diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
new file mode 100644
index 0000000..e110655
--- /dev/null
+++ b/drivers/md/dm-log.c
@@ -0,0 +1,711 @@
+/*
+ * Copyright (C) 2003 Sistina Software
+ *
+ * This file is released under the LGPL.
+ */
+
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/vmalloc.h>
+
+#include "dm-log.h"
+#include "dm-io.h"
+
+static LIST_HEAD(_log_types);
+static DEFINE_SPINLOCK(_lock);
+
+int dm_register_dirty_log_type(struct dirty_log_type *type)
+{
+	spin_lock(&_lock);
+	type->use_count = 0;
+	list_add(&type->list, &_log_types);
+	spin_unlock(&_lock);
+
+	return 0;
+}
+
+int dm_unregister_dirty_log_type(struct dirty_log_type *type)
+{
+	spin_lock(&_lock);
+
+	if (type->use_count)
+		DMWARN("Attempt to unregister a log type that is still in use");
+	else
+		list_del(&type->list);
+
+	spin_unlock(&_lock);
+
+	return 0;
+}
+
+static struct dirty_log_type *get_type(const char *type_name)
+{
+	struct dirty_log_type *type;
+
+	spin_lock(&_lock);
+	list_for_each_entry (type, &_log_types, list)
+		if (!strcmp(type_name, type->name)) {
+			if (!type->use_count && !try_module_get(type->module)){
+				spin_unlock(&_lock);
+				return NULL;
+			}
+			type->use_count++;
+			spin_unlock(&_lock);
+			return type;
+		}
+
+	spin_unlock(&_lock);
+	return NULL;
+}
+
+static void put_type(struct dirty_log_type *type)
+{
+	spin_lock(&_lock);
+	if (!--type->use_count)
+		module_put(type->module);
+	spin_unlock(&_lock);
+}
+
+struct dirty_log *dm_create_dirty_log(const char *type_name, struct dm_target *ti,
+				      unsigned int argc, char **argv)
+{
+	struct dirty_log_type *type;
+	struct dirty_log *log;
+
+	log = kmalloc(sizeof(*log), GFP_KERNEL);
+	if (!log)
+		return NULL;
+
+	type = get_type(type_name);
+	if (!type) {
+		kfree(log);
+		return NULL;
+	}
+
+	log->type = type;
+	if (type->ctr(log, ti, argc, argv)) {
+		kfree(log);
+		put_type(type);
+		return NULL;
+	}
+
+	return log;
+}
+
+void dm_destroy_dirty_log(struct dirty_log *log)
+{
+	log->type->dtr(log);
+	put_type(log->type);
+	kfree(log);
+}
+
+/*-----------------------------------------------------------------
+ * Persistent and core logs share a lot of their implementation.
+ * FIXME: need a reload method to be called from a resume
+ *---------------------------------------------------------------*/
+/*
+ * Magic for persistent mirrors: "MiRr"
+ */
+#define MIRROR_MAGIC 0x4D695272
+
+/*
+ * The on-disk version of the metadata.
+ */
+#define MIRROR_DISK_VERSION 1
+#define LOG_OFFSET 2
+
+struct log_header {
+	uint32_t magic;
+
+	/*
+	 * Simple, incrementing version. no backward
+	 * compatibility.
+	 */
+	uint32_t version;
+	sector_t nr_regions;
+};
+
+struct log_c {
+	struct dm_target *ti;
+	int touched;
+	uint32_t region_size;
+	unsigned int region_count;
+	region_t sync_count;
+
+	unsigned bitset_uint32_count;
+	uint32_t *clean_bits;
+	uint32_t *sync_bits;
+	uint32_t *recovering_bits;	/* FIXME: this seems excessive */
+
+	int sync_search;
+
+	/* Resync flag */
+	enum sync {
+		DEFAULTSYNC,	/* Synchronize if necessary */
+		NOSYNC,		/* Devices known to be already in sync */
+		FORCESYNC,	/* Force a sync to happen */
+	} sync;
+
+	/*
+	 * Disk log fields
+	 */
+	struct dm_dev *log_dev;
+	struct log_header header;
+
+	struct io_region header_location;
+	struct log_header *disk_header;
+
+	struct io_region bits_location;
+	uint32_t *disk_bits;
+};
+
+/*
+ * The touched member needs to be updated every time we access
+ * one of the bitsets.
