Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2718 insertions, 0 deletions

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
new file mode 100644
index 0000000000..6f9ff14971
--- /dev/null
+++ b/drivers/md/md-bitmap.c
@@ -0,0 +1,2718 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 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 <trace/events/block.h>
+#include "md.h"
+#include "md-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 md_bitmap_checkpage(struct bitmap_counts *bitmap,
+			       unsigned long page, int create, int no_hijack)
+__releases(bitmap->lock)
+__acquires(bitmap->lock)
+{
+	unsigned char *mappage;
+
+	WARN_ON_ONCE(page >= bitmap->pages);
+	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);
+	/* It is possible that this is being called inside a
+	 * prepare_to_wait/finish_wait loop from raid5c:make_request().
+	 * In general it is not permitted to sleep in that context as it
+	 * can cause the loop to spin freely.
+	 * That doesn't apply here as we can only reach this point
+	 * once with any loop.
+	 * When this function completes, either bp[page].map or
+	 * bp[page].hijacked.  In either case, this function will
+	 * abort before getting to this point again.  So there is
+	 * no risk of a free-spin, and so it is safe to assert
+	 * that sleeping here is allowed.
+	 */
+	sched_annotate_sleep();
+	mappage = kzalloc(PAGE_SIZE, GFP_NOIO);
+	spin_lock_irq(&bitmap->lock);
+
+	if (mappage == NULL) {
+		pr_debug("md/bitmap: map page allocation failed, hijacking\n");
+		/* We don't support hijack for cluster raid */
+		if (no_hijack)
+			return -ENOMEM;
+		/* 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);
+	} 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 md_bitmap_checkfree(struct bitmap_counts *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 */
+
+/* choose a good rdev and read the page from there */
+static int read_sb_page(struct mddev *mddev, loff_t offset,
+		struct page *page, unsigned long index, int size)
+{
+
+	sector_t sector = mddev->bitmap_info.offset + offset +
+		index * (PAGE_SIZE / SECTOR_SIZE);
+	struct md_rdev *rdev;
+
+	rdev_for_each(rdev, mddev) {
+		u32 iosize = roundup(size, bdev_logical_block_size(rdev->bdev));
+
+		if (!test_bit(In_sync, &rdev->flags) ||
+		    test_bit(Faulty, &rdev->flags) ||
+		    test_bit(Bitmap_sync, &rdev->flags))
+			continue;
+
+		if (sync_page_io(rdev, sector, iosize, page, REQ_OP_READ, true))
+			return 0;
+	}
+	return -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_entry_continue_rcu.
+	 *
+	 * Note that if entered with 'rdev == NULL' to start at the
+	 * beginning, we temporarily assign 'rdev' to an address which
+	 * isn't really an rdev, but which can be used by
+	 * list_for_each_entry_continue_rcu() to find the first entry.
+	 */
+	rcu_read_lock();
+	if (rdev == NULL)
+		/* start at the beginning */
+		rdev = list_entry(&mddev->disks, struct md_rdev, same_set);
+	else {
+		/* release the previous rdev and start from there. */
+		rdev_dec_pending(rdev, mddev);
+	}
+	list_for_each_entry_continue_rcu(rdev, &mddev->disks, 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 unsigned int optimal_io_size(struct block_device *bdev,
+				    unsigned int last_page_size,
+				    unsigned int io_size)
+{
+	if (bdev_io_opt(bdev) > bdev_logical_block_size(bdev))
+		return roundup(last_page_size, bdev_io_opt(bdev));
+	return io_size;
+}
+
+static unsigned int bitmap_io_size(unsigned int io_size, unsigned int opt_size,
+				   loff_t start, loff_t boundary)
+{
+	if (io_size != opt_size &&
+	    start + opt_size / SECTOR_SIZE <= boundary)
+		return opt_size;
+	if (start + io_size / SECTOR_SIZE <= boundary)
+		return io_size;
+
+	/* Overflows boundary */
+	return 0;
+}
+
+static int __write_sb_page(struct md_rdev *rdev, struct bitmap *bitmap,
+			   unsigned long pg_index, struct page *page)
+{
+	struct block_device *bdev;
+	struct mddev *mddev = bitmap->mddev;
+	struct bitmap_storage *store = &bitmap->storage;
+	loff_t sboff, offset = mddev->bitmap_info.offset;
+	sector_t ps = pg_index * PAGE_SIZE / SECTOR_SIZE;
+	unsigned int size = PAGE_SIZE;
+	unsigned int opt_size = PAGE_SIZE;
+	sector_t doff;
+
+	bdev = (rdev->meta_bdev) ? rdev->meta_bdev : rdev->bdev;
+	if (pg_index == store->file_pages - 1) {
+		unsigned int last_page_size = store->bytes & (PAGE_SIZE - 1);
+
+		if (last_page_size == 0)
+			last_page_size = PAGE_SIZE;
+		size = roundup(last_page_size, bdev_logical_block_size(bdev));
+		opt_size = optimal_io_size(bdev, last_page_size, size);
+	}
+
+	sboff = rdev->sb_start + offset;
+	doff = rdev->data_offset;
+
+	/* Just make sure we aren't corrupting data or metadata */
+	if (mddev->external) {
+		/* Bitmap could be anywhere. */
+		if (sboff + ps > doff &&
+		    sboff < (doff + mddev->dev_sectors + PAGE_SIZE / SECTOR_SIZE))
+			return -EINVAL;
+	} else if (offset < 0) {
+		/* DATA  BITMAP METADATA  */
+		size = bitmap_io_size(size, opt_size, offset + ps, 0);
+		if (size == 0)
+			/* bitmap runs in to metadata */
+			return -EINVAL;
+
+		if (doff + mddev->dev_sectors > sboff)
+			/* data runs in to bitmap */
+			return -EINVAL;
+	} else if (rdev->sb_start < rdev->data_offset) {
+		/* METADATA BITMAP DATA */
+		size = bitmap_io_size(size, opt_size, sboff + ps, doff);
+		if (size == 0)
+			/* bitmap runs in to data */
+			return -EINVAL;
+	} else {
+		/* DATA METADATA BITMAP - no problems */
+	}
+
+	md_super_write(mddev, rdev, sboff + ps, (int) size, page);
+	return 0;
+}
+
+static void write_sb_page(struct bitmap *bitmap, unsigned long pg_index,
+			  struct page *page, bool wait)
+{
+	struct mddev *mddev = bitmap->mddev;
+
+	do {
+		struct md_rdev *rdev = NULL;
+
+		while ((rdev = next_active_rdev(rdev, mddev)) != NULL) {
+			if (__write_sb_page(rdev, bitmap, pg_index, page) < 0) {
+				set_bit(BITMAP_WRITE_ERROR, &bitmap->flags);
+				return;
+			}
+		}
+	} while (wait && md_super_wait(mddev) < 0);
+}
+
+static void md_bitmap_file_kick(struct bitmap *bitmap);
+
+#ifdef CONFIG_MD_BITMAP_FILE
+static void write_file_page(struct bitmap *bitmap, struct page *page, int wait)
+{
+	struct buffer_head *bh = page_buffers(page);
+
+	while (bh && bh->b_blocknr) {
+		atomic_inc(&bitmap->pending_writes);
+		set_buffer_locked(bh);
+		set_buffer_mapped(bh);
+		submit_bh(REQ_OP_WRITE | REQ_SYNC, bh);
+		bh = bh->b_this_page;
+	}
+
+	if (wait)
+		wait_event(bitmap->write_wait,
+			   atomic_read(&bitmap->pending_writes) == 0);
+}
+
+static void end_bitmap_write(struct buffer_head *bh, int uptodate)
+{
+	struct bitmap *bitmap = bh->b_private;
+
+	if (!uptodate)
+		set_bit(BITMAP_WRITE_ERROR, &bitmap->flags);
+	if (atomic_dec_and_test(&bitmap->pending_writes))
+		wake_up(&bitmap->write_wait);
+}
+
+static void free_buffers(struct page *page)
+{
+	struct buffer_head *bh;
+
+	if (!PagePrivate(page))
+		return;
+
+	bh = page_buffers(page);
+	while (bh) {
+		struct buffer_head *next = bh->b_this_page;
+		free_buffer_head(bh);
+		bh = next;
+	}
+	detach_page_private(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 int read_file_page(struct file *file, unsigned long index,
+		struct bitmap *bitmap, unsigned long count, struct page *page)
+{
+	int ret = 0;
+	struct inode *inode = file_inode(file);
+	struct buffer_head *bh;
+	sector_t block, blk_cur;
+	unsigned long blocksize = i_blocksize(inode);
+
+	pr_debug("read bitmap file (%dB @ %llu)\n", (int)PAGE_SIZE,
+		 (unsigned long long)index << PAGE_SHIFT);
+
+	bh = alloc_page_buffers(page, blocksize, false);
+	if (!bh) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	attach_page_private(page, bh);
+	blk_cur = index << (PAGE_SHIFT - inode->i_blkbits);
+	while (bh) {
+		block = blk_cur;
+
+		if (count == 0)
+			bh->b_blocknr = 0;
+		else {
+			ret = bmap(inode, &block);
+			if (ret || !block) {
+				ret = -EINVAL;
+				bh->b_blocknr = 0;
+				goto out;
+			}
+
+			bh->b_blocknr = block;
+			bh->b_bdev = inode->i_sb->s_bdev;
+			if (count < blocksize)
+				count = 0;
+			else
+				count -= blocksize;
+
+			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(REQ_OP_READ, bh);
+		}
+		blk_cur++;
+		bh = bh->b_this_page;
+	}
+
+	wait_event(bitmap->write_wait,
+		   atomic_read(&bitmap->pending_writes)==0);
+	if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))
+		ret = -EIO;
+out:
+	if (ret)
+		pr_err("md: bitmap read error: (%dB @ %llu): %d\n",
+		       (int)PAGE_SIZE,
+		       (unsigned long long)index << PAGE_SHIFT,
+		       ret);
+	return ret;
+}
+#else /* CONFIG_MD_BITMAP_FILE */
+static void write_file_page(struct bitmap *bitmap, struct page *page, int wait)
+{
+}
+static int read_file_page(struct file *file, unsigned long index,
+		struct bitmap *bitmap, unsigned long count, struct page *page)
+{
+	return -EIO;
+}
+static void free_buffers(struct page *page)
+{
+	put_page(page);
+}
+#endif /* CONFIG_MD_BITMAP_FILE */
+
+/*
+ * bitmap file superblock operations
+ */
+
+/*
+ * write out a page to a file
+ */
+static void filemap_write_page(struct bitmap *bitmap, unsigned long pg_index,
+			       bool wait)
+{
+	struct bitmap_storage *store = &bitmap->storage;
+	struct page *page = store->filemap[pg_index];
+
+	if (mddev_is_clustered(bitmap->mddev)) {
+		pg_index += bitmap->cluster_slot *
+			DIV_ROUND_UP(store->bytes, PAGE_SIZE);
+	}
+
+	if (store->file)
+		write_file_page(bitmap, page, wait);
+	else
+		write_sb_page(bitmap, pg_index, page, wait);
+}
+
+/*
+ * md_bitmap_wait_writes() should be called before writing any bitmap
+ * blocks, to ensure previous writes, particularly from
+ * md_bitmap_daemon_work(), have completed.
