diff --git a/Makefile b/Makefile
index 9e58028..bd32121 100644
--- a/Makefile
+++ b/Makefile
@@ -13,7 +13,8 @@ objects = ctree.o disk-io.o radix-tree.o extent-tree.o print-tree.o \
 cmds_objects = cmds-subvolume.o cmds-filesystem.o cmds-device.o cmds-scrub.o \
 	       cmds-inspect.o cmds-balance.o cmds-send.o cmds-receive.o \
 	       cmds-quota.o cmds-qgroup.o cmds-replace.o cmds-check.o \
-	       cmds-restore.o cmds-chunk.o cmds-dedup.o cmds-rescue.o
+	       cmds-restore.o cmds-dedup.o cmds-rescue.o \
+	       chunk-recover.o
 libbtrfs_objects = send-stream.o send-utils.o rbtree.o btrfs-list.o crc32c.o \
 		   uuid-tree.o
 libbtrfs_headers = send-stream.h send-utils.h send.h rbtree.h btrfs-list.h \
diff --git a/chunk-recover.c b/chunk-recover.c
new file mode 100644
index 0000000..45da9a6
--- /dev/null
+++ b/chunk-recover.c
@@ -0,0 +1,1745 @@
+/*
+ * Copyright (C) 2013 Fujitsu.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License v2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 021110-1307, USA.
+ */
+#define _XOPEN_SOURCE 500
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdio_ext.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <uuid/uuid.h>
+
+#include "kerncompat.h"
+#include "list.h"
+#include "radix-tree.h"
+#include "ctree.h"
+#include "extent-cache.h"
+#include "disk-io.h"
+#include "volumes.h"
+#include "transaction.h"
+#include "crc32c.h"
+#include "utils.h"
+#include "version.h"
+#include "btrfsck.h"
+#include "commands.h"
+
+#define BTRFS_STRIPE_LEN			(64 * 1024)
+#define BTRFS_NUM_MIRRORS			2
+
+struct recover_control {
+	int verbose;
+	int yes;
+
+	u16 csum_size;
+	u32 sectorsize;
+	u32 leafsize;
+	u64 generation;
+	u64 chunk_root_generation;
+
+	struct btrfs_fs_devices *fs_devices;
+
+	struct cache_tree chunk;
+	struct block_group_tree bg;
+	struct device_extent_tree devext;
+	struct cache_tree eb_cache;
+
+	struct list_head good_chunks;
+	struct list_head bad_chunks;
+	struct list_head unrepaired_chunks;
+};
+
+struct extent_record {
+	struct cache_extent cache;
+	u64 generation;
+	u8 csum[BTRFS_CSUM_SIZE];
+	struct btrfs_device *devices[BTRFS_NUM_MIRRORS];
+	u64 offsets[BTRFS_NUM_MIRRORS];
+	int nmirrors;
+};
+
+static struct extent_record *btrfs_new_extent_record(struct extent_buffer *eb)
+{
+	struct extent_record *rec;
+
+	rec = malloc(sizeof(*rec));
+	if (!rec) {
+		fprintf(stderr, "Fail to allocate memory for extent record.\n");
+		exit(1);
+	}
+
+	memset(rec, 0, sizeof(*rec));
+	rec->cache.start = btrfs_header_bytenr(eb);
+	rec->cache.size = eb->len;
+	rec->generation = btrfs_header_generation(eb);
+	read_extent_buffer(eb, rec->csum, (unsigned long)btrfs_header_csum(eb),
+			   BTRFS_CSUM_SIZE);
+	return rec;
+}
+
+static int process_extent_buffer(struct cache_tree *eb_cache,
+				 struct extent_buffer *eb,
+				 struct btrfs_device *device, u64 offset)
+{
+	struct extent_record *rec;
+	struct extent_record *exist;
+	struct cache_extent *cache;
+	int ret = 0;
+
+	rec = btrfs_new_extent_record(eb);
+	if (!rec->cache.size)
+		goto free_out;
+again:
+	cache = lookup_cache_extent(eb_cache,
+				    rec->cache.start,
+				    rec->cache.size);
+	if (cache) {