+ */
+static  inline int log_test_bit(uint32_t *bs, unsigned bit)
+{
+	return test_bit(bit, (unsigned long *) bs) ? 1 : 0;
+}
+
+static inline void log_set_bit(struct log_c *l,
+			       uint32_t *bs, unsigned bit)
+{
+	set_bit(bit, (unsigned long *) bs);
+	l->touched = 1;
+}
+
+static inline void log_clear_bit(struct log_c *l,
+				 uint32_t *bs, unsigned bit)
+{
+	clear_bit(bit, (unsigned long *) bs);
+	l->touched = 1;
+}
+
+/*----------------------------------------------------------------
+ * Header IO
+ *--------------------------------------------------------------*/
+static void header_to_disk(struct log_header *core, struct log_header *disk)
+{
+	disk->magic = cpu_to_le32(core->magic);
+	disk->version = cpu_to_le32(core->version);
+	disk->nr_regions = cpu_to_le64(core->nr_regions);
+}
+
+static void header_from_disk(struct log_header *core, struct log_header *disk)
+{
+	core->magic = le32_to_cpu(disk->magic);
+	core->version = le32_to_cpu(disk->version);
+	core->nr_regions = le64_to_cpu(disk->nr_regions);
+}
+
+static int read_header(struct log_c *log)
+{
+	int r;
+	unsigned long ebits;
+
+	r = dm_io_sync_vm(1, &log->header_location, READ,
+			  log->disk_header, &ebits);
+	if (r)
+		return r;
+
+	header_from_disk(&log->header, log->disk_header);
+
+	/* New log required? */
+	if (log->sync != DEFAULTSYNC || log->header.magic != MIRROR_MAGIC) {
+		log->header.magic = MIRROR_MAGIC;
+		log->header.version = MIRROR_DISK_VERSION;
+		log->header.nr_regions = 0;
+	}
+
+	if (log->header.version != MIRROR_DISK_VERSION) {
+		DMWARN("incompatible disk log version");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static inline int write_header(struct log_c *log)
+{
+	unsigned long ebits;
+
+	header_to_disk(&log->header, log->disk_header);
+	return dm_io_sync_vm(1, &log->header_location, WRITE,
+			     log->disk_header, &ebits);
+}
+
+/*----------------------------------------------------------------
+ * Bits IO
+ *--------------------------------------------------------------*/
+static inline void bits_to_core(uint32_t *core, uint32_t *disk, unsigned count)
+{
+	unsigned i;
+
+	for (i = 0; i < count; i++)
+		core[i] = le32_to_cpu(disk[i]);
+}
+
+static inline void bits_to_disk(uint32_t *core, uint32_t *disk, unsigned count)
+{
+	unsigned i;
+
+	/* copy across the clean/dirty bitset */
+	for (i = 0; i < count; i++)
+		disk[i] = cpu_to_le32(core[i]);
+}
+
+static int read_bits(struct log_c *log)
+{
+	int r;
+	unsigned long ebits;
+
+	r = dm_io_sync_vm(1, &log->bits_location, READ,
+			  log->disk_bits, &ebits);
+	if (r)
+		return r;
+
+	bits_to_core(log->clean_bits, log->disk_bits,
+		     log->bitset_uint32_count);
+	return 0;
+}
+
+static int write_bits(struct log_c *log)
+{
+	unsigned long ebits;
+	bits_to_disk(log->clean_bits, log->disk_bits,
+		     log->bitset_uint32_count);
+	return dm_io_sync_vm(1, &log->bits_location, WRITE,
+			     log->disk_bits, &ebits);
+}
+
+/*----------------------------------------------------------------
+ * core log constructor/destructor
+ *
+ * argv contains region_size followed optionally by [no]sync
+ *--------------------------------------------------------------*/
+#define BYTE_SHIFT 3
+static int core_ctr(struct dirty_log *log, struct dm_target *ti,
+		    unsigned int argc, char **argv)
+{
+	enum sync sync = DEFAULTSYNC;
+
+	struct log_c *lc;
+	uint32_t region_size;
+	unsigned int region_count;
+	size_t bitset_size;
+
+	if (argc < 1 || argc > 2) {
+		DMWARN("wrong number of arguments to mirror log");
+		return -EINVAL;
+	}
+
+	if (argc > 1) {
+		if (!strcmp(argv[1], "sync"))
+			sync = FORCESYNC;
+		else if (!strcmp(argv[1], "nosync"))
+			sync = NOSYNC;
+		else {
+			DMWARN("unrecognised sync argument to mirror log: %s",
+			       argv[1]);
+			return -EINVAL;
+		}
+	}
+
+	if (sscanf(argv[0], "%u", &region_size) != 1) {
+		DMWARN("invalid region size string");
+		return -EINVAL;
+	}
+
+	region_count = dm_sector_div_up(ti->len, region_size);
+
+	lc = kmalloc(sizeof(*lc), GFP_KERNEL);
+	if (!lc) {
+		DMWARN("couldn't allocate core log");
+		return -ENOMEM;
+	}
+
+	lc->ti = ti;
+	lc->touched = 0;
+	lc->region_size = region_size;
+	lc->region_count = region_count;
+	lc->sync = sync;
+
+	/*
+	 * Work out how many words we need to hold the bitset.
