[PATCH] md: optimised resync using Bitmap based intent logging

With this patch, the intent to write to some block in the array can be logged
to a bitmap file.  Each bit represents some number of sectors and is set
before any update happens, and only cleared when all writes relating to all
sectors are complete.

After an unclean shutdown, information in this bitmap can be used to optimise
resync - only sectors which could be out-of-sync need to be updated.

Also if a drive is removed and then added back into an array, the recovery can
make use of the bitmap to optimise reconstruction.  This is not implemented in
this patch.

Currently the bitmap is stored in a file which must (obviously) be stored on a
separate device.

The patch only provided infrastructure.  It does not update any personalities
to bitmap intent logging.

Md arrays can still be used with no bitmap file.  This patch has minimal
impact on such arrays.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1519 insertions, 0 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
new file mode 100644
index 0000000..34ffc13
--- /dev/null
+++ b/drivers/md/bitmap.c
@@ -0,0 +1,1519 @@
+/*
+ * 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
+ * - added bitmap daemon (to asynchronously clear bitmap bits from disk)
+ */
+
+/*
+ * Still to do:
+ *
+ * flush after percent set rather than just time based. (maybe both).
+ * wait if count gets too high, wake when it drops to half.
+ * allow bitmap to be mirrored with superblock (before or after...)
+ * allow hot-add to re-instate a current device.
+ * allow hot-add of bitmap after quiessing device
+ */
+
+#include <linux/module.h>
+#include <linux/version.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/config.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/raid/md.h>
+#include <linux/raid/bitmap.h>
+
+/* debug macros */
+
+#define DEBUG 0
+
+#if DEBUG
+/* these are for debugging purposes only! */
+
+/* define one and only one of these */
+#define INJECT_FAULTS_1 0 /* cause bitmap_alloc_page to fail always */
+#define INJECT_FAULTS_2 0 /* cause bitmap file to be kicked when first bit set*/
+#define INJECT_FAULTS_3 0 /* treat bitmap file as kicked at init time */
+#define INJECT_FAULTS_4 0 /* undef */
+#define INJECT_FAULTS_5 0 /* undef */
+#define INJECT_FAULTS_6 0
+
+/* if these are defined, the driver will fail! debug only */
+#define INJECT_FATAL_FAULT_1 0 /* fail kmalloc, causing bitmap_create to fail */
+#define INJECT_FATAL_FAULT_2 0 /* undef */
+#define INJECT_FATAL_FAULT_3 0 /* undef */
+#endif
+
+//#define DPRINTK PRINTK /* set this NULL to avoid verbose debug output */
+#define DPRINTK(x...) do { } while(0)
+
+#ifndef PRINTK
+#  if DEBUG > 0
+#    define PRINTK(x...) printk(KERN_DEBUG x)
+#  else
+#    define PRINTK(x...)
+#  endif
+#endif
+
+static inline char * bmname(struct bitmap *bitmap)
+{
+	return bitmap->mddev ? mdname(bitmap->mddev) : "mdX";
+}
+
+
+/*
+ * test if the bitmap is active
+ */
+int bitmap_active(struct bitmap *bitmap)
+{
+	unsigned long flags;
+	int res = 0;
+
+	if (!bitmap)
+		return res;
+	spin_lock_irqsave(&bitmap->lock, flags);
+	res = bitmap->flags & BITMAP_ACTIVE;
+	spin_unlock_irqrestore(&bitmap->lock, flags);
+	return res;
+}
+
+#define WRITE_POOL_SIZE 256
+/* mempool for queueing pending writes on the bitmap file */
+static void *write_pool_alloc(unsigned int gfp_flags, void *data)
+{
+	return kmalloc(sizeof(struct page_list), gfp_flags);
+}
+
+static void write_pool_free(void *ptr, void *data)
+{
+	kfree(ptr);
+}
+
+/*
+ * just a placeholder - calls kmalloc for bitmap pages
+ */
+static unsigned char *bitmap_alloc_page(struct bitmap *bitmap)
+{
+	unsigned char *page;
+
+#if INJECT_FAULTS_1
+	page = NULL;
+#else
+	page = kmalloc(PAGE_SIZE, GFP_NOIO);
+#endif
+	if (!page)
+		printk("%s: bitmap_alloc_page FAILED\n", bmname(bitmap));
+	else
+		printk("%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)
+{
+	PRINTK("%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)
+{
+	unsigned char *mappage;
+
+	if (page >= bitmap->pages) {
+		printk(KERN_ALERT
+			"%s: invalid bitmap page request: %lu (> %lu)\n",
+			bmname(bitmap), page, bitmap->pages-1);
+		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;
+
+	spin_unlock_irq(&bitmap->lock);
