diff --git a/btrfs-image.c b/btrfs-image.c
index 22239fe4..82aa4f39 100644
--- a/btrfs-image.c
+++ b/btrfs-image.c
@@ -35,6 +35,7 @@
 #include "utils.h"
 #include "version.h"
 #include "volumes.h"
+#include "extent_io.h"
 
 #define HEADER_MAGIC		0xbd5c25e27295668bULL
 #define MAX_PENDING_SIZE	(256 * 1024)
@@ -136,6 +137,9 @@ struct mdrestore_struct {
 	int done;
 	int error;
 	int old_restore;
+	int fixup_offset;
+	int multi_devices;
+	struct btrfs_fs_info *info;
 };
 
 static int search_for_chunk_blocks(struct mdrestore_struct *mdres,
@@ -1169,9 +1173,9 @@ static int copy_from_extent_tree(struct metadump_struct *metadump,
 
 		bytenr = key.objectid;
 		if (key.type == BTRFS_METADATA_ITEM_KEY)
-			num_bytes = key.offset;
-		else
 			num_bytes = extent_root->leafsize;
+		else
+			num_bytes = key.offset;
 
 		if (btrfs_item_size_nr(leaf, path->slots[0]) > sizeof(*ei)) {
 			ei = btrfs_item_ptr(leaf, path->slots[0],
@@ -1589,9 +1593,10 @@ static void *restore_worker(void *data)
 	u8 *outbuf;
 	int outfd;
 	int ret;
+	int compress_size = MAX_PENDING_SIZE * 4;
 
 	outfd = fileno(mdres->out);
-	buffer = malloc(MAX_PENDING_SIZE * 2);
+	buffer = malloc(compress_size);
 	if (!buffer) {
 		fprintf(stderr, "Error allocing buffer\n");
 		pthread_mutex_lock(&mdres->mutex);
@@ -1619,7 +1624,7 @@ static void *restore_worker(void *data)
 		pthread_mutex_unlock(&mdres->mutex);
 
 		if (mdres->compress_method == COMPRESS_ZLIB) {
-			size = MAX_PENDING_SIZE * 2;
+			size = compress_size; 
 			ret = uncompress(buffer, (unsigned long *)&size,
 					 async->buffer, async->bufsize);
 			if (ret != Z_OK) {
@@ -1633,44 +1638,60 @@ static void *restore_worker(void *data)
 			size = async->bufsize;
 		}
 
-		if (async->start == BTRFS_SUPER_INFO_OFFSET) {
-			if (mdres->old_restore) {
-				update_super_old(outbuf);
-			} else {
-				ret = update_super(outbuf);
+		if (!mdres->multi_devices) {
+			if (async->start == BTRFS_SUPER_INFO_OFFSET) {
+				if (mdres->old_restore) {
+					update_super_old(outbuf);
+				} else {
+					ret = update_super(outbuf);
+					if (ret)
+						err = ret;
+				}
+			} else if (!mdres->old_restore) {
+				ret = fixup_chunk_tree_block(mdres, async, outbuf, size);
 				if (ret)
 					err = ret;
 			}
-		} else if (!mdres->old_restore) {
-			ret = fixup_chunk_tree_block(mdres, async, outbuf, size);
-			if (ret)
-				err = ret;
 		}
 
-		while (size) {
-			u64 chunk_size = size;
-			bytenr = logical_to_physical(mdres,
-						     async->start + offset,
-						     &chunk_size);
-			ret = pwrite64(outfd, outbuf+offset, chunk_size,
-				       bytenr);
-			if (ret < chunk_size) {
-				if (ret < 0) {
-					fprintf(stderr, "Error writing to "
-						"device %d\n", errno);
-					err = errno;
-					break;
-				} else {
-					fprintf(stderr, "Short write\n");
-					err = -EIO;
-					break;
+		if (!mdres->fixup_offset) {
+			while (size) {
+				u64 chunk_size = size;
+				if (!mdres->multi_devices)
+					bytenr = logical_to_physical(mdres,
+								     async->start + offset,
+								     &chunk_size);
+				else
+					bytenr = async->start + offset;
+
+				ret = pwrite64(outfd, outbuf+offset, chunk_size,
+					       bytenr);
+				if (ret != chunk_size) {
+					if (ret < 0) {
+						fprintf(stderr, "Error writing to "
+							"device %d\n", errno);
+						err = errno;
+						break;
+					} else {
+						fprintf(stderr, "Short write\n");
+						err = -EIO;
+						break;
+					}
 				}
+				size -= chunk_size;
+				offset += chunk_size;
+			}
+		} else if (async->start != BTRFS_SUPER_INFO_OFFSET) {
+			ret = write_data_to_disk(mdres->info, outbuf, async->start, size, 0);
+			if (ret) {
+				printk("Error write data\n");
+				exit(1);
 			}
-			size -= chunk_size;
-			offset += chunk_size;
 		}
 
