Moved, renamed, and deleted files

The original directory structure was scattered and unorganized.
Changes are basically to make it look like kernel structure.

1 files changed, 2113 insertions, 0 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
new file mode 100644
index 00000000..17e2b472
--- /dev/null
+++ b/drivers/md/bitmap.c
@@ -0,0 +1,2113 @@
+/*
+ * 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 <linux/seq_file.h>
+#include "md.h"
+#include "bitmap.h"
+
+static inline char *bmname(struct bitmap *bitmap)
+{
+	return bitmap->mddev ? mdname(bitmap->mddev) : "mdX";
+}
+
+/*
+ * 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 = kzalloc(PAGE_SIZE, GFP_NOIO);
+	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 */
+		kfree(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++;
+		kfree(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;
+	}
+
+	rdev_for_each(rdev, mddev) {
+		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;
+
+	if (!bitmap || !bitmap->mddev) /* no bitmap for this array */
+		return;
+	if (bitmap->mddev->bitmap_info.external)
+		return;
+	if (!bitmap->sb_page) /* no superblock */
+		return;
+	sb = kmap_atomic(bitmap->sb_page);
+	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);
+	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);
+	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);
+}
+
+/*
+ * 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);
+
+	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);
+		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);
+
+	kunmap_atomic(sb);
+
+	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);
+
+	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) {
+		/*
+		 * We have a persistent array superblock, so 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);
+		}
+	}
+
+	/* 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);
+	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;
+	int old;
+
+	if (!bitmap->sb_page) /* can't set the state */
+		return 0;
+	sb = kmap_atomic(bitmap->sb_page);
+	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);
+	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 >> bitmap->chunkshift;
+
+	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);
+	if (bitmap->flags & BITMAP_HOSTENDIAN)
+		set_bit(bit, kaddr);
+	else
+		__set_bit_le(bit, kaddr);
+	kunmap_atomic(kaddr);
+	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);
+				memset(paddr + offset, 0xff,
+				       PAGE_SIZE - offset);
+				kunmap_atomic(paddr);
+				write_page(bitmap, page, 1);
+
+				ret = -EIO;
+				if (bitmap->flags & BITMAP_WRITE_ERROR)
+					goto err;
+			}
+		}
+		paddr = kmap_atomic(page);
+		if (bitmap->flags & BITMAP_HOSTENDIAN)
+			b = test_bit(bit, paddr);
+		else
+			b = test_bit_le(bit, paddr);
+		kunmap_atomic(paddr);
+		if (b) {
+			/* if the disk bit is set, set the memory bit */
+			int needed = ((sector_t)(i+1) << bitmap->chunkshift
+				      >= start);
+			bitmap_set_memory_bits(bitmap,
+					       (sector_t)i << bitmap->chunkshift,
+					       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 >> bitmap->chunkshift;
+	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);
+				sb->events_cleared =
+					cpu_to_le64(bitmap->events_cleared);
+				kunmap_atomic(sb);
+				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 << bitmap->chunkshift,
+					 &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 << bitmap->chunkshift,
+						  -1);
+
+				/* clear the bit */
+				paddr = kmap_atomic(page);
+				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);
+			} 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 >> bitmap->chunkshift;
+	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) << (bitmap->chunkshift +
+					  PAGE_COUNTER_SHIFT - 1);
+	else
+		csize = ((sector_t)1) << bitmap->chunkshift;
+	*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 >> bitmap->chunkshift),
+				      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 >> bitmap->chunkshift),
+					      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 << bitmap->chunkshift) - 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 >> bitmap->chunkshift);
+		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 << bitmap->chunkshift;
+		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)
+			      - BITMAP_BLOCK_SHIFT);
+
+	chunks = (blocks + (1 << bitmap->chunkshift) - 1) >>
+			bitmap->chunkshift;
+	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;
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	err = bitmap_init_from_disk(bitmap, start);
+	mutex_unlock(&mddev->bitmap_info.mutex);
+
+	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);
+
+void bitmap_status(struct seq_file *seq, struct bitmap *bitmap)
+{
+	unsigned long chunk_kb;
+	unsigned long flags;
+
+	if (!bitmap)
+		return;
+
+	spin_lock_irqsave(&bitmap->lock, flags);
+	chunk_kb = bitmap->mddev->bitmap_info.chunksize >> 10;
+	seq_printf(seq, "bitmap: %lu/%lu pages [%luKB], "
+		   "%lu%s chunk",
+		   bitmap->pages - bitmap->missing_pages,
+		   bitmap->pages,
+		   (bitmap->pages - bitmap->missing_pages)
+		   << (PAGE_SHIFT - 10),
+		   chunk_kb ? chunk_kb : bitmap->mddev->bitmap_info.chunksize,
+		   chunk_kb ? "KB" : "B");
+	if (bitmap->file) {
+		seq_printf(seq, ", file: ");
+		seq_path(seq, &bitmap->file->f_path, " \t\n");
+	}
+
+	seq_printf(seq, "\n");
+	spin_unlock_irqrestore(&bitmap->lock, flags);
+}
+
+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)
+					rv = bitmap_load(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,
+};
+