+
+	/* this page has not been allocated yet */
+
+	if ((mappage = bitmap_alloc_page(bitmap)) == NULL) {
+		PRINTK("%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 */
+		spin_lock_irq(&bitmap->lock);
+		if (!bitmap->bp[page].map)
+			bitmap->bp[page].hijacked = 1;
+		goto out;
+	}
+
+	/* got a page */
+
+	spin_lock_irq(&bitmap->lock);
+
+	/* recheck the page */
+
+	if (bitmap->bp[page].map || bitmap->bp[page].hijacked) {
+		/* somebody beat us to getting the page */
+		bitmap_free_page(bitmap, mappage);
+		return 0;
+	}
+
+	/* no page was in place and we have one, so install it */
+
+	memset(mappage, 0, PAGE_SIZE);
+	bitmap->bp[page].map = mappage;
+	bitmap->missing_pages--;
+out:
+	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 inline 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;
+		return;
+	}
+
+	/* normal case, free the page */
+
+#if 0
+/* actually ... let's not.  We will probably need the page again exactly when
+ * memory is tight and we are flusing to disk
+ */
+	return;
+#else
+	ptr = bitmap->bp[page].map;
+	bitmap->bp[page].map = NULL;
+	bitmap->missing_pages++;
+	bitmap_free_page(bitmap, ptr);
+	return;
+#endif
+}
+
+
+/*
+ * bitmap file handling - read and write the bitmap file and its superblock
+ */
+
+/* copy the pathname of a file to a buffer */
+char *file_path(struct file *file, char *buf, int count)
+{
+	struct dentry *d;
+	struct vfsmount *v;
+
+	if (!buf)
+		return NULL;
+
+	d = file->f_dentry;
+	v = file->f_vfsmnt;
+
+	buf = d_path(d, v, buf, count);
+
+	return IS_ERR(buf) ? NULL : buf;
+}
+
+/*
+ * basic page I/O operations
+ */
+
+/*
+ * write out a page
+ */
+static int write_page(struct page *page, int wait)
+{
+	int ret = -ENOMEM;
+
+	lock_page(page);
+
+	if (page->mapping == NULL)
+		goto unlock_out;
+	else if (i_size_read(page->mapping->host) < page->index << PAGE_SHIFT) {
+		ret = -ENOENT;
+		goto unlock_out;
+	}
+
+	ret = page->mapping->a_ops->prepare_write(NULL, page, 0, PAGE_SIZE);
+	if (!ret)
+		ret = page->mapping->a_ops->commit_write(NULL, page, 0,
+			PAGE_SIZE);
+	if (ret) {
+unlock_out:
+		unlock_page(page);
+		return ret;
+	}
+
+	set_page_dirty(page); /* force it to be written out */
+	return write_one_page(page, wait);
+}
+
+/* read a page from a file, pinning it into cache, and return bytes_read */
+static struct page *read_page(struct file *file, unsigned long index,
+					unsigned long *bytes_read)
+{
+	struct inode *inode = file->f_mapping->host;
+	struct page *page = NULL;
+	loff_t isize = i_size_read(inode);
+	unsigned long end_index = isize >> PAGE_CACHE_SHIFT;
+
+	PRINTK("read bitmap file (%dB @ %Lu)\n", (int)PAGE_CACHE_SIZE,
+			(unsigned long long)index << PAGE_CACHE_SHIFT);
+
+	page = read_cache_page(inode->i_mapping, index,
+			(filler_t *)inode->i_mapping->a_ops->readpage, file);
+	if (IS_ERR(page))
+		goto out;
+	wait_on_page_locked(page);
+	if (!PageUptodate(page) || PageError(page)) {
+		page_cache_release(page);
+		page = ERR_PTR(-EIO);
+		goto out;
+	}
+
+	if (index > end_index) /* we have read beyond EOF */
+		*bytes_read = 0;
+	else if (index == end_index) /* possible short read */
+		*bytes_read = isize & ~PAGE_CACHE_MASK;
+	else
+		*bytes_read = PAGE_CACHE_SIZE; /* got a full page */
+out:
+	if (IS_ERR(page))
+		printk(KERN_ALERT "md: bitmap read error: (%dB @ %Lu): %ld\n",
+			(int)PAGE_CACHE_SIZE,
+			(unsigned long long)index << PAGE_CACHE_SHIFT,
+			PTR_ERR(page));
+	return page;
+}
+
+/*
+ * bitmap file superblock operations
+ */
+
+/* update the event counter and sync the superblock to disk */
+int bitmap_update_sb(struct bitmap *bitmap)
+{
+	bitmap_super_t *sb;
+	unsigned long flags;
+
+	if (!bitmap || !bitmap->mddev) /* no bitmap for this array */
+		return 0;
+	spin_lock_irqsave(&bitmap->lock, flags);
+	if (!bitmap->sb_page) { /* no superblock */
+		spin_unlock_irqrestore(&bitmap->lock, flags);
+		return 0;
+	}
+	page_cache_get(bitmap->sb_page);
+	spin_unlock_irqrestore(&bitmap->lock, flags);
+	sb = (bitmap_super_t *)kmap(bitmap->sb_page);
+	sb->events = cpu_to_le64(bitmap->mddev->events);
+	if (!bitmap->mddev->degraded)
+		sb->events_cleared = cpu_to_le64(bitmap->mddev->events);
+	kunmap(bitmap->sb_page);
+	write_page(bitmap->sb_page, 0);
+	return 0;
+}
+
+/* print out the bitmap file superblock */