-		if (async->start == BTRFS_SUPER_INFO_OFFSET)
+
+		/* backup super blocks are already there at fixup_offset stage */
+		if (!mdres->multi_devices && async->start == BTRFS_SUPER_INFO_OFFSET)
 			write_backup_supers(outfd, outbuf);
 
 		pthread_mutex_lock(&mdres->mutex);
@@ -1714,7 +1735,8 @@ static void mdrestore_destroy(struct mdrestore_struct *mdres)
 
 static int mdrestore_init(struct mdrestore_struct *mdres,
 			  FILE *in, FILE *out, int old_restore,
-			  int num_threads)
+			  int num_threads, int fixup_offset,
+			  struct btrfs_fs_info *info, int multi_devices)
 {
 	int i, ret = 0;
 
@@ -1726,6 +1748,9 @@ static int mdrestore_init(struct mdrestore_struct *mdres,
 	mdres->out = out;
 	mdres->old_restore = old_restore;
 	mdres->chunk_tree.rb_node = NULL;
+	mdres->fixup_offset = fixup_offset;
+	mdres->info = info;
+	mdres->multi_devices = multi_devices;
 
 	if (!num_threads)
 		return 0;
@@ -2186,12 +2211,14 @@ static int build_chunk_tree(struct mdrestore_struct *mdres,
 	return search_for_chunk_blocks(mdres, chunk_root_bytenr, 0);
 }
 
-static int restore_metadump(const char *input, FILE *out, int old_restore,
-			    int num_threads)
+static int __restore_metadump(const char *input, FILE *out, int old_restore,
+			      int num_threads, int fixup_offset,
+			      const char *target, int multi_devices)
 {
 	struct meta_cluster *cluster = NULL;
 	struct meta_cluster_header *header;
 	struct mdrestore_struct mdrestore;
+	struct btrfs_fs_info *info = NULL;
 	u64 bytenr = 0;
 	FILE *in = NULL;
 	int ret = 0;
@@ -2206,26 +2233,36 @@ static int restore_metadump(const char *input, FILE *out, int old_restore,
 		}
 	}
 
+	/* NOTE: open with write mode */
+	if (fixup_offset) {
+		BUG_ON(!target);
+		info = open_ctree_fs_info_restore(target, 0, 0, 1, 1);
+		if (!info) {
+			fprintf(stderr, "%s: open ctree failed\n", __func__);
+			ret = -EIO;
+			goto failed_open;
+		}
+	}
+
 	cluster = malloc(BLOCK_SIZE);
 	if (!cluster) {
 		fprintf(stderr, "Error allocating cluster\n");
-		if (in != stdin)
-			fclose(in);
-		return -ENOMEM;
+		ret = -ENOMEM;
+		goto failed_info;
 	}
 
-	ret = mdrestore_init(&mdrestore, in, out, old_restore, num_threads);
+	ret = mdrestore_init(&mdrestore, in, out, old_restore, num_threads,
+			     fixup_offset, info, multi_devices);
 	if (ret) {
 		fprintf(stderr, "Error initing mdrestore %d\n", ret);
-		if (in != stdin)
-			fclose(in);
-		free(cluster);
-		return ret;
+		goto failed_cluster;
 	}
 
-	ret = build_chunk_tree(&mdrestore, cluster);
-	if (ret)
-		goto out;
+	if (!multi_devices) {
+		ret = build_chunk_tree(&mdrestore, cluster);
+		if (ret)
+			goto out;
+	}
 
 	if (in != stdin && fseek(in, 0, SEEK_SET)) {
 		fprintf(stderr, "Error seeking %d\n", errno);
@@ -2259,12 +2296,123 @@ static int restore_metadump(const char *input, FILE *out, int old_restore,
 	}
 out:
 	mdrestore_destroy(&mdrestore);
+failed_cluster:
 	free(cluster);
+failed_info:
+	if (fixup_offset && info)
+		close_ctree(info->chunk_root);
+failed_open:
 	if (in != stdin)
 		fclose(in);
 	return ret;
 }
 
