diff --git a/drivers/md/dm.c b/drivers/md/dm.c
new file mode 100644
index 0000000..243ff68
--- /dev/null
+++ b/drivers/md/dm.c
@@ -0,0 +1,1194 @@
+/*
+ * Copyright (C) 2001, 2002 Sistina Software (UK) Limited.
+ * Copyright (C) 2004 Red Hat, Inc. All rights reserved.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "dm.h"
+#include "dm-bio-list.h"
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/blkpg.h>
+#include <linux/bio.h>
+#include <linux/buffer_head.h>
+#include <linux/mempool.h>
+#include <linux/slab.h>
+#include <linux/idr.h>
+
+static const char *_name = DM_NAME;
+
+static unsigned int major = 0;
+static unsigned int _major = 0;
+
+/*
+ * One of these is allocated per bio.
+ */
+struct dm_io {
+	struct mapped_device *md;
+	int error;
+	struct bio *bio;
+	atomic_t io_count;
+};
+
+/*
+ * One of these is allocated per target within a bio.  Hopefully
+ * this will be simplified out one day.
+ */
+struct target_io {
+	struct dm_io *io;
+	struct dm_target *ti;
+	union map_info info;
+};
+
+union map_info *dm_get_mapinfo(struct bio *bio)
+{
+        if (bio && bio->bi_private)
+                return &((struct target_io *)bio->bi_private)->info;
+        return NULL;
+}
+
+/*
+ * Bits for the md->flags field.
+ */
+#define DMF_BLOCK_IO 0
+#define DMF_SUSPENDED 1
+#define DMF_FS_LOCKED 2
+
+struct mapped_device {
+	struct rw_semaphore lock;
+	rwlock_t map_lock;
+	atomic_t holders;
+
+	unsigned long flags;
+
+	request_queue_t *queue;
+	struct gendisk *disk;
+
+	void *interface_ptr;
+
+	/*
+	 * A list of ios that arrived while we were suspended.
+	 */
+	atomic_t pending;
+	wait_queue_head_t wait;
+ 	struct bio_list deferred;
+
+	/*
+	 * The current mapping.
+	 */
+	struct dm_table *map;
+
+	/*
+	 * io objects are allocated from here.
+	 */
+	mempool_t *io_pool;
+	mempool_t *tio_pool;
+
+	/*
+	 * Event handling.
+	 */
+	atomic_t event_nr;
+	wait_queue_head_t eventq;
+
+	/*
+	 * freeze/thaw support require holding onto a super block
+	 */
+	struct super_block *frozen_sb;
+};
+
+#define MIN_IOS 256
+static kmem_cache_t *_io_cache;
+static kmem_cache_t *_tio_cache;
+
+static struct bio_set *dm_set;
+
+static int __init local_init(void)
+{
+	int r;
+
+	dm_set = bioset_create(16, 16, 4);
+	if (!dm_set)
+		return -ENOMEM;
+
+	/* allocate a slab for the dm_ios */
+	_io_cache = kmem_cache_create("dm_io",
+				      sizeof(struct dm_io), 0, 0, NULL, NULL);
+	if (!_io_cache)
+		return -ENOMEM;
+
+	/* allocate a slab for the target ios */
+	_tio_cache = kmem_cache_create("dm_tio", sizeof(struct target_io),
+				       0, 0, NULL, NULL);
+	if (!_tio_cache) {
+		kmem_cache_destroy(_io_cache);
+		return -ENOMEM;
+	}
+
+	_major = major;
+	r = register_blkdev(_major, _name);
+	if (r < 0) {
+		kmem_cache_destroy(_tio_cache);
+		kmem_cache_destroy(_io_cache);
+		return r;
+	}
+
+	if (!_major)
+		_major = r;
+
+	return 0;
+}
+
+static void local_exit(void)
+{
+	kmem_cache_destroy(_tio_cache);
+	kmem_cache_destroy(_io_cache);
+
+	bioset_free(dm_set);
+
+	if (unregister_blkdev(_major, _name) < 0)
+		DMERR("devfs_unregister_blkdev failed");
+
+	_major = 0;
+
+	DMINFO("cleaned up");
+}
+
+int (*_inits[])(void) __initdata = {
+	local_init,
+	dm_target_init,
+	dm_linear_init,
+	dm_stripe_init,
+	dm_interface_init,
+};
+
+void (*_exits[])(void) = {
+	local_exit,
+	dm_target_exit,
+	dm_linear_exit,
+	dm_stripe_exit,
+	dm_interface_exit,
+};
+
+static int __init dm_init(void)
+{
+	const int count = ARRAY_SIZE(_inits);
+
+	int r, i;
+
+	for (i = 0; i < count; i++) {
+		r = _inits[i]();
