md/bitmap: disentangle two different 'pending' flags.

[deliverable/linux.git] / drivers / md / bitmap.c

/*
 * bitmap.c two-level bitmap (C) Peter T. Breuer (ptb@ot.uc3m.es) 2003
 *
 * bitmap_create  - sets up the bitmap structure
 * bitmap_destroy - destroys the bitmap structure
 *
 * additions, Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.:
 * - added disk storage for bitmap
 * - changes to allow various bitmap chunk sizes
 */

/*
 * Still to do:
 *
 * flush after percent set rather than just time based. (maybe both).
 */

#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/timer.h>
#include <linux/sched.h>
#include <linux/list.h>
#include <linux/file.h>
#include <linux/mount.h>
#include <linux/buffer_head.h>
#include <linux/seq_file.h>
#include "md.h"
#include "bitmap.h"

static inline char *bmname(struct bitmap *bitmap)
{
        return bitmap->mddev ? mdname(bitmap->mddev) : "mdX";
}

/*
 * check a page and, if necessary, allocate it (or hijack it if the alloc fails)
 *
 * 1) check to see if this page is allocated, if it's not then try to alloc
 * 2) if the alloc fails, set the page's hijacked flag so we'll use the
 *    page pointer directly as a counter
 *
 * if we find our page, we increment the page's refcount so that it stays
 * allocated while we're using it
 */
static int bitmap_checkpage(struct bitmap *bitmap,
                            unsigned long page, int create)
__releases(bitmap->lock)
__acquires(bitmap->lock)
{
        unsigned char *mappage;

        if (page >= bitmap->pages) {
                /* This can happen if bitmap_start_sync goes beyond
                 * End-of-device while looking for a whole page.
                 * It is harmless.
                 */
                return -EINVAL;
        }

        if (bitmap->bp[page].hijacked) /* it's hijacked, don't try to alloc */
                return 0;

        if (bitmap->bp[page].map) /* page is already allocated, just return */
                return 0;

        if (!create)
                return -ENOENT;

        /* this page has not been allocated yet */

        spin_unlock_irq(&bitmap->lock);
        mappage = kzalloc(PAGE_SIZE, GFP_NOIO);
        spin_lock_irq(&bitmap->lock);

        if (mappage == NULL) {
                pr_debug("%s: bitmap map page allocation failed, hijacking\n",
                         bmname(bitmap));
                /* failed - set the hijacked flag so that we can use the
                 * pointer as a counter */
                if (!bitmap->bp[page].map)
                        bitmap->bp[page].hijacked = 1;
        } else if (bitmap->bp[page].map ||
                   bitmap->bp[page].hijacked) {
                /* somebody beat us to getting the page */
                kfree(mappage);
                return 0;
        } else {

                /* no page was in place and we have one, so install it */

                bitmap->bp[page].map = mappage;
                bitmap->missing_pages--;
        }
        return 0;
}

/* if page is completely empty, put it back on the free list, or dealloc it */
/* if page was hijacked, unmark the flag so it might get alloced next time */
/* Note: lock should be held when calling this */
static void bitmap_checkfree(struct bitmap *bitmap, unsigned long page)
{
        char *ptr;

        if (bitmap->bp[page].count) /* page is still busy */
                return;

        /* page is no longer in use, it can be released */

        if (bitmap->bp[page].hijacked) { /* page was hijacked, undo this now */
                bitmap->bp[page].hijacked = 0;
                bitmap->bp[page].map = NULL;
        } else {
                /* normal case, free the page */
                ptr = bitmap->bp[page].map;
                bitmap->bp[page].map = NULL;
                bitmap->missing_pages++;
                kfree(ptr);
        }
}

/*
 * bitmap file handling - read and write the bitmap file and its superblock
 */

/*
 * basic page I/O operations
 */

/* IO operations when bitmap is stored near all superblocks */
static struct page *read_sb_page(struct mddev *mddev, loff_t offset,
                                 struct page *page,
                                 unsigned long index, int size)
{
        /* choose a good rdev and read the page from there */

        struct md_rdev *rdev;
        sector_t target;
        int did_alloc = 0;

        if (!page) {
                page = alloc_page(GFP_KERNEL);
                if (!page)
                        return ERR_PTR(-ENOMEM);
                did_alloc = 1;
        }

        rdev_for_each(rdev, mddev) {
                if (! test_bit(In_sync, &rdev->flags)
                    || test_bit(Faulty, &rdev->flags))
                        continue;

                target = offset + index * (PAGE_SIZE/512);

                if (sync_page_io(rdev, target,
                                 roundup(size, bdev_logical_block_size(rdev->bdev)),
                                 page, READ, true)) {
                        page->index = index;
                        attach_page_buffers(page, NULL); /* so that free_buffer will
                                                          * quietly no-op */
                        return page;
                }
        }
        if (did_alloc)
                put_page(page);
        return ERR_PTR(-EIO);

}

static struct md_rdev *next_active_rdev(struct md_rdev *rdev, struct mddev *mddev)
{
        /* Iterate the disks of an mddev, using rcu to protect access to the
         * linked list, and raising the refcount of devices we return to ensure
         * they don't disappear while in use.
         * As devices are only added or removed when raid_disk is < 0 and
         * nr_pending is 0 and In_sync is clear, the entries we return will
         * still be in the same position on the list when we re-enter
         * list_for_each_continue_rcu.
         */
        struct list_head *pos;
        rcu_read_lock();
        if (rdev == NULL)
                /* start at the beginning */
                pos = &mddev->disks;
        else {
                /* release the previous rdev and start from there. */
                rdev_dec_pending(rdev, mddev);
                pos = &rdev->same_set;
        }
        list_for_each_continue_rcu(pos, &mddev->disks) {
                rdev = list_entry(pos, struct md_rdev, same_set);
                if (rdev->raid_disk >= 0 &&
                    !test_bit(Faulty, &rdev->flags)) {
                        /* this is a usable devices */
                        atomic_inc(&rdev->nr_pending);
                        rcu_read_unlock();
                        return rdev;
                }
        }
        rcu_read_unlock();
        return NULL;
}

static int write_sb_page(struct bitmap *bitmap, struct page *page, int wait)
{
        struct md_rdev *rdev = NULL;
        struct block_device *bdev;
        struct mddev *mddev = bitmap->mddev;

        while ((rdev = next_active_rdev(rdev, mddev)) != NULL) {
                int size = PAGE_SIZE;
                loff_t offset = mddev->bitmap_info.offset;

                bdev = (rdev->meta_bdev) ? rdev->meta_bdev : rdev->bdev;

                if (page->index == bitmap->file_pages-1)
                        size = roundup(bitmap->last_page_size,
                                       bdev_logical_block_size(bdev));
                /* Just make sure we aren't corrupting data or
                 * metadata
                 */
                if (mddev->external) {
                        /* Bitmap could be anywhere. */
                        if (rdev->sb_start + offset + (page->index
                                                       * (PAGE_SIZE/512))
                            > rdev->data_offset
                            &&
                            rdev->sb_start + offset
                            < (rdev->data_offset + mddev->dev_sectors
                             + (PAGE_SIZE/512)))
                                goto bad_alignment;
                } else if (offset < 0) {
                        /* DATA  BITMAP METADATA  */
                        if (offset
                            + (long)(page->index * (PAGE_SIZE/512))
                            + size/512 > 0)
                                /* bitmap runs in to metadata */
                                goto bad_alignment;
                        if (rdev->data_offset + mddev->dev_sectors
                            > rdev->sb_start + offset)
                                /* data runs in to bitmap */
                                goto bad_alignment;
                } else if (rdev->sb_start < rdev->data_offset) {
                        /* METADATA BITMAP DATA */
                        if (rdev->sb_start
                            + offset
                            + page->index*(PAGE_SIZE/512) + size/512
                            > rdev->data_offset)
                                /* bitmap runs in to data */
                                goto bad_alignment;
                } else {
                        /* DATA METADATA BITMAP - no problems */
                }
                md_super_write(mddev, rdev,
                               rdev->sb_start + offset
                               + page->index * (PAGE_SIZE/512),
                               size,
                               page);
        }

        if (wait)
                md_super_wait(mddev);
        return 0;

 bad_alignment:
        return -EINVAL;
}

static void bitmap_file_kick(struct bitmap *bitmap);
/*
 * write out a page to a file
 */
static void write_page(struct bitmap *bitmap, struct page *page, int wait)
{
        struct buffer_head *bh;

        if (bitmap->file == NULL) {
                switch (write_sb_page(bitmap, page, wait)) {
                case -EINVAL:
                        bitmap->flags |= BITMAP_WRITE_ERROR;
                }
        } else {

                bh = page_buffers(page);

                while (bh && bh->b_blocknr) {
                        atomic_inc(&bitmap->pending_writes);
                        set_buffer_locked(bh);
                        set_buffer_mapped(bh);
                        submit_bh(WRITE | REQ_SYNC, bh);
                        bh = bh->b_this_page;
                }

                if (wait)
                        wait_event(bitmap->write_wait,
                                   atomic_read(&bitmap->pending_writes)==0);
        }
        if (bitmap->flags & BITMAP_WRITE_ERROR)
                bitmap_file_kick(bitmap);
}

static void end_bitmap_write(struct buffer_head *bh, int uptodate)
{
        struct bitmap *bitmap = bh->b_private;
        unsigned long flags;

        if (!uptodate) {
                spin_lock_irqsave(&bitmap->lock, flags);
                bitmap->flags |= BITMAP_WRITE_ERROR;
                spin_unlock_irqrestore(&bitmap->lock, flags);
        }
        if (atomic_dec_and_test(&bitmap->pending_writes))
                wake_up(&bitmap->write_wait);
}