+ */
+static void md_bitmap_wait_writes(struct bitmap *bitmap)
+{
+	if (bitmap->storage.file)
+		wait_event(bitmap->write_wait,
+			   atomic_read(&bitmap->pending_writes)==0);
+	else
+		/* Note that we ignore the return value.  The writes
+		 * might have failed, but that would just mean that
+		 * some bits which should be cleared haven't been,
+		 * which is safe.  The relevant bitmap blocks will
+		 * probably get written again, but there is no great
+		 * loss if they aren't.
+		 */
+		md_super_wait(bitmap->mddev);
+}
+
+
+/* update the event counter and sync the superblock to disk */
+void md_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->storage.sb_page) /* no superblock */
+		return;
+	sb = kmap_atomic(bitmap->storage.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);
+	/*
+	 * clear BITMAP_WRITE_ERROR bit to protect against the case that
+	 * a bitmap write error occurred but the later writes succeeded.
+	 */
+	sb->state = cpu_to_le32(bitmap->flags & ~BIT(BITMAP_WRITE_ERROR));
+	/* 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);
+	/* This might have been changed by a reshape */
+	sb->sync_size = cpu_to_le64(bitmap->mddev->resync_max_sectors);
+	sb->chunksize = cpu_to_le32(bitmap->mddev->bitmap_info.chunksize);
+	sb->nodes = cpu_to_le32(bitmap->mddev->bitmap_info.nodes);
+	sb->sectors_reserved = cpu_to_le32(bitmap->mddev->
+					   bitmap_info.space);
+	kunmap_atomic(sb);
+
+	if (bitmap->storage.file)
+		write_file_page(bitmap, bitmap->storage.sb_page, 1);
+	else
+		write_sb_page(bitmap, bitmap->storage.sb_index,
+			      bitmap->storage.sb_page, 1);
+}
+EXPORT_SYMBOL(md_bitmap_update_sb);
+
+/* print out the bitmap file superblock */
+void md_bitmap_print_sb(struct bitmap *bitmap)
+{
+	bitmap_super_t *sb;
+
+	if (!bitmap || !bitmap->storage.sb_page)
+		return;
+	sb = kmap_atomic(bitmap->storage.sb_page);
+	pr_debug("%s: bitmap file superblock:\n", bmname(bitmap));
+	pr_debug("         magic: %08x\n", le32_to_cpu(sb->magic));
+	pr_debug("       version: %u\n", le32_to_cpu(sb->version));
+	pr_debug("          uuid: %08x.%08x.%08x.%08x\n",
+		 le32_to_cpu(*(__le32 *)(sb->uuid+0)),
+		 le32_to_cpu(*(__le32 *)(sb->uuid+4)),
+		 le32_to_cpu(*(__le32 *)(sb->uuid+8)),
+		 le32_to_cpu(*(__le32 *)(sb->uuid+12)));
+	pr_debug("        events: %llu\n",
+		 (unsigned long long) le64_to_cpu(sb->events));
+	pr_debug("events cleared: %llu\n",
+		 (unsigned long long) le64_to_cpu(sb->events_cleared));
+	pr_debug("         state: %08x\n", le32_to_cpu(sb->state));
+	pr_debug("     chunksize: %u B\n", le32_to_cpu(sb->chunksize));
+	pr_debug("  daemon sleep: %us\n", le32_to_cpu(sb->daemon_sleep));
+	pr_debug("     sync size: %llu KB\n",
+		 (unsigned long long)le64_to_cpu(sb->sync_size)/2);
+	pr_debug("max write behind: %u\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 md_bitmap_new_disk_sb(struct bitmap *bitmap)
+{
+	bitmap_super_t *sb;
+	unsigned long chunksize, daemon_sleep, write_behind;
+
+	bitmap->storage.sb_page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+	if (bitmap->storage.sb_page == NULL)
+		return -ENOMEM;
+	bitmap->storage.sb_index = 0;
+
+	sb = kmap_atomic(bitmap->storage.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);
+		pr_warn("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 > MAX_SCHEDULE_TIMEOUT)) {
+		pr_debug("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);
+
+	set_bit(BITMAP_STALE, &bitmap->flags);
+	sb->state = cpu_to_le32(bitmap->flags);
+	bitmap->events_cleared = bitmap->mddev->events;
+	sb->events_cleared = cpu_to_le64(bitmap->mddev->events);
+	bitmap->mddev->bitmap_info.nodes = 0;
+
+	kunmap_atomic(sb);
+
+	return 0;
+}
+
+/* read the superblock from the bitmap file and initialize some bitmap fields */
+static int md_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 nodes = 0;
+	unsigned long sectors_reserved = 0;
+	int err = -EINVAL;
+	struct page *sb_page;
+	loff_t offset = 0;
+
+	if (!bitmap->storage.file && !bitmap->mddev->bitmap_info.offset) {
+		chunksize = 128 * 1024 * 1024;
+		daemon_sleep = 5 * HZ;
+		write_behind = 0;
+		set_bit(BITMAP_STALE, &bitmap->flags);
+		err = 0;
+		goto out_no_sb;
+	}
+	/* page 0 is the superblock, read it... */
+	sb_page = alloc_page(GFP_KERNEL);
+	if (!sb_page)
+		return -ENOMEM;
+	bitmap->storage.sb_page = sb_page;
+
+re_read:
+	/* If cluster_slot is set, the cluster is setup */
+	if (bitmap->cluster_slot >= 0) {
+		sector_t bm_blocks = bitmap->mddev->resync_max_sectors;
+
+		bm_blocks = DIV_ROUND_UP_SECTOR_T(bm_blocks,
+			   (bitmap->mddev->bitmap_info.chunksize >> 9));
+		/* bits to bytes */
+		bm_blocks = ((bm_blocks+7) >> 3) + sizeof(bitmap_super_t);
+		/* to 4k blocks */
+		bm_blocks = DIV_ROUND_UP_SECTOR_T(bm_blocks, 4096);
+		offset = bitmap->cluster_slot * (bm_blocks << 3);
+		pr_debug("%s:%d bm slot: %d offset: %llu\n", __func__, __LINE__,
+			bitmap->cluster_slot, offset);
+	}
+
+	if (bitmap->storage.file) {
+		loff_t isize = i_size_read(bitmap->storage.file->f_mapping->host);
+		int bytes = isize > PAGE_SIZE ? PAGE_SIZE : isize;
+
+		err = read_file_page(bitmap->storage.file, 0,
+				bitmap, bytes, sb_page);
+	} else {
+		err = read_sb_page(bitmap->mddev, offset, sb_page, 0,
+				   sizeof(bitmap_super_t));
+	}
+	if (err)
+		return err;
+
+	err = -EINVAL;
+	sb = kmap_atomic(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);
+	sectors_reserved = le32_to_cpu(sb->sectors_reserved);
+
+	/* 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_CLUSTERED)
+		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) {
+		pr_warn("%s: invalid bitmap file superblock: %s\n",
+			bmname(bitmap), reason);
+		goto out;
+	}
+
+	/*
+	 * Setup nodes/clustername only if bitmap version is
+	 * cluster-compatible
+	 */
+	if (sb->version == cpu_to_le32(BITMAP_MAJOR_CLUSTERED)) {
+		nodes = le32_to_cpu(sb->nodes);
+		strscpy(bitmap->mddev->bitmap_info.cluster_name,
+				sb->cluster_name, 64);
+	}
+
+	/* 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)) {
+			pr_warn("%s: bitmap superblock UUID mismatch\n",
+				bmname(bitmap));
+			goto out;
+		}
+		events = le64_to_cpu(sb->events);
+		if (!nodes && (events < bitmap->mddev->events)) {
+			pr_warn("%s: bitmap file is out of date (%llu < %llu) -- forcing full recovery\n",
+				bmname(bitmap), events,
+				(unsigned long long) bitmap->mddev->events);
+			set_bit(BITMAP_STALE, &bitmap->flags);
+		}
+	}
+
+	/* assign fields using values from superblock */
+	bitmap->flags |= le32_to_cpu(sb->state);
+	if (le32_to_cpu(sb->version) == BITMAP_MAJOR_HOSTENDIAN)
+		set_bit(BITMAP_HOSTENDIAN, &bitmap->flags);
+	bitmap->events_cleared = le64_to_cpu(sb->events_cleared);
+	err = 0;
+
+out:
+	kunmap_atomic(sb);
+	if (err == 0 && nodes && (bitmap->cluster_slot < 0)) {
+		/* Assigning chunksize is required for "re_read" */
+		bitmap->mddev->bitmap_info.chunksize = chunksize;