+		if (r)
+			goto bad;
+	}
+
+	return 0;
+
+      bad:
+	while (i--)
+		_exits[i]();
+
+	return r;
+}
+
+static void __exit dm_exit(void)
+{
+	int i = ARRAY_SIZE(_exits);
+
+	while (i--)
+		_exits[i]();
+}
+
+/*
+ * Block device functions
+ */
+static int dm_blk_open(struct inode *inode, struct file *file)
+{
+	struct mapped_device *md;
+
+	md = inode->i_bdev->bd_disk->private_data;
+	dm_get(md);
+	return 0;
+}
+
+static int dm_blk_close(struct inode *inode, struct file *file)
+{
+	struct mapped_device *md;
+
+	md = inode->i_bdev->bd_disk->private_data;
+	dm_put(md);
+	return 0;
+}
+
+static inline struct dm_io *alloc_io(struct mapped_device *md)
+{
+	return mempool_alloc(md->io_pool, GFP_NOIO);
+}
+
+static inline void free_io(struct mapped_device *md, struct dm_io *io)
+{
+	mempool_free(io, md->io_pool);
+}
+
+static inline struct target_io *alloc_tio(struct mapped_device *md)
+{
+	return mempool_alloc(md->tio_pool, GFP_NOIO);
+}
+
+static inline void free_tio(struct mapped_device *md, struct target_io *tio)
+{
+	mempool_free(tio, md->tio_pool);
+}
+
+/*
+ * Add the bio to the list of deferred io.
+ */
+static int queue_io(struct mapped_device *md, struct bio *bio)
+{
+	down_write(&md->lock);
+
+	if (!test_bit(DMF_BLOCK_IO, &md->flags)) {
+		up_write(&md->lock);
+		return 1;
+	}
+
+	bio_list_add(&md->deferred, bio);
+
+	up_write(&md->lock);
+	return 0;		/* deferred successfully */
+}
+
+/*
+ * Everyone (including functions in this file), should use this
+ * function to access the md->map field, and make sure they call
+ * dm_table_put() when finished.
+ */
+struct dm_table *dm_get_table(struct mapped_device *md)
+{
+	struct dm_table *t;
+
+	read_lock(&md->map_lock);
+	t = md->map;
+	if (t)
+		dm_table_get(t);
+	read_unlock(&md->map_lock);
+
+	return t;
+}
+
+/*-----------------------------------------------------------------
+ * CRUD START:
+ *   A more elegant soln is in the works that uses the queue
+ *   merge fn, unfortunately there are a couple of changes to
+ *   the block layer that I want to make for this.  So in the
+ *   interests of getting something for people to use I give
+ *   you this clearly demarcated crap.
+ *---------------------------------------------------------------*/
+
+/*
+ * Decrements the number of outstanding ios that a bio has been
+ * cloned into, completing the original io if necc.
+ */
+static inline void dec_pending(struct dm_io *io, int error)
+{
+	if (error)
+		io->error = error;
+
+	if (atomic_dec_and_test(&io->io_count)) {
+		if (atomic_dec_and_test(&io->md->pending))
+			/* nudge anyone waiting on suspend queue */
+			wake_up(&io->md->wait);
+
+		bio_endio(io->bio, io->bio->bi_size, io->error);
+		free_io(io->md, io);
+	}
+}
+
+static int clone_endio(struct bio *bio, unsigned int done, int error)
+{
+	int r = 0;
+	struct target_io *tio = bio->bi_private;
+	struct dm_io *io = tio->io;
+	dm_endio_fn endio = tio->ti->type->end_io;
+
+	if (bio->bi_size)
+		return 1;
+
+	if (!bio_flagged(bio, BIO_UPTODATE) && !error)
+		error = -EIO;
+
+	if (endio) {
+		r = endio(tio->ti, bio, error, &tio->info);
+		if (r < 0)
+			error = r;
+
+		else if (r > 0)
+			/* the target wants another shot at the io */
+			return 1;
+	}
+
+	free_tio(io->md, tio);
+	dec_pending(io, error);
+	bio_put(bio);
+	return r;
+}
+
+static sector_t max_io_len(struct mapped_device *md,
+			   sector_t sector, struct dm_target *ti)
+{
+	sector_t offset = sector - ti->begin;
+	sector_t len = ti->len - offset;
+
+	/*
+	 * Does the target need to split even further ?