/* copied from buffer.c */
static void
__clear_page_buffers(struct page *page)
{
        ClearPagePrivate(page);
        set_page_private(page, 0);
        page_cache_release(page);
}
static void free_buffers(struct page *page)
{
        struct buffer_head *bh = page_buffers(page);

        while (bh) {
                struct buffer_head *next = bh->b_this_page;
                free_buffer_head(bh);
                bh = next;
        }
        __clear_page_buffers(page);
        put_page(page);
}

/* read a page from a file.
 * We both read the page, and attach buffers to the page to record the
 * address of each block (using bmap).  These addresses will be used
 * to write the block later, completely bypassing the filesystem.
 * This usage is similar to how swap files are handled, and allows us
 * to write to a file with no concerns of memory allocation failing.
 */
static struct page *read_page(struct file *file, unsigned long index,
                              struct bitmap *bitmap,
                              unsigned long count)
{
        struct page *page = NULL;
        struct inode *inode = file->f_path.dentry->d_inode;
        struct buffer_head *bh;
        sector_t block;

        pr_debug("read bitmap file (%dB @ %llu)\n", (int)PAGE_SIZE,
                 (unsigned long long)index << PAGE_SHIFT);

        page = alloc_page(GFP_KERNEL);
        if (!page)
                page = ERR_PTR(-ENOMEM);
        if (IS_ERR(page))
                goto out;

        bh = alloc_page_buffers(page, 1<<inode->i_blkbits, 0);
        if (!bh) {
                put_page(page);
                page = ERR_PTR(-ENOMEM);
                goto out;
        }
        attach_page_buffers(page, bh);
        block = index << (PAGE_SHIFT - inode->i_blkbits);
        while (bh) {
                if (count == 0)
                        bh->b_blocknr = 0;
                else {
                        bh->b_blocknr = bmap(inode, block);
                        if (bh->b_blocknr == 0) {
                                /* Cannot use this file! */
                                free_buffers(page);
                                page = ERR_PTR(-EINVAL);
                                goto out;
                        }
                        bh->b_bdev = inode->i_sb->s_bdev;
                        if (count < (1<<inode->i_blkbits))
                                count = 0;
                        else
                                count -= (1<<inode->i_blkbits);

                        bh->b_end_io = end_bitmap_write;
                        bh->b_private = bitmap;
                        atomic_inc(&bitmap->pending_writes);
                        set_buffer_locked(bh);
                        set_buffer_mapped(bh);
                        submit_bh(READ, bh);
                }
                block++;
                bh = bh->b_this_page;
        }
        page->index = index;

        wait_event(bitmap->write_wait,
                   atomic_read(&bitmap->pending_writes)==0);
        if (bitmap->flags & BITMAP_WRITE_ERROR) {
                free_buffers(page);
                page = ERR_PTR(-EIO);
        }
out:
        if (IS_ERR(page))
                printk(KERN_ALERT "md: bitmap read error: (%dB @ %llu): %ld\n",
                        (int)PAGE_SIZE,
                        (unsigned long long)index << PAGE_SHIFT,
                        PTR_ERR(page));
        return page;
}

/*
 * bitmap file superblock operations
 */

/* update the event counter and sync the superblock to disk */
void bitmap_update_sb(struct bitmap *bitmap)
{
        bitmap_super_t *sb;

        if (!bitmap || !bitmap->mddev) /* no bitmap for this array */
                return;
        if (bitmap->mddev->bitmap_info.external)
                return;
        if (!bitmap->sb_page) /* no superblock */
                return;
        sb = kmap_atomic(bitmap->sb_page);
        sb->events = cpu_to_le64(bitmap->mddev->events);
        if (bitmap->mddev->events < bitmap->events_cleared)
                /* rocking back to read-only */
                bitmap->events_cleared = bitmap->mddev->events;
        sb->events_cleared = cpu_to_le64(bitmap->events_cleared);
        sb->state = cpu_to_le32(bitmap->flags);
        /* Just in case these have been changed via sysfs: */
        sb->daemon_sleep = cpu_to_le32(bitmap->mddev->bitmap_info.daemon_sleep/HZ);
        sb->write_behind = cpu_to_le32(bitmap->mddev->bitmap_info.max_write_behind);
        kunmap_atomic(sb);
        write_page(bitmap, bitmap->sb_page, 1);
}

/* print out the bitmap file superblock */
void bitmap_print_sb(struct bitmap *bitmap)
{
        bitmap_super_t *sb;

        if (!bitmap || !bitmap->sb_page)
                return;
        sb = kmap_atomic(bitmap->sb_page);
        printk(KERN_DEBUG "%s: bitmap file superblock:\n", bmname(bitmap));
        printk(KERN_DEBUG "         magic: %08x\n", le32_to_cpu(sb->magic));
        printk(KERN_DEBUG "       version: %d\n", le32_to_cpu(sb->version));
        printk(KERN_DEBUG "          uuid: %08x.%08x.%08x.%08x\n",
                                        *(__u32 *)(sb->uuid+0),
                                        *(__u32 *)(sb->uuid+4),
                                        *(__u32 *)(sb->uuid+8),
                                        *(__u32 *)(sb->uuid+12));
        printk(KERN_DEBUG "        events: %llu\n",
                        (unsigned long long) le64_to_cpu(sb->events));
        printk(KERN_DEBUG "events cleared: %llu\n",
                        (unsigned long long) le64_to_cpu(sb->events_cleared));
        printk(KERN_DEBUG "         state: %08x\n", le32_to_cpu(sb->state));
        printk(KERN_DEBUG "     chunksize: %d B\n", le32_to_cpu(sb->chunksize));
        printk(KERN_DEBUG "  daemon sleep: %ds\n", le32_to_cpu(sb->daemon_sleep));
        printk(KERN_DEBUG "     sync size: %llu KB\n",
                        (unsigned long long)le64_to_cpu(sb->sync_size)/2);
        printk(KERN_DEBUG "max write behind: %d\n", le32_to_cpu(sb->write_behind));
        kunmap_atomic(sb);
}

/*
 * bitmap_new_disk_sb
 * @bitmap
 *
 * This function is somewhat the reverse of bitmap_read_sb.  bitmap_read_sb
 * reads and verifies the on-disk bitmap superblock and populates bitmap_info.
 * This function verifies 'bitmap_info' and populates the on-disk bitmap
 * structure, which is to be written to disk.
 *
 * Returns: 0 on success, -Exxx on error
 */
static int bitmap_new_disk_sb(struct bitmap *bitmap)
{
        bitmap_super_t *sb;
        unsigned long chunksize, daemon_sleep, write_behind;
        int err = -EINVAL;

        bitmap->sb_page = alloc_page(GFP_KERNEL);
        if (IS_ERR(bitmap->sb_page)) {
                err = PTR_ERR(bitmap->sb_page);
                bitmap->sb_page = NULL;
                return err;
        }
        bitmap->sb_page->index = 0;

        sb = kmap_atomic(bitmap->sb_page);

        sb->magic = cpu_to_le32(BITMAP_MAGIC);
        sb->version = cpu_to_le32(BITMAP_MAJOR_HI);

        chunksize = bitmap->mddev->bitmap_info.chunksize;
        BUG_ON(!chunksize);
        if (!is_power_of_2(chunksize)) {
                kunmap_atomic(sb);
                printk(KERN_ERR "bitmap chunksize not a power of 2\n");
                return -EINVAL;
        }
        sb->chunksize = cpu_to_le32(chunksize);

        daemon_sleep = bitmap->mddev->bitmap_info.daemon_sleep;
        if (!daemon_sleep ||
            (daemon_sleep < 1) || (daemon_sleep > MAX_SCHEDULE_TIMEOUT)) {
                printk(KERN_INFO "Choosing daemon_sleep default (5 sec)\n");
                daemon_sleep = 5 * HZ;
        }
        sb->daemon_sleep = cpu_to_le32(daemon_sleep);
        bitmap->mddev->bitmap_info.daemon_sleep = daemon_sleep;