+	 */
+	bitset_size = dm_round_up(region_count,
+				  sizeof(*lc->clean_bits) << BYTE_SHIFT);
+	bitset_size >>= BYTE_SHIFT;
+
+	lc->bitset_uint32_count = bitset_size / 4;
+	lc->clean_bits = vmalloc(bitset_size);
+	if (!lc->clean_bits) {
+		DMWARN("couldn't allocate clean bitset");
+		kfree(lc);
+		return -ENOMEM;
+	}
+	memset(lc->clean_bits, -1, bitset_size);
+
+	lc->sync_bits = vmalloc(bitset_size);
+	if (!lc->sync_bits) {
+		DMWARN("couldn't allocate sync bitset");
+		vfree(lc->clean_bits);
+		kfree(lc);
+		return -ENOMEM;
+	}
+	memset(lc->sync_bits, (sync == NOSYNC) ? -1 : 0, bitset_size);
+	lc->sync_count = (sync == NOSYNC) ? region_count : 0;
+
+	lc->recovering_bits = vmalloc(bitset_size);
+	if (!lc->recovering_bits) {
+		DMWARN("couldn't allocate sync bitset");
+		vfree(lc->sync_bits);
+		vfree(lc->clean_bits);
+		kfree(lc);
+		return -ENOMEM;
+	}
+	memset(lc->recovering_bits, 0, bitset_size);
+	lc->sync_search = 0;
+	log->context = lc;
+	return 0;
+}
+
+static void core_dtr(struct dirty_log *log)
+{
+	struct log_c *lc = (struct log_c *) log->context;
+	vfree(lc->clean_bits);
+	vfree(lc->sync_bits);
+	vfree(lc->recovering_bits);
+	kfree(lc);
+}
+
+/*----------------------------------------------------------------
+ * disk log constructor/destructor
+ *
+ * argv contains log_device region_size followed optionally by [no]sync
+ *--------------------------------------------------------------*/
+static int disk_ctr(struct dirty_log *log, struct dm_target *ti,
+		    unsigned int argc, char **argv)
+{
+	int r;
+	size_t size;
+	struct log_c *lc;
+	struct dm_dev *dev;
+
+	if (argc < 2 || argc > 3) {
+		DMWARN("wrong number of arguments to disk mirror log");
+		return -EINVAL;
+	}
+
+	r = dm_get_device(ti, argv[0], 0, 0 /* FIXME */,
+			  FMODE_READ | FMODE_WRITE, &dev);
+	if (r)
+		return r;
+
+	r = core_ctr(log, ti, argc - 1, argv + 1);
+	if (r) {
+		dm_put_device(ti, dev);
+		return r;
+	}
+
+	lc = (struct log_c *) log->context;
+	lc->log_dev = dev;
+
+	/* setup the disk header fields */
+	lc->header_location.bdev = lc->log_dev->bdev;
+	lc->header_location.sector = 0;
+	lc->header_location.count = 1;
+
+	/*
+	 * We can't read less than this amount, even though we'll
+	 * not be using most of this space.