+	 */
+	if (ti->split_io) {
+		sector_t boundary;
+		boundary = ((offset + ti->split_io) & ~(ti->split_io - 1))
+			   - offset;
+		if (len > boundary)
+			len = boundary;
+	}
+
+	return len;
+}
+
+static void __map_bio(struct dm_target *ti, struct bio *clone,
+		      struct target_io *tio)
+{
+	int r;
+
+	/*
+	 * Sanity checks.
+	 */
+	BUG_ON(!clone->bi_size);
+
+	clone->bi_end_io = clone_endio;
+	clone->bi_private = tio;
+
+	/*
+	 * Map the clone.  If r == 0 we don't need to do
+	 * anything, the target has assumed ownership of
+	 * this io.
+	 */
+	atomic_inc(&tio->io->io_count);
+	r = ti->type->map(ti, clone, &tio->info);
+	if (r > 0)
+		/* the bio has been remapped so dispatch it */
+		generic_make_request(clone);
+
+	else if (r < 0) {
+		/* error the io and bail out */
+		struct dm_io *io = tio->io;
+		free_tio(tio->io->md, tio);
+		dec_pending(io, -EIO);
+		bio_put(clone);
+	}
+}
+
+struct clone_info {
+	struct mapped_device *md;
+	struct dm_table *map;
+	struct bio *bio;
+	struct dm_io *io;
+	sector_t sector;
+	sector_t sector_count;
+	unsigned short idx;
+};
+
+/*
+ * Creates a little bio that is just does part of a bvec.
+ */
+static struct bio *split_bvec(struct bio *bio, sector_t sector,
+			      unsigned short idx, unsigned int offset,
+			      unsigned int len)
+{
+	struct bio *clone;
+	struct bio_vec *bv = bio->bi_io_vec + idx;
+
+	clone = bio_alloc_bioset(GFP_NOIO, 1, dm_set);
+	*clone->bi_io_vec = *bv;
+
+	clone->bi_sector = sector;
+	clone->bi_bdev = bio->bi_bdev;
+	clone->bi_rw = bio->bi_rw;
+	clone->bi_vcnt = 1;
+	clone->bi_size = to_bytes(len);
+	clone->bi_io_vec->bv_offset = offset;
+	clone->bi_io_vec->bv_len = clone->bi_size;
+
+	return clone;
+}
+
+/*
+ * Creates a bio that consists of range of complete bvecs.
+ */
+static struct bio *clone_bio(struct bio *bio, sector_t sector,
+			     unsigned short idx, unsigned short bv_count,
+			     unsigned int len)
+{
+	struct bio *clone;
+
+	clone = bio_clone(bio, GFP_NOIO);
+	clone->bi_sector = sector;
+	clone->bi_idx = idx;
+	clone->bi_vcnt = idx + bv_count;
+	clone->bi_size = to_bytes(len);
+	clone->bi_flags &= ~(1 << BIO_SEG_VALID);
+
+	return clone;
+}
+
+static void __clone_and_map(struct clone_info *ci)
+{
+	struct bio *clone, *bio = ci->bio;
+	struct dm_target *ti = dm_table_find_target(ci->map, ci->sector);
+	sector_t len = 0, max = max_io_len(ci->md, ci->sector, ti);
+	struct target_io *tio;
+
+	/*
+	 * Allocate a target io object.
+	 */
+	tio = alloc_tio(ci->md);
+	tio->io = ci->io;
+	tio->ti = ti;
+	memset(&tio->info, 0, sizeof(tio->info));
+
+	if (ci->sector_count <= max) {
+		/*
+		 * Optimise for the simple case where we can do all of
+		 * the remaining io with a single clone.