        /*
         * FIXME: write_behind for RAID1.  If not specified, what
         * is a good choice?  We choose COUNTER_MAX / 2 arbitrarily.
         */
        write_behind = bitmap->mddev->bitmap_info.max_write_behind;
        if (write_behind > COUNTER_MAX)
                write_behind = COUNTER_MAX / 2;
        sb->write_behind = cpu_to_le32(write_behind);
        bitmap->mddev->bitmap_info.max_write_behind = write_behind;

        /* keep the array size field of the bitmap superblock up to date */
        sb->sync_size = cpu_to_le64(bitmap->mddev->resync_max_sectors);

        memcpy(sb->uuid, bitmap->mddev->uuid, 16);

        bitmap->flags |= BITMAP_STALE;
        sb->state |= cpu_to_le32(BITMAP_STALE);
        bitmap->events_cleared = bitmap->mddev->events;
        sb->events_cleared = cpu_to_le64(bitmap->mddev->events);

        kunmap_atomic(sb);

        return 0;
}

/* read the superblock from the bitmap file and initialize some bitmap fields */
static int bitmap_read_sb(struct bitmap *bitmap)
{
        char *reason = NULL;
        bitmap_super_t *sb;
        unsigned long chunksize, daemon_sleep, write_behind;
        unsigned long long events;
        int err = -EINVAL;

        /* page 0 is the superblock, read it... */
        if (bitmap->file) {
                loff_t isize = i_size_read(bitmap->file->f_mapping->host);
                int bytes = isize > PAGE_SIZE ? PAGE_SIZE : isize;

                bitmap->sb_page = read_page(bitmap->file, 0, bitmap, bytes);
        } else {
                bitmap->sb_page = read_sb_page(bitmap->mddev,
                                               bitmap->mddev->bitmap_info.offset,
                                               NULL,
                                               0, sizeof(bitmap_super_t));
        }
        if (IS_ERR(bitmap->sb_page)) {
                err = PTR_ERR(bitmap->sb_page);
                bitmap->sb_page = NULL;
                return err;
        }

        sb = kmap_atomic(bitmap->sb_page);

        chunksize = le32_to_cpu(sb->chunksize);
        daemon_sleep = le32_to_cpu(sb->daemon_sleep) * HZ;
        write_behind = le32_to_cpu(sb->write_behind);

        /* verify that the bitmap-specific fields are valid */
        if (sb->magic != cpu_to_le32(BITMAP_MAGIC))
                reason = "bad magic";
        else if (le32_to_cpu(sb->version) < BITMAP_MAJOR_LO ||
                 le32_to_cpu(sb->version) > BITMAP_MAJOR_HI)
                reason = "unrecognized superblock version";
        else if (chunksize < 512)
                reason = "bitmap chunksize too small";
        else if (!is_power_of_2(chunksize))
                reason = "bitmap chunksize not a power of 2";
        else if (daemon_sleep < 1 || daemon_sleep > MAX_SCHEDULE_TIMEOUT)
                reason = "daemon sleep period out of range";
        else if (write_behind > COUNTER_MAX)
                reason = "write-behind limit out of range (0 - 16383)";
        if (reason) {
                printk(KERN_INFO "%s: invalid bitmap file superblock: %s\n",
                        bmname(bitmap), reason);
                goto out;
        }

        /* keep the array size field of the bitmap superblock up to date */
        sb->sync_size = cpu_to_le64(bitmap->mddev->resync_max_sectors);

        if (bitmap->mddev->persistent) {
                /*
                 * We have a persistent array superblock, so compare the
                 * bitmap's UUID and event counter to the mddev's
                 */
                if (memcmp(sb->uuid, bitmap->mddev->uuid, 16)) {
                        printk(KERN_INFO
                               "%s: bitmap superblock UUID mismatch\n",
                               bmname(bitmap));
                        goto out;
                }
                events = le64_to_cpu(sb->events);
                if (events < bitmap->mddev->events) {
                        printk(KERN_INFO
                               "%s: bitmap file is out of date (%llu < %llu) "
                               "-- forcing full recovery\n",
                               bmname(bitmap), events,
                               (unsigned long long) bitmap->mddev->events);
                        sb->state |= cpu_to_le32(BITMAP_STALE);
                }
        }

        /* assign fields using values from superblock */
        bitmap->mddev->bitmap_info.chunksize = chunksize;
        bitmap->mddev->bitmap_info.daemon_sleep = daemon_sleep;
        bitmap->mddev->bitmap_info.max_write_behind = write_behind;
        bitmap->flags |= le32_to_cpu(sb->state);
        if (le32_to_cpu(sb->version) == BITMAP_MAJOR_HOSTENDIAN)
                bitmap->flags |= BITMAP_HOSTENDIAN;
        bitmap->events_cleared = le64_to_cpu(sb->events_cleared);
        if (bitmap->flags & BITMAP_STALE)
                bitmap->events_cleared = bitmap->mddev->events;
        err = 0;
out:
        kunmap_atomic(sb);
        if (err)
                bitmap_print_sb(bitmap);
        return err;
}

enum bitmap_mask_op {
        MASK_SET,
        MASK_UNSET
};

/* record the state of the bitmap in the superblock.  Return the old value */
static int bitmap_mask_state(struct bitmap *bitmap, enum bitmap_state bits,
                             enum bitmap_mask_op op)
{
        bitmap_super_t *sb;
        int old;

        if (!bitmap->sb_page) /* can't set the state */
                return 0;
        sb = kmap_atomic(bitmap->sb_page);
        old = le32_to_cpu(sb->state) & bits;
        switch (op) {
        case MASK_SET:
                sb->state |= cpu_to_le32(bits);
                bitmap->flags |= bits;
                break;
        case MASK_UNSET:
                sb->state &= cpu_to_le32(~bits);
                bitmap->flags &= ~bits;
                break;
        default:
                BUG();
        }
        kunmap_atomic(sb);
        return old;
}

/*
 * general bitmap file operations
 */

/*
 * on-disk bitmap:
 *
 * Use one bit per "chunk" (block set). We do the disk I/O on the bitmap
 * file a page at a time. There's a superblock at the start of the file.
 */
/* calculate the index of the page that contains this bit */
static inline unsigned long file_page_index(struct bitmap *bitmap, unsigned long chunk)
{
        if (!bitmap->mddev->bitmap_info.external)
                chunk += sizeof(bitmap_super_t) << 3;
        return chunk >> PAGE_BIT_SHIFT;
}

/* calculate the (bit) offset of this bit within a page */
static inline unsigned long file_page_offset(struct bitmap *bitmap, unsigned long chunk)
{
        if (!bitmap->mddev->bitmap_info.external)
                chunk += sizeof(bitmap_super_t) << 3;
        return chunk & (PAGE_BITS - 1);
}

/*
 * return a pointer to the page in the filemap that contains the given bit
 *
 * this lookup is complicated by the fact that the bitmap sb might be exactly
 * 1 page (e.g., x86) or less than 1 page -- so the bitmap might start on page
 * 0 or page 1
 */
static inline struct page *filemap_get_page(struct bitmap *bitmap,
                                            unsigned long chunk)
{
        if (file_page_index(bitmap, chunk) >= bitmap->file_pages)
                return NULL;
        return bitmap->filemap[file_page_index(bitmap, chunk)
                               - file_page_index(bitmap, 0)];
}

static void bitmap_file_unmap(struct bitmap *bitmap)
{
        struct page **map, *sb_page;
        unsigned long *attr;
        int pages;
        unsigned long flags;

        spin_lock_irqsave(&bitmap->lock, flags);
        map = bitmap->filemap;
        bitmap->filemap = NULL;
        attr = bitmap->filemap_attr;
        bitmap->filemap_attr = NULL;
        pages = bitmap->file_pages;
        bitmap->file_pages = 0;
        sb_page = bitmap->sb_page;
        bitmap->sb_page = NULL;
        spin_unlock_irqrestore(&bitmap->lock, flags);

        while (pages--)
                if (map[pages] != sb_page) /* 0 is sb_page, release it below */
                        free_buffers(map[pages]);
        kfree(map);
        kfree(attr);

        if (sb_page)
                free_buffers(sb_page);
}

static void bitmap_file_put(struct bitmap *bitmap)
{
        struct file *file;
        unsigned long flags;

        spin_lock_irqsave(&bitmap->lock, flags);
        file = bitmap->file;
        bitmap->file = NULL;
        spin_unlock_irqrestore(&bitmap->lock, flags);

        if (file)
                wait_event(bitmap->write_wait,
                           atomic_read(&bitmap->pending_writes)==0);
        bitmap_file_unmap(bitmap);

        if (file) {
                struct inode *inode = file->f_path.dentry->d_inode;
                invalidate_mapping_pages(inode->i_mapping, 0, -1);
                fput(file);
        }
}