+static int restore_metadump(const char *input, FILE *out, int old_restore,
+			    int num_threads, int multi_devices)
+{
+	return __restore_metadump(input, out, old_restore, num_threads, 0, NULL,
+				  multi_devices);
+}
+
+static int fixup_metadump(const char *input, FILE *out, int num_threads,
+			  const char *target)
+{
+	return __restore_metadump(input, out, 0, num_threads, 1, target, 1);
+}
+
+static int update_disk_super_on_device(struct btrfs_fs_info *info,
+				       const char *other_dev, u64 cur_devid)
+{
+	struct btrfs_key key;
+	struct extent_buffer *leaf;
+	struct btrfs_path path;
+	struct btrfs_dev_item *dev_item;
+	struct btrfs_super_block *disk_super;
+	char dev_uuid[BTRFS_UUID_SIZE];
+	char fs_uuid[BTRFS_UUID_SIZE];
+	u64 devid, type, io_align, io_width;
+	u64 sector_size, total_bytes, bytes_used;
+	char *buf;
+	int fp;
+	int ret;
+
+	key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
+	key.type = BTRFS_DEV_ITEM_KEY;
+	key.offset = cur_devid;
+
+	btrfs_init_path(&path);
+	ret = btrfs_search_slot(NULL, info->chunk_root, &key, &path, 0, 0); 
+	if (ret) {
+		fprintf(stderr, "search key fails\n");
+		exit(1);
+	}
+
+	leaf = path.nodes[0];
+	dev_item = btrfs_item_ptr(leaf, path.slots[0],
+				  struct btrfs_dev_item);
+
+	devid = btrfs_device_id(leaf, dev_item);
+	if (devid != cur_devid) {
+		printk("devid %llu mismatch with %llu\n", devid, cur_devid);
+		exit(1);
+	}
+
+	type = btrfs_device_type(leaf, dev_item);
+	io_align = btrfs_device_io_align(leaf, dev_item);
+	io_width = btrfs_device_io_width(leaf, dev_item);
+	sector_size = btrfs_device_sector_size(leaf, dev_item);
+	total_bytes = btrfs_device_total_bytes(leaf, dev_item);
+	bytes_used = btrfs_device_bytes_used(leaf, dev_item);
+	read_extent_buffer(leaf, dev_uuid, (unsigned long)btrfs_device_uuid(dev_item), BTRFS_UUID_SIZE);
+	read_extent_buffer(leaf, fs_uuid, (unsigned long)btrfs_device_fsid(dev_item), BTRFS_UUID_SIZE);
+
+	btrfs_release_path(info->chunk_root, &path);
+
+	printk("update disk super on %s devid=%llu\n", other_dev, devid);
+
+	/* update other devices' super block */
+	fp = open(other_dev, O_CREAT | O_RDWR, 0600);
+	if (fp < 0) {
+		fprintf(stderr, "could not open %s\n", other_dev);
+		exit(1);
+	}
+
+	buf = malloc(BTRFS_SUPER_INFO_SIZE);
+	if (!buf) {
+		ret = -ENOMEM;
+		exit(1);
+	}
+
+	memcpy(buf, info->super_copy, BTRFS_SUPER_INFO_SIZE);
+
+	disk_super = (struct btrfs_super_block *)buf;
+	dev_item = &disk_super->dev_item;
+
+	btrfs_set_stack_device_type(dev_item, type);
+	btrfs_set_stack_device_id(dev_item, devid);
+	btrfs_set_stack_device_total_bytes(dev_item, total_bytes);
+	btrfs_set_stack_device_bytes_used(dev_item, bytes_used);
+	btrfs_set_stack_device_io_align(dev_item, io_align);
+	btrfs_set_stack_device_io_width(dev_item, io_width);
+	btrfs_set_stack_device_sector_size(dev_item, sector_size);
+	memcpy(dev_item->uuid, dev_uuid, BTRFS_UUID_SIZE);
+	memcpy(dev_item->fsid, fs_uuid, BTRFS_UUID_SIZE);
+	csum_block((u8 *)buf, BTRFS_SUPER_INFO_SIZE);
+
+	ret = pwrite64(fp, buf, BTRFS_SUPER_INFO_SIZE, BTRFS_SUPER_INFO_OFFSET);
+	if (ret != BTRFS_SUPER_INFO_SIZE) {
+		ret = -EIO;
+		goto out;
+	}
+
+	write_backup_supers(fp, (u8 *)buf);
+
+out:
+	free(buf);
+	close(fp);
+	return 0;
+}
+
 static void print_usage(void)
 {
 	fprintf(stderr, "usage: btrfs-image [options] source target\n");
@@ -2272,7 +2420,7 @@ static void print_usage(void)
 	fprintf(stderr, "\t-c value\tcompression level (0 ~ 9)\n");
 	fprintf(stderr, "\t-t value\tnumber of threads (1 ~ 32)\n");
 	fprintf(stderr, "\t-o      \tdon't mess with the chunk tree when restoring\n");
-	fprintf(stderr, "\t-s      \tsanitize file names, use once to just use garbage, use twice if you want crc collisions");
+	fprintf(stderr, "\t-s      \tsanitize file names, use once to just use garbage, use twice if you want crc collisions\n");
 	fprintf(stderr, "\t-w      \twalk all trees instead of using extent tree, do this if your extent tree is broken\n");
 	exit(1);
 }
@@ -2286,12 +2434,14 @@ int main(int argc, char *argv[])
 	int create = 1;
 	int old_restore = 0;
 	int walk_trees = 0;
+	int multi_devices = 0;
 	int ret;
 	int sanitize = 0;
+	int dev_cnt = 0;
 	FILE *out;
 
 	while (1) {
-		int c = getopt(argc, argv, "rc:t:osw");
+		int c = getopt(argc, argv, "rc:t:oswm");
 		if (c < 0)
 			break;
 		switch (c) {
@@ -2317,17 +2467,26 @@ int main(int argc, char *argv[])
 		case 'w':
 			walk_trees = 1;
 			break;
+		case 'm':
+			create = 0;
+			multi_devices = 1;
+			break;
 		default:
 			print_usage();
 		}
 	}
 
-	if (old_restore && create)
+	if ((old_restore) && create)
 		print_usage();
 
 	argc = argc - optind;
-	if (argc != 2)
+	dev_cnt = argc - 1;
+
+	if (multi_devices && dev_cnt < 2)
 		print_usage();
+	if (!multi_devices && dev_cnt != 1)
+		print_usage();
+
 	source = argv[optind];
 	target = argv[optind + 1];
 