+void bitmap_print_sb(struct bitmap *bitmap)
+{
+	bitmap_super_t *sb;
+
+	if (!bitmap || !bitmap->sb_page)
+		return;
+	sb = (bitmap_super_t *)kmap(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_clred: %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", le64_to_cpu(sb->sync_size));
+	kunmap(bitmap->sb_page);
+}
+
+/* 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;
+	unsigned long bytes_read;
+	unsigned long long events;
+	int err = -EINVAL;
+
+	/* page 0 is the superblock, read it... */
+	bitmap->sb_page = read_page(bitmap->file, 0, &bytes_read);
+	if (IS_ERR(bitmap->sb_page)) {
+		err = PTR_ERR(bitmap->sb_page);
+		bitmap->sb_page = NULL;
+		return err;
+	}
+
+	sb = (bitmap_super_t *)kmap(bitmap->sb_page);
+
+	if (bytes_read < sizeof(*sb)) { /* short read */
+		printk(KERN_INFO "%s: bitmap file superblock truncated\n",
+			bmname(bitmap));
+		err = -ENOSPC;
+		goto out;
+	}
+
+	chunksize = le32_to_cpu(sb->chunksize);
+	daemon_sleep = le32_to_cpu(sb->daemon_sleep);
+
+	/* verify that the bitmap-specific fields are valid */
+	if (sb->magic != cpu_to_le32(BITMAP_MAGIC))
+		reason = "bad magic";
+	else if (sb->version != cpu_to_le32(BITMAP_MAJOR))
+		reason = "unrecognized superblock version";
+	else if (chunksize < 512 || chunksize > (1024 * 1024 * 4))
+		reason = "bitmap chunksize out of range (512B - 4MB)";
+	else if ((1 << ffz(~chunksize)) != chunksize)
+		reason = "bitmap chunksize not a power of 2";
+	else if (daemon_sleep < 1 || daemon_sleep > 15)
+		reason = "daemon sleep period out of range";
+	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 |= BITMAP_STALE;
+	}
+success:
+	/* assign fields using values from superblock */
+	bitmap->chunksize = chunksize;
+	bitmap->daemon_sleep = daemon_sleep;
+	bitmap->flags |= sb->state;
+	bitmap->events_cleared = le64_to_cpu(sb->events_cleared);
+	err = 0;
+out:
+	kunmap(bitmap->sb_page);
+	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 */
+static void bitmap_mask_state(struct bitmap *bitmap, enum bitmap_state bits,
+				enum bitmap_mask_op op)
+{
+	bitmap_super_t *sb;
+	unsigned long flags;
+
+	spin_lock_irqsave(&bitmap->lock, flags);
+	if (!bitmap || !bitmap->sb_page) { /* can't set the state */
+		spin_unlock_irqrestore(&bitmap->lock, flags);
+		return;
+	}
+	page_cache_get(bitmap->sb_page);
+	spin_unlock_irqrestore(&bitmap->lock, flags);
+	sb = (bitmap_super_t *)kmap(bitmap->sb_page);
+	switch (op) {
+		case MASK_SET: sb->state |= bits;
+				break;
+		case MASK_UNSET: sb->state &= ~bits;
+				break;
+		default: BUG();
+	}
+	kunmap(bitmap->sb_page);
+	page_cache_release(bitmap->sb_page);
+}
+
+/*
+ * general bitmap file operations
+ */
+
+/* calculate the index of the page that contains this bit */
+static inline unsigned long file_page_index(unsigned long chunk)
+{
+	return CHUNK_BIT_OFFSET(chunk) >> PAGE_BIT_SHIFT;
+}
+
+/* calculate the (bit) offset of this bit within a page */
+static inline unsigned long file_page_offset(unsigned long chunk)
+{
+	return CHUNK_BIT_OFFSET(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)
+{
+	return bitmap->filemap[file_page_index(chunk) - file_page_index(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]->index != 0) /* 0 is sb_page, release it below */
+			page_cache_release(map[pages]);
+	kfree(map);
+	kfree(attr);
+
+	if (sb_page)
+		page_cache_release(sb_page);
+}
+
+static void bitmap_stop_daemons(struct bitmap *bitmap);
+
+/* dequeue the next item in a page list -- don't call from irq context */
+static struct page_list *dequeue_page(struct bitmap *bitmap,
+					struct list_head *head)
+{
+	struct page_list *item = NULL;
+
+	spin_lock(&bitmap->write_lock);
+	if (list_empty(head))
+		goto out;
+	item = list_entry(head->prev, struct page_list, list);
+	list_del(head->prev);
+out:
+	spin_unlock(&bitmap->write_lock);
+	return item;
+}
+
+static void drain_write_queues(struct bitmap *bitmap)
+{
+	struct list_head *queues[] = { 	&bitmap->complete_pages, NULL };
+	struct list_head *head;
+	struct page_list *item;
+	int i;
+
+	for (i = 0; queues[i]; i++) {
+		head = queues[i];
+		while ((item = dequeue_page(bitmap, head))) {
+			page_cache_release(item->page);
+			mempool_free(item, bitmap->write_pool);
+		}
+	}
+
+	spin_lock(&bitmap->write_lock);
+	bitmap->writes_pending = 0; /* make sure waiters continue */
