(*bmc)) {
  		*bmc &= ~RESYNC_MASK;
  
  		if (!NEEDED(*bmc) && aborted)
  			*bmc |= NEEDED_MASK;
  		else {
  			if (*bmc <= 2) {
  				set_page_attr(bitmap,
  					      filemap_get_page(bitmap, offset >> CHUNK_BLOCK_SHIFT(bitmap)),
  					      BITMAP_PAGE_PENDING);
  				bitmap->allclean = 0;
  			}
  		}
  	}
   unlock:
  	spin_unlock_irqrestore(&bitmap->lock, flags);
  }
  EXPORT_SYMBOL(bitmap_end_sync);
  
  void bitmap_close_sync(struct bitmap *bitmap)
  {
  	/* Sync has finished, and any bitmap chunks that weren't synced
  	 * properly have been aborted.  It remains to us to clear the
  	 * RESYNC bit wherever it is still on
  	 */
  	sector_t sector = 0;
  	sector_t blocks;
  	if (!bitmap)
  		return;
  	while (sector < bitmap->mddev->resync_max_sectors) {
  		bitmap_end_sync(bitmap, sector, &blocks, 0);
  		sector += blocks;
  	}
  }
  EXPORT_SYMBOL(bitmap_close_sync);
  
  void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector)
  {
  	sector_t s = 0;
  	sector_t blocks;
  
  	if (!bitmap)
  		return;
  	if (sector == 0) {
  		bitmap->last_end_sync = jiffies;
  		return;
  	}
  	if (time_before(jiffies, (bitmap->last_end_sync
  				  + bitmap->mddev->bitmap_info.daemon_sleep)))
  		return;
  	wait_event(bitmap->mddev->recovery_wait,
  		   atomic_read(&bitmap->mddev->recovery_active) == 0);
  
  	bitmap->mddev->curr_resync_completed = sector;
  	set_bit(MD_CHANGE_CLEAN, &bitmap->mddev->flags);
  	sector &= ~((1ULL << CHUNK_BLOCK_SHIFT(bitmap)) - 1);
  	s = 0;
  	while (s < sector && s < bitmap->mddev->resync_max_sectors) {
  		bitmap_end_sync(bitmap, s, &blocks, 0);
  		s += blocks;
  	}
  	bitmap->last_end_sync = jiffies;
  	sysfs_notify(&bitmap->mddev->kobj, NULL, "sync_completed");
  }
  EXPORT_SYMBOL(bitmap_cond_end_sync);
  
  static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int needed)
  {
  	/* For each chunk covered by any of these sectors, set the
  	 * counter to 1 and set resync_needed.  They should all
  	 * be 0 at this point
  	 */
  
  	sector_t secs;
  	bitmap_counter_t *bmc;
  	spin_lock_irq(&bitmap->lock);
  	bmc = bitmap_get_counter(bitmap, offset, &secs, 1);
  	if (!bmc) {
  		spin_unlock_irq(&bitmap->lock);
  		return;
  	}
  	if (!*bmc) {
  		struct page *page;
  		*bmc = 2 | (needed ? NEEDED_MASK : 0);
  		bitmap_count_page(bitmap, offset, 1);
  		page = filemap_get_page(bitmap, offset >> CHUNK_BLOCK_SHIFT(bitmap));
  		set_page_attr(bitmap, page, BITMAP_PAGE_PENDING);
  		bitmap->allclean = 0;
  	}
  	spin_unlock_irq(&bitmap->lock);
  }
  
  /* dirty the memory and file bits for bitmap chunks "s" to "e" */
  void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e)
  {
  	unsigned long chunk;
  
  	for (chunk = s; chunk <= e; chunk++) {
  		sector_t sec = (sector_t)chunk << CHUNK_BLOCK_SHIFT(bitmap);
  		bitmap_set_memory_bits(bitmap, sec, 1);
  		spin_lock_irq(&bitmap->lock);
  		bitmap_file_set_bit(bitmap, sec);
  		spin_unlock_irq(&bitmap->lock);
  		if (sec < bitmap->mddev->recovery_cp)
  			/* We are asserting that the array is dirty,
  			 * so move the recovery_cp address back so
  			 * that it is obvious that it is dirty
  			 */
  			bitmap->mddev->recovery_cp = sec;
  	}
  }
  