@@ -2351,8 +2510,60 @@ int main(int argc, char *argv[])
 		ret = create_metadump(source, out, num_threads,
 				      compress_level, sanitize, walk_trees);
 	else
-		ret = restore_metadump(source, out, old_restore, 1);
+		ret = restore_metadump(source, out, old_restore, 1,
+				       multi_devices);
+	if (ret) {
+		printk("%s failed (%s)\n", (create) ? "create" : "restore",
+		       strerror(errno));
+		goto out;
+	}
 
+	 /* extended support for multiple devices */
+	if (!create && multi_devices) {
+		struct btrfs_fs_info *info;
+		u64 total_devs;
+		int i;
+
+		info = open_ctree_fs_info_restore(target, 0, 0, 0, 1);
+		if (!info) {
+			int e = errno;
+			fprintf(stderr, "unable to open %s error = %s\n",
+				target, strerror(e));
+			return 1;
+		}
+
+		total_devs = btrfs_super_num_devices(info->super_copy);
+		if (total_devs != dev_cnt) {
+			printk("it needs %llu devices but has only %d\n",
+				total_devs, dev_cnt);
+			close_ctree(info->chunk_root);
+			goto out;
+		}
+
+		/* update super block on other disks */
+		for (i = 2; i <= dev_cnt; i++) {
+			ret = update_disk_super_on_device(info,
+					argv[optind + i], (u64)i);
+			if (ret) {
+				printk("update disk super failed devid=%d (error=%d)\n",
+					i, ret);
+				close_ctree(info->chunk_root);
+				exit(1);
+			}
+		}
+
+		close_ctree(info->chunk_root);
+
+		/* fix metadata block to map correct chunk */
+		ret = fixup_metadump(source, out, 1, target);
+		if (ret) {
+			fprintf(stderr, "fix metadump failed (error=%d)\n",
+				ret);
+			exit(1);
+		}
+	}
+
+out:
 	if (out == stdout)
 		fflush(out);
 	else
diff --git a/ctree.h b/ctree.h
index 4347c8a1..0b0d701f 100644
--- a/ctree.h
+++ b/ctree.h
@@ -949,6 +949,7 @@ struct btrfs_fs_info {
 	struct list_head space_info;
 	int system_allocs;
 	int readonly;
+	int on_restoring;
 	int (*free_extent_hook)(struct btrfs_trans_handle *trans,
 				struct btrfs_root *root,
 				u64 bytenr, u64 num_bytes, u64 parent,
diff --git a/disk-io.c b/disk-io.c
index a41d1660..13dbe277 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -192,7 +192,7 @@ out:
 }
 
 
-static int read_whole_eb(struct btrfs_fs_info *info, struct extent_buffer *eb, int mirror)
+int read_whole_eb(struct btrfs_fs_info *info, struct extent_buffer *eb, int mirror)
 {
 	unsigned long offset = 0;
 	struct btrfs_multi_bio *multi = NULL;
@@ -203,26 +203,40 @@ static int read_whole_eb(struct btrfs_fs_info *info, struct extent_buffer *eb, i
 
 	while (bytes_left) {
 		read_len = bytes_left;
-		ret = btrfs_map_block(&info->mapping_tree, READ,
-				      eb->start + offset, &read_len, &multi,
-				      mirror, NULL);
-		if (ret) {
-			printk("Couldn't map the block %Lu\n", eb->start + offset);
-			kfree(multi);
-			return -EIO;
-		}
-		device = multi->stripes[0].dev;
+		device = NULL;
 
-		if (device->fd == 0) {
-			kfree(multi);
-			return -EIO;
-		}
+		if (!info->on_restoring) {
+			ret = btrfs_map_block(&info->mapping_tree, READ,
+					      eb->start + offset, &read_len, &multi,
+					      mirror, NULL);
+			if (ret) {
+				printk("Couldn't map the block %Lu\n", eb->start + offset);
+				kfree(multi);
+				return -EIO;
+			}
+			device = multi->stripes[0].dev;
 
-		eb->fd = device->fd;
-		device->total_ios++;
-		eb->dev_bytenr = multi->stripes[0].physical;
-		kfree(multi);
-		multi = NULL;
+			if (device->fd == 0) {
+				kfree(multi);
+				return -EIO;
+			}
+
+			eb->fd = device->fd;
+			device->total_ios++;
+			eb->dev_bytenr = multi->stripes[0].physical;
+			kfree(multi);
+			multi = NULL;
+		} else {
+			/* special case for restore metadump */
+			list_for_each_entry(device, &info->fs_devices->devices, dev_list) {
+				if (device->devid == 1)
+					break;
+			}
+
+			eb->fd = device->fd;
+			eb->dev_bytenr = eb->start;
+			device->total_ios++;
+		}
 
 		if (read_len > bytes_left)
 			read_len = bytes_left;
@@ -291,149 +305,6 @@ struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
 	return NULL;
 }
 