+		 */
+		clone = clone_bio(bio, ci->sector, ci->idx,
+				  bio->bi_vcnt - ci->idx, ci->sector_count);
+		__map_bio(ti, clone, tio);
+		ci->sector_count = 0;
+
+	} else if (to_sector(bio->bi_io_vec[ci->idx].bv_len) <= max) {
+		/*
+		 * There are some bvecs that don't span targets.
+		 * Do as many of these as possible.
+		 */
+		int i;
+		sector_t remaining = max;
+		sector_t bv_len;
+
+		for (i = ci->idx; remaining && (i < bio->bi_vcnt); i++) {
+			bv_len = to_sector(bio->bi_io_vec[i].bv_len);
+
+			if (bv_len > remaining)
+				break;
+
+			remaining -= bv_len;
+			len += bv_len;
+		}
+
+		clone = clone_bio(bio, ci->sector, ci->idx, i - ci->idx, len);
+		__map_bio(ti, clone, tio);
+
+		ci->sector += len;
+		ci->sector_count -= len;
+		ci->idx = i;
+
+	} else {
+		/*
+		 * Create two copy bios to deal with io that has
+		 * been split across a target.
+		 */
+		struct bio_vec *bv = bio->bi_io_vec + ci->idx;
+
+		clone = split_bvec(bio, ci->sector, ci->idx,
+				   bv->bv_offset, max);
+		__map_bio(ti, clone, tio);
+
+		ci->sector += max;
+		ci->sector_count -= max;
+		ti = dm_table_find_target(ci->map, ci->sector);
+
+		len = to_sector(bv->bv_len) - max;
+		clone = split_bvec(bio, ci->sector, ci->idx,
+				   bv->bv_offset + to_bytes(max), len);
+		tio = alloc_tio(ci->md);
+		tio->io = ci->io;
+		tio->ti = ti;
+		memset(&tio->info, 0, sizeof(tio->info));
+		__map_bio(ti, clone, tio);
+
+		ci->sector += len;
+		ci->sector_count -= len;
+		ci->idx++;
+	}
+}
+
+/*
+ * Split the bio into several clones.
+ */
+static void __split_bio(struct mapped_device *md, struct bio *bio)
+{
+	struct clone_info ci;
+
+	ci.map = dm_get_table(md);
+	if (!ci.map) {
+		bio_io_error(bio, bio->bi_size);
+		return;
+	}
+
+	ci.md = md;
+	ci.bio = bio;
+	ci.io = alloc_io(md);
+	ci.io->error = 0;
+	atomic_set(&ci.io->io_count, 1);
+	ci.io->bio = bio;
+	ci.io->md = md;
+	ci.sector = bio->bi_sector;
+	ci.sector_count = bio_sectors(bio);
+	ci.idx = bio->bi_idx;
+
+	atomic_inc(&md->pending);
+	while (ci.sector_count)
+		__clone_and_map(&ci);
+
+	/* drop the extra reference count */
+	dec_pending(ci.io, 0);
+	dm_table_put(ci.map);
+}
+/*-----------------------------------------------------------------
+ * CRUD END
+ *---------------------------------------------------------------*/
+
+/*
+ * The request function that just remaps the bio built up by
+ * dm_merge_bvec.
+ */
+static int dm_request(request_queue_t *q, struct bio *bio)
+{
+	int r;
+	struct mapped_device *md = q->queuedata;
+
+	down_read(&md->lock);
+
+	/*
+	 * If we're suspended we have to queue
+	 * this io for later.
+	 */
+	while (test_bit(DMF_BLOCK_IO, &md->flags)) {
+		up_read(&md->lock);
+
+		if (bio_rw(bio) == READA) {
+			bio_io_error(bio, bio->bi_size);
+			return 0;
+		}
+
+		r = queue_io(md, bio);
+		if (r < 0) {
+			bio_io_error(bio, bio->bi_size);
+			return 0;
+
+		} else if (r == 0)
+			return 0;	/* deferred successfully */
+
+		/*
+		 * We're in a while loop, because someone could suspend
+		 * before we get to the following read lock.