+	wake_up(&bitmap->write_wait);
+	spin_unlock(&bitmap->write_lock);
+}
+
+static void bitmap_file_put(struct bitmap *bitmap)
+{
+	struct file *file;
+	struct inode *inode;
+	unsigned long flags;
+
+	spin_lock_irqsave(&bitmap->lock, flags);
+	file = bitmap->file;
+	bitmap->file = NULL;
+	spin_unlock_irqrestore(&bitmap->lock, flags);
+
+	bitmap_stop_daemons(bitmap);
+
+	drain_write_queues(bitmap);
+
+	bitmap_file_unmap(bitmap);
+
+	if (file) {
+		inode = file->f_mapping->host;
+		spin_lock(&inode->i_lock);
+		atomic_set(&inode->i_writecount, 1); /* allow writes again */
+		spin_unlock(&inode->i_lock);
+		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;
+
+	bitmap_mask_state(bitmap, BITMAP_STALE, MASK_SET);
+	bitmap_update_sb(bitmap);
+
+	path = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (path)
+		ptr = file_path(bitmap->file, path, PAGE_SIZE);
+
+	printk(KERN_ALERT "%s: kicking failed bitmap file %s from array!\n",
+		bmname(bitmap), ptr ? ptr : "");
+
+	kfree(path);
+
+	bitmap_file_put(bitmap);
+
+	return;
+}
+
+enum bitmap_page_attr {
+	BITMAP_PAGE_DIRTY = 1, // there are set bits that need to be synced
+	BITMAP_PAGE_CLEAN = 2, // there are bits that might need to be cleared
+	BITMAP_PAGE_NEEDWRITE=4, // 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)
+{
+	bitmap->filemap_attr[page->index] |= attr;
+}
+
+static inline void clear_page_attr(struct bitmap *bitmap, struct page *page,
+				enum bitmap_page_attr attr)
+{
+	bitmap->filemap_attr[page->index] &= ~attr;
+}
+
+static inline unsigned long get_page_attr(struct bitmap *bitmap, struct page *page)
+{
+	return bitmap->filemap_attr[page->index];
+}
+
+/*
+ * 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->file || !bitmap->filemap) {
+		return;
+	}
+
+	page = filemap_get_page(bitmap, chunk);
+	bit = file_page_offset(chunk);
+
+
+	/* make sure the page stays cached until it gets written out */
+	if (! (get_page_attr(bitmap, page) & BITMAP_PAGE_DIRTY))
+		page_cache_get(page);
+
+ 	/* set the bit */
+	kaddr = kmap_atomic(page, KM_USER0);
+	set_bit(bit, kaddr);
+	kunmap_atomic(kaddr, KM_USER0);
+	PRINTK("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 */
+int bitmap_unplug(struct bitmap *bitmap)
+{
+	unsigned long i, attr, flags;
+	struct page *page;
+	int wait = 0;
+
+	if (!bitmap)
+		return 0;
+
+	/* 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->file || !bitmap->filemap) {
+			spin_unlock_irqrestore(&bitmap->lock, flags);
+			return 0;
+		}
+		page = bitmap->filemap[i];
+		attr = get_page_attr(bitmap, page);
+		clear_page_attr(bitmap, page, BITMAP_PAGE_DIRTY);
+		clear_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
+		if ((attr & BITMAP_PAGE_DIRTY))
+			wait = 1;
+		spin_unlock_irqrestore(&bitmap->lock, flags);
+
+		if (attr & (BITMAP_PAGE_DIRTY | BITMAP_PAGE_NEEDWRITE))
+			write_page(page, 0);
+	}
+	if (wait) { /* if any writes were performed, we need to wait on them */
+		spin_lock_irq(&bitmap->write_lock);
+		wait_event_lock_irq(bitmap->write_wait,
+			bitmap->writes_pending == 0, bitmap->write_lock,
+			wake_up_process(bitmap->writeback_daemon->tsk));
+		spin_unlock_irq(&bitmap->write_lock);
+	}
+	return 0;
+}
+
+static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset,
+	unsigned long sectors, int set);
+/* * 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.
+ */
+static int bitmap_init_from_disk(struct bitmap *bitmap)
+{
+	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, dummy;
+	int outofdate;
+	int ret = -ENOSPC;
+
+	chunks = bitmap->chunks;
+	file = bitmap->file;
+
+	if (!file) { /* no file, dirty all the in-memory bits */
+		printk(KERN_INFO "%s: no bitmap file, doing full recovery\n",
+			bmname(bitmap));
+		bitmap_set_memory_bits(bitmap, 0,
+				       chunks << CHUNK_BLOCK_SHIFT(bitmap), 1);
+		return 0;
+	}
+
+#if INJECT_FAULTS_3
+	outofdate = 1;
+#else
+	outofdate = bitmap->flags & BITMAP_STALE;
+#endif
+	if (outofdate)
+		printk(KERN_INFO "%s: bitmap file is out of date, doing full "
+			"recovery\n", bmname(bitmap));
+
+	bytes = (chunks + 7) / 8;
+	num_pages = (bytes + PAGE_SIZE - 1) / PAGE_SIZE;
+	if (i_size_read(file->f_mapping->host) < bytes + sizeof(bitmap_super_t)) {
+		printk(KERN_INFO "%s: bitmap file too short %lu < %lu\n",