-static int rmw_eb(struct btrfs_fs_info *info,
-		  struct extent_buffer *eb, struct extent_buffer *orig_eb)
-{
-	int ret;
-	unsigned long orig_off = 0;
-	unsigned long dest_off = 0;
-	unsigned long copy_len = eb->len;
-
-	ret = read_whole_eb(info, eb, 0);
-	if (ret)
-		return ret;
-
-	if (eb->start + eb->len <= orig_eb->start ||
-	    eb->start >= orig_eb->start + orig_eb->len)
-		return 0;
-	/*
-	 * | ----- orig_eb ------- |
-	 *         | ----- stripe -------  |
-	 *         | ----- orig_eb ------- |
-	 *              | ----- orig_eb ------- |
-	 */
-	if (eb->start > orig_eb->start)
-		orig_off = eb->start - orig_eb->start;
-	if (orig_eb->start > eb->start)
-		dest_off = orig_eb->start - eb->start;
-
-	if (copy_len > orig_eb->len - orig_off)
-		copy_len = orig_eb->len - orig_off;
-	if (copy_len > eb->len - dest_off)
-		copy_len = eb->len - dest_off;
-
-	memcpy(eb->data + dest_off, orig_eb->data + orig_off, copy_len);
-	return 0;
-}
-
-static void split_eb_for_raid56(struct btrfs_fs_info *info,
-				struct extent_buffer *orig_eb,
-			       struct extent_buffer **ebs,
-			       u64 stripe_len, u64 *raid_map,
-			       int num_stripes)
-{
-	struct extent_buffer *eb;
-	u64 start = orig_eb->start;
-	u64 this_eb_start;
-	int i;
-	int ret;
-
-	for (i = 0; i < num_stripes; i++) {
-		if (raid_map[i] >= BTRFS_RAID5_P_STRIPE)
-			break;
-
-		eb = malloc(sizeof(struct extent_buffer) + stripe_len);
-		if (!eb)
-			BUG();
-		memset(eb, 0, sizeof(struct extent_buffer) + stripe_len);
-
-		eb->start = raid_map[i];
-		eb->len = stripe_len;
-		eb->refs = 1;
-		eb->flags = 0;
-		eb->fd = -1;
-		eb->dev_bytenr = (u64)-1;
-
-		this_eb_start = raid_map[i];
-
-		if (start > this_eb_start ||
-		    start + orig_eb->len < this_eb_start + stripe_len) {
-			ret = rmw_eb(info, eb, orig_eb);
-			BUG_ON(ret);
-		} else {
-			memcpy(eb->data, orig_eb->data + eb->start - start, stripe_len);
-		}
-		ebs[i] = eb;
-	}
-}
-
-static int write_raid56_with_parity(struct btrfs_fs_info *info,
-				    struct extent_buffer *eb,
-				    struct btrfs_multi_bio *multi,
-				    u64 stripe_len, u64 *raid_map)
-{
-	struct extent_buffer *ebs[multi->num_stripes], *p_eb = NULL, *q_eb = NULL;
-	int i;
-	int j;
-	int ret;
-	int alloc_size = eb->len;
-
-	if (stripe_len > alloc_size)
-		alloc_size = stripe_len;
-
-	split_eb_for_raid56(info, eb, ebs, stripe_len, raid_map,
-			    multi->num_stripes);
-
-	for (i = 0; i < multi->num_stripes; i++) {
-		struct extent_buffer *new_eb;
-		if (raid_map[i] < BTRFS_RAID5_P_STRIPE) {
-			ebs[i]->dev_bytenr = multi->stripes[i].physical;
-			ebs[i]->fd = multi->stripes[i].dev->fd;
-			multi->stripes[i].dev->total_ios++;
-			BUG_ON(ebs[i]->start != raid_map[i]);
-			continue;
-		}
-		new_eb = kmalloc(sizeof(*eb) + alloc_size, GFP_NOFS);
-		BUG_ON(!new_eb);
-		new_eb->dev_bytenr = multi->stripes[i].physical;
-		new_eb->fd = multi->stripes[i].dev->fd;
-		multi->stripes[i].dev->total_ios++;
-		new_eb->len = stripe_len;
-
-		if (raid_map[i] == BTRFS_RAID5_P_STRIPE)
-			p_eb = new_eb;
-		else if (raid_map[i] == BTRFS_RAID6_Q_STRIPE)
-			q_eb = new_eb;
-	}
-	if (q_eb) {
-		void *pointers[multi->num_stripes];
-		ebs[multi->num_stripes - 2] = p_eb;
-		ebs[multi->num_stripes - 1] = q_eb;
-
-		for (i = 0; i < multi->num_stripes; i++)
-			pointers[i] = ebs[i]->data;
-
-		raid6_gen_syndrome(multi->num_stripes, stripe_len, pointers);
-	} else {
-		ebs[multi->num_stripes - 1] = p_eb;
-		memcpy(p_eb->data, ebs[0]->data, stripe_len);
-		for (j = 1; j < multi->num_stripes - 1; j++) {
-			for (i = 0; i < stripe_len; i += sizeof(unsigned long)) {
-				*(unsigned long *)(p_eb->data + i) ^=
-					*(unsigned long *)(ebs[j]->data + i);
-			}
-		}
-	}
-
-	for (i = 0; i < multi->num_stripes; i++) {
-		ret = write_extent_to_disk(ebs[i]);
-		BUG_ON(ret);
-		if (ebs[i] != eb)
-			kfree(ebs[i]);
-	}
-	return 0;
-}
-
 int write_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 		     struct extent_buffer *eb)
 {
@@ -445,6 +316,7 @@ int write_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 
 	if (check_tree_block(root, eb))
 		BUG();
+
 	if (!btrfs_buffer_uptodate(eb, trans->transid))
 		BUG();
 