+		err = md_setup_cluster(bitmap->mddev, nodes);
+		if (err) {
+			pr_warn("%s: Could not setup cluster service (%d)\n",
+				bmname(bitmap), err);
+			goto out_no_sb;
+		}
+		bitmap->cluster_slot = md_cluster_ops->slot_number(bitmap->mddev);
+		goto re_read;
+	}
+
+out_no_sb:
+	if (err == 0) {
+		if (test_bit(BITMAP_STALE, &bitmap->flags))
+			bitmap->events_cleared = bitmap->mddev->events;
+		bitmap->mddev->bitmap_info.chunksize = chunksize;
+		bitmap->mddev->bitmap_info.daemon_sleep = daemon_sleep;
+		bitmap->mddev->bitmap_info.max_write_behind = write_behind;
+		bitmap->mddev->bitmap_info.nodes = nodes;
+		if (bitmap->mddev->bitmap_info.space == 0 ||
+			bitmap->mddev->bitmap_info.space > sectors_reserved)
+			bitmap->mddev->bitmap_info.space = sectors_reserved;
+	} else {
+		md_bitmap_print_sb(bitmap);
+		if (bitmap->cluster_slot < 0)
+			md_cluster_stop(bitmap->mddev);
+	}
+	return err;
+}
+
+/*
+ * 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_storage *store,
+					    unsigned long chunk)
+{
+	if (store->sb_page)
+		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_storage *store,
+					     unsigned long chunk)
+{
+	if (store->sb_page)
+		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
+ *
+ */
+static inline struct page *filemap_get_page(struct bitmap_storage *store,
+					    unsigned long chunk)
+{
+	if (file_page_index(store, chunk) >= store->file_pages)
+		return NULL;
+	return store->filemap[file_page_index(store, chunk)];
+}
+
+static int md_bitmap_storage_alloc(struct bitmap_storage *store,
+				   unsigned long chunks, int with_super,
+				   int slot_number)
+{
+	int pnum, offset = 0;
+	unsigned long num_pages;
+	unsigned long bytes;
+
+	bytes = DIV_ROUND_UP(chunks, 8);
+	if (with_super)
+		bytes += sizeof(bitmap_super_t);
+
+	num_pages = DIV_ROUND_UP(bytes, PAGE_SIZE);
+	offset = slot_number * num_pages;
+
+	store->filemap = kmalloc_array(num_pages, sizeof(struct page *),
+				       GFP_KERNEL);
+	if (!store->filemap)
+		return -ENOMEM;
+
+	if (with_super && !store->sb_page) {
+		store->sb_page = alloc_page(GFP_KERNEL|__GFP_ZERO);
+		if (store->sb_page == NULL)
+			return -ENOMEM;
+	}
+
+	pnum = 0;
+	if (store->sb_page) {
+		store->filemap[0] = store->sb_page;
+		pnum = 1;
+		store->sb_index = offset;
+	}
+
+	for ( ; pnum < num_pages; pnum++) {
+		store->filemap[pnum] = alloc_page(GFP_KERNEL|__GFP_ZERO);
+		if (!store->filemap[pnum]) {
+			store->file_pages = pnum;
+			return -ENOMEM;
+		}
+	}
+	store->file_pages = pnum;
+
+	/* We need 4 bits per page, rounded up to a multiple
+	 * of sizeof(unsigned long) */
+	store->filemap_attr = kzalloc(
+		roundup(DIV_ROUND_UP(num_pages*4, 8), sizeof(unsigned long)),
+		GFP_KERNEL);
+	if (!store->filemap_attr)
+		return -ENOMEM;
+
+	store->bytes = bytes;
+
+	return 0;
+}
+
+static void md_bitmap_file_unmap(struct bitmap_storage *store)
+{
+	struct file *file = store->file;
+	struct page *sb_page = store->sb_page;
+	struct page **map = store->filemap;
+	int pages = store->file_pages;
+
+	while (pages--)
+		if (map[pages] != sb_page) /* 0 is sb_page, release it below */
+			free_buffers(map[pages]);
+	kfree(map);
+	kfree(store->filemap_attr);
+
+	if (sb_page)
+		free_buffers(sb_page);
+
+	if (file) {
+		struct inode *inode = file_inode(file);
+		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 md_bitmap_file_kick(struct bitmap *bitmap)
+{
+	if (!test_and_set_bit(BITMAP_STALE, &bitmap->flags)) {
+		md_bitmap_update_sb(bitmap);
+
+		if (bitmap->storage.file) {
+			pr_warn("%s: kicking failed bitmap file %pD4 from array!\n",
+				bmname(bitmap), bitmap->storage.file);
+
+		} else
+			pr_warn("%s: disabling internal bitmap due to errors\n",
+				bmname(bitmap));
+	}
+}
+
+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, int pnum,
+				 enum bitmap_page_attr attr)
+{
+	set_bit((pnum<<2) + attr, bitmap->storage.filemap_attr);
+}
+
+static inline void clear_page_attr(struct bitmap *bitmap, int pnum,
+				   enum bitmap_page_attr attr)
+{
+	clear_bit((pnum<<2) + attr, bitmap->storage.filemap_attr);
+}
+
+static inline int test_page_attr(struct bitmap *bitmap, int pnum,
+				 enum bitmap_page_attr attr)
+{
+	return test_bit((pnum<<2) + attr, bitmap->storage.filemap_attr);
+}
+
+static inline int test_and_clear_page_attr(struct bitmap *bitmap, int pnum,
+					   enum bitmap_page_attr attr)
+{
+	return test_and_clear_bit((pnum<<2) + attr,
+				  bitmap->storage.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 md_bitmap_file_set_bit(struct bitmap *bitmap, sector_t block)
+{
+	unsigned long bit;
+	struct page *page;
+	void *kaddr;
+	unsigned long chunk = block >> bitmap->counts.chunkshift;
+	struct bitmap_storage *store = &bitmap->storage;
+	unsigned long index = file_page_index(store, chunk);
+	unsigned long node_offset = 0;
+
+	if (mddev_is_clustered(bitmap->mddev))
+		node_offset = bitmap->cluster_slot * store->file_pages;
+
+	page = filemap_get_page(&bitmap->storage, chunk);
+	if (!page)
+		return;
+	bit = file_page_offset(&bitmap->storage, chunk);
+
+	/* set the bit */
+	kaddr = kmap_atomic(page);
+	if (test_bit(BITMAP_HOSTENDIAN, &bitmap->flags))
+		set_bit(bit, kaddr);
+	else
+		set_bit_le(bit, kaddr);
+	kunmap_atomic(kaddr);
+	pr_debug("set file bit %lu page %lu\n", bit, index);
+	/* record page number so it gets flushed to disk when unplug occurs */
+	set_page_attr(bitmap, index - node_offset, BITMAP_PAGE_DIRTY);
+}
+
+static void md_bitmap_file_clear_bit(struct bitmap *bitmap, sector_t block)
+{
+	unsigned long bit;
+	struct page *page;
+	void *paddr;
+	unsigned long chunk = block >> bitmap->counts.chunkshift;
+	struct bitmap_storage *store = &bitmap->storage;
+	unsigned long index = file_page_index(store, chunk);
+	unsigned long node_offset = 0;
+
+	if (mddev_is_clustered(bitmap->mddev))
+		node_offset = bitmap->cluster_slot * store->file_pages;
+
+	page = filemap_get_page(&bitmap->storage, chunk);
+	if (!page)
+		return;
+	bit = file_page_offset(&bitmap->storage, chunk);
+	paddr = kmap_atomic(page);
+	if (test_bit(BITMAP_HOSTENDIAN, &bitmap->flags))
+		clear_bit(bit, paddr);
+	else
+		clear_bit_le(bit, paddr);
+	kunmap_atomic(paddr);
+	if (!test_page_attr(bitmap, index - node_offset, BITMAP_PAGE_NEEDWRITE)) {
+		set_page_attr(bitmap, index - node_offset, BITMAP_PAGE_PENDING);
+		bitmap->allclean = 0;
+	}
+}
+
+static int md_bitmap_file_test_bit(struct bitmap *bitmap, sector_t block)
+{
+	unsigned long bit;
+	struct page *page;
+	void *paddr;
+	unsigned long chunk = block >> bitmap->counts.chunkshift;
+	int set = 0;
+
+	page = filemap_get_page(&bitmap->storage, chunk);
+	if (!page)
+		return -EINVAL;
+	bit = file_page_offset(&bitmap->storage, chunk);
+	paddr = kmap_atomic(page);
+	if (test_bit(BITMAP_HOSTENDIAN, &bitmap->flags))
+		set = test_bit(bit, paddr);
+	else
+		set = test_bit_le(bit, paddr);
+	kunmap_atomic(paddr);
+	return set;
+}
+