+			bmname(bitmap),
+			(unsigned long) i_size_read(file->f_mapping->host),
+			bytes + sizeof(bitmap_super_t));
+		goto out;
+	}
+	num_pages++;
+	bitmap->filemap = kmalloc(sizeof(struct page *) * num_pages, GFP_KERNEL);
+	if (!bitmap->filemap) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	bitmap->filemap_attr = kmalloc(sizeof(long) * num_pages, GFP_KERNEL);
+	if (!bitmap->filemap_attr) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	memset(bitmap->filemap_attr, 0, sizeof(long) * num_pages);
+
+	oldindex = ~0L;
+
+	for (i = 0; i < chunks; i++) {
+		index = file_page_index(i);
+		bit = file_page_offset(i);
+		if (index != oldindex) { /* this is a new page, read it in */
+			/* unmap the old page, we're done with it */
+			if (oldpage != NULL)
+				kunmap(oldpage);
+			if (index == 0) {
+				/*
+				 * 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);
+			} else {
+				page = read_page(file, index, &dummy);
+				if (IS_ERR(page)) { /* read error */
+					ret = PTR_ERR(page);
+					goto out;
+				}
+				offset = 0;
+			}
+			oldindex = index;
+			oldpage = page;
+			kmap(page);
+
+			if (outofdate) {
+				/*
+				 * if bitmap is out of date, dirty the
+			 	 * whole page and write it out
+				 */
+				memset(page_address(page) + offset, 0xff,
+					PAGE_SIZE - offset);
+				ret = write_page(page, 1);
+				if (ret) {
+					kunmap(page);
+					/* release, page not in filemap yet */
+					page_cache_release(page);
+					goto out;
+				}
+			}
+
+			bitmap->filemap[bitmap->file_pages++] = page;
+		}
+		if (test_bit(bit, page_address(page))) {
+			/* if the disk bit is set, set the memory bit */
+			bitmap_set_memory_bits(bitmap,
+					i << CHUNK_BLOCK_SHIFT(bitmap), 1, 1);
+			bit_cnt++;
+		}
+#if 0
+		else
+			bitmap_set_memory_bits(bitmap,
+				       i << CHUNK_BLOCK_SHIFT(bitmap), 1, 0);
+#endif
+	}
+
+ 	/* everything went OK */
+	ret = 0;
+	bitmap_mask_state(bitmap, BITMAP_STALE, MASK_UNSET);
+
+	if (page) /* unmap the last page */
+		kunmap(page);
+
+	if (bit_cnt) { /* Kick recovery if any bits were set */
+		set_bit(MD_RECOVERY_NEEDED, &bitmap->mddev->recovery);
+		md_wakeup_thread(bitmap->mddev->thread);
+	}
+
+out:
+	printk(KERN_INFO "%s: bitmap initialized from disk: "
+		"read %lu/%lu pages, set %lu bits, status: %d\n",
+		bmname(bitmap), bitmap->file_pages, num_pages, bit_cnt, ret);
+
+	return ret;
+}
+
+
+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;
+/*
+	if (page == 0) printk("count page 0, offset %llu: %d gives %d\n",
+			      (unsigned long long)offset, inc, bitmap->bp[page].count);
+*/
+	bitmap_checkfree(bitmap, page);
+}
+static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
+					    sector_t offset, int *blocks,
+					    int create);
+
+/*
+ * bitmap daemon -- periodically wakes up to clean bits and flush pages
+ *			out to disk
+ */
+
+int bitmap_daemon_work(struct bitmap *bitmap)
+{
+	unsigned long bit, j;
+	unsigned long flags;
+	struct page *page = NULL, *lastpage = NULL;
+	int err = 0;
+	int blocks;
+	int attr;
+
+	if (bitmap == NULL)
+		return 0;
+	if (time_before(jiffies, bitmap->daemon_lastrun + bitmap->daemon_sleep*HZ))
+		return 0;
+	bitmap->daemon_lastrun = jiffies;
+
+	for (j = 0; j < bitmap->chunks; j++) {
+		bitmap_counter_t *bmc;
+		spin_lock_irqsave(&bitmap->lock, flags);
+		if (!bitmap->file || !bitmap->filemap) {
+			/* error or shutdown */
+			spin_unlock_irqrestore(&bitmap->lock, flags);
+			break;
+		}
+
+		page = filemap_get_page(bitmap, j);
+		/* skip this page unless it's marked as needing cleaning */
+		if (!((attr=get_page_attr(bitmap, page)) & BITMAP_PAGE_CLEAN)) {
+			if (attr & BITMAP_PAGE_NEEDWRITE) {
+				page_cache_get(page);
+				clear_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
+			}
+			spin_unlock_irqrestore(&bitmap->lock, flags);
+			if (attr & BITMAP_PAGE_NEEDWRITE) {
+				if (write_page(page, 0))
+					bitmap_file_kick(bitmap);
+				page_cache_release(page);
+			}
+			continue;
+		}
+
+		bit = file_page_offset(j);
+
+		if (page != lastpage) {
+			/* grab the new page, sync and release the old */
+			page_cache_get(page);
+			if (lastpage != NULL) {
+				if (get_page_attr(bitmap, lastpage) & BITMAP_PAGE_NEEDWRITE) {
+					clear_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
+					spin_unlock_irqrestore(&bitmap->lock, flags);