@@ -1106,7 +978,7 @@ int btrfs_setup_chunk_tree_and_device_map(struct btrfs_fs_info *fs_info)
 static struct btrfs_fs_info *__open_ctree_fd(int fp, const char *path,
 					     u64 sb_bytenr,
 					     u64 root_tree_bytenr, int writes,
-					     int partial)
+					     int partial, int restore)
 {
 	struct btrfs_fs_info *fs_info;
 	struct btrfs_super_block *disk_super;
@@ -1126,6 +998,8 @@ static struct btrfs_fs_info *__open_ctree_fd(int fp, const char *path,
 		fprintf(stderr, "Failed to allocate memory for fs_info\n");
 		return NULL;
 	}
+	if (restore)
+		fs_info->on_restoring = 1;
 
 	ret = btrfs_scan_fs_devices(fp, path, &fs_devices);
 	if (ret)
@@ -1182,6 +1056,29 @@ out:
 	return NULL;
 }
 
+struct btrfs_fs_info *open_ctree_fs_info_restore(const char *filename,
+					 u64 sb_bytenr, u64 root_tree_bytenr,
+					 int writes, int partial)
+{
+	int fp;
+	struct btrfs_fs_info *info;
+	int flags = O_CREAT | O_RDWR;
+	int restore = 1;
+
+	if (!writes)
+		flags = O_RDONLY;
+
+	fp = open(filename, flags, 0600);
+	if (fp < 0) {
+		fprintf (stderr, "Could not open %s\n", filename);
+		return NULL;
+	}
+	info = __open_ctree_fd(fp, filename, sb_bytenr, root_tree_bytenr,
+			       writes, partial, restore);
+	close(fp);
+	return info;
+}
+
 struct btrfs_fs_info *open_ctree_fs_info(const char *filename,
 					 u64 sb_bytenr, u64 root_tree_bytenr,
 					 int writes, int partial)
@@ -1199,7 +1096,7 @@ struct btrfs_fs_info *open_ctree_fs_info(const char *filename,
 		return NULL;
 	}
 	info = __open_ctree_fd(fp, filename, sb_bytenr, root_tree_bytenr,
-			       writes, partial);
+			       writes, partial, 0);
 	close(fp);
 	return info;
 }
@@ -1218,7 +1115,7 @@ struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr,
 				 int writes)
 {
 	struct btrfs_fs_info *info;
-	info = __open_ctree_fd(fp, path, sb_bytenr, 0, writes, 0);
+	info = __open_ctree_fd(fp, path, sb_bytenr, 0, writes, 0, 0);
 	if (!info)
 		return NULL;
 	return info->fs_root;
diff --git a/disk-io.h b/disk-io.h
index 5fed663c..effaa9fd 100644
--- a/disk-io.h
+++ b/disk-io.h
@@ -35,10 +35,13 @@ static inline u64 btrfs_sb_offset(int mirror)
 
 struct btrfs_device;
 
+int read_whole_eb(struct btrfs_fs_info *info, struct extent_buffer *eb, int mirror);
 struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
 				      u32 blocksize, u64 parent_transid);
 int readahead_tree_block(struct btrfs_root *root, u64 bytenr, u32 blocksize,
 			 u64 parent_transid);
+int write_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root *root,
+		     struct extent_buffer *eb);
 struct extent_buffer *btrfs_find_create_tree_block(struct btrfs_root *root,
 						   u64 bytenr, u32 blocksize);
 
@@ -62,6 +65,9 @@ int btrfs_setup_chunk_tree_and_device_map(struct btrfs_fs_info *fs_info);
 struct btrfs_root *open_ctree(const char *filename, u64 sb_bytenr, int writes);
 struct btrfs_root *open_ctree_fd(int fp, const char *path, u64 sb_bytenr,
 				 int writes);
+struct btrfs_fs_info *open_ctree_fs_info_restore(const char *filename,
+					 u64 sb_bytenr, u64 root_tree_bytenr,
+					 int writes, int partial);
 struct btrfs_fs_info *open_ctree_fs_info(const char *filename,
 					 u64 sb_bytenr, u64 root_tree_bytenr,
 					 int writes, int partial);
diff --git a/extent_io.c b/extent_io.c
index 377dec09..464bd07e 100644
--- a/extent_io.c
+++ b/extent_io.c
@@ -749,6 +749,93 @@ int read_data_from_disk(struct btrfs_fs_info *info, void *buf, u64 offset,
 	return 0;
 }
 