  /*
   * flush out any pending updates
   */
  void bitmap_flush(struct mddev *mddev)
  {
  	struct bitmap *bitmap = mddev->bitmap;
  	long sleep;
  
  	if (!bitmap) /* there was no bitmap */
  		return;
  
  	/* run the daemon_work three time to ensure everything is flushed
  	 * that can be
  	 */
  	sleep = mddev->bitmap_info.daemon_sleep * 2;
  	bitmap->daemon_lastrun -= sleep;
  	bitmap_daemon_work(mddev);
  	bitmap->daemon_lastrun -= sleep;
  	bitmap_daemon_work(mddev);
  	bitmap->daemon_lastrun -= sleep;
  	bitmap_daemon_work(mddev);
  	bitmap_update_sb(bitmap);
  }
  
  /*
   * free memory that was allocated
   */
  static void bitmap_free(struct bitmap *bitmap)
  {
  	unsigned long k, pages;
  	struct bitmap_page *bp;
  
  	if (!bitmap) /* there was no bitmap */
  		return;
  
  	/* release the bitmap file and kill the daemon */
  	bitmap_file_put(bitmap);
  
  	bp = bitmap->bp;
  	pages = bitmap->pages;
  
  	/* free all allocated memory */
  
  	if (bp) /* deallocate the page memory */
  		for (k = 0; k < pages; k++)
  			if (bp[k].map && !bp[k].hijacked)
  				kfree(bp[k].map);
  	kfree(bp);
  	kfree(bitmap);
  }
  
  void bitmap_destroy(struct mddev *mddev)
  {
  	struct bitmap *bitmap = mddev->bitmap;
  
  	if (!bitmap) /* there was no bitmap */
  		return;
  
  	mutex_lock(&mddev->bitmap_info.mutex);
  	mddev->bitmap = NULL; /* disconnect from the md device */
  	mutex_unlock(&mddev->bitmap_info.mutex);
  	if (mddev->thread)
  		mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;
  
  	if (bitmap->sysfs_can_clear)
  		sysfs_put(bitmap->sysfs_can_clear);
  
  	bitmap_free(bitmap);
  }
  
  /*
   * initialize the bitmap structure
   * if this returns an error, bitmap_destroy must be called to do clean up
   */
  int bitmap_create(struct mddev *mddev)
  {
  	struct bitmap *bitmap;
  	sector_t blocks = mddev->resync_max_sectors;
  	unsigned long chunks;
  	unsigned long pages;
  	struct file *file = mddev->bitmap_info.file;
  	int err;
  	struct sysfs_dirent *bm = NULL;
  
  	BUILD_BUG_ON(sizeof(bitmap_super_t) != 256);
  
  	if (!file
  	    && !mddev->bitmap_info.offset) /* bitmap disabled, nothing to do */
  		return 0;
  
  	BUG_ON(file && mddev->bitmap_info.offset);
  
  	bitmap = kzalloc(sizeof(*bitmap), GFP_KERNEL);
  	if (!bitmap)
  		return -ENOMEM;
  
  	spin_lock_init(&bitmap->lock);
  	atomic_set(&bitmap->pending_writes, 0);
  	init_waitqueue_head(&bitmap->write_wait);
  	init_waitqueue_head(&bitmap->overflow_wait);
  	init_waitqueue_head(&bitmap->behind_wait);
  
  	bitmap->mddev = mddev;
  
  	if (mddev->kobj.sd)
  		bm = sysfs_get_dirent(mddev->kobj.sd, NULL, "bitmap");
  	if (bm) {
  		bitmap->sysfs_can_clear = sysfs_get_dirent(bm, NULL, "can_clear");
  		sysfs_put(bm);
  	} else
  		bitmap->sysfs_can_clear = NULL;
  
  	bitmap->file = file;
  	if (file) {
  		get_file(file);
  		/* As future accesses to this file will use bmap,
  		 * and bypass the page cache, we must sync the file
  		 * first.
  		 */
  		vfs_fsync(file, 1);
  	}
  	/* read superblock from bitmap file (this sets mddev->bitmap_info.chunksize) */
  	if (!mddev->bitmap_info.external) {
  		/*
  		 * If 'MD_ARRAY_FIRST_USE' is set, then device-mapper is
  		 * instructing us to create a new on-disk bitmap instance.
  		 */
  		if (test_and_clear_bit(MD_ARRAY_FIRST_USE, &mddev->flags))
  			err = bitmap_new_disk_sb(bitmap);
  		else
  			err = bitmap_read_sb(bitmap);
  	} else {
  		err = 0;
  		if (mddev->bitmap_info.chunksize == 0 ||
  		    mddev->bitmap_info.daemon_sleep == 0)
  			/* chunksize and time_base need to be
  			 * set first. */
  			err = -EINVAL;
  	}
  	if (err)
  		goto error;
  
  	bitmap->daemon_lastrun = jiffies;
  	bitmap->chunkshift = ffz(~mddev->bitmap_info.chunksize);
  