+					write_page(lastpage, 0);
+				} else {
+					set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
+					spin_unlock_irqrestore(&bitmap->lock, flags);
+				}
+				kunmap(lastpage);
+				page_cache_release(lastpage);
+				if (err)
+					bitmap_file_kick(bitmap);
+			} else
+				spin_unlock_irqrestore(&bitmap->lock, flags);
+			lastpage = page;
+			kmap(page);
+/*
+			printk("bitmap clean at page %lu\n", j);
+*/
+			spin_lock_irqsave(&bitmap->lock, flags);
+			clear_page_attr(bitmap, page, BITMAP_PAGE_CLEAN);
+		}
+		bmc = bitmap_get_counter(bitmap, j << CHUNK_BLOCK_SHIFT(bitmap),
+					&blocks, 0);
+		if (bmc) {
+/*
+  if (j < 100) printk("bitmap: j=%lu, *bmc = 0x%x\n", j, *bmc);
+*/
+			if (*bmc == 2) {
+				*bmc=1; /* maybe clear the bit next time */
+				set_page_attr(bitmap, page, BITMAP_PAGE_CLEAN);
+			} else if (*bmc == 1) {
+				/* we can clear the bit */
+				*bmc = 0;
+				bitmap_count_page(bitmap, j << CHUNK_BLOCK_SHIFT(bitmap),
+						  -1);
+
+				/* clear the bit */
+				clear_bit(bit, page_address(page));
+			}
+		}
+		spin_unlock_irqrestore(&bitmap->lock, flags);
+	}
+
+	/* now sync the final page */
+	if (lastpage != NULL) {
+		kunmap(lastpage);
+		spin_lock_irqsave(&bitmap->lock, flags);
+		if (get_page_attr(bitmap, lastpage) &BITMAP_PAGE_NEEDWRITE) {
+			clear_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
+			spin_unlock_irqrestore(&bitmap->lock, flags);
+			write_page(lastpage, 0);
+		} else {
+			set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
+			spin_unlock_irqrestore(&bitmap->lock, flags);
+		}
+
+		page_cache_release(lastpage);
+	}
+
+	return err;
+}
+
+static void daemon_exit(struct bitmap *bitmap, mdk_thread_t **daemon)
+{
+	mdk_thread_t *dmn;
+	unsigned long flags;
+
+	/* if no one is waiting on us, we'll free the md thread struct
+	 * and exit, otherwise we let the waiter clean things up */
+	spin_lock_irqsave(&bitmap->lock, flags);
+	if ((dmn = *daemon)) { /* no one is waiting, cleanup and exit */
+		*daemon = NULL;
+		spin_unlock_irqrestore(&bitmap->lock, flags);
+		kfree(dmn);
+		complete_and_exit(NULL, 0); /* do_exit not exported */
+	}
+	spin_unlock_irqrestore(&bitmap->lock, flags);
+}
+
+static void bitmap_writeback_daemon(mddev_t *mddev)
+{
+	struct bitmap *bitmap = mddev->bitmap;
+	struct page *page;
+	struct page_list *item;
+	int err = 0;
+
+	while (1) {
+		PRINTK("%s: bitmap writeback daemon waiting...\n", bmname(bitmap));
+		down_interruptible(&bitmap->write_done);
+		if (signal_pending(current)) {
+			printk(KERN_INFO
+			    "%s: bitmap writeback daemon got signal, exiting...\n",
+			    bmname(bitmap));
+			break;
+		}
+
+		PRINTK("%s: bitmap writeback daemon woke up...\n", bmname(bitmap));
+		/* wait on bitmap page writebacks */
+		while ((item = dequeue_page(bitmap, &bitmap->complete_pages))) {
+			page = item->page;
+			mempool_free(item, bitmap->write_pool);
+			PRINTK("wait on page writeback: %p %lu\n", page, bitmap->writes_pending);
+			wait_on_page_writeback(page);
+			PRINTK("finished page writeback: %p %lu\n", page, bitmap->writes_pending);
+			spin_lock(&bitmap->write_lock);
+			if (!--bitmap->writes_pending)
+				wake_up(&bitmap->write_wait);
+			spin_unlock(&bitmap->write_lock);
+			err = PageError(page);
+			page_cache_release(page);
+			if (err) {
+				printk(KERN_WARNING "%s: bitmap file writeback "
+					"failed (page %lu): %d\n",
+					bmname(bitmap), page->index, err);
+				bitmap_file_kick(bitmap);
+				goto out;
+			}
+		}
+	}
+out:
+	if (err) {
+		printk(KERN_INFO "%s: bitmap writeback daemon exiting (%d)\n",
+			bmname(bitmap), err);
+		daemon_exit(bitmap, &bitmap->writeback_daemon);
+	}
+	return;
+}
+
+static int bitmap_start_daemon(struct bitmap *bitmap, mdk_thread_t **ptr,
+				void (*func)(mddev_t *), char *name)
+{
+	mdk_thread_t *daemon;
+	unsigned long flags;
+	char namebuf[32];
+
+	spin_lock_irqsave(&bitmap->lock, flags);
+	*ptr = NULL;
+	if (!bitmap->file) /* no need for daemon if there's no backing file */
+		goto out_unlock;
+
+	spin_unlock_irqrestore(&bitmap->lock, flags);
+
+#if INJECT_FATAL_FAULT_2
+	daemon = NULL;
+#else
+	sprintf(namebuf, "%%s_%s", name);
+	daemon = md_register_thread(func, bitmap->mddev, namebuf);
+#endif
+	if (!daemon) {