/*
 * bitmap_file_kick - if an error occurs while manipulating the bitmap file
 * then it is no longer reliable, so we stop using it and we mark the file
 * as failed in the superblock
 */
static void bitmap_file_kick(struct bitmap *bitmap)
{
        char *path, *ptr = NULL;

        if (bitmap_mask_state(bitmap, BITMAP_STALE, MASK_SET) == 0) {
                bitmap_update_sb(bitmap);

                if (bitmap->file) {
                        path = kmalloc(PAGE_SIZE, GFP_KERNEL);
                        if (path)
                                ptr = d_path(&bitmap->file->f_path, path,
                                             PAGE_SIZE);

                        printk(KERN_ALERT
                              "%s: kicking failed bitmap file %s from array!\n",
                              bmname(bitmap), IS_ERR(ptr) ? "" : ptr);

                        kfree(path);
                } else
                        printk(KERN_ALERT
                               "%s: disabling internal bitmap due to errors\n",
                               bmname(bitmap));
        }

        bitmap_file_put(bitmap);

        return;
}

enum bitmap_page_attr {
        BITMAP_PAGE_DIRTY = 0,     /* there are set bits that need to be synced */
        BITMAP_PAGE_PENDING = 1,   /* there are bits that are being cleaned.
                                    * i.e. counter is 1 or 2. */
        BITMAP_PAGE_NEEDWRITE = 2, /* there are cleared bits that need to be synced */
};

static inline void set_page_attr(struct bitmap *bitmap, struct page *page,
                                enum bitmap_page_attr attr)
{
        __set_bit((page->index<<2) + attr, bitmap->filemap_attr);
}

static inline void clear_page_attr(struct bitmap *bitmap, struct page *page,
                                enum bitmap_page_attr attr)
{
        __clear_bit((page->index<<2) + attr, bitmap->filemap_attr);
}

static inline unsigned long test_page_attr(struct bitmap *bitmap, struct page *page,
                                           enum bitmap_page_attr attr)
{
        return test_bit((page->index<<2) + attr, bitmap->filemap_attr);
}

/*
 * bitmap_file_set_bit -- called before performing a write to the md device
 * to set (and eventually sync) a particular bit in the bitmap file
 *
 * we set the bit immediately, then we record the page number so that
 * when an unplug occurs, we can flush the dirty pages out to disk
 */
static void bitmap_file_set_bit(struct bitmap *bitmap, sector_t block)
{
        unsigned long bit;
        struct page *page;
        void *kaddr;
        unsigned long chunk = block >> bitmap->chunkshift;

        if (!bitmap->filemap)
                return;

        page = filemap_get_page(bitmap, chunk);
        if (!page)
                return;
        bit = file_page_offset(bitmap, chunk);

        /* set the bit */
        kaddr = kmap_atomic(page);
        if (bitmap->flags & BITMAP_HOSTENDIAN)
                set_bit(bit, kaddr);
        else
                __set_bit_le(bit, kaddr);
        kunmap_atomic(kaddr);
        pr_debug("set file bit %lu page %lu\n", bit, page->index);
        /* record page number so it gets flushed to disk when unplug occurs */
        set_page_attr(bitmap, page, BITMAP_PAGE_DIRTY);
}

/* this gets called when the md device is ready to unplug its underlying
 * (slave) device queues -- before we let any writes go down, we need to
 * sync the dirty pages of the bitmap file to disk */
void bitmap_unplug(struct bitmap *bitmap)
{
        unsigned long i, flags;
        int dirty, need_write;
        struct page *page;
        int wait = 0;

        if (!bitmap)
                return;

        /* look at each page to see if there are any set bits that need to be
         * flushed out to disk */
        for (i = 0; i < bitmap->file_pages; i++) {
                spin_lock_irqsave(&bitmap->lock, flags);
                if (!bitmap->filemap) {
                        spin_unlock_irqrestore(&bitmap->lock, flags);
                        return;
                }
                page = bitmap->filemap[i];
                dirty = test_page_attr(bitmap, page, BITMAP_PAGE_DIRTY);
                need_write = test_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
                clear_page_attr(bitmap, page, BITMAP_PAGE_DIRTY);
                clear_page_attr(bitmap, page, BITMAP_PAGE_NEEDWRITE);
                if (dirty || need_write)
                        clear_page_attr(bitmap, page, BITMAP_PAGE_PENDING);
                if (dirty)
                        wait = 1;
                spin_unlock_irqrestore(&bitmap->lock, flags);

                if (dirty || need_write)
                        write_page(bitmap, page, 0);
        }
        if (wait) { /* if any writes were performed, we need to wait on them */
                if (bitmap->file)
                        wait_event(bitmap->write_wait,
                                   atomic_read(&bitmap->pending_writes)==0);
                else
                        md_super_wait(bitmap->mddev);
        }
        if (bitmap->flags & BITMAP_WRITE_ERROR)
                bitmap_file_kick(bitmap);
}
EXPORT_SYMBOL(bitmap_unplug);

static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int needed);
/* * bitmap_init_from_disk -- called at bitmap_create time to initialize
 * the in-memory bitmap from the on-disk bitmap -- also, sets up the
 * memory mapping of the bitmap file
 * Special cases:
 *   if there's no bitmap file, or if the bitmap file had been
 *   previously kicked from the array, we mark all the bits as
 *   1's in order to cause a full resync.
 *
 * We ignore all bits for sectors that end earlier than 'start'.
 * This is used when reading an out-of-date bitmap...
 */
static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
{
        unsigned long i, chunks, index, oldindex, bit;
        struct page *page = NULL, *oldpage = NULL;
        unsigned long num_pages, bit_cnt = 0;
        struct file *file;
        unsigned long bytes, offset;
        int outofdate;
        int ret = -ENOSPC;
        void *paddr;

        chunks = bitmap->chunks;
        file = bitmap->file;

        BUG_ON(!file && !bitmap->mddev->bitmap_info.offset);

        outofdate = bitmap->flags & BITMAP_STALE;
        if (outofdate)
                printk(KERN_INFO "%s: bitmap file is out of date, doing full "
                        "recovery\n", bmname(bitmap));

        bytes = DIV_ROUND_UP(bitmap->chunks, 8);
        if (!bitmap->mddev->bitmap_info.external)
                bytes += sizeof(bitmap_super_t);

        num_pages = DIV_ROUND_UP(bytes, PAGE_SIZE);

        if (file && i_size_read(file->f_mapping->host) < bytes) {
                printk(KERN_INFO "%s: bitmap file too short %lu < %lu\n",
                        bmname(bitmap),
                        (unsigned long) i_size_read(file->f_mapping->host),
                        bytes);
                goto err;
        }

        ret = -ENOMEM;

        bitmap->filemap = kmalloc(sizeof(struct page *) * num_pages, GFP_KERNEL);
        if (!bitmap->filemap)
                goto err;

        /* We need 4 bits per page, rounded up to a multiple of sizeof(unsigned long) */
        bitmap->filemap_attr = kzalloc(
                roundup(DIV_ROUND_UP(num_pages*4, 8), sizeof(unsigned long)),
                GFP_KERNEL);
        if (!bitmap->filemap_attr)
                goto err;

        oldindex = ~0L;

        for (i = 0; i < chunks; i++) {
                int b;
                index = file_page_index(bitmap, i);
                bit = file_page_offset(bitmap, i);
                if (index != oldindex) { /* this is a new page, read it in */
                        int count;
                        /* unmap the old page, we're done with it */
                        if (index == num_pages-1)
                                count = bytes - index * PAGE_SIZE;
                        else
                                count = PAGE_SIZE;
                        if (index == 0 && bitmap->sb_page) {
                                /*
                                 * if we're here then the superblock page
                                 * contains some bits (PAGE_SIZE != sizeof sb)
                                 * we've already read it in, so just use it
                                 */
                                page = bitmap->sb_page;
                                offset = sizeof(bitmap_super_t);
                                if (!file)
                                        page = read_sb_page(
                                                bitmap->mddev,
                                                bitmap->mddev->bitmap_info.offset,
                                                page,
                                                index, count);
                        } else if (file) {
                                page = read_page(file, index, bitmap, count);
                                offset = 0;
                        } else {
                                page = read_sb_page(bitmap->mddev,
                                                    bitmap->mddev->bitmap_info.offset,
                                                    NULL,
                                                    index, count);
                                offset = 0;
                        }
                        if (IS_ERR(page)) { /* read error */
                                ret = PTR_ERR(page);
                                goto err;
                        }

                        oldindex = index;
                        oldpage = page;

                        bitmap->filemap[bitmap->file_pages++] = page;
                        bitmap->last_page_size = count;

                        if (outofdate) {
                                /*
                                 * if bitmap is out of date, dirty the
                                 * whole page and write it out
                                 */
                                paddr = kmap_atomic(page);
                                memset(paddr + offset, 0xff,
                                       PAGE_SIZE - offset);
                                kunmap_atomic(paddr);
                                write_page(bitmap, page, 1);