  	/* now that chunksize and chunkshift are set, we can use these macros */
  	chunks = (blocks + CHUNK_BLOCK_RATIO(bitmap) - 1) >>
  			CHUNK_BLOCK_SHIFT(bitmap);
  	pages = (chunks + PAGE_COUNTER_RATIO - 1) / PAGE_COUNTER_RATIO;
  
  	BUG_ON(!pages);
  
  	bitmap->chunks = chunks;
  	bitmap->pages = pages;
  	bitmap->missing_pages = pages;
  
  	bitmap->bp = kzalloc(pages * sizeof(*bitmap->bp), GFP_KERNEL);
  
  	err = -ENOMEM;
  	if (!bitmap->bp)
  		goto error;
  
  	printk(KERN_INFO "created bitmap (%lu pages) for device %s\n",
  		pages, bmname(bitmap));
  
  	mddev->bitmap = bitmap;
  
  
  	return (bitmap->flags & BITMAP_WRITE_ERROR) ? -EIO : 0;
  
   error:
  	bitmap_free(bitmap);
  	return err;
  }
  
  int bitmap_load(struct mddev *mddev)
  {
  	int err = 0;
  	sector_t start = 0;
  	sector_t sector = 0;
  	struct bitmap *bitmap = mddev->bitmap;
  
  	if (!bitmap)
  		goto out;
  
  	/* Clear out old bitmap info first:  Either there is none, or we
  	 * are resuming after someone else has possibly changed things,
  	 * so we should forget old cached info.
  	 * All chunks should be clean, but some might need_sync.
  	 */
  	while (sector < mddev->resync_max_sectors) {
  		sector_t blocks;
  		bitmap_start_sync(bitmap, sector, &blocks, 0);
  		sector += blocks;
  	}
  	bitmap_close_sync(bitmap);
  
  	if (mddev->degraded == 0
  	    || bitmap->events_cleared == mddev->events)
  		/* no need to keep dirty bits to optimise a
  		 * re-add of a missing device */
  		start = mddev->recovery_cp;
  
  	err = bitmap_init_from_disk(bitmap, start);
  
  	if (err)
  		goto out;
  
  	mddev->thread->timeout = mddev->bitmap_info.daemon_sleep;
  	md_wakeup_thread(mddev->thread);
  
  	bitmap_update_sb(bitmap);
  
  	if (bitmap->flags & BITMAP_WRITE_ERROR)
  		err = -EIO;
  out:
  	return err;
  }
  EXPORT_SYMBOL_GPL(bitmap_load);
  
  static ssize_t
  location_show(struct mddev *mddev, char *page)
  {
  	ssize_t len;
  	if (mddev->bitmap_info.file)
  		len = sprintf(page, "file");
  	else if (mddev->bitmap_info.offset)
  		len = sprintf(page, "%+lld", (long long)mddev->bitmap_info.offset);
  	else
  		len = sprintf(page, "none");
  	len += sprintf(page+len, "\n");
  	return len;
  }
  
  static ssize_t
  location_store(struct mddev *mddev, const char *buf, size_t len)
  {
  
  	if (mddev->pers) {
  		if (!mddev->pers->quiesce)
  			return -EBUSY;
  		if (mddev->recovery || mddev->sync_thread)
  			return -EBUSY;
  	}
  