+		printk(KERN_ERR "%s: failed to start bitmap daemon\n",
+			bmname(bitmap));
+		return -ECHILD;
+	}
+
+	spin_lock_irqsave(&bitmap->lock, flags);
+	*ptr = daemon;
+
+	md_wakeup_thread(daemon); /* start it running */
+
+	PRINTK("%s: %s daemon (pid %d) started...\n",
+		bmname(bitmap), name, bitmap->daemon->tsk->pid);
+out_unlock:
+	spin_unlock_irqrestore(&bitmap->lock, flags);
+	return 0;
+}
+
+static int bitmap_start_daemons(struct bitmap *bitmap)
+{
+	int err = bitmap_start_daemon(bitmap, &bitmap->writeback_daemon,
+					bitmap_writeback_daemon, "bitmap_wb");
+	return err;
+}
+
+static void bitmap_stop_daemon(struct bitmap *bitmap, mdk_thread_t **ptr)
+{
+	mdk_thread_t *daemon;
+	unsigned long flags;
+
+	spin_lock_irqsave(&bitmap->lock, flags);
+	daemon = *ptr;
+	*ptr = NULL;
+	spin_unlock_irqrestore(&bitmap->lock, flags);
+	if (daemon)
+		md_unregister_thread(daemon); /* destroy the thread */
+}
+
+static void bitmap_stop_daemons(struct bitmap *bitmap)
+{
+	/* the daemons can't stop themselves... they'll just exit instead... */
+	if (bitmap->writeback_daemon &&
+	    current->pid != bitmap->writeback_daemon->tsk->pid)
+		bitmap_stop_daemon(bitmap, &bitmap->writeback_daemon);
+}
+
+static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
+					    sector_t offset, int *blocks,
+					    int create)
+{
+	/* 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;
+
+	if (bitmap_checkpage(bitmap, page, create) < 0) {
+		csize = ((sector_t)1) << (CHUNK_BLOCK_SHIFT(bitmap));
+		*blocks = csize - (offset & (csize- 1));
+		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);
+		csize = ((sector_t)1) << (CHUNK_BLOCK_SHIFT(bitmap) +
+					  PAGE_COUNTER_SHIFT - 1);
+		*blocks = csize - (offset & (csize- 1));
+		return  &((bitmap_counter_t *)
+			  &bitmap->bp[page].map)[hi];
+	} else { /* page is allocated */
+		csize = ((sector_t)1) << (CHUNK_BLOCK_SHIFT(bitmap));
+		*blocks = csize - (offset & (csize- 1));
+		return (bitmap_counter_t *)
+			&(bitmap->bp[page].map[pageoff]);
+	}
+}
+
+int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors)
+{
+	if (!bitmap) return 0;
+	while (sectors) {
+		int 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;
+		}
+
+		switch(*bmc) {
+		case 0:
+			bitmap_file_set_bit(bitmap, offset);
+			bitmap_count_page(bitmap,offset, 1);
+			blk_plug_device(bitmap->mddev->queue);
+			/* fall through */
+		case 1:
+			*bmc = 2;
+		}
+		if ((*bmc & COUNTER_MAX) == COUNTER_MAX) BUG();
+		(*bmc)++;
+
+		spin_unlock_irq(&bitmap->lock);
+
+		offset += blocks;
+		if (sectors > blocks)
+			sectors -= blocks;
+		else sectors = 0;
+	}
+	return 0;
+}
+
+void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors,
+		     int success)
+{
+	if (!bitmap) return;
+	while (sectors) {
+		int 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 && ! (*bmc & NEEDED_MASK))
+			*bmc |= NEEDED_MASK;
+
+		(*bmc)--;
+		if (*bmc <= 2) {
+			set_page_attr(bitmap,
+				      filemap_get_page(bitmap, offset >> CHUNK_BLOCK_SHIFT(bitmap)),
+				      BITMAP_PAGE_CLEAN);
+		}
+		spin_unlock_irqrestore(&bitmap->lock, flags);
+		offset += blocks;
+		if (sectors > blocks)
+			sectors -= blocks;
+		else sectors = 0;
+	}
+}
+
+int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, int *blocks)
+{
+	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;
+			*bmc |= RESYNC_MASK;
+			*bmc &= ~NEEDED_MASK;
+		}
+	}
+	spin_unlock_irq(&bitmap->lock);
+	return rv;
+}
+
+void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, int *blocks, int aborted)
+{
+	bitmap_counter_t *bmc;
+	unsigned long flags;
+/*
+	if (offset == 0) printk("bitmap_end_sync 0 (%d)\n", aborted);
+*/	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 (offset == 0) printk("bitmap_end sync found 0x%x, blocks %d\n", *bmc, *blocks);
+*/
+	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_CLEAN);
+			}
+		}
+	}
+ unlock:
+	spin_unlock_irqrestore(&bitmap->lock, flags);
+}
+
+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;
+	int blocks;
+	if (!bitmap) return;
+	while (sector < bitmap->mddev->resync_max_sectors) {
+		bitmap_end_sync(bitmap, sector, &blocks, 0);
+/*
+		if (sector < 500) printk("bitmap_close_sync: sec %llu blks %d\n",
+					 (unsigned long long)sector, blocks);
+*/		sector += blocks;
+	}
+}
+
+static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset,