+	 */
+	lc->disk_header = vmalloc(1 << SECTOR_SHIFT);
+	if (!lc->disk_header)
+		goto bad;
+
+	/* setup the disk bitset fields */
+	lc->bits_location.bdev = lc->log_dev->bdev;
+	lc->bits_location.sector = LOG_OFFSET;
+
+	size = dm_round_up(lc->bitset_uint32_count * sizeof(uint32_t),
+			   1 << SECTOR_SHIFT);
+	lc->bits_location.count = size >> SECTOR_SHIFT;
+	lc->disk_bits = vmalloc(size);
+	if (!lc->disk_bits) {
+		vfree(lc->disk_header);
+		goto bad;
+	}
+	return 0;
+
+ bad:
+	dm_put_device(ti, lc->log_dev);
+	core_dtr(log);
+	return -ENOMEM;
+}
+
+static void disk_dtr(struct dirty_log *log)
+{
+	struct log_c *lc = (struct log_c *) log->context;
+	dm_put_device(lc->ti, lc->log_dev);
+	vfree(lc->disk_header);
+	vfree(lc->disk_bits);
+	core_dtr(log);
+}
+
+static int count_bits32(uint32_t *addr, unsigned size)
+{
+	int count = 0, i;
+
+	for (i = 0; i < size; i++) {
+		count += hweight32(*(addr+i));
+	}
+	return count;
+}
+
+static int disk_resume(struct dirty_log *log)
+{
+	int r;
+	unsigned i;
+	struct log_c *lc = (struct log_c *) log->context;
+	size_t size = lc->bitset_uint32_count * sizeof(uint32_t);
+
+	/* read the disk header */
+	r = read_header(lc);
+	if (r)
+		return r;
+
+	/* read the bits */
+	r = read_bits(lc);
+	if (r)
+		return r;
+
+	/* set or clear any new bits */
+	if (lc->sync == NOSYNC)
+		for (i = lc->header.nr_regions; i < lc->region_count; i++)
+			/* FIXME: amazingly inefficient */
+			log_set_bit(lc, lc->clean_bits, i);
+	else
+		for (i = lc->header.nr_regions; i < lc->region_count; i++)
+			/* FIXME: amazingly inefficient */
+			log_clear_bit(lc, lc->clean_bits, i);
+
+	/* copy clean across to sync */
+	memcpy(lc->sync_bits, lc->clean_bits, size);
+	lc->sync_count = count_bits32(lc->clean_bits, lc->bitset_uint32_count);
+
+	/* write the bits */
+	r = write_bits(lc);
+	if (r)
+		return r;
+
+	/* set the correct number of regions in the header */
+	lc->header.nr_regions = lc->region_count;
+
+	/* write the new header */
+	return write_header(lc);
+}
+
+static uint32_t core_get_region_size(struct dirty_log *log)
+{
+	struct log_c *lc = (struct log_c *) log->context;
+	return lc->region_size;
+}
+
+static int core_is_clean(struct dirty_log *log, region_t region)
+{
+	struct log_c *lc = (struct log_c *) log->context;
+	return log_test_bit(lc->clean_bits, region);
+}
+
+static int core_in_sync(struct dirty_log *log, region_t region, int block)
+{
+	struct log_c *lc = (struct log_c *) log->context;
+	return log_test_bit(lc->sync_bits, region);
+}
+
+static int core_flush(struct dirty_log *log)
+{
+	/* no op */
+	return 0;
+}
+
+static int disk_flush(struct dirty_log *log)
+{
+	int r;
+	struct log_c *lc = (struct log_c *) log->context;
+
+	/* only write if the log has changed */
+	if (!lc->touched)
+		return 0;
+
+	r = write_bits(lc);
+	if (!r)
+		lc->touched = 0;
+
+	return r;
+}
+
+static void core_mark_region(struct dirty_log *log, region_t region)
+{
+	struct log_c *lc = (struct log_c *) log->context;
+	log_clear_bit(lc, lc->clean_bits, region);
+}
+
+static void core_clear_region(struct dirty_log *log, region_t region)
+{
+	struct log_c *lc = (struct log_c *) log->context;
+	log_set_bit(lc, lc->clean_bits, region);
+}
+
+static int core_get_resync_work(struct dirty_log *log, region_t *region)
+{
+	struct log_c *lc = (struct log_c *) log->context;
+
+	if (lc->sync_search >= lc->region_count)
+		return 0;
+
+	do {