+int write_data_to_disk(struct btrfs_fs_info *info, void *buf, u64 offset,
+		      u64 bytes, int mirror)
+{
+	struct btrfs_multi_bio *multi = NULL;
+	struct btrfs_device *device;
+	u64 bytes_left = bytes;
+	u64 this_len;
+	u64 total_write = 0;
+	u64 *raid_map = NULL;
+	u64 dev_bytenr;
+	int dev_nr;
+	int ret = 0;
+
+	while (bytes_left > 0) {
+		this_len = bytes_left;
+		dev_nr = 0;
+
+		ret = btrfs_map_block(&info->mapping_tree, WRITE, offset,
+				      &this_len, &multi, mirror, &raid_map);
+		if (ret) {
+			fprintf(stderr, "Couldn't map the block %Lu\n",
+				offset);
+			return -EIO;
+		}
+
+		if (raid_map) {
+			struct extent_buffer *eb;
+			u64 stripe_len = this_len;
+
+			this_len = min(this_len, bytes_left);
+			this_len = min(this_len, (u64)info->tree_root->leafsize);
+
+			eb = malloc(sizeof(struct extent_buffer) + this_len);
+			BUG_ON(!eb);
+
+			memset(eb, 0, sizeof(struct extent_buffer) + this_len);
+			eb->start = offset;
+			eb->len = this_len;
+
+			memcpy(eb->data, buf + total_write, this_len);
+			ret = write_raid56_with_parity(info, eb, multi,
+						       stripe_len, raid_map);
+			BUG_ON(ret);
+
+			free(eb);
+			kfree(raid_map);
+			raid_map = NULL;
+		} else while (dev_nr < multi->num_stripes) {
+			device = multi->stripes[dev_nr].dev;
+			if (device->fd == 0) {
+				kfree(multi);
+				return -EIO;
+			}
+
+			dev_bytenr = multi->stripes[dev_nr].physical;
+			this_len = min(this_len, bytes_left);
+			dev_nr++;
+
+			ret = pwrite(device->fd, buf + total_write, this_len, dev_bytenr);
+			if (ret != this_len) {
+				if (ret < 0) {
+					fprintf(stderr, "Error writing to "
+						"device %d\n", errno);
+					ret = errno;
+					kfree(multi);
+					return ret;
+				} else {
+					fprintf(stderr, "Short write\n");
+					kfree(multi);
+					return -EIO;
+				}
+			}
+		}
+
+		BUG_ON(bytes_left < this_len);
+
+		bytes_left -= this_len;
+		offset += this_len;
+		total_write += this_len;
+
+		kfree(multi);
+		multi = NULL;
+	}
+	return 0;
+}
+
+
 int set_extent_buffer_uptodate(struct extent_buffer *eb)
 {
 	eb->flags |= EXTENT_UPTODATE;
diff --git a/extent_io.h b/extent_io.h
index 2f5ff023..2604dcef 100644
--- a/extent_io.h
+++ b/extent_io.h
@@ -132,4 +132,6 @@ int set_extent_buffer_dirty(struct extent_buffer *eb);
 int clear_extent_buffer_dirty(struct extent_buffer *eb);
 int read_data_from_disk(struct btrfs_fs_info *info, void *buf, u64 offset,
 			u64 bytes, int mirror);
+int write_data_to_disk(struct btrfs_fs_info *info, void *buf, u64 offset,
+		       u64 bytes, int mirror);
 #endif
diff --git a/volumes.c b/volumes.c
index ab282d3d..437e219a 100644
--- a/volumes.c
+++ b/volumes.c
@@ -189,6 +189,10 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices, int flags)
 
 	list_for_each(cur, head) {
 		device = list_entry(cur, struct btrfs_device, dev_list);
+		if (!device->name) {
+			printk("no name for device %llu, skip it now\n", device->devid);
+			continue;
+		}
 