+				   unsigned long sectors, int set)
+{
+	/* For each chunk covered by any of these sectors, set the
+	 * resync needed bit, and the counter to 1.  They should all
+	 * be 0 at this point
+	 */
+	while (sectors) {
+		int 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 (set && !NEEDED(*bmc)) {
+			BUG_ON(*bmc);
+			*bmc = NEEDED_MASK | 1;
+			bitmap_count_page(bitmap, offset, 1);
+		}
+		spin_unlock_irq(&bitmap->lock);
+		if (sectors > secs)
+			sectors -= secs;
+		else
+			sectors = 0;
+	}
+}
+
+/* dirty the entire bitmap */
+int bitmap_setallbits(struct bitmap *bitmap)
+{
+	unsigned long flags;
+	unsigned long j;
+
+	/* dirty the in-memory bitmap */
+	bitmap_set_memory_bits(bitmap, 0, bitmap->chunks << CHUNK_BLOCK_SHIFT(bitmap), 1);
+
+	/* dirty the bitmap file */
+	for (j = 0; j < bitmap->file_pages; j++) {
+		struct page *page = bitmap->filemap[j];
+
+		spin_lock_irqsave(&bitmap->lock, flags);
+		page_cache_get(page);
+		spin_unlock_irqrestore(&bitmap->lock, flags);
+		memset(kmap(page), 0xff, PAGE_SIZE);
+		kunmap(page);
+		write_page(page, 0);
+	}
+
+	return 0;
+}
+
+/*
+ * free memory that was allocated
+ */
+void bitmap_destroy(mddev_t *mddev)
+{
+	unsigned long k, pages;
+	struct bitmap_page *bp;
+	struct bitmap *bitmap = mddev->bitmap;
+
+	if (!bitmap) /* there was no bitmap */
+		return;
+
+	mddev->bitmap = NULL; /* disconnect from the md device */
+
+	/* release the bitmap file and kill the daemon */
+	bitmap_file_put(bitmap);
+
+	bp = bitmap->bp;
+	pages = bitmap->pages;
+
+	/* free all allocated memory */
+
+	mempool_destroy(bitmap->write_pool);
+
+	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);
+}
+
+/*
+ * initialize the bitmap structure
+ * if this returns an error, bitmap_destroy must be called to do clean up
+ */
+int bitmap_create(mddev_t *mddev)
+{
+	struct bitmap *bitmap;
+	unsigned long blocks = mddev->resync_max_sectors;
+	unsigned long chunks;
+	unsigned long pages;
+	struct file *file = mddev->bitmap_file;
+	int err;
+
+	BUG_ON(sizeof(bitmap_super_t) != 256);
+
+	if (!file) /* bitmap disabled, nothing to do */
+		return 0;
+
+	bitmap = kmalloc(sizeof(*bitmap), GFP_KERNEL);
+	if (!bitmap)
+		return -ENOMEM;
+
+	memset(bitmap, 0, sizeof(*bitmap));
+
+	spin_lock_init(&bitmap->lock);
+	bitmap->mddev = mddev;
+	mddev->bitmap = bitmap;
+
+	spin_lock_init(&bitmap->write_lock);
+	init_MUTEX_LOCKED(&bitmap->write_done);
+	INIT_LIST_HEAD(&bitmap->complete_pages);
+	init_waitqueue_head(&bitmap->write_wait);
+	bitmap->write_pool = mempool_create(WRITE_POOL_SIZE, write_pool_alloc,
+				write_pool_free, NULL);
+	if (!bitmap->write_pool)
+		return -ENOMEM;
+
+	bitmap->file = file;
+	get_file(file);
+	/* read superblock from bitmap file (this sets bitmap->chunksize) */
+	err = bitmap_read_sb(bitmap);
+	if (err)
+		return err;
+
+	bitmap->chunkshift = find_first_bit(&bitmap->chunksize,
+					sizeof(bitmap->chunksize));
+
+	/* now that chunksize and chunkshift are set, we can use these macros */
+ 	chunks = (blocks + CHUNK_BLOCK_RATIO(bitmap) - 1) /
+			CHUNK_BLOCK_RATIO(bitmap);
+ 	pages = (chunks + PAGE_COUNTER_RATIO - 1) / PAGE_COUNTER_RATIO;
+
+	BUG_ON(!pages);
+
+	bitmap->chunks = chunks;
+	bitmap->pages = pages;
+	bitmap->missing_pages = pages;
+	bitmap->counter_bits = COUNTER_BITS;
+
+	bitmap->syncchunk = ~0UL;
+
+#if INJECT_FATAL_FAULT_1
+	bitmap->bp = NULL;
+#else
+	bitmap->bp = kmalloc(pages * sizeof(*bitmap->bp), GFP_KERNEL);
+#endif
+	if (!bitmap->bp)
+		return -ENOMEM;
+	memset(bitmap->bp, 0, pages * sizeof(*bitmap->bp));
+
+	bitmap->flags |= BITMAP_ACTIVE;
+
+	/* now that we have some pages available, initialize the in-memory
+	 * bitmap from the on-disk bitmap */
+	err = bitmap_init_from_disk(bitmap);
+	if (err)
+		return err;
+
+	printk(KERN_INFO "created bitmap (%lu pages) for device %s\n",
+		pages, bmname(bitmap));
+
+	/* kick off the bitmap daemons */
+	err = bitmap_start_daemons(bitmap);
+	if (err)
+		return err;
+	return bitmap_update_sb(bitmap);
+}
+
+/* the bitmap API -- for raid personalities */
+EXPORT_SYMBOL(bitmap_startwrite);
+EXPORT_SYMBOL(bitmap_endwrite);
+EXPORT_SYMBOL(bitmap_start_sync);
+EXPORT_SYMBOL(bitmap_end_sync);
+EXPORT_SYMBOL(bitmap_unplug);
+EXPORT_SYMBOL(bitmap_close_sync);
+EXPORT_SYMBOL(bitmap_daemon_work);