+/* 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 md_bitmap_unplug(struct bitmap *bitmap)
+{
+	unsigned long i;
+	int dirty, need_write;
+	int writing = 0;
+
+	if (!md_bitmap_enabled(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->storage.file_pages; i++) {
+		dirty = test_and_clear_page_attr(bitmap, i, BITMAP_PAGE_DIRTY);
+		need_write = test_and_clear_page_attr(bitmap, i,
+						      BITMAP_PAGE_NEEDWRITE);
+		if (dirty || need_write) {
+			if (!writing) {
+				md_bitmap_wait_writes(bitmap);
+				if (bitmap->mddev->queue)
+					blk_add_trace_msg(bitmap->mddev->queue,
+							  "md bitmap_unplug");
+			}
+			clear_page_attr(bitmap, i, BITMAP_PAGE_PENDING);
+			filemap_write_page(bitmap, i, false);
+			writing = 1;
+		}
+	}
+	if (writing)
+		md_bitmap_wait_writes(bitmap);
+
+	if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))
+		md_bitmap_file_kick(bitmap);
+}
+EXPORT_SYMBOL(md_bitmap_unplug);
+
+struct bitmap_unplug_work {
+	struct work_struct work;
+	struct bitmap *bitmap;
+	struct completion *done;
+};
+
+static void md_bitmap_unplug_fn(struct work_struct *work)
+{
+	struct bitmap_unplug_work *unplug_work =
+		container_of(work, struct bitmap_unplug_work, work);
+
+	md_bitmap_unplug(unplug_work->bitmap);
+	complete(unplug_work->done);
+}
+
+void md_bitmap_unplug_async(struct bitmap *bitmap)
+{
+	DECLARE_COMPLETION_ONSTACK(done);
+	struct bitmap_unplug_work unplug_work;
+
+	INIT_WORK_ONSTACK(&unplug_work.work, md_bitmap_unplug_fn);
+	unplug_work.bitmap = bitmap;
+	unplug_work.done = &done;
+
+	queue_work(md_bitmap_wq, &unplug_work.work);
+	wait_for_completion(&done);
+}
+EXPORT_SYMBOL(md_bitmap_unplug_async);
+
+static void md_bitmap_set_memory_bits(struct bitmap *bitmap, sector_t offset, int needed);
+
+/*
+ * Initialize the in-memory bitmap from the on-disk bitmap and set up the memory
+ * mapping of the bitmap file.
+ *
+ * Special case: 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 md_bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
+{
+	bool outofdate = test_bit(BITMAP_STALE, &bitmap->flags);
+	struct mddev *mddev = bitmap->mddev;
+	unsigned long chunks = bitmap->counts.chunks;
+	struct bitmap_storage *store = &bitmap->storage;
+	struct file *file = store->file;
+	unsigned long node_offset = 0;
+	unsigned long bit_cnt = 0;
+	unsigned long i;
+	int ret;
+
+	if (!file && !mddev->bitmap_info.offset) {
+		/* No permanent bitmap - fill with '1s'. */
+		store->filemap = NULL;
+		store->file_pages = 0;
+		for (i = 0; i < chunks ; i++) {
+			/* if the disk bit is set, set the memory bit */
+			int needed = ((sector_t)(i+1) << (bitmap->counts.chunkshift)
+				      >= start);
+			md_bitmap_set_memory_bits(bitmap,
+						  (sector_t)i << bitmap->counts.chunkshift,
+						  needed);
+		}
+		return 0;
+	}
+
+	if (file && i_size_read(file->f_mapping->host) < store->bytes) {
+		pr_warn("%s: bitmap file too short %lu < %lu\n",
+			bmname(bitmap),
+			(unsigned long) i_size_read(file->f_mapping->host),
+			store->bytes);
+		ret = -ENOSPC;
+		goto err;
+	}
+
+	if (mddev_is_clustered(mddev))
+		node_offset = bitmap->cluster_slot * (DIV_ROUND_UP(store->bytes, PAGE_SIZE));
+
+	for (i = 0; i < store->file_pages; i++) {
+		struct page *page = store->filemap[i];
+		int count;
+
+		/* unmap the old page, we're done with it */
+		if (i == store->file_pages - 1)
+			count = store->bytes - i * PAGE_SIZE;
+		else
+			count = PAGE_SIZE;
+
+		if (file)
+			ret = read_file_page(file, i, bitmap, count, page);
+		else
+			ret = read_sb_page(mddev, 0, page, i + node_offset,
+					   count);
+		if (ret)
+			goto err;
+	}
+
+	if (outofdate) {
+		pr_warn("%s: bitmap file is out of date, doing full recovery\n",
+			bmname(bitmap));
+
+		for (i = 0; i < store->file_pages; i++) {
+			struct page *page = store->filemap[i];
+			unsigned long offset = 0;
+			void *paddr;
+
+			if (i == 0 && !mddev->bitmap_info.external)
+				offset = sizeof(bitmap_super_t);
+
+			/*
+			 * If the 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);
+
+			filemap_write_page(bitmap, i, true);
+			if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags)) {
+				ret = -EIO;
+				goto err;
+			}
+		}
+	}
+
+	for (i = 0; i < chunks; i++) {
+		struct page *page = filemap_get_page(&bitmap->storage, i);
+		unsigned long bit = file_page_offset(&bitmap->storage, i);
+		void *paddr;
+		bool was_set;
+
+		paddr = kmap_atomic(page);
+		if (test_bit(BITMAP_HOSTENDIAN, &bitmap->flags))
+			was_set = test_bit(bit, paddr);
+		else
+			was_set = test_bit_le(bit, paddr);
+		kunmap_atomic(paddr);
+
+		if (was_set) {
+			/* if the disk bit is set, set the memory bit */
+			int needed = ((sector_t)(i+1) << bitmap->counts.chunkshift
+				      >= start);
+			md_bitmap_set_memory_bits(bitmap,
+						  (sector_t)i << bitmap->counts.chunkshift,
+						  needed);
+			bit_cnt++;
+		}
+	}
+
+	pr_debug("%s: bitmap initialized from disk: read %lu pages, set %lu of %lu bits\n",
+		 bmname(bitmap), store->file_pages,
+		 bit_cnt, chunks);
+
+	return 0;
+
+ err:
+	pr_warn("%s: bitmap initialisation failed: %d\n",
+		bmname(bitmap), ret);
+	return ret;
+}
+
+void md_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;
+
+	if (!bitmap || !bitmap->storage.filemap)
+		return;
+	if (bitmap->storage.file)
+		/* Only one copy, so nothing needed */
+		return;
+
+	for (i = 0; i < bitmap->storage.file_pages; i++)
+		set_page_attr(bitmap, i,
+			      BITMAP_PAGE_NEEDWRITE);
+	bitmap->allclean = 0;
+}
+
+static void md_bitmap_count_page(struct bitmap_counts *bitmap,
+				 sector_t offset, int inc)
+{
+	sector_t chunk = offset >> bitmap->chunkshift;
+	unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
+	bitmap->bp[page].count += inc;
+	md_bitmap_checkfree(bitmap, page);
+}
+
+static void md_bitmap_set_pending(struct bitmap_counts *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 *md_bitmap_get_counter(struct bitmap_counts *bitmap,
+					       sector_t offset, sector_t *blocks,
+					       int create);
+
+static void mddev_set_timeout(struct mddev *mddev, unsigned long timeout,
+			      bool force)
+{
+	struct md_thread *thread;
+
+	rcu_read_lock();
+	thread = rcu_dereference(mddev->thread);
+
+	if (!thread)
+		goto out;
+
+	if (force || thread->timeout < MAX_SCHEDULE_TIMEOUT)
+		thread->timeout = timeout;
+
+out:
+	rcu_read_unlock();
+}
+
+/*
+ * bitmap daemon -- periodically wakes up to clean bits and flush pages
+ *			out to disk
+ */
+void md_bitmap_daemon_work(struct mddev *mddev)
+{
+	struct bitmap *bitmap;
+	unsigned long j;
+	unsigned long nextpage;
+	sector_t blocks;
+	struct bitmap_counts *counts;
+
+	/* 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_set_timeout(mddev, MAX_SCHEDULE_TIMEOUT, true);
+		goto done;
+	}
+	bitmap->allclean = 1;
+
+	if (bitmap->mddev->queue)
+		blk_add_trace_msg(bitmap->mddev->queue,
+				  "md bitmap_daemon_work");
+
+	/* 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.