+		*region = find_next_zero_bit((unsigned long *) lc->sync_bits,
+					     lc->region_count,
+					     lc->sync_search);
+		lc->sync_search = *region + 1;
+
+		if (*region == lc->region_count)
+			return 0;
+
+	} while (log_test_bit(lc->recovering_bits, *region));
+
+	log_set_bit(lc, lc->recovering_bits, *region);
+	return 1;
+}
+
+static void core_complete_resync_work(struct dirty_log *log, region_t region,
+				      int success)
+{
+	struct log_c *lc = (struct log_c *) log->context;
+
+	log_clear_bit(lc, lc->recovering_bits, region);
+	if (success) {
+		log_set_bit(lc, lc->sync_bits, region);
+                lc->sync_count++;
+        }
+}
+
+static region_t core_get_sync_count(struct dirty_log *log)
+{
+        struct log_c *lc = (struct log_c *) log->context;
+
+        return lc->sync_count;
+}
+
+#define	DMEMIT_SYNC \
+	if (lc->sync != DEFAULTSYNC) \
+		DMEMIT("%ssync ", lc->sync == NOSYNC ? "no" : "")
+
+static int core_status(struct dirty_log *log, status_type_t status,
+		       char *result, unsigned int maxlen)
+{
+	int sz = 0;
+	struct log_c *lc = log->context;
+
+	switch(status) {
+	case STATUSTYPE_INFO:
+		break;
+
+	case STATUSTYPE_TABLE:
+		DMEMIT("%s %u %u ", log->type->name,
+		       lc->sync == DEFAULTSYNC ? 1 : 2, lc->region_size);
+		DMEMIT_SYNC;
+	}
+
+	return sz;
+}
+
+static int disk_status(struct dirty_log *log, status_type_t status,
+		       char *result, unsigned int maxlen)
+{
+	int sz = 0;
+	char buffer[16];
+	struct log_c *lc = log->context;
+
+	switch(status) {
+	case STATUSTYPE_INFO:
+		break;
+
+	case STATUSTYPE_TABLE:
+		format_dev_t(buffer, lc->log_dev->bdev->bd_dev);
+		DMEMIT("%s %u %s %u ", log->type->name,
+		       lc->sync == DEFAULTSYNC ? 2 : 3, buffer,
+		       lc->region_size);
+		DMEMIT_SYNC;
+	}
+
+	return sz;
+}
+
+static struct dirty_log_type _core_type = {
+	.name = "core",
+	.module = THIS_MODULE,
+	.ctr = core_ctr,
+	.dtr = core_dtr,
+	.get_region_size = core_get_region_size,
+	.is_clean = core_is_clean,
+	.in_sync = core_in_sync,
+	.flush = core_flush,
+	.mark_region = core_mark_region,
+	.clear_region = core_clear_region,
+	.get_resync_work = core_get_resync_work,
+	.complete_resync_work = core_complete_resync_work,
+	.get_sync_count = core_get_sync_count,
+	.status = core_status,
+};
+
+static struct dirty_log_type _disk_type = {
+	.name = "disk",
+	.module = THIS_MODULE,
+	.ctr = disk_ctr,
+	.dtr = disk_dtr,
+	.suspend = disk_flush,
+	.resume = disk_resume,
+	.get_region_size = core_get_region_size,
+	.is_clean = core_is_clean,
+	.in_sync = core_in_sync,
+	.flush = disk_flush,
+	.mark_region = core_mark_region,
+	.clear_region = core_clear_region,
+	.get_resync_work = core_get_resync_work,
+	.complete_resync_work = core_complete_resync_work,
+	.get_sync_count = core_get_sync_count,
+	.status = disk_status,
+};
+
+int __init dm_dirty_log_init(void)
+{
+	int r;
+
+	r = dm_register_dirty_log_type(&_core_type);
+	if (r)
+		DMWARN("couldn't register core log");
+
+	r = dm_register_dirty_log_type(&_disk_type);
+	if (r) {
+		DMWARN("couldn't register disk type");
+		dm_unregister_dirty_log_type(&_core_type);
+	}
+
+	return r;
+}
+
+void dm_dirty_log_exit(void)
+{
+	dm_unregister_dirty_log_type(&_disk_type);
+	dm_unregister_dirty_log_type(&_core_type);
+}
+
+EXPORT_SYMBOL(dm_register_dirty_log_type);
+EXPORT_SYMBOL(dm_unregister_dirty_log_type);
+EXPORT_SYMBOL(dm_create_dirty_log);
+EXPORT_SYMBOL(dm_destroy_dirty_log);