                                ret = -EIO;
                                if (bitmap->flags & BITMAP_WRITE_ERROR)
                                        goto err;
                        }
                }
                paddr = kmap_atomic(page);
                if (bitmap->flags & BITMAP_HOSTENDIAN)
                        b = test_bit(bit, paddr);
                else
                        b = test_bit_le(bit, paddr);
                kunmap_atomic(paddr);
                if (b) {
                        /* if the disk bit is set, set the memory bit */
                        int needed = ((sector_t)(i+1) << bitmap->chunkshift
                                      >= start);
                        bitmap_set_memory_bits(bitmap,
                                               (sector_t)i << bitmap->chunkshift,
                                               needed);
                        bit_cnt++;
                }
        }

        /* everything went OK */
        ret = 0;
        bitmap_mask_state(bitmap, BITMAP_STALE, MASK_UNSET);

        if (bit_cnt) { /* Kick recovery if any bits were set */
                set_bit(MD_RECOVERY_NEEDED, &bitmap->mddev->recovery);
                md_wakeup_thread(bitmap->mddev->thread);
        }

        printk(KERN_INFO "%s: bitmap initialized from disk: "
               "read %lu/%lu pages, set %lu of %lu bits\n",
               bmname(bitmap), bitmap->file_pages, num_pages, bit_cnt, chunks);

        return 0;

 err:
        printk(KERN_INFO "%s: bitmap initialisation failed: %d\n",
               bmname(bitmap), ret);
        return ret;
}

void bitmap_write_all(struct bitmap *bitmap)
{
        /* We don't actually write all bitmap blocks here,
         * just flag them as needing to be written
         */
        int i;

        spin_lock_irq(&bitmap->lock);
        for (i = 0; i < bitmap->file_pages; i++)
                set_page_attr(bitmap, bitmap->filemap[i],
                              BITMAP_PAGE_NEEDWRITE);
        bitmap->allclean = 0;
        spin_unlock_irq(&bitmap->lock);
}

static void bitmap_count_page(struct bitmap *bitmap, sector_t offset, int inc)
{
        sector_t chunk = offset >> bitmap->chunkshift;
        unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
        bitmap->bp[page].count += inc;
        bitmap_checkfree(bitmap, page);
}

static void bitmap_set_pending(struct bitmap *bitmap, sector_t offset)
{
        sector_t chunk = offset >> bitmap->chunkshift;
        unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
        struct bitmap_page *bp = &bitmap->bp[page];

        if (!bp->pending)
                bp->pending = 1;
}

static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
                                            sector_t offset, sector_t *blocks,
                                            int create);

/*
 * bitmap daemon -- periodically wakes up to clean bits and flush pages
 *                      out to disk
 */

void bitmap_daemon_work(struct mddev *mddev)
{
        struct bitmap *bitmap;
        unsigned long j;
        unsigned long nextpage;
        unsigned long flags;
        sector_t blocks;
        void *paddr;

        /* Use a mutex to guard daemon_work against
         * bitmap_destroy.
         */
        mutex_lock(&mddev->bitmap_info.mutex);
        bitmap = mddev->bitmap;
        if (bitmap == NULL) {
                mutex_unlock(&mddev->bitmap_info.mutex);
                return;
        }
        if (time_before(jiffies, bitmap->daemon_lastrun
                        + mddev->bitmap_info.daemon_sleep))
                goto done;

        bitmap->daemon_lastrun = jiffies;
        if (bitmap->allclean) {
                mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;
                goto done;
        }
        bitmap->allclean = 1;

        /* Any file-page which is PENDING now needs to be written.
         * So set NEEDWRITE now, then after we make any last-minute changes
         * we will write it.
         */
        spin_lock_irqsave(&bitmap->lock, flags);
        if (!bitmap->filemap)
                /* error or shutdown */
                goto out;

        for (j = 0; j < bitmap->file_pages; j++)
                if (test_page_attr(bitmap, bitmap->filemap[j],
                                   BITMAP_PAGE_PENDING)) {
                        set_page_attr(bitmap, bitmap->filemap[j],
                                      BITMAP_PAGE_NEEDWRITE);
                        clear_page_attr(bitmap, bitmap->filemap[j],
                                        BITMAP_PAGE_PENDING);
                }

        if (bitmap->need_sync &&
            mddev->bitmap_info.external == 0) {
                /* Arrange for superblock update as well as
                 * other changes */
                bitmap_super_t *sb;
                bitmap->need_sync = 0;
                sb = kmap_atomic(bitmap->sb_page);
                sb->events_cleared =
                        cpu_to_le64(bitmap->events_cleared);
                kunmap_atomic(sb);
                set_page_attr(bitmap, bitmap->sb_page, BITMAP_PAGE_NEEDWRITE);
        }
        /* Now look at the bitmap counters and if any are '2' or '1',
         * decrement and handle accordingly.
         */
        nextpage = 0;
        for (j = 0; j < bitmap->chunks; j++) {
                bitmap_counter_t *bmc;

                if (j == nextpage) {
                        nextpage += PAGE_COUNTER_RATIO;
                        if (!bitmap->bp[j >> PAGE_COUNTER_SHIFT].pending) {
                                j |= PAGE_COUNTER_MASK;
                                continue;
                        }
                        bitmap->bp[j >> PAGE_COUNTER_SHIFT].pending = 0;
                }
                bmc = bitmap_get_counter(bitmap,
                                         (sector_t)j << bitmap->chunkshift,
                                         &blocks, 0);

                if (!bmc) {
                        j |= PAGE_COUNTER_MASK;
                        continue;
                }
                if (*bmc == 1 && !bitmap->need_sync) {
                        /* We can clear the bit */
                        struct page *page;
                        *bmc = 0;
                        bitmap_count_page(
                                bitmap,
                                (sector_t)j << bitmap->chunkshift,
                                -1);

                        page = filemap_get_page(bitmap, j);
                        paddr = kmap_atomic(page);
                        if (bitmap->flags & BITMAP_HOSTENDIAN)
                                clear_bit(file_page_offset(bitmap, j),
                                          paddr);
                        else
                                __clear_bit_le(file_page_offset(bitmap, j),
                                               paddr);
                        kunmap_atomic(paddr);
                        if (!test_page_attr(bitmap, page,
                                            BITMAP_PAGE_NEEDWRITE)) {
                                set_page_attr(bitmap, page,
                                              BITMAP_PAGE_PENDING);
                                bitmap->allclean = 0;
                        }
                } else if (*bmc && *bmc <= 2) {
                        *bmc = 1;
                        bitmap_set_pending(
                                bitmap,
                                (sector_t)j << bitmap->chunkshift);
                        bitmap->allclean = 0;
                }
        }

        /* Now start writeout on any page in NEEDWRITE that isn't DIRTY.
         * DIRTY pages need to be written by bitmap_unplug so it can wait
         * for them.
         * If we find any DIRTY page we stop there and let bitmap_unplug
         * handle all the rest.  This is important in the case where
         * the first blocking holds the superblock and it has been updated.
         * We mustn't write any other blocks before the superblock.
         */
        for (j = 0; j < bitmap->file_pages; j++) {
                struct page *page = bitmap->filemap[j];

                if (test_page_attr(bitmap, page,
                                   BITMAP_PAGE_DIRTY))
                        /* bitmap_unplug will handle the rest */
                        break;
                if (test_page_attr(bitmap, page,
                                   BITMAP_PAGE_NEEDWRITE)) {
                        clear_page_attr(bitmap, page,
                                        BITMAP_PAGE_NEEDWRITE);
                        spin_unlock_irqrestore(&bitmap->lock, flags);
                        write_page(bitmap, page, 0);
                        spin_lock_irqsave(&bitmap->lock, flags);
                        if (!bitmap->filemap)
                                break;
                }
        }
out:
        spin_unlock_irqrestore(&bitmap->lock, flags);

 done:
        if (bitmap->allclean == 0)
                mddev->thread->timeout =
                        mddev->bitmap_info.daemon_sleep;
        mutex_unlock(&mddev->bitmap_info.mutex);
}

static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
                                            sector_t offset, sector_t *blocks,
                                            int create)
__releases(bitmap->lock)
__acquires(bitmap->lock)
{
        /* If 'create', we might release the lock and reclaim it.
         * The lock must have been taken with interrupts enabled.
         * If !create, we don't release the lock.
         */
        sector_t chunk = offset >> bitmap->chunkshift;
        unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
        unsigned long pageoff = (chunk & PAGE_COUNTER_MASK) << COUNTER_BYTE_SHIFT;
        sector_t csize;
        int err;

        err = bitmap_checkpage(bitmap, page, create);

        if (bitmap->bp[page].hijacked ||
            bitmap->bp[page].map == NULL)
                csize = ((sector_t)1) << (bitmap->chunkshift +
                                          PAGE_COUNTER_SHIFT - 1);
        else
                csize = ((sector_t)1) << bitmap->chunkshift;
        *blocks = csize - (offset & (csize - 1));

        if (err < 0)
                return NULL;