+	 */
+	for (j = 0; j < bitmap->storage.file_pages; j++)
+		if (test_and_clear_page_attr(bitmap, j,
+					     BITMAP_PAGE_PENDING))
+			set_page_attr(bitmap, j,
+				      BITMAP_PAGE_NEEDWRITE);
+
+	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;
+		if (bitmap->storage.filemap) {
+			sb = kmap_atomic(bitmap->storage.sb_page);
+			sb->events_cleared =
+				cpu_to_le64(bitmap->events_cleared);
+			kunmap_atomic(sb);
+			set_page_attr(bitmap, 0,
+				      BITMAP_PAGE_NEEDWRITE);
+		}
+	}
+	/* Now look at the bitmap counters and if any are '2' or '1',
+	 * decrement and handle accordingly.
+	 */
+	counts = &bitmap->counts;
+	spin_lock_irq(&counts->lock);
+	nextpage = 0;
+	for (j = 0; j < counts->chunks; j++) {
+		bitmap_counter_t *bmc;
+		sector_t  block = (sector_t)j << counts->chunkshift;
+
+		if (j == nextpage) {
+			nextpage += PAGE_COUNTER_RATIO;
+			if (!counts->bp[j >> PAGE_COUNTER_SHIFT].pending) {
+				j |= PAGE_COUNTER_MASK;
+				continue;
+			}
+			counts->bp[j >> PAGE_COUNTER_SHIFT].pending = 0;
+		}
+
+		bmc = md_bitmap_get_counter(counts, block, &blocks, 0);
+		if (!bmc) {
+			j |= PAGE_COUNTER_MASK;
+			continue;
+		}
+		if (*bmc == 1 && !bitmap->need_sync) {
+			/* We can clear the bit */
+			*bmc = 0;
+			md_bitmap_count_page(counts, block, -1);
+			md_bitmap_file_clear_bit(bitmap, block);
+		} else if (*bmc && *bmc <= 2) {
+			*bmc = 1;
+			md_bitmap_set_pending(counts, block);
+			bitmap->allclean = 0;
+		}
+	}
+	spin_unlock_irq(&counts->lock);
+
+	md_bitmap_wait_writes(bitmap);
+	/* 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->storage.file_pages
+		     && !test_bit(BITMAP_STALE, &bitmap->flags);
+	     j++) {
+		if (test_page_attr(bitmap, j,
+				   BITMAP_PAGE_DIRTY))
+			/* bitmap_unplug will handle the rest */
+			break;
+		if (bitmap->storage.filemap &&
+		    test_and_clear_page_attr(bitmap, j,
+					     BITMAP_PAGE_NEEDWRITE))
+			filemap_write_page(bitmap, j, false);
+	}
+
+ done:
+	if (bitmap->allclean == 0)
+		mddev_set_timeout(mddev, mddev->bitmap_info.daemon_sleep, true);
+	mutex_unlock(&mddev->bitmap_info.mutex);
+}
+
+static bitmap_counter_t *md_bitmap_get_counter(struct bitmap_counts *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;
+
+	if (page >= bitmap->pages) {
+		/*
+		 * This can happen if bitmap_start_sync goes beyond
+		 * End-of-device while looking for a whole page or
+		 * user set a huge number to sysfs bitmap_set_bits.
+		 */
+		return NULL;
+	}
+	err = md_bitmap_checkpage(bitmap, page, create, 0);
+
+	if (bitmap->bp[page].hijacked ||
+	    bitmap->bp[page].map == NULL)
+		csize = ((sector_t)1) << (bitmap->chunkshift +
+					  PAGE_COUNTER_SHIFT);
+	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 md_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->counts.lock);
+		bmc = md_bitmap_get_counter(&bitmap->counts, offset, &blocks, 1);
+		if (!bmc) {
+			spin_unlock_irq(&bitmap->counts.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->counts.lock);
+			schedule();
+			finish_wait(&bitmap->overflow_wait, &__wait);
+			continue;
+		}
+
+		switch (*bmc) {
+		case 0:
+			md_bitmap_file_set_bit(bitmap, offset);
+			md_bitmap_count_page(&bitmap->counts, offset, 1);
+			fallthrough;
+		case 1:
+			*bmc = 2;
+		}
+
+		(*bmc)++;
+
+		spin_unlock_irq(&bitmap->counts.lock);
+
+		offset += blocks;
+		if (sectors > blocks)
+			sectors -= blocks;
+		else
+			sectors = 0;
+	}
+	return 0;
+}
+EXPORT_SYMBOL(md_bitmap_startwrite);
+
+void md_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->counts.lock, flags);
+		bmc = md_bitmap_get_counter(&bitmap->counts, offset, &blocks, 0);
+		if (!bmc) {
+			spin_unlock_irqrestore(&bitmap->counts.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) {
+			md_bitmap_set_pending(&bitmap->counts, offset);
+			bitmap->allclean = 0;
+		}
+		spin_unlock_irqrestore(&bitmap->counts.lock, flags);
+		offset += blocks;
+		if (sectors > blocks)
+			sectors -= blocks;
+		else
+			sectors = 0;
+	}
+}
+EXPORT_SYMBOL(md_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->counts.lock);
+	bmc = md_bitmap_get_counter(&bitmap->counts, 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->counts.lock);
+	return rv;
+}
+
+int md_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(md_bitmap_start_sync);
+
+void md_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->counts.lock, flags);
+	bmc = md_bitmap_get_counter(&bitmap->counts, 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) {
+				md_bitmap_set_pending(&bitmap->counts, offset);
+				bitmap->allclean = 0;
+			}
+		}
+	}
+ unlock:
+	spin_unlock_irqrestore(&bitmap->counts.lock, flags);
+}
+EXPORT_SYMBOL(md_bitmap_end_sync);
+
+void md_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) {
+		md_bitmap_end_sync(bitmap, sector, &blocks, 0);
+		sector += blocks;
+	}
+}
+EXPORT_SYMBOL(md_bitmap_close_sync);
+
+void md_bitmap_cond_end_sync(struct bitmap *bitmap, sector_t sector, bool force)
+{
+	sector_t s = 0;
+	sector_t blocks;
+
+	if (!bitmap)
+		return;
+	if (sector == 0) {
+		bitmap->last_end_sync = jiffies;
+		return;
+	}
+	if (!force && 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_SB_CHANGE_CLEAN, &bitmap->mddev->sb_flags);
+	sector &= ~((1ULL << bitmap->counts.chunkshift) - 1);
+	s = 0;
+	while (s < sector && s < bitmap->mddev->resync_max_sectors) {
+		md_bitmap_end_sync(bitmap, s, &blocks, 0);
+		s += blocks;
+	}
+	bitmap->last_end_sync = jiffies;
+	sysfs_notify_dirent_safe(bitmap->mddev->sysfs_completed);
+}
+EXPORT_SYMBOL(md_bitmap_cond_end_sync);
+
+void md_bitmap_sync_with_cluster(struct mddev *mddev,
+			      sector_t old_lo, sector_t old_hi,
+			      sector_t new_lo, sector_t new_hi)
+{
+	struct bitmap *bitmap = mddev->bitmap;
+	sector_t sector, blocks = 0;
+
+	for (sector = old_lo; sector < new_lo; ) {
+		md_bitmap_end_sync(bitmap, sector, &blocks, 0);
+		sector += blocks;
+	}
+	WARN((blocks > new_lo) && old_lo, "alignment is not correct for lo\n");
+
+	for (sector = old_hi; sector < new_hi; ) {
+		md_bitmap_start_sync(bitmap, sector, &blocks, 0);
+		sector += blocks;
+	}
+	WARN((blocks > new_hi) && old_hi, "alignment is not correct for hi\n");
+}
+EXPORT_SYMBOL(md_bitmap_sync_with_cluster);
+
+static void md_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 2 and possibly set resync_needed.  They should all
+	 * be 0 at this point
+	 */
+
+	sector_t secs;
+	bitmap_counter_t *bmc;
+	spin_lock_irq(&bitmap->counts.lock);
+	bmc = md_bitmap_get_counter(&bitmap->counts, offset, &secs, 1);
+	if (!bmc) {
+		spin_unlock_irq(&bitmap->counts.lock);
+		return;
+	}
+	if (!*bmc) {
+		*bmc = 2;
+		md_bitmap_count_page(&bitmap->counts, offset, 1);
+		md_bitmap_set_pending(&bitmap->counts, offset);
+		bitmap->allclean = 0;
+	}
+	if (needed)
+		*bmc |= NEEDED_MASK;
+	spin_unlock_irq(&bitmap->counts.lock);
+}
+
+/* dirty the memory and file bits for bitmap chunks "s" to "e" */
+void md_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->counts.chunkshift;
+		md_bitmap_set_memory_bits(bitmap, sec, 1);
+		md_bitmap_file_set_bit(bitmap, sec);
+		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 md_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;
+	md_bitmap_daemon_work(mddev);
+	bitmap->daemon_lastrun -= sleep;
+	md_bitmap_daemon_work(mddev);
+	bitmap->daemon_lastrun -= sleep;
+	md_bitmap_daemon_work(mddev);
+	if (mddev->bitmap_info.external)