+		 */
+		down_read(&md->lock);
+	}
+
+	__split_bio(md, bio);
+	up_read(&md->lock);
+	return 0;
+}
+
+static int dm_flush_all(request_queue_t *q, struct gendisk *disk,
+			sector_t *error_sector)
+{
+	struct mapped_device *md = q->queuedata;
+	struct dm_table *map = dm_get_table(md);
+	int ret = -ENXIO;
+
+	if (map) {
+		ret = dm_table_flush_all(md->map);
+		dm_table_put(map);
+	}
+
+	return ret;
+}
+
+static void dm_unplug_all(request_queue_t *q)
+{
+	struct mapped_device *md = q->queuedata;
+	struct dm_table *map = dm_get_table(md);
+
+	if (map) {
+		dm_table_unplug_all(map);
+		dm_table_put(map);
+	}
+}
+
+static int dm_any_congested(void *congested_data, int bdi_bits)
+{
+	int r;
+	struct mapped_device *md = (struct mapped_device *) congested_data;
+	struct dm_table *map = dm_get_table(md);
+
+	if (!map || test_bit(DMF_BLOCK_IO, &md->flags))
+		r = bdi_bits;
+	else
+		r = dm_table_any_congested(map, bdi_bits);
+
+	dm_table_put(map);
+	return r;
+}
+
+/*-----------------------------------------------------------------
+ * An IDR is used to keep track of allocated minor numbers.
+ *---------------------------------------------------------------*/
+static DECLARE_MUTEX(_minor_lock);
+static DEFINE_IDR(_minor_idr);
+
+static void free_minor(unsigned int minor)
+{
+	down(&_minor_lock);
+	idr_remove(&_minor_idr, minor);
+	up(&_minor_lock);
+}
+
+/*
+ * See if the device with a specific minor # is free.
+ */
+static int specific_minor(struct mapped_device *md, unsigned int minor)
+{
+	int r, m;
+
+	if (minor >= (1 << MINORBITS))
+		return -EINVAL;
+
+	down(&_minor_lock);
+
+	if (idr_find(&_minor_idr, minor)) {
+		r = -EBUSY;
+		goto out;
+	}
+
+	r = idr_pre_get(&_minor_idr, GFP_KERNEL);
+	if (!r) {
+		r = -ENOMEM;
+		goto out;
+	}
+
+	r = idr_get_new_above(&_minor_idr, md, minor, &m);
+	if (r) {
+		goto out;
+	}
+
+	if (m != minor) {
+		idr_remove(&_minor_idr, m);
+		r = -EBUSY;
+		goto out;
+	}
+
+out:
+	up(&_minor_lock);
+	return r;
+}
+
+static int next_free_minor(struct mapped_device *md, unsigned int *minor)
+{
+	int r;
+	unsigned int m;
+
+	down(&_minor_lock);
+
+	r = idr_pre_get(&_minor_idr, GFP_KERNEL);
+	if (!r) {
+		r = -ENOMEM;
+		goto out;
+	}
+
+	r = idr_get_new(&_minor_idr, md, &m);
+	if (r) {
+		goto out;
+	}
+
+	if (m >= (1 << MINORBITS)) {
+		idr_remove(&_minor_idr, m);
+		r = -ENOSPC;
+		goto out;
+	}
+
+	*minor = m;
+
+out:
+	up(&_minor_lock);
+	return r;
+}
+
+static struct block_device_operations dm_blk_dops;
+
+/*
+ * Allocate and initialise a blank device with a given minor.