        /* now locked ... */

        if (bitmap->bp[page].hijacked) { /* hijacked pointer */
                /* should we use the first or second counter field
                 * of the hijacked pointer? */
                int hi = (pageoff > PAGE_COUNTER_MASK);
                return  &((bitmap_counter_t *)
                          &bitmap->bp[page].map)[hi];
        } else /* page is allocated */
                return (bitmap_counter_t *)
                        &(bitmap->bp[page].map[pageoff]);
}

int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors, int behind)
{
        if (!bitmap)
                return 0;

        if (behind) {
                int bw;
                atomic_inc(&bitmap->behind_writes);
                bw = atomic_read(&bitmap->behind_writes);
                if (bw > bitmap->behind_writes_used)
                        bitmap->behind_writes_used = bw;

                pr_debug("inc write-behind count %d/%lu\n",
                         bw, bitmap->mddev->bitmap_info.max_write_behind);
        }

        while (sectors) {
                sector_t blocks;
                bitmap_counter_t *bmc;

                spin_lock_irq(&bitmap->lock);
                bmc = bitmap_get_counter(bitmap, offset, &blocks, 1);
                if (!bmc) {
                        spin_unlock_irq(&bitmap->lock);
                        return 0;
                }

                if (unlikely(COUNTER(*bmc) == COUNTER_MAX)) {
                        DEFINE_WAIT(__wait);
                        /* note that it is safe to do the prepare_to_wait
                         * after the test as long as we do it before dropping
                         * the spinlock.
                         */
                        prepare_to_wait(&bitmap->overflow_wait, &__wait,
                                        TASK_UNINTERRUPTIBLE);
                        spin_unlock_irq(&bitmap->lock);
                        io_schedule();
                        finish_wait(&bitmap->overflow_wait, &__wait);
                        continue;
                }

                switch (*bmc) {
                case 0:
                        bitmap_file_set_bit(bitmap, offset);
                        bitmap_count_page(bitmap, offset, 1);
                        /* fall through */
                case 1:
                        *bmc = 2;
                }

                (*bmc)++;

                spin_unlock_irq(&bitmap->lock);

                offset += blocks;
                if (sectors > blocks)
                        sectors -= blocks;
                else
                        sectors = 0;
        }
        return 0;
}
EXPORT_SYMBOL(bitmap_startwrite);

void bitmap_endwrite(struct bitmap *bitmap, sector_t offset, unsigned long sectors,
                     int success, int behind)
{
        if (!bitmap)
                return;
        if (behind) {
                if (atomic_dec_and_test(&bitmap->behind_writes))
                        wake_up(&bitmap->behind_wait);
                pr_debug("dec write-behind count %d/%lu\n",
                         atomic_read(&bitmap->behind_writes),
                         bitmap->mddev->bitmap_info.max_write_behind);
        }

        while (sectors) {
                sector_t blocks;
                unsigned long flags;
                bitmap_counter_t *bmc;

                spin_lock_irqsave(&bitmap->lock, flags);
                bmc = bitmap_get_counter(bitmap, offset, &blocks, 0);
                if (!bmc) {
                        spin_unlock_irqrestore(&bitmap->lock, flags);
                        return;
                }

                if (success && !bitmap->mddev->degraded &&
                    bitmap->events_cleared < bitmap->mddev->events) {
                        bitmap->events_cleared = bitmap->mddev->events;
                        bitmap->need_sync = 1;
                        sysfs_notify_dirent_safe(bitmap->sysfs_can_clear);
                }

                if (!success && !NEEDED(*bmc))
                        *bmc |= NEEDED_MASK;

                if (COUNTER(*bmc) == COUNTER_MAX)
                        wake_up(&bitmap->overflow_wait);

                (*bmc)--;
                if (*bmc <= 2) {
                        bitmap_set_pending(bitmap, offset);
                        bitmap->allclean = 0;
                }
                spin_unlock_irqrestore(&bitmap->lock, flags);
                offset += blocks;
                if (sectors > blocks)
                        sectors -= blocks;
                else
                        sectors = 0;
        }
}
EXPORT_SYMBOL(bitmap_endwrite);

static int __bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks,
                               int degraded)
{
        bitmap_counter_t *bmc;
        int rv;
        if (bitmap == NULL) {/* FIXME or bitmap set as 'failed' */
                *blocks = 1024;
                return 1; /* always resync if no bitmap */
        }
        spin_lock_irq(&bitmap->lock);
        bmc = bitmap_get_counter(bitmap, offset, blocks, 0);
        rv = 0;
        if (bmc) {
                /* locked */
                if (RESYNC(*bmc))
                        rv = 1;
                else if (NEEDED(*bmc)) {
                        rv = 1;
                        if (!degraded) { /* don't set/clear bits if degraded */
                                *bmc |= RESYNC_MASK;
                                *bmc &= ~NEEDED_MASK;
                        }
                }
        }
        spin_unlock_irq(&bitmap->lock);
        return rv;
}

int bitmap_start_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks,
                      int degraded)
{
        /* bitmap_start_sync must always report on multiples of whole
         * pages, otherwise resync (which is very PAGE_SIZE based) will
         * get confused.
         * So call __bitmap_start_sync repeatedly (if needed) until
         * At least PAGE_SIZE>>9 blocks are covered.
         * Return the 'or' of the result.
         */
        int rv = 0;
        sector_t blocks1;

        *blocks = 0;
        while (*blocks < (PAGE_SIZE>>9)) {
                rv |= __bitmap_start_sync(bitmap, offset,
                                          &blocks1, degraded);
                offset += blocks1;
                *blocks += blocks1;
        }
        return rv;
}
EXPORT_SYMBOL(bitmap_start_sync);

void bitmap_end_sync(struct bitmap *bitmap, sector_t offset, sector_t *blocks, int aborted)
{
        bitmap_counter_t *bmc;
        unsigned long flags;

        if (bitmap == NULL) {
                *blocks = 1024;
                return;
        }
        spin_lock_irqsave(&bitmap->lock, flags);
        bmc = bitmap_get_counter(bitmap, offset, blocks, 0);
        if (bmc == NULL)
                goto unlock;
        /* locked */
        if (RESYNC(*bmc)) {
                *bmc &= ~RESYNC_MASK;

                if (!NEEDED(*bmc) && aborted)
                        *bmc |= NEEDED_MASK;
                else {
                        if (*bmc <= 2) {
                                bitmap_set_pending(bitmap, offset);
                                bitmap->allclean = 0;
                        }
                }
        }
 unlock:
        spin_unlock_irqrestore(&bitmap->lock, flags);
}
EXPORT_SYMBOL(bitmap_end_sync);

void bitmap_close_sync(struct bitmap *bitmap)
{
        /* Sync has finished, and any bitmap chunks that weren't synced
         * properly have been aborted.  It remains to us to clear the
         * RESYNC bit wherever it is still on
         */
        sector_t sector = 0;
        sector_t blocks;
        if (!bitmap)
                return;
        while (sector < bitmap->mddev->resync_max_sectors) {
                bitmap_end_sync(bitmap, sector, &blocks, 0);
                sector += blocks;
        }
}
EXPORT_SYMBOL(bitmap_close_sync);

void bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector)
{
        sector_t s = 0;
        sector_t blocks;

        if (!bitmap)
                return;
        if (sector == 0) {
                bitmap->last_end_sync = jiffies;
                return;
        }
        if (time_before(jiffies, (bitmap->last_end_sync
                                  + bitmap->mddev->bitmap_info.daemon_sleep)))
                return;
        wait_event(bitmap->mddev->recovery_wait,
                   atomic_read(&bitmap->mddev->recovery_active) == 0);

        bitmap->mddev->curr_resync_completed = sector;
        set_bit(MD_CHANGE_CLEAN, &bitmap->mddev->flags);
        sector &= ~((1ULL << bitmap->chunkshift) - 1);
        s = 0;
        while (s < sector && s < bitmap->mddev->resync_max_sectors) {
                bitmap_end_sync(bitmap, s, &blocks, 0);
                s += blocks;
        }
        bitmap->last_end_sync = jiffies;
        sysfs_notify(&bitmap->mddev->kobj, NULL, "sync_completed");
}
EXPORT_SYMBOL(bitmap_cond_end_sync);

static void bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int needed)
{
        /* For each chunk covered by any of these sectors, set the
         * counter to 1 and set resync_needed.  They should all
         * be 0 at this point
         */

        sector_t secs;
        bitmap_counter_t *bmc;
        spin_lock_irq(&bitmap->lock);
        bmc = bitmap_get_counter(bitmap, offset, &secs, 1);
        if (!bmc) {
                spin_unlock_irq(&bitmap->lock);
                return;
        }
        if (!*bmc) {
                *bmc = 2 | (needed ? NEEDED_MASK : 0);
                bitmap_count_page(bitmap, offset, 1);
                bitmap_set_pending(bitmap, offset);
                bitmap->allclean = 0;
        }
        spin_unlock_irq(&bitmap->lock);
}

