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32 results

bitmap.c

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  • bitmap.c 41.72 KiB
    /*
     * 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;
    
    #ifdef 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
     */
    
    /* IO operations when bitmap is stored near all superblocks */
    static struct page *read_sb_page(mddev_t *mddev, long offset, unsigned long index)
    {
    	/* choose a good rdev and read the page from there */
    
    	mdk_rdev_t *rdev;
    	struct list_head *tmp;
    	struct page *page = alloc_page(GFP_KERNEL);
    	sector_t target;
    
    	if (!page)
    		return ERR_PTR(-ENOMEM);
    	do {
    		ITERATE_RDEV(mddev, rdev, tmp)
    			if (rdev->in_sync && !rdev->faulty)
    				goto found;
    		return ERR_PTR(-EIO);
    
    	found:
    		target = (rdev->sb_offset << 1) + offset + index * (PAGE_SIZE/512);
    
    	} while (!sync_page_io(rdev->bdev, target, PAGE_SIZE, page, READ));
    
    	page->index = index;
    	return page;
    }
    
    static int write_sb_page(mddev_t *mddev, long offset, struct page *page, int wait)
    {
    	mdk_rdev_t *rdev;
    	struct list_head *tmp;
    
    	ITERATE_RDEV(mddev, rdev, tmp)
    		if (rdev->in_sync && !rdev->faulty)
    			md_super_write(mddev, rdev,
    				       (rdev->sb_offset<<1) + offset
    				       + page->index * (PAGE_SIZE/512),
    				       PAGE_SIZE,
    				       page);
    
    	if (wait)
    		wait_event(mddev->sb_wait, atomic_read(&mddev->pending_writes)==0);
    	return 0;
    }
    
    /*
     * write out a page to a file
     */
    static int write_page(struct bitmap *bitmap, struct page *page, int wait)
    {
    	int ret = -ENOMEM;
    
    	if (bitmap->file == NULL)
    		return write_sb_page(bitmap->mddev, bitmap->offset, page, wait);
    
    	if (wait)
    		lock_page(page);
    	else {
    		if (TestSetPageLocked(page))
    			return -EAGAIN; /* already locked */
    		if (PageWriteback(page)) {
    			unlock_page(page);
    			return -EAGAIN;
    		}
    	}
    
    	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_page(page);
    		return ret;
    	}
    
    	set_page_dirty(page); /* force it to be written out */
    
    	if (!wait) {
    		/* add to list to be waited for by daemon */
    		struct page_list *item = mempool_alloc(bitmap->write_pool, GFP_NOIO);
    		item->page = page;
    		page_cache_get(page);
    		spin_lock(&bitmap->write_lock);
    		list_add(&item->list, &bitmap->complete_pages);
    		spin_unlock(&bitmap->write_lock);
    		md_wakeup_thread(bitmap->writeback_daemon);
    	}
    	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;
    	}
    	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);
    	return 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 = (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 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);
    	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... */
    	if (bitmap->file)
    		bitmap->sb_page = read_page(bitmap->file, 0, &bytes_read);
    	else {
    		bitmap->sb_page = read_sb_page(bitmap->mddev, bitmap->offset, 0);
    		bytes_read = PAGE_SIZE;
    	}
    	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);
    	if (sb->state & BITMAP_STALE)
    		bitmap->events_cleared = bitmap->mddev->events;
    	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 page_list *item = NULL;
    	struct list_head *head = &bitmap->complete_pages;
    
    	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 page_list *item;
    
    	while ((item = dequeue_page(bitmap))) {
    		/* don't bother to wait */
    		page_cache_release(item->page);
    		mempool_free(item, bitmap->write_pool);
    	}
    
    	wake_up(&bitmap->write_wait);
    }
    
    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);
    
    	if (bitmap->file) {
    		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->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;
    	int err;
    
    	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->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)) {
    			err = write_page(bitmap, page, 0);
    			if (err == -EAGAIN) {
    				if (attr & BITMAP_PAGE_DIRTY)
    					err = write_page(bitmap, page, 1);
    				else
    					err = 0;
    			}
    			if (err)
    				return 1;
    		}
    	}
    	if (wait) { /* if any writes were performed, we need to wait on them */
    		if (bitmap->file) {
    			spin_lock_irq(&bitmap->write_lock);
    			wait_event_lock_irq(bitmap->write_wait,
    					    list_empty(&bitmap->complete_pages), bitmap->write_lock,
    					    wake_up_process(bitmap->writeback_daemon->tsk));
    			spin_unlock_irq(&bitmap->write_lock);
    		} else
    			wait_event(bitmap->mddev->sb_wait,
    				   atomic_read(&bitmap->mddev->pending_writes)==0);
    	}
    	return 0;
    }
    
    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, dummy;
    	int outofdate;
    	int ret = -ENOSPC;
    
    	chunks = bitmap->chunks;
    	file = bitmap->file;
    
    	BUG_ON(!file && !bitmap->offset);
    