+ */
+static struct mapped_device *alloc_dev(unsigned int minor, int persistent)
+{
+	int r;
+	struct mapped_device *md = kmalloc(sizeof(*md), GFP_KERNEL);
+
+	if (!md) {
+		DMWARN("unable to allocate device, out of memory.");
+		return NULL;
+	}
+
+	/* get a minor number for the dev */
+	r = persistent ? specific_minor(md, minor) : next_free_minor(md, &minor);
+	if (r < 0)
+		goto bad1;
+
+	memset(md, 0, sizeof(*md));
+	init_rwsem(&md->lock);
+	rwlock_init(&md->map_lock);
+	atomic_set(&md->holders, 1);
+	atomic_set(&md->event_nr, 0);
+
+	md->queue = blk_alloc_queue(GFP_KERNEL);
+	if (!md->queue)
+		goto bad1;
+
+	md->queue->queuedata = md;
+	md->queue->backing_dev_info.congested_fn = dm_any_congested;
+	md->queue->backing_dev_info.congested_data = md;
+	blk_queue_make_request(md->queue, dm_request);
+	md->queue->unplug_fn = dm_unplug_all;
+	md->queue->issue_flush_fn = dm_flush_all;
+
+	md->io_pool = mempool_create(MIN_IOS, mempool_alloc_slab,
+				     mempool_free_slab, _io_cache);
+ 	if (!md->io_pool)
+ 		goto bad2;
+
+	md->tio_pool = mempool_create(MIN_IOS, mempool_alloc_slab,
+				      mempool_free_slab, _tio_cache);
+	if (!md->tio_pool)
+		goto bad3;
+
+	md->disk = alloc_disk(1);
+	if (!md->disk)
+		goto bad4;
+
+	md->disk->major = _major;
+	md->disk->first_minor = minor;
+	md->disk->fops = &dm_blk_dops;
+	md->disk->queue = md->queue;
+	md->disk->private_data = md;
+	sprintf(md->disk->disk_name, "dm-%d", minor);
+	add_disk(md->disk);
+
+	atomic_set(&md->pending, 0);
+	init_waitqueue_head(&md->wait);
+	init_waitqueue_head(&md->eventq);
+
+	return md;
+
+ bad4:
+	mempool_destroy(md->tio_pool);
+ bad3:
+	mempool_destroy(md->io_pool);
+ bad2:
+	blk_put_queue(md->queue);
+	free_minor(minor);
+ bad1:
+	kfree(md);
+	return NULL;
+}
+
+static void free_dev(struct mapped_device *md)
+{
+	free_minor(md->disk->first_minor);
+	mempool_destroy(md->tio_pool);
+	mempool_destroy(md->io_pool);
+	del_gendisk(md->disk);
+	put_disk(md->disk);
+	blk_put_queue(md->queue);
+	kfree(md);
+}
+
+/*
+ * Bind a table to the device.
+ */
+static void event_callback(void *context)
+{
+	struct mapped_device *md = (struct mapped_device *) context;
+
+	atomic_inc(&md->event_nr);
+	wake_up(&md->eventq);
+}
+
+static void __set_size(struct gendisk *disk, sector_t size)
+{
+	struct block_device *bdev;
+
+	set_capacity(disk, size);
+	bdev = bdget_disk(disk, 0);
+	if (bdev) {
+		down(&bdev->bd_inode->i_sem);
+		i_size_write(bdev->bd_inode, (loff_t)size << SECTOR_SHIFT);
+		up(&bdev->bd_inode->i_sem);
+		bdput(bdev);
+	}
+}
+
+static int __bind(struct mapped_device *md, struct dm_table *t)
+{
+	request_queue_t *q = md->queue;
+	sector_t size;
+
+	size = dm_table_get_size(t);
+	__set_size(md->disk, size);
+	if (size == 0)
+		return 0;
+
+	write_lock(&md->map_lock);
+	md->map = t;
+	write_unlock(&md->map_lock);
+
+	dm_table_get(t);
+	dm_table_event_callback(md->map, event_callback, md);
+	dm_table_set_restrictions(t, q);
+	return 0;
+}
+
+static void __unbind(struct mapped_device *md)
+{
+	struct dm_table *map = md->map;
+
+	if (!map)
+		return;
+
+	dm_table_event_callback(map, NULL, NULL);
+	write_lock(&md->map_lock);
+	md->map = NULL;
+	write_unlock(&md->map_lock);
+	dm_table_put(map);
+}
+
+/*
+ * Constructor for a new device.