/* dirty the memory and file bits for bitmap chunks "s" to "e" */
void bitmap_dirty_bits(struct bitmap *bitmap, unsigned long s, unsigned long e)
{
        unsigned long chunk;

        for (chunk = s; chunk <= e; chunk++) {
                sector_t sec = (sector_t)chunk << bitmap->chunkshift;
                bitmap_set_memory_bits(bitmap, sec, 1);
                spin_lock_irq(&bitmap->lock);
                bitmap_file_set_bit(bitmap, sec);
                spin_unlock_irq(&bitmap->lock);
                if (sec < bitmap->mddev->recovery_cp)
                        /* We are asserting that the array is dirty,
                         * so move the recovery_cp address back so
                         * that it is obvious that it is dirty
                         */
                        bitmap->mddev->recovery_cp = sec;
        }
}

/*
 * flush out any pending updates
 */
void bitmap_flush(struct mddev *mddev)
{
        struct bitmap *bitmap = mddev->bitmap;
        long sleep;

        if (!bitmap) /* there was no bitmap */
                return;

        /* run the daemon_work three time to ensure everything is flushed
         * that can be
         */
        sleep = mddev->bitmap_info.daemon_sleep * 2;
        bitmap->daemon_lastrun -= sleep;
        bitmap_daemon_work(mddev);
        bitmap->daemon_lastrun -= sleep;
        bitmap_daemon_work(mddev);
        bitmap->daemon_lastrun -= sleep;
        bitmap_daemon_work(mddev);
        bitmap_update_sb(bitmap);
}

/*
 * free memory that was allocated
 */
static void bitmap_free(struct bitmap *bitmap)
{
        unsigned long k, pages;
        struct bitmap_page *bp;

        if (!bitmap) /* there was no bitmap */
                return;

        /* release the bitmap file and kill the daemon */
        bitmap_file_put(bitmap);

        bp = bitmap->bp;
        pages = bitmap->pages;

        /* free all allocated memory */

        if (bp) /* deallocate the page memory */
                for (k = 0; k < pages; k++)
                        if (bp[k].map && !bp[k].hijacked)
                                kfree(bp[k].map);
        kfree(bp);
        kfree(bitmap);
}

void bitmap_destroy(struct mddev *mddev)
{
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap) /* there was no bitmap */
                return;

        mutex_lock(&mddev->bitmap_info.mutex);
        mddev->bitmap = NULL; /* disconnect from the md device */
        mutex_unlock(&mddev->bitmap_info.mutex);
        if (mddev->thread)
                mddev->thread->timeout = MAX_SCHEDULE_TIMEOUT;

        if (bitmap->sysfs_can_clear)
                sysfs_put(bitmap->sysfs_can_clear);

        bitmap_free(bitmap);
}

/*
 * initialize the bitmap structure
 * if this returns an error, bitmap_destroy must be called to do clean up
 */
int bitmap_create(struct mddev *mddev)
{
        struct bitmap *bitmap;
        sector_t blocks = mddev->resync_max_sectors;
        unsigned long chunks;
        unsigned long pages;
        struct file *file = mddev->bitmap_info.file;
        int err;
        struct sysfs_dirent *bm = NULL;

        BUILD_BUG_ON(sizeof(bitmap_super_t) != 256);

        if (!file
            && !mddev->bitmap_info.offset) /* bitmap disabled, nothing to do */
                return 0;

        BUG_ON(file && mddev->bitmap_info.offset);

        bitmap = kzalloc(sizeof(*bitmap), GFP_KERNEL);
        if (!bitmap)
                return -ENOMEM;

        spin_lock_init(&bitmap->lock);
        atomic_set(&bitmap->pending_writes, 0);
        init_waitqueue_head(&bitmap->write_wait);
        init_waitqueue_head(&bitmap->overflow_wait);
        init_waitqueue_head(&bitmap->behind_wait);

        bitmap->mddev = mddev;

        if (mddev->kobj.sd)
                bm = sysfs_get_dirent(mddev->kobj.sd, NULL, "bitmap");
        if (bm) {
                bitmap->sysfs_can_clear = sysfs_get_dirent(bm, NULL, "can_clear");
                sysfs_put(bm);
        } else
                bitmap->sysfs_can_clear = NULL;

        bitmap->file = file;
        if (file) {
                get_file(file);
                /* As future accesses to this file will use bmap,
                 * and bypass the page cache, we must sync the file
                 * first.
                 */
                vfs_fsync(file, 1);
        }
        /* read superblock from bitmap file (this sets mddev->bitmap_info.chunksize) */
        if (!mddev->bitmap_info.external) {
                /*
                 * If 'MD_ARRAY_FIRST_USE' is set, then device-mapper is
                 * instructing us to create a new on-disk bitmap instance.
                 */
                if (test_and_clear_bit(MD_ARRAY_FIRST_USE, &mddev->flags))
                        err = bitmap_new_disk_sb(bitmap);
                else
                        err = bitmap_read_sb(bitmap);
        } else {
                err = 0;
                if (mddev->bitmap_info.chunksize == 0 ||
                    mddev->bitmap_info.daemon_sleep == 0)
                        /* chunksize and time_base need to be
                         * set first. */
                        err = -EINVAL;
        }
        if (err)
                goto error;

        bitmap->daemon_lastrun = jiffies;
        bitmap->chunkshift = (ffz(~mddev->bitmap_info.chunksize)
                              - BITMAP_BLOCK_SHIFT);

        chunks = (blocks + (1 << bitmap->chunkshift) - 1) >>
                        bitmap->chunkshift;
        pages = (chunks + PAGE_COUNTER_RATIO - 1) / PAGE_COUNTER_RATIO;

        BUG_ON(!pages);

        bitmap->chunks = chunks;
        bitmap->pages = pages;
        bitmap->missing_pages = pages;

        bitmap->bp = kzalloc(pages * sizeof(*bitmap->bp), GFP_KERNEL);

        err = -ENOMEM;
        if (!bitmap->bp)
                goto error;

        printk(KERN_INFO "created bitmap (%lu pages) for device %s\n",
                pages, bmname(bitmap));

        mddev->bitmap = bitmap;


        return (bitmap->flags & BITMAP_WRITE_ERROR) ? -EIO : 0;

 error:
        bitmap_free(bitmap);
        return err;
}

int bitmap_load(struct mddev *mddev)
{
        int err = 0;
        sector_t start = 0;
        sector_t sector = 0;
        struct bitmap *bitmap = mddev->bitmap;

        if (!bitmap)
                goto out;

        /* Clear out old bitmap info first:  Either there is none, or we
         * are resuming after someone else has possibly changed things,
         * so we should forget old cached info.
         * All chunks should be clean, but some might need_sync.
         */
        while (sector < mddev->resync_max_sectors) {
                sector_t blocks;
                bitmap_start_sync(bitmap, sector, &blocks, 0);
                sector += blocks;
        }
        bitmap_close_sync(bitmap);

        if (mddev->degraded == 0
            || bitmap->events_cleared == mddev->events)
                /* no need to keep dirty bits to optimise a
                 * re-add of a missing device */
                start = mddev->recovery_cp;

        mutex_lock(&mddev->bitmap_info.mutex);
        err = bitmap_init_from_disk(bitmap, start);
        mutex_unlock(&mddev->bitmap_info.mutex);

        if (err)
                goto out;

        mddev->thread->timeout = mddev->bitmap_info.daemon_sleep;
        md_wakeup_thread(mddev->thread);

        bitmap_update_sb(bitmap);

        if (bitmap->flags & BITMAP_WRITE_ERROR)
                err = -EIO;
out:
        return err;
}
EXPORT_SYMBOL_GPL(bitmap_load);

void bitmap_status(struct seq_file *seq, struct bitmap *bitmap)
{
        unsigned long chunk_kb;
        unsigned long flags;

        if (!bitmap)
                return;

        spin_lock_irqsave(&bitmap->lock, flags);
        chunk_kb = bitmap->mddev->bitmap_info.chunksize >> 10;
        seq_printf(seq, "bitmap: %lu/%lu pages [%luKB], "
                   "%lu%s chunk",
                   bitmap->pages - bitmap->missing_pages,
                   bitmap->pages,
                   (bitmap->pages - bitmap->missing_pages)
                   << (PAGE_SHIFT - 10),
                   chunk_kb ? chunk_kb : bitmap->mddev->bitmap_info.chunksize,
                   chunk_kb ? "KB" : "B");
        if (bitmap->file) {
                seq_printf(seq, ", file: ");
                seq_path(seq, &bitmap->file->f_path, " \t\n");
        }

        seq_printf(seq, "\n");
        spin_unlock_irqrestore(&bitmap->lock, flags);
}

static ssize_t
location_show(struct mddev *mddev, char *page)
{
        ssize_t len;
        if (mddev->bitmap_info.file)
                len = sprintf(page, "file");
        else if (mddev->bitmap_info.offset)
                len = sprintf(page, "%+lld", (long long)mddev->bitmap_info.offset);
        else
                len = sprintf(page, "none");
        len += sprintf(page+len, "\n");
        return len;
}