+		md_super_wait(mddev);
+	md_bitmap_update_sb(bitmap);
+}
+
+/*
+ * free memory that was allocated
+ */
+void md_bitmap_free(struct bitmap *bitmap)
+{
+	unsigned long k, pages;
+	struct bitmap_page *bp;
+
+	if (!bitmap) /* there was no bitmap */
+		return;
+
+	if (bitmap->sysfs_can_clear)
+		sysfs_put(bitmap->sysfs_can_clear);
+
+	if (mddev_is_clustered(bitmap->mddev) && bitmap->mddev->cluster_info &&
+		bitmap->cluster_slot == md_cluster_ops->slot_number(bitmap->mddev))
+		md_cluster_stop(bitmap->mddev);
+
+	/* Shouldn't be needed - but just in case.... */
+	wait_event(bitmap->write_wait,
+		   atomic_read(&bitmap->pending_writes) == 0);
+
+	/* release the bitmap file  */
+	md_bitmap_file_unmap(&bitmap->storage);
+
+	bp = bitmap->counts.bp;
+	pages = bitmap->counts.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);
+}
+EXPORT_SYMBOL(md_bitmap_free);
+
+void md_bitmap_wait_behind_writes(struct mddev *mddev)
+{
+	struct bitmap *bitmap = mddev->bitmap;
+
+	/* wait for behind writes to complete */
+	if (bitmap && atomic_read(&bitmap->behind_writes) > 0) {
+		pr_debug("md:%s: behind writes in progress - waiting to stop.\n",
+			 mdname(mddev));
+		/* need to kick something here to make sure I/O goes? */
+		wait_event(bitmap->behind_wait,
+			   atomic_read(&bitmap->behind_writes) == 0);
+	}
+}
+
+void md_bitmap_destroy(struct mddev *mddev)
+{
+	struct bitmap *bitmap = mddev->bitmap;
+
+	if (!bitmap) /* there was no bitmap */
+		return;
+
+	md_bitmap_wait_behind_writes(mddev);
+	if (!mddev->serialize_policy)
+		mddev_destroy_serial_pool(mddev, NULL, true);
+
+	mutex_lock(&mddev->bitmap_info.mutex);
+	spin_lock(&mddev->lock);
+	mddev->bitmap = NULL; /* disconnect from the md device */
+	spin_unlock(&mddev->lock);
+	mutex_unlock(&mddev->bitmap_info.mutex);
+	mddev_set_timeout(mddev, MAX_SCHEDULE_TIMEOUT, true);
+
+	md_bitmap_free(bitmap);
+}
+
+/*
+ * initialize the bitmap structure
+ * if this returns an error, bitmap_destroy must be called to do clean up
+ * once mddev->bitmap is set
+ */
+struct bitmap *md_bitmap_create(struct mddev *mddev, int slot)
+{
+	struct bitmap *bitmap;
+	sector_t blocks = mddev->resync_max_sectors;
+	struct file *file = mddev->bitmap_info.file;
+	int err;
+	struct kernfs_node *bm = NULL;
+
+	BUILD_BUG_ON(sizeof(bitmap_super_t) != 256);
+
+	BUG_ON(file && mddev->bitmap_info.offset);
+
+	if (test_bit(MD_HAS_JOURNAL, &mddev->flags)) {
+		pr_notice("md/raid:%s: array with journal cannot have bitmap\n",
+			  mdname(mddev));
+		return ERR_PTR(-EBUSY);
+	}
+
+	bitmap = kzalloc(sizeof(*bitmap), GFP_KERNEL);
+	if (!bitmap)
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock_init(&bitmap->counts.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;
+	bitmap->cluster_slot = slot;
+
+	if (mddev->kobj.sd)
+		bm = sysfs_get_dirent(mddev->kobj.sd, "bitmap");
+	if (bm) {
+		bitmap->sysfs_can_clear = sysfs_get_dirent(bm, "can_clear");
+		sysfs_put(bm);
+	} else
+		bitmap->sysfs_can_clear = NULL;
+
+	bitmap->storage.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 = md_bitmap_new_disk_sb(bitmap);
+		else
+			err = md_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;
+	err = md_bitmap_resize(bitmap, blocks, mddev->bitmap_info.chunksize, 1);
+	if (err)
+		goto error;
+
+	pr_debug("created bitmap (%lu pages) for device %s\n",
+		 bitmap->counts.pages, bmname(bitmap));
+
+	err = test_bit(BITMAP_WRITE_ERROR, &bitmap->flags) ? -EIO : 0;
+	if (err)
+		goto error;
+
+	return bitmap;
+ error:
+	md_bitmap_free(bitmap);
+	return ERR_PTR(err);
+}
+
+int md_bitmap_load(struct mddev *mddev)
+{
+	int err = 0;
+	sector_t start = 0;
+	sector_t sector = 0;
+	struct bitmap *bitmap = mddev->bitmap;
+	struct md_rdev *rdev;
+
+	if (!bitmap)
+		goto out;
+
+	rdev_for_each(rdev, mddev)
+		mddev_create_serial_pool(mddev, rdev, true);
+
+	if (mddev_is_clustered(mddev))
+		md_cluster_ops->load_bitmaps(mddev, mddev->bitmap_info.nodes);
+
+	/* 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;
+		md_bitmap_start_sync(bitmap, sector, &blocks, 0);
+		sector += blocks;
+	}
+	md_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 = md_bitmap_init_from_disk(bitmap, start);
+	mutex_unlock(&mddev->bitmap_info.mutex);
+
+	if (err)
+		goto out;
+	clear_bit(BITMAP_STALE, &bitmap->flags);
+
+	/* Kick recovery in case any bits were set */
+	set_bit(MD_RECOVERY_NEEDED, &bitmap->mddev->recovery);
+
+	mddev_set_timeout(mddev, mddev->bitmap_info.daemon_sleep, true);
+	md_wakeup_thread(mddev->thread);
+
+	md_bitmap_update_sb(bitmap);
+
+	if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))
+		err = -EIO;
+out:
+	return err;
+}
+EXPORT_SYMBOL_GPL(md_bitmap_load);
+
+/* caller need to free returned bitmap with md_bitmap_free() */
+struct bitmap *get_bitmap_from_slot(struct mddev *mddev, int slot)
+{
+	int rv = 0;
+	struct bitmap *bitmap;
+
+	bitmap = md_bitmap_create(mddev, slot);
+	if (IS_ERR(bitmap)) {
+		rv = PTR_ERR(bitmap);
+		return ERR_PTR(rv);
+	}
+
+	rv = md_bitmap_init_from_disk(bitmap, 0);
+	if (rv) {
+		md_bitmap_free(bitmap);
+		return ERR_PTR(rv);
+	}
+
+	return bitmap;
+}
+EXPORT_SYMBOL(get_bitmap_from_slot);
+
+/* Loads the bitmap associated with slot and copies the resync information
+ * to our bitmap
+ */
+int md_bitmap_copy_from_slot(struct mddev *mddev, int slot,
+		sector_t *low, sector_t *high, bool clear_bits)
+{
+	int rv = 0, i, j;
+	sector_t block, lo = 0, hi = 0;
+	struct bitmap_counts *counts;
+	struct bitmap *bitmap;
+
+	bitmap = get_bitmap_from_slot(mddev, slot);
+	if (IS_ERR(bitmap)) {
+		pr_err("%s can't get bitmap from slot %d\n", __func__, slot);
+		return -1;
+	}
+
+	counts = &bitmap->counts;
+	for (j = 0; j < counts->chunks; j++) {
+		block = (sector_t)j << counts->chunkshift;
+		if (md_bitmap_file_test_bit(bitmap, block)) {
+			if (!lo)
+				lo = block;
+			hi = block;
+			md_bitmap_file_clear_bit(bitmap, block);
+			md_bitmap_set_memory_bits(mddev->bitmap, block, 1);
+			md_bitmap_file_set_bit(mddev->bitmap, block);
+		}
+	}
+
+	if (clear_bits) {
+		md_bitmap_update_sb(bitmap);
+		/* BITMAP_PAGE_PENDING is set, but bitmap_unplug needs
+		 * BITMAP_PAGE_DIRTY or _NEEDWRITE to write ... */
+		for (i = 0; i < bitmap->storage.file_pages; i++)
+			if (test_page_attr(bitmap, i, BITMAP_PAGE_PENDING))
+				set_page_attr(bitmap, i, BITMAP_PAGE_NEEDWRITE);
+		md_bitmap_unplug(bitmap);
+	}
+	md_bitmap_unplug(mddev->bitmap);
+	*low = lo;
+	*high = hi;
+	md_bitmap_free(bitmap);
+
+	return rv;
+}
+EXPORT_SYMBOL_GPL(md_bitmap_copy_from_slot);
+
+
+void md_bitmap_status(struct seq_file *seq, struct bitmap *bitmap)
+{
+	unsigned long chunk_kb;
+	struct bitmap_counts *counts;
+
+	if (!bitmap)
+		return;
+
+	counts = &bitmap->counts;
+
+	chunk_kb = bitmap->mddev->bitmap_info.chunksize >> 10;
+	seq_printf(seq, "bitmap: %lu/%lu pages [%luKB], "
+		   "%lu%s chunk",
+		   counts->pages - counts->missing_pages,
+		   counts->pages,
+		   (counts->pages - counts->missing_pages)
+		   << (PAGE_SHIFT - 10),
+		   chunk_kb ? chunk_kb : bitmap->mddev->bitmap_info.chunksize,
+		   chunk_kb ? "KB" : "B");
+	if (bitmap->storage.file) {
+		seq_printf(seq, ", file: ");
+		seq_file_path(seq, bitmap->storage.file, " \t\n");
+	}
+
+	seq_printf(seq, "\n");
+}
+
+int md_bitmap_resize(struct bitmap *bitmap, sector_t blocks,
+		  int chunksize, int init)
+{
+	/* If chunk_size is 0, choose an appropriate chunk size.