 		fd = open(device->name, flags);
 		if (fd < 0) {
@@ -1769,3 +1773,146 @@ struct list_head *btrfs_scanned_uuids(void)
 {
 	return &fs_uuids;
 }
+
+static int rmw_eb(struct btrfs_fs_info *info,
+		  struct extent_buffer *eb, struct extent_buffer *orig_eb)
+{
+	int ret;
+	unsigned long orig_off = 0;
+	unsigned long dest_off = 0;
+	unsigned long copy_len = eb->len;
+
+	ret = read_whole_eb(info, eb, 0);
+	if (ret)
+		return ret;
+
+	if (eb->start + eb->len <= orig_eb->start ||
+	    eb->start >= orig_eb->start + orig_eb->len)
+		return 0;
+	/*
+	 * | ----- orig_eb ------- |
+	 *         | ----- stripe -------  |
+	 *         | ----- orig_eb ------- |
+	 *              | ----- orig_eb ------- |
+	 */
+	if (eb->start > orig_eb->start)
+		orig_off = eb->start - orig_eb->start;
+	if (orig_eb->start > eb->start)
+		dest_off = orig_eb->start - eb->start;
+
+	if (copy_len > orig_eb->len - orig_off)
+		copy_len = orig_eb->len - orig_off;
+	if (copy_len > eb->len - dest_off)
+		copy_len = eb->len - dest_off;
+
+	memcpy(eb->data + dest_off, orig_eb->data + orig_off, copy_len);
+	return 0;
+}
+
+static void split_eb_for_raid56(struct btrfs_fs_info *info,
+				struct extent_buffer *orig_eb,
+			       struct extent_buffer **ebs,
+			       u64 stripe_len, u64 *raid_map,
+			       int num_stripes)
+{
+	struct extent_buffer *eb;
+	u64 start = orig_eb->start;
+	u64 this_eb_start;
+	int i;
+	int ret;
+
+	for (i = 0; i < num_stripes; i++) {
+		if (raid_map[i] >= BTRFS_RAID5_P_STRIPE)
+			break;
+
+		eb = malloc(sizeof(struct extent_buffer) + stripe_len);
+		if (!eb)
+			BUG();
+		memset(eb, 0, sizeof(struct extent_buffer) + stripe_len);
+
+		eb->start = raid_map[i];
+		eb->len = stripe_len;
+		eb->refs = 1;
+		eb->flags = 0;
+		eb->fd = -1;
+		eb->dev_bytenr = (u64)-1;
+
+		this_eb_start = raid_map[i];
+
+		if (start > this_eb_start ||
+		    start + orig_eb->len < this_eb_start + stripe_len) {
+			ret = rmw_eb(info, eb, orig_eb);
+			BUG_ON(ret);
+		} else {
+			memcpy(eb->data, orig_eb->data + eb->start - start, stripe_len);
+		}
+		ebs[i] = eb;
+	}
+}
+
+int write_raid56_with_parity(struct btrfs_fs_info *info,
+			     struct extent_buffer *eb,
+			     struct btrfs_multi_bio *multi,
+			     u64 stripe_len, u64 *raid_map)
+{
+	struct extent_buffer *ebs[multi->num_stripes], *p_eb = NULL, *q_eb = NULL;
+	int i;
+	int j;
+	int ret;
+	int alloc_size = eb->len;
+
+	if (stripe_len > alloc_size)
+		alloc_size = stripe_len;
+
+	split_eb_for_raid56(info, eb, ebs, stripe_len, raid_map,
+			    multi->num_stripes);
+
+	for (i = 0; i < multi->num_stripes; i++) {
+		struct extent_buffer *new_eb;
+		if (raid_map[i] < BTRFS_RAID5_P_STRIPE) {
+			ebs[i]->dev_bytenr = multi->stripes[i].physical;
+			ebs[i]->fd = multi->stripes[i].dev->fd;
+			multi->stripes[i].dev->total_ios++;
+			BUG_ON(ebs[i]->start != raid_map[i]);
+			continue;
+		}
+		new_eb = kmalloc(sizeof(*eb) + alloc_size, GFP_NOFS);
+		BUG_ON(!new_eb);
+		new_eb->dev_bytenr = multi->stripes[i].physical;
+		new_eb->fd = multi->stripes[i].dev->fd;
+		multi->stripes[i].dev->total_ios++;
+		new_eb->len = stripe_len;
+
+		if (raid_map[i] == BTRFS_RAID5_P_STRIPE)
+			p_eb = new_eb;
+		else if (raid_map[i] == BTRFS_RAID6_Q_STRIPE)
+			q_eb = new_eb;
+	}
+	if (q_eb) {
+		void *pointers[multi->num_stripes];
+		ebs[multi->num_stripes - 2] = p_eb;
+		ebs[multi->num_stripes - 1] = q_eb;
+
+		for (i = 0; i < multi->num_stripes; i++)
+			pointers[i] = ebs[i]->data;
+
+		raid6_gen_syndrome(multi->num_stripes, stripe_len, pointers);
+	} else {
+		ebs[multi->num_stripes - 1] = p_eb;
+		memcpy(p_eb->data, ebs[0]->data, stripe_len);
+		for (j = 1; j < multi->num_stripes - 1; j++) {
+			for (i = 0; i < stripe_len; i += sizeof(unsigned long)) {
+				*(unsigned long *)(p_eb->data + i) ^=
+					*(unsigned long *)(ebs[j]->data + i);
+			}
+		}
+	}
+
+	for (i = 0; i < multi->num_stripes; i++) {
+		ret = write_extent_to_disk(ebs[i]);
+		BUG_ON(ret);
+		if (ebs[i] != eb)
+			kfree(ebs[i]);
+	}
+	return 0;
+}
diff --git a/volumes.h b/volumes.h
index 0b894fd5..e36f2f57 100644
--- a/volumes.h
+++ b/volumes.h
@@ -195,4 +195,8 @@ btrfs_find_device_by_devid(struct btrfs_fs_devices *fs_devices,
 			   u64 devid, int instance);
 struct btrfs_device *btrfs_find_device(struct btrfs_root *root, u64 devid,
 				       u8 *uuid, u8 *fsid);
+int write_raid56_with_parity(struct btrfs_fs_info *info,
+			     struct extent_buffer *eb,
+			     struct btrfs_multi_bio *multi,
+			     u64 stripe_len, u64 *raid_map);
 #endif