  	if (mddev->bitmap || mddev->bitmap_info.file ||
  	    mddev->bitmap_info.offset) {
  		/* bitmap already configured.  Only option is to clear it */
  		if (strncmp(buf, "none", 4) != 0)
  			return -EBUSY;
  		if (mddev->pers) {
  			mddev->pers->quiesce(mddev, 1);
  			bitmap_destroy(mddev);
  			mddev->pers->quiesce(mddev, 0);
  		}
  		mddev->bitmap_info.offset = 0;
  		if (mddev->bitmap_info.file) {
  			struct file *f = mddev->bitmap_info.file;
  			mddev->bitmap_info.file = NULL;
  			restore_bitmap_write_access(f);
  			fput(f);
  		}
  	} else {
  		/* No bitmap, OK to set a location */
  		long long offset;
  		if (strncmp(buf, "none", 4) == 0)
  			/* nothing to be done */;
  		else if (strncmp(buf, "file:", 5) == 0) {
  			/* Not supported yet */
  			return -EINVAL;
  		} else {
  			int rv;
  			if (buf[0] == '+')
  				rv = strict_strtoll(buf+1, 10, &offset);
  			else
  				rv = strict_strtoll(buf, 10, &offset);
  			if (rv)
  				return rv;
  			if (offset == 0)
  				return -EINVAL;
  			if (mddev->bitmap_info.external == 0 &&
  			    mddev->major_version == 0 &&
  			    offset != mddev->bitmap_info.default_offset)
  				return -EINVAL;
  			mddev->bitmap_info.offset = offset;
  			if (mddev->pers) {
  				mddev->pers->quiesce(mddev, 1);
  				rv = bitmap_create(mddev);
  				if (rv) {
  					bitmap_destroy(mddev);
  					mddev->bitmap_info.offset = 0;
  				}
  				mddev->pers->quiesce(mddev, 0);
  				if (rv)
  					return rv;
  			}
  		}
  	}
  	if (!mddev->external) {
  		/* Ensure new bitmap info is stored in
  		 * metadata promptly.
  		 */
  		set_bit(MD_CHANGE_DEVS, &mddev->flags);
  		md_wakeup_thread(mddev->thread);
  	}
  	return len;
  }
  
  static struct md_sysfs_entry bitmap_location =
  __ATTR(location, S_IRUGO|S_IWUSR, location_show, location_store);
  
  static ssize_t
  timeout_show(struct mddev *mddev, char *page)
  {
  	ssize_t len;
  	unsigned long secs = mddev->bitmap_info.daemon_sleep / HZ;
  	unsigned long jifs = mddev->bitmap_info.daemon_sleep % HZ;
  
  	len = sprintf(page, "%lu", secs);
  	if (jifs)
  		len += sprintf(page+len, ".%03u", jiffies_to_msecs(jifs));
  	len += sprintf(page+len, "\n");
  	return len;
  }
  
  static ssize_t
  timeout_store(struct mddev *mddev, const char *buf, size_t len)
  {
  	/* timeout can be set at any time */
  	unsigned long timeout;
  	int rv = strict_strtoul_scaled(buf, &timeout, 4);
  	if (rv)
  		return rv;
  
  	/* just to make sure we don't overflow... */
  	if (timeout >= LONG_MAX / HZ)
  		return -EINVAL;
  
  	timeout = timeout * HZ / 10000;
  
  	if (timeout >= MAX_SCHEDULE_TIMEOUT)
  		timeout = MAX_SCHEDULE_TIMEOUT-1;
  	if (timeout < 1)
  		timeout = 1;
  	mddev->bitmap_info.daemon_sleep = timeout;
  	if (mddev->thread) {
  		/* if thread->timeout is MAX_SCHEDULE_TIMEOUT, then
  		 * the bitmap is all clean and we don't need to
  		 * adjust the timeout right now
  		 */
  		if (mddev->thread->timeout < MAX_SCHEDULE_TIMEOUT) {
  			mddev->thread->timeout = timeout;
  			md_wakeup_thread(mddev->thread);
  		}
  	}
  	return len;
  }
  
  static struct md_sysfs_entry bitmap_timeout =
  __ATTR(time_base, S_IRUGO|S_IWUSR, timeout_show, timeout_store);
  
  static ssize_t
  backlog_show(struct mddev *mddev, char *page)
  {
  	return sprintf(page, "%lu\n", mddev->bitmap_info.max_write_behind);
  }
  
  static ssize_t
  backlog_store(struct mddev *mddev, const char *buf, size_t len)
  {
  	unsigned long backlog;
  	int rv = strict_strtoul(buf, 10, &backlog);
  	if (rv)
  		return rv;
  	if (backlog > COUNTER_MAX)
  		return -EINVAL;
  	mddev->bitmap_info.max_write_behind = backlog;
  	return len;
  }
  