+	 * Then possibly allocate new storage space.
+	 * Then quiesce, copy bits, replace bitmap, and re-start
+	 *
+	 * This function is called both to set up the initial bitmap
+	 * and to resize the bitmap while the array is active.
+	 * If this happens as a result of the array being resized,
+	 * chunksize will be zero, and we need to choose a suitable
+	 * chunksize, otherwise we use what we are given.
+	 */
+	struct bitmap_storage store;
+	struct bitmap_counts old_counts;
+	unsigned long chunks;
+	sector_t block;
+	sector_t old_blocks, new_blocks;
+	int chunkshift;
+	int ret = 0;
+	long pages;
+	struct bitmap_page *new_bp;
+
+	if (bitmap->storage.file && !init) {
+		pr_info("md: cannot resize file-based bitmap\n");
+		return -EINVAL;
+	}
+
+	if (chunksize == 0) {
+		/* If there is enough space, leave the chunk size unchanged,
+		 * else increase by factor of two until there is enough space.
+		 */
+		long bytes;
+		long space = bitmap->mddev->bitmap_info.space;
+
+		if (space == 0) {
+			/* We don't know how much space there is, so limit
+			 * to current size - in sectors.
+			 */
+			bytes = DIV_ROUND_UP(bitmap->counts.chunks, 8);
+			if (!bitmap->mddev->bitmap_info.external)
+				bytes += sizeof(bitmap_super_t);
+			space = DIV_ROUND_UP(bytes, 512);
+			bitmap->mddev->bitmap_info.space = space;
+		}
+		chunkshift = bitmap->counts.chunkshift;
+		chunkshift--;
+		do {
+			/* 'chunkshift' is shift from block size to chunk size */
+			chunkshift++;
+			chunks = DIV_ROUND_UP_SECTOR_T(blocks, 1 << chunkshift);
+			bytes = DIV_ROUND_UP(chunks, 8);
+			if (!bitmap->mddev->bitmap_info.external)
+				bytes += sizeof(bitmap_super_t);
+		} while (bytes > (space << 9) && (chunkshift + BITMAP_BLOCK_SHIFT) <
+			(BITS_PER_BYTE * sizeof(((bitmap_super_t *)0)->chunksize) - 1));
+	} else
+		chunkshift = ffz(~chunksize) - BITMAP_BLOCK_SHIFT;
+
+	chunks = DIV_ROUND_UP_SECTOR_T(blocks, 1 << chunkshift);
+	memset(&store, 0, sizeof(store));
+	if (bitmap->mddev->bitmap_info.offset || bitmap->mddev->bitmap_info.file)
+		ret = md_bitmap_storage_alloc(&store, chunks,
+					      !bitmap->mddev->bitmap_info.external,
+					      mddev_is_clustered(bitmap->mddev)
+					      ? bitmap->cluster_slot : 0);
+	if (ret) {
+		md_bitmap_file_unmap(&store);
+		goto err;
+	}
+
+	pages = DIV_ROUND_UP(chunks, PAGE_COUNTER_RATIO);
+
+	new_bp = kcalloc(pages, sizeof(*new_bp), GFP_KERNEL);
+	ret = -ENOMEM;
+	if (!new_bp) {
+		md_bitmap_file_unmap(&store);
+		goto err;
+	}
+
+	if (!init)
+		bitmap->mddev->pers->quiesce(bitmap->mddev, 1);
+
+	store.file = bitmap->storage.file;
+	bitmap->storage.file = NULL;
+
+	if (store.sb_page && bitmap->storage.sb_page)
+		memcpy(page_address(store.sb_page),
+		       page_address(bitmap->storage.sb_page),
+		       sizeof(bitmap_super_t));
+	spin_lock_irq(&bitmap->counts.lock);
+	md_bitmap_file_unmap(&bitmap->storage);
+	bitmap->storage = store;
+
+	old_counts = bitmap->counts;
+	bitmap->counts.bp = new_bp;
+	bitmap->counts.pages = pages;
+	bitmap->counts.missing_pages = pages;
+	bitmap->counts.chunkshift = chunkshift;
+	bitmap->counts.chunks = chunks;
+	bitmap->mddev->bitmap_info.chunksize = 1UL << (chunkshift +
+						     BITMAP_BLOCK_SHIFT);
+
+	blocks = min(old_counts.chunks << old_counts.chunkshift,
+		     chunks << chunkshift);
+
+	/* For cluster raid, need to pre-allocate bitmap */
+	if (mddev_is_clustered(bitmap->mddev)) {
+		unsigned long page;
+		for (page = 0; page < pages; page++) {
+			ret = md_bitmap_checkpage(&bitmap->counts, page, 1, 1);
+			if (ret) {
+				unsigned long k;
+
+				/* deallocate the page memory */
+				for (k = 0; k < page; k++) {
+					kfree(new_bp[k].map);
+				}
+				kfree(new_bp);
+
+				/* restore some fields from old_counts */
+				bitmap->counts.bp = old_counts.bp;
+				bitmap->counts.pages = old_counts.pages;
+				bitmap->counts.missing_pages = old_counts.pages;
+				bitmap->counts.chunkshift = old_counts.chunkshift;
+				bitmap->counts.chunks = old_counts.chunks;
+				bitmap->mddev->bitmap_info.chunksize =
+					1UL << (old_counts.chunkshift + BITMAP_BLOCK_SHIFT);
+				blocks = old_counts.chunks << old_counts.chunkshift;
+				pr_warn("Could not pre-allocate in-memory bitmap for cluster raid\n");
+				break;
+			} else
+				bitmap->counts.bp[page].count += 1;
+		}
+	}
+
+	for (block = 0; block < blocks; ) {
+		bitmap_counter_t *bmc_old, *bmc_new;
+		int set;
+
+		bmc_old = md_bitmap_get_counter(&old_counts, block, &old_blocks, 0);
+		set = bmc_old && NEEDED(*bmc_old);
+
+		if (set) {
+			bmc_new = md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1);
+			if (bmc_new) {
+				if (*bmc_new == 0) {
+					/* need to set on-disk bits too. */
+					sector_t end = block + new_blocks;
+					sector_t start = block >> chunkshift;
+
+					start <<= chunkshift;
+					while (start < end) {
+						md_bitmap_file_set_bit(bitmap, block);
+						start += 1 << chunkshift;
+					}
+					*bmc_new = 2;
+					md_bitmap_count_page(&bitmap->counts, block, 1);
+					md_bitmap_set_pending(&bitmap->counts, block);
+				}
+				*bmc_new |= NEEDED_MASK;
+			}
+			if (new_blocks < old_blocks)
+				old_blocks = new_blocks;
+		}
+		block += old_blocks;
+	}
+
+	if (bitmap->counts.bp != old_counts.bp) {
+		unsigned long k;
+		for (k = 0; k < old_counts.pages; k++)
+			if (!old_counts.bp[k].hijacked)
+				kfree(old_counts.bp[k].map);
+		kfree(old_counts.bp);
+	}
+
+	if (!init) {
+		int i;
+		while (block < (chunks << chunkshift)) {
+			bitmap_counter_t *bmc;
+			bmc = md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1);
+			if (bmc) {
+				/* new space.  It needs to be resynced, so
+				 * we set NEEDED_MASK.