    #ifdef 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 + sizeof(bitmap_super_t) + PAGE_SIZE - 1) / PAGE_SIZE;
    
    	if (file && 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;
    	}
    
    	ret = -ENOMEM;
    
    	bitmap->filemap = kmalloc(sizeof(struct page *) * num_pages, GFP_KERNEL);
    	if (!bitmap->filemap)
    		goto out;
    
    	bitmap->filemap_attr = kmalloc(sizeof(long) * num_pages, GFP_KERNEL);
    	if (!bitmap->filemap_attr)
    		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 if (file) {
    				page = read_page(file, index, &dummy);
    				offset = 0;
    			} else {
    				page = read_sb_page(bitmap->mddev, bitmap->offset, index);
    				offset = 0;
    			}
    			if (IS_ERR(page)) { /* read error */
    				ret = PTR_ERR(page);
    				goto out;
    			}
    
    			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(bitmap, 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),
    					       ((i+1) << (CHUNK_BLOCK_SHIFT(bitmap)) >= start)
    				);
    			bit_cnt++;
    			set_page_attr(bitmap, page, BITMAP_PAGE_CLEAN);
    		}
    	}
    
     	/* 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;
    }
    
    void bitmap_write_all(struct bitmap *bitmap)
    {
    	/* We don't actually write all bitmap blocks here,
    	 * just flag them as needing to be written
    	 */
    
    	unsigned long chunks = bitmap->chunks;
    	unsigned long bytes = (chunks+7)/8 + sizeof(bitmap_super_t);
    	unsigned long num_pages = (bytes + PAGE_SIZE-1) / PAGE_SIZE;
    	while (num_pages--)
    		bitmap->filemap_attr[num_pages] |= BITMAP_PAGE_NEEDWRITE;
    }
    
    
    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 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->filemap) {
    			/* error or shutdown */
    			spin_unlock_irqrestore(&bitmap->lock, flags);
    			break;
    		}
    
    		page = filemap_get_page(bitmap, j);
    
    		if (page != lastpage) {
    			/* 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) {
    					switch (write_page(bitmap, page, 0)) {
    					case -EAGAIN:
    						set_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
    						break;
    					case 0:
    						break;
    					default:
    						bitmap_file_kick(bitmap);
    					}
    					page_cache_release(page);
    				}
    				continue;
    			}
    
    			/* 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);
    					err = write_page(bitmap, lastpage, 0);
    					if (err == -EAGAIN) {
    						err = 0;
    						set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
    					}
    				} 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(file_page_offset(j), 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);
    			err = write_page(bitmap, lastpage, 0);
    			if (err == -EAGAIN) {
    				set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
    				err = 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;
    
    	if (signal_pending(current)) {
    		printk(KERN_INFO
    		       "%s: bitmap writeback daemon got signal, exiting...\n",
    		       bmname(bitmap));
    		err = -EINTR;
    		goto out;
    	}
    
    	PRINTK("%s: bitmap writeback daemon woke up...\n", bmname(bitmap));
    	/* wait on bitmap page writebacks */
    	while ((item = dequeue_page(bitmap))) {
    		page = item->page;
    		mempool_free(item, bitmap->write_pool);
    		PRINTK("wait on page writeback: %p\n", page);
    		wait_on_page_writeback(page);
    		PRINTK("finished page writeback: %p\n", page);
    
    		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:
    	wake_up(&bitmap->write_wait);
    	if (err) {
    		printk(KERN_INFO "%s: bitmap writeback daemon exiting (%d)\n",
    		       bmname(bitmap), err);
    		daemon_exit(bitmap, &bitmap->writeback_daemon);
    	}
    }
    
    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);
    
    #ifdef 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, 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,
    			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;
    }
    
    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, 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
    	 */
    
    	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 (! *bmc) {
    		struct page *page;
    		*bmc = 1 | (needed?NEEDED_MASK:0);
    		bitmap_count_page(bitmap, offset, 1);
    		page = filemap_get_page(bitmap, offset >> CHUNK_BLOCK_SHIFT(bitmap));
    		set_page_attr(bitmap, page, BITMAP_PAGE_CLEAN);
    	}
    	spin_unlock_irq(&bitmap->lock);
    
    }
    
    /*
     * flush out any pending updates
     */
    void bitmap_flush(mddev_t *mddev)
    {
    	struct bitmap *bitmap = mddev->bitmap;
    	int sleep;
    
    	if (!bitmap) /* there was no bitmap */
    		return;
    
    	/* run the daemon_work three time to ensure everything is flushed
    	 * that can be
    	 */
    	sleep = bitmap->daemon_sleep;
    	bitmap->daemon_sleep = 0;
    	bitmap_daemon_work(bitmap);
    	bitmap_daemon_work(bitmap);
    	bitmap_daemon_work(bitmap);
    	bitmap->daemon_sleep = sleep;
    	bitmap_update_sb(bitmap);
    }
    
    /*
     * 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;
    	sector_t start;
    
    	BUG_ON(sizeof(bitmap_super_t) != 256);
    
    	if (!file && !mddev->bitmap_offset) /* bitmap disabled, nothing to do */
    		return 0;
    
    	BUG_ON(file && mddev->bitmap_offset);
    
    	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_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;
    	bitmap->offset = mddev->bitmap_offset;
    	if (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;
    
    #ifdef 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 */
    	start = 0;
    	if (mddev->degraded == 0
    	    || bitmap->events_cleared == mddev->events)
    		/* no need to keep dirty bits to optimise a re-add of a missing device */
    		start = mddev->recovery_cp;
    	err = bitmap_init_from_disk(bitmap, start);
    
    	if (err)
    		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);