  static struct md_sysfs_entry bitmap_backlog =
  __ATTR(backlog, S_IRUGO|S_IWUSR, backlog_show, backlog_store);
  
  static ssize_t
  chunksize_show(struct mddev *mddev, char *page)
  {
  	return sprintf(page, "%lu\n", mddev->bitmap_info.chunksize);
  }
  
  static ssize_t
  chunksize_store(struct mddev *mddev, const char *buf, size_t len)
  {
  	/* Can only be changed when no bitmap is active */
  	int rv;
  	unsigned long csize;
  	if (mddev->bitmap)
  		return -EBUSY;
  	rv = strict_strtoul(buf, 10, &csize);
  	if (rv)
  		return rv;
  	if (csize < 512 ||
  	    !is_power_of_2(csize))
  		return -EINVAL;
  	mddev->bitmap_info.chunksize = csize;
  	return len;
  }
  
  static struct md_sysfs_entry bitmap_chunksize =
  __ATTR(chunksize, S_IRUGO|S_IWUSR, chunksize_show, chunksize_store);
  
  static ssize_t metadata_show(struct mddev *mddev, char *page)
  {
  	return sprintf(page, "%s\n", (mddev->bitmap_info.external
  				      ? "external" : "internal"));
  }
  
  static ssize_t metadata_store(struct mddev *mddev, const char *buf, size_t len)
  {
  	if (mddev->bitmap ||
  	    mddev->bitmap_info.file ||
  	    mddev->bitmap_info.offset)
  		return -EBUSY;
  	if (strncmp(buf, "external", 8) == 0)
  		mddev->bitmap_info.external = 1;
  	else if (strncmp(buf, "internal", 8) == 0)
  		mddev->bitmap_info.external = 0;
  	else
  		return -EINVAL;
  	return len;
  }
  
  static struct md_sysfs_entry bitmap_metadata =
  __ATTR(metadata, S_IRUGO|S_IWUSR, metadata_show, metadata_store);
  
  static ssize_t can_clear_show(struct mddev *mddev, char *page)
  {
  	int len;
  	if (mddev->bitmap)
  		len = sprintf(page, "%s\n", (mddev->bitmap->need_sync ?
  					     "false" : "true"));
  	else
  		len = sprintf(page, "\n");
  	return len;
  }
  
  static ssize_t can_clear_store(struct mddev *mddev, const char *buf, size_t len)
  {
  	if (mddev->bitmap == NULL)
  		return -ENOENT;
  	if (strncmp(buf, "false", 5) == 0)
  		mddev->bitmap->need_sync = 1;
  	else if (strncmp(buf, "true", 4) == 0) {
  		if (mddev->degraded)
  			return -EBUSY;
  		mddev->bitmap->need_sync = 0;
  	} else
  		return -EINVAL;
  	return len;
  }
  
  static struct md_sysfs_entry bitmap_can_clear =
  __ATTR(can_clear, S_IRUGO|S_IWUSR, can_clear_show, can_clear_store);
  
  static ssize_t
  behind_writes_used_show(struct mddev *mddev, char *page)
  {
  	if (mddev->bitmap == NULL)
  		return sprintf(page, "0\n");
  	return sprintf(page, "%lu\n",
  		       mddev->bitmap->behind_writes_used);
  }
  
  static ssize_t
  behind_writes_used_reset(struct mddev *mddev, const char *buf, size_t len)
  {
  	if (mddev->bitmap)
  		mddev->bitmap->behind_writes_used = 0;
  	return len;
  }
  
  static struct md_sysfs_entry max_backlog_used =
  __ATTR(max_backlog_used, S_IRUGO | S_IWUSR,
         behind_writes_used_show, behind_writes_used_reset);
  
  static struct attribute *md_bitmap_attrs[] = {
  	&bitmap_location.attr,
  	&bitmap_timeout.attr,
  	&bitmap_backlog.attr,
  	&bitmap_chunksize.attr,
  	&bitmap_metadata.attr,
  	&bitmap_can_clear.attr,
  	&max_backlog_used.attr,
  	NULL
  };
  struct attribute_group md_bitmap_group = {
  	.name = "bitmap",
  	.attrs = md_bitmap_attrs,
  };
  
  