+ */
+static int create_aux(unsigned int minor, int persistent,
+		      struct mapped_device **result)
+{
+	struct mapped_device *md;
+
+	md = alloc_dev(minor, persistent);
+	if (!md)
+		return -ENXIO;
+
+	*result = md;
+	return 0;
+}
+
+int dm_create(struct mapped_device **result)
+{
+	return create_aux(0, 0, result);
+}
+
+int dm_create_with_minor(unsigned int minor, struct mapped_device **result)
+{
+	return create_aux(minor, 1, result);
+}
+
+void *dm_get_mdptr(dev_t dev)
+{
+	struct mapped_device *md;
+	void *mdptr = NULL;
+	unsigned minor = MINOR(dev);
+
+	if (MAJOR(dev) != _major || minor >= (1 << MINORBITS))
+		return NULL;
+
+	down(&_minor_lock);
+
+	md = idr_find(&_minor_idr, minor);
+
+	if (md && (dm_disk(md)->first_minor == minor))
+		mdptr = md->interface_ptr;
+
+	up(&_minor_lock);
+
+	return mdptr;
+}
+
+void dm_set_mdptr(struct mapped_device *md, void *ptr)
+{
+	md->interface_ptr = ptr;
+}
+
+void dm_get(struct mapped_device *md)
+{
+	atomic_inc(&md->holders);
+}
+
+void dm_put(struct mapped_device *md)
+{
+	struct dm_table *map = dm_get_table(md);
+
+	if (atomic_dec_and_test(&md->holders)) {
+		if (!test_bit(DMF_SUSPENDED, &md->flags) && map) {
+			dm_table_presuspend_targets(map);
+			dm_table_postsuspend_targets(map);
+		}
+		__unbind(md);
+		free_dev(md);
+	}
+
+	dm_table_put(map);
+}
+
+/*
+ * Process the deferred bios
+ */
+static void __flush_deferred_io(struct mapped_device *md, struct bio *c)
+{
+	struct bio *n;
+
+	while (c) {
+		n = c->bi_next;
+		c->bi_next = NULL;
+		__split_bio(md, c);
+		c = n;
+	}
+}
+
+/*
+ * Swap in a new table (destroying old one).
+ */
+int dm_swap_table(struct mapped_device *md, struct dm_table *table)
+{
+	int r;
+
+	down_write(&md->lock);
+
+	/* device must be suspended */
+	if (!test_bit(DMF_SUSPENDED, &md->flags)) {
+		up_write(&md->lock);
+		return -EPERM;
+	}
+
+	__unbind(md);
+	r = __bind(md, table);
+	if (r)
+		return r;
+
+	up_write(&md->lock);
+	return 0;
+}
+
+/*
+ * Functions to lock and unlock any filesystem running on the
+ * device.
+ */
+static int __lock_fs(struct mapped_device *md)
+{
+	struct block_device *bdev;
+
+	if (test_and_set_bit(DMF_FS_LOCKED, &md->flags))
+		return 0;
+
+	bdev = bdget_disk(md->disk, 0);
+	if (!bdev) {
+		DMWARN("bdget failed in __lock_fs");
+		return -ENOMEM;
+	}
+
+	WARN_ON(md->frozen_sb);
+	md->frozen_sb = freeze_bdev(bdev);
+	/* don't bdput right now, we don't want the bdev
+	 * to go away while it is locked.  We'll bdput
+	 * in __unlock_fs
+	 */
+	return 0;
+}
+
+static int __unlock_fs(struct mapped_device *md)
+{
+	struct block_device *bdev;
+
+	if (!test_and_clear_bit(DMF_FS_LOCKED, &md->flags))
+		return 0;
+
+	bdev = bdget_disk(md->disk, 0);
+	if (!bdev) {
+		DMWARN("bdget failed in __unlock_fs");
+		return -ENOMEM;
+	}
+
+	thaw_bdev(bdev, md->frozen_sb);
+	md->frozen_sb = NULL;
+	bdput(bdev);
+	bdput(bdev);
+	return 0;
+}
+
+/*
+ * We need to be able to change a mapping table under a mounted
+ * filesystem.  For example we might want to move some data in
+ * the background.  Before the table can be swapped with
+ * dm_bind_table, dm_suspend must be called to flush any in
+ * flight bios and ensure that any further io gets deferred.