static ssize_t
location_store(struct mddev *mddev, const char *buf, size_t len)
{

        if (mddev->pers) {
                if (!mddev->pers->quiesce)
                        return -EBUSY;
                if (mddev->recovery || mddev->sync_thread)
                        return -EBUSY;
        }

        if (mddev->bitmap || mddev->bitmap_info.file ||
            mddev->bitmap_info.offset) {
                /* bitmap already configured.  Only option is to clear it */
                if (strncmp(buf, "none", 4) != 0)
                        return -EBUSY;
                if (mddev->pers) {
                        mddev->pers->quiesce(mddev, 1);
                        bitmap_destroy(mddev);
                        mddev->pers->quiesce(mddev, 0);
                }
                mddev->bitmap_info.offset = 0;
                if (mddev->bitmap_info.file) {
                        struct file *f = mddev->bitmap_info.file;
                        mddev->bitmap_info.file = NULL;
                        restore_bitmap_write_access(f);
                        fput(f);
                }
        } else {
                /* No bitmap, OK to set a location */
                long long offset;
                if (strncmp(buf, "none", 4) == 0)
                        /* nothing to be done */;
                else if (strncmp(buf, "file:", 5) == 0) {
                        /* Not supported yet */
                        return -EINVAL;
                } else {
                        int rv;
                        if (buf[0] == '+')
                                rv = strict_strtoll(buf+1, 10, &offset);
                        else
                                rv = strict_strtoll(buf, 10, &offset);
                        if (rv)
                                return rv;
                        if (offset == 0)
                                return -EINVAL;
                        if (mddev->bitmap_info.external == 0 &&
                            mddev->major_version == 0 &&
                            offset != mddev->bitmap_info.default_offset)
                                return -EINVAL;
                        mddev->bitmap_info.offset = offset;
                        if (mddev->pers) {
                                mddev->pers->quiesce(mddev, 1);
                                rv = bitmap_create(mddev);
                                if (!rv)
                                        rv = bitmap_load(mddev);
                                if (rv) {
                                        bitmap_destroy(mddev);
                                        mddev->bitmap_info.offset = 0;
                                }
                                mddev->pers->quiesce(mddev, 0);
                                if (rv)
                                        return rv;
                        }
                }
        }
        if (!mddev->external) {
                /* Ensure new bitmap info is stored in
                 * metadata promptly.
                 */
                set_bit(MD_CHANGE_DEVS, &mddev->flags);
                md_wakeup_thread(mddev->thread);
        }
        return len;
}

static struct md_sysfs_entry bitmap_location =
__ATTR(location, S_IRUGO|S_IWUSR, location_show, location_store);

static ssize_t
timeout_show(struct mddev *mddev, char *page)
{
        ssize_t len;
        unsigned long secs = mddev->bitmap_info.daemon_sleep / HZ;
        unsigned long jifs = mddev->bitmap_info.daemon_sleep % HZ;

        len = sprintf(page, "%lu", secs);
        if (jifs)
                len += sprintf(page+len, ".%03u", jiffies_to_msecs(jifs));
        len += sprintf(page+len, "\n");
        return len;
}

static ssize_t
timeout_store(struct mddev *mddev, const char *buf, size_t len)
{
        /* timeout can be set at any time */
        unsigned long timeout;
        int rv = strict_strtoul_scaled(buf, &timeout, 4);
        if (rv)
                return rv;

        /* just to make sure we don't overflow... */
        if (timeout >= LONG_MAX / HZ)
                return -EINVAL;

        timeout = timeout * HZ / 10000;

        if (timeout >= MAX_SCHEDULE_TIMEOUT)
                timeout = MAX_SCHEDULE_TIMEOUT-1;
        if (timeout < 1)
                timeout = 1;
        mddev->bitmap_info.daemon_sleep = timeout;
        if (mddev->thread) {
                /* if thread->timeout is MAX_SCHEDULE_TIMEOUT, then
                 * the bitmap is all clean and we don't need to
                 * adjust the timeout right now
                 */
                if (mddev->thread->timeout < MAX_SCHEDULE_TIMEOUT) {
                        mddev->thread->timeout = timeout;
                        md_wakeup_thread(mddev->thread);
                }
        }
        return len;
}

static struct md_sysfs_entry bitmap_timeout =
__ATTR(time_base, S_IRUGO|S_IWUSR, timeout_show, timeout_store);

static ssize_t
backlog_show(struct mddev *mddev, char *page)
{
        return sprintf(page, "%lu\n", mddev->bitmap_info.max_write_behind);
}

static ssize_t
backlog_store(struct mddev *mddev, const char *buf, size_t len)
{
        unsigned long backlog;
        int rv = strict_strtoul(buf, 10, &backlog);
        if (rv)
                return rv;
        if (backlog > COUNTER_MAX)
                return -EINVAL;
        mddev->bitmap_info.max_write_behind = backlog;
        return len;
}

static struct md_sysfs_entry bitmap_backlog =
__ATTR(backlog, S_IRUGO|S_IWUSR, backlog_show, backlog_store);

static ssize_t
chunksize_show(struct mddev *mddev, char *page)
{
        return sprintf(page, "%lu\n", mddev->bitmap_info.chunksize);
}

static ssize_t
chunksize_store(struct mddev *mddev, const char *buf, size_t len)
{
        /* Can only be changed when no bitmap is active */
        int rv;
        unsigned long csize;
        if (mddev->bitmap)
                return -EBUSY;
        rv = strict_strtoul(buf, 10, &csize);
        if (rv)
                return rv;
        if (csize < 512 ||
            !is_power_of_2(csize))
                return -EINVAL;
        mddev->bitmap_info.chunksize = csize;
        return len;
}

static struct md_sysfs_entry bitmap_chunksize =
__ATTR(chunksize, S_IRUGO|S_IWUSR, chunksize_show, chunksize_store);

static ssize_t metadata_show(struct mddev *mddev, char *page)
{
        return sprintf(page, "%s\n", (mddev->bitmap_info.external
                                      ? "external" : "internal"));
}

static ssize_t metadata_store(struct mddev *mddev, const char *buf, size_t len)
{
        if (mddev->bitmap ||
            mddev->bitmap_info.file ||
            mddev->bitmap_info.offset)
                return -EBUSY;
        if (strncmp(buf, "external", 8) == 0)
                mddev->bitmap_info.external = 1;
        else if (strncmp(buf, "internal", 8) == 0)
                mddev->bitmap_info.external = 0;
        else
                return -EINVAL;
        return len;
}

static struct md_sysfs_entry bitmap_metadata =
__ATTR(metadata, S_IRUGO|S_IWUSR, metadata_show, metadata_store);

static ssize_t can_clear_show(struct mddev *mddev, char *page)
{
        int len;
        if (mddev->bitmap)
                len = sprintf(page, "%s\n", (mddev->bitmap->need_sync ?
                                             "false" : "true"));
        else
                len = sprintf(page, "\n");
        return len;
}

static ssize_t can_clear_store(struct mddev *mddev, const char *buf, size_t len)
{
        if (mddev->bitmap == NULL)
                return -ENOENT;
        if (strncmp(buf, "false", 5) == 0)
                mddev->bitmap->need_sync = 1;
        else if (strncmp(buf, "true", 4) == 0) {
                if (mddev->degraded)
                        return -EBUSY;
                mddev->bitmap->need_sync = 0;
        } else
                return -EINVAL;
        return len;
}

static struct md_sysfs_entry bitmap_can_clear =
__ATTR(can_clear, S_IRUGO|S_IWUSR, can_clear_show, can_clear_store);

static ssize_t
behind_writes_used_show(struct mddev *mddev, char *page)
{
        if (mddev->bitmap == NULL)
                return sprintf(page, "0\n");
        return sprintf(page, "%lu\n",
                       mddev->bitmap->behind_writes_used);
}

static ssize_t
behind_writes_used_reset(struct mddev *mddev, const char *buf, size_t len)
{
        if (mddev->bitmap)
                mddev->bitmap->behind_writes_used = 0;
        return len;
}

static struct md_sysfs_entry max_backlog_used =
__ATTR(max_backlog_used, S_IRUGO | S_IWUSR,
       behind_writes_used_show, behind_writes_used_reset);

static struct attribute *md_bitmap_attrs[] = {
        &bitmap_location.attr,
        &bitmap_timeout.attr,
        &bitmap_backlog.attr,
        &bitmap_chunksize.attr,
        &bitmap_metadata.attr,
        &bitmap_can_clear.attr,
        &max_backlog_used.attr,
        NULL
};
struct attribute_group md_bitmap_group = {
        .name = "bitmap",
        .attrs = md_bitmap_attrs,
};