+				 */
+				if (*bmc == 0) {
+					*bmc = NEEDED_MASK | 2;
+					md_bitmap_count_page(&bitmap->counts, block, 1);
+					md_bitmap_set_pending(&bitmap->counts, block);
+				}
+			}
+			block += new_blocks;
+		}
+		for (i = 0; i < bitmap->storage.file_pages; i++)
+			set_page_attr(bitmap, i, BITMAP_PAGE_DIRTY);
+	}
+	spin_unlock_irq(&bitmap->counts.lock);
+
+	if (!init) {
+		md_bitmap_unplug(bitmap);
+		bitmap->mddev->pers->quiesce(bitmap->mddev, 0);
+	}
+	ret = 0;
+err:
+	return ret;
+}
+EXPORT_SYMBOL_GPL(md_bitmap_resize);
+
+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)
+{
+	int rv;
+
+	rv = mddev_lock(mddev);
+	if (rv)
+		return rv;
+	if (mddev->pers) {
+		if (!mddev->pers->quiesce) {
+			rv = -EBUSY;
+			goto out;
+		}
+		if (mddev->recovery || mddev->sync_thread) {
+			rv = -EBUSY;
+			goto out;
+		}
+	}
+
+	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) {
+			rv = -EBUSY;
+			goto out;
+		}
+		if (mddev->pers) {
+			mddev_suspend(mddev);
+			md_bitmap_destroy(mddev);
+			mddev_resume(mddev);
+		}
+		mddev->bitmap_info.offset = 0;
+		if (mddev->bitmap_info.file) {
+			struct file *f = mddev->bitmap_info.file;
+			mddev->bitmap_info.file = NULL;
+			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 */
+			rv = -EINVAL;
+			goto out;
+		} else {
+			if (buf[0] == '+')
+				rv = kstrtoll(buf+1, 10, &offset);
+			else
+				rv = kstrtoll(buf, 10, &offset);
+			if (rv)
+				goto out;
+			if (offset == 0) {
+				rv = -EINVAL;
+				goto out;
+			}
+			if (mddev->bitmap_info.external == 0 &&
+			    mddev->major_version == 0 &&
+			    offset != mddev->bitmap_info.default_offset) {
+				rv = -EINVAL;
+				goto out;
+			}
+			mddev->bitmap_info.offset = offset;
+			if (mddev->pers) {
+				struct bitmap *bitmap;
+				bitmap = md_bitmap_create(mddev, -1);
+				mddev_suspend(mddev);
+				if (IS_ERR(bitmap))
+					rv = PTR_ERR(bitmap);
+				else {
+					mddev->bitmap = bitmap;
+					rv = md_bitmap_load(mddev);
+					if (rv)
+						mddev->bitmap_info.offset = 0;
+				}
+				if (rv) {
+					md_bitmap_destroy(mddev);
+					mddev_resume(mddev);
+					goto out;
+				}
+				mddev_resume(mddev);
+			}
+		}
+	}
+	if (!mddev->external) {
+		/* Ensure new bitmap info is stored in
+		 * metadata promptly.
+		 */
+		set_bit(MD_SB_CHANGE_DEVS, &mddev->sb_flags);
+		md_wakeup_thread(mddev->thread);
+	}
+	rv = 0;
+out:
+	mddev_unlock(mddev);
+	if (rv)
+		return rv;
+	return len;
+}
+
+static struct md_sysfs_entry bitmap_location =
+__ATTR(location, S_IRUGO|S_IWUSR, location_show, location_store);
+
+/* 'bitmap/space' is the space available at 'location' for the
+ * bitmap.  This allows the kernel to know when it is safe to
+ * resize the bitmap to match a resized array.
+ */
+static ssize_t
+space_show(struct mddev *mddev, char *page)
+{
+	return sprintf(page, "%lu\n", mddev->bitmap_info.space);
+}
+
+static ssize_t
+space_store(struct mddev *mddev, const char *buf, size_t len)
+{
+	unsigned long sectors;
+	int rv;
+
+	rv = kstrtoul(buf, 10, &sectors);
+	if (rv)
+		return rv;
+
+	if (sectors == 0)
+		return -EINVAL;
+
+	if (mddev->bitmap &&
+	    sectors < (mddev->bitmap->storage.bytes + 511) >> 9)
+		return -EFBIG; /* Bitmap is too big for this small space */
+
+	/* could make sure it isn't too big, but that isn't really
+	 * needed - user-space should be careful.
+	 */
+	mddev->bitmap_info.space = sectors;
+	return len;
+}
+
+static struct md_sysfs_entry bitmap_space =
+__ATTR(space, S_IRUGO|S_IWUSR, space_show, space_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;
+	mddev_set_timeout(mddev, timeout, false);
+	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;
+	unsigned long old_mwb = mddev->bitmap_info.max_write_behind;
+	struct md_rdev *rdev;
+	bool has_write_mostly = false;
+	int rv = kstrtoul(buf, 10, &backlog);
+	if (rv)
+		return rv;
+	if (backlog > COUNTER_MAX)
+		return -EINVAL;
+
+	rv = mddev_lock(mddev);
+	if (rv)
+		return rv;
+
+	/*
+	 * Without write mostly device, it doesn't make sense to set
+	 * backlog for max_write_behind.
+	 */
+	rdev_for_each(rdev, mddev) {
+		if (test_bit(WriteMostly, &rdev->flags)) {
+			has_write_mostly = true;
+			break;
+		}
+	}
+	if (!has_write_mostly) {
+		pr_warn_ratelimited("%s: can't set backlog, no write mostly device available\n",
+				    mdname(mddev));
+		mddev_unlock(mddev);
+		return -EINVAL;
+	}
+
+	mddev->bitmap_info.max_write_behind = backlog;
+	if (!backlog && mddev->serial_info_pool) {
+		/* serial_info_pool is not needed if backlog is zero */
+		if (!mddev->serialize_policy)
+			mddev_destroy_serial_pool(mddev, NULL, false);
+	} else if (backlog && !mddev->serial_info_pool) {
+		/* serial_info_pool is needed since backlog is not zero */
+		rdev_for_each(rdev, mddev)
+			mddev_create_serial_pool(mddev, rdev, false);
+	}
+	if (old_mwb != backlog)
+		md_bitmap_update_sb(mddev->bitmap);
+
+	mddev_unlock(mddev);
+	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 = kstrtoul(buf, 10, &csize);
+	if (rv)
+		return rv;
+	if (csize < 512 ||
+	    !is_power_of_2(csize))
+		return -EINVAL;
+	if (BITS_PER_LONG > 32 && csize >= (1ULL << (BITS_PER_BYTE *
+		sizeof(((bitmap_super_t *)0)->chunksize))))
+		return -EOVERFLOW;
+	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)
+{
+	if (mddev_is_clustered(mddev))
+		return sprintf(page, "clustered\n");
+	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) ||
+			(strncmp(buf, "clustered", 9) == 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;
+	spin_lock(&mddev->lock);
+	if (mddev->bitmap)
+		len = sprintf(page, "%s\n", (mddev->bitmap->need_sync ?
+					     "false" : "true"));
+	else
+		len = sprintf(page, "\n");
+	spin_unlock(&mddev->lock);
+	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)
+{
+	ssize_t ret;
+	spin_lock(&mddev->lock);
+	if (mddev->bitmap == NULL)
+		ret = sprintf(page, "0\n");
+	else
+		ret = sprintf(page, "%lu\n",
+			      mddev->bitmap->behind_writes_used);
+	spin_unlock(&mddev->lock);
+	return ret;
+}
+
+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_space.attr,
+	&bitmap_timeout.attr,
+	&bitmap_backlog.attr,
+	&bitmap_chunksize.attr,
+	&bitmap_metadata.attr,
+	&bitmap_can_clear.attr,
+	&max_backlog_used.attr,
+	NULL
+};
+const struct attribute_group md_bitmap_group = {
+	.name = "bitmap",
+	.attrs = md_bitmap_attrs,
+};