+ */
+int dm_suspend(struct mapped_device *md)
+{
+	struct dm_table *map;
+	DECLARE_WAITQUEUE(wait, current);
+
+	/* Flush I/O to the device. */
+	down_read(&md->lock);
+	if (test_bit(DMF_BLOCK_IO, &md->flags)) {
+		up_read(&md->lock);
+		return -EINVAL;
+	}
+
+	map = dm_get_table(md);
+	if (map)
+		dm_table_presuspend_targets(map);
+	__lock_fs(md);
+
+	up_read(&md->lock);
+
+	/*
+	 * First we set the BLOCK_IO flag so no more ios will be
+	 * mapped.
+	 */
+	down_write(&md->lock);
+	if (test_bit(DMF_BLOCK_IO, &md->flags)) {
+		/*
+		 * If we get here we know another thread is
+		 * trying to suspend as well, so we leave the fs
+		 * locked for this thread.
+		 */
+		up_write(&md->lock);
+		return -EINVAL;
+	}
+
+	set_bit(DMF_BLOCK_IO, &md->flags);
+	add_wait_queue(&md->wait, &wait);
+	up_write(&md->lock);
+
+	/* unplug */
+	if (map) {
+		dm_table_unplug_all(map);
+		dm_table_put(map);
+	}
+
+	/*
+	 * Then we wait for the already mapped ios to
+	 * complete.
+	 */
+	while (1) {
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		if (!atomic_read(&md->pending) || signal_pending(current))
+			break;
+
+		io_schedule();
+	}
+	set_current_state(TASK_RUNNING);
+
+	down_write(&md->lock);
+	remove_wait_queue(&md->wait, &wait);
+
+	/* were we interrupted ? */
+	if (atomic_read(&md->pending)) {
+		__unlock_fs(md);
+		clear_bit(DMF_BLOCK_IO, &md->flags);
+		up_write(&md->lock);
+		return -EINTR;
+	}
+
+	set_bit(DMF_SUSPENDED, &md->flags);
+
+	map = dm_get_table(md);
+	if (map)
+		dm_table_postsuspend_targets(map);
+	dm_table_put(map);
+	up_write(&md->lock);
+
+	return 0;
+}
+
+int dm_resume(struct mapped_device *md)
+{
+	struct bio *def;
+	struct dm_table *map = dm_get_table(md);
+
+	down_write(&md->lock);
+	if (!map ||
+	    !test_bit(DMF_SUSPENDED, &md->flags) ||
+	    !dm_table_get_size(map)) {
+		up_write(&md->lock);
+		dm_table_put(map);
+		return -EINVAL;
+	}
+
+	dm_table_resume_targets(map);
+	clear_bit(DMF_SUSPENDED, &md->flags);
+	clear_bit(DMF_BLOCK_IO, &md->flags);
+
+	def = bio_list_get(&md->deferred);
+	__flush_deferred_io(md, def);
+	up_write(&md->lock);
+	__unlock_fs(md);
+	dm_table_unplug_all(map);
+	dm_table_put(map);
+
+	return 0;
+}
+
+/*-----------------------------------------------------------------
+ * Event notification.
+ *---------------------------------------------------------------*/
+uint32_t dm_get_event_nr(struct mapped_device *md)
+{
+	return atomic_read(&md->event_nr);
+}
+
+int dm_wait_event(struct mapped_device *md, int event_nr)
+{
+	return wait_event_interruptible(md->eventq,
+			(event_nr != atomic_read(&md->event_nr)));
+}
+
+/*
+ * The gendisk is only valid as long as you have a reference
+ * count on 'md'.
+ */
+struct gendisk *dm_disk(struct mapped_device *md)
+{
+	return md->disk;
+}
+
+int dm_suspended(struct mapped_device *md)
+{
+	return test_bit(DMF_SUSPENDED, &md->flags);
+}
+
+static struct block_device_operations dm_blk_dops = {
+	.open = dm_blk_open,
+	.release = dm_blk_close,
+	.owner = THIS_MODULE
+};
+
+EXPORT_SYMBOL(dm_get_mapinfo);
+
+/*
+ * module hooks
+ */
+module_init(dm_init);
+module_exit(dm_exit);
+
+module_param(major, uint, 0);
+MODULE_PARM_DESC(major, "The major number of the device mapper");
+MODULE_DESCRIPTION(DM_NAME " driver");
+MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
+MODULE_LICENSE("GPL");