+		exist = container_of(cache, struct extent_record, cache);
+
+		if (exist->generation > rec->generation)
+			goto free_out;
+		if (exist->generation == rec->generation) {
+			if (exist->cache.start != rec->cache.start ||
+			    exist->cache.size != rec->cache.size ||
+			    memcmp(exist->csum, rec->csum, BTRFS_CSUM_SIZE)) {
+				ret = -EEXIST;
+			} else {
+				BUG_ON(exist->nmirrors >= BTRFS_NUM_MIRRORS);
+				exist->devices[exist->nmirrors] = device;
+				exist->offsets[exist->nmirrors] = offset;
+				exist->nmirrors++;
+			}
+			goto free_out;
+		}
+		remove_cache_extent(eb_cache, cache);
+		free(exist);
+		goto again;
+	}
+
+	rec->devices[0] = device;
+	rec->offsets[0] = offset;
+	rec->nmirrors++;
+	ret = insert_cache_extent(eb_cache, &rec->cache);
+	BUG_ON(ret);
+out:
+	return ret;
+free_out:
+	free(rec);
+	goto out;
+}
+
+static void free_extent_record(struct cache_extent *cache)
+{
+	struct extent_record *er;
+
+	er = container_of(cache, struct extent_record, cache);
+	free(er);
+}
+
+FREE_EXTENT_CACHE_BASED_TREE(extent_record, free_extent_record);
+
+static struct btrfs_chunk *create_chunk_item(struct chunk_record *record)
+{
+	struct btrfs_chunk *ret;
+	struct btrfs_stripe *chunk_stripe;
+	int i;
+
+	if (!record || record->num_stripes == 0)
+		return NULL;
+	ret = malloc(btrfs_chunk_item_size(record->num_stripes));
+	if (!ret)
+		return NULL;
+	btrfs_set_stack_chunk_length(ret, record->length);
+	btrfs_set_stack_chunk_owner(ret, record->owner);
+	btrfs_set_stack_chunk_stripe_len(ret, record->stripe_len);
+	btrfs_set_stack_chunk_type(ret, record->type_flags);
+	btrfs_set_stack_chunk_io_align(ret, record->io_align);
+	btrfs_set_stack_chunk_io_width(ret, record->io_width);
+	btrfs_set_stack_chunk_sector_size(ret, record->sector_size);
+	btrfs_set_stack_chunk_num_stripes(ret, record->num_stripes);
+	btrfs_set_stack_chunk_sub_stripes(ret, record->sub_stripes);
+	for (i = 0, chunk_stripe = &ret->stripe; i < record->num_stripes;
+	     i++, chunk_stripe++) {
+		btrfs_set_stack_stripe_devid(chunk_stripe,
+				record->stripes[i].devid);
+		btrfs_set_stack_stripe_offset(chunk_stripe,
+				record->stripes[i].offset);
+		memcpy(chunk_stripe->dev_uuid, record->stripes[i].dev_uuid,
+		       BTRFS_UUID_SIZE);
+	}
+	return ret;
+}
+
+static void init_recover_control(struct recover_control *rc, int verbose,
+		int yes)
+{
+	memset(rc, 0, sizeof(struct recover_control));
+	cache_tree_init(&rc->chunk);
+	cache_tree_init(&rc->eb_cache);
+	block_group_tree_init(&rc->bg);
+	device_extent_tree_init(&rc->devext);
+
+	INIT_LIST_HEAD(&rc->good_chunks);
+	INIT_LIST_HEAD(&rc->bad_chunks);
+	INIT_LIST_HEAD(&rc->unrepaired_chunks);
+
+	rc->verbose = verbose;
+	rc->yes = yes;
+}
+
+static void free_recover_control(struct recover_control *rc)
+{
+	free_block_group_tree(&rc->bg);
+	free_chunk_cache_tree(&rc->chunk);
+	free_device_extent_tree(&rc->devext);
+	free_extent_record_tree(&rc->eb_cache);
+}
+
+static int process_block_group_item(struct block_group_tree *bg_cache,
+				    struct extent_buffer *leaf,
+				    struct btrfs_key *key, int slot)
+{
+	struct block_group_record *rec;
+	struct block_group_record *exist;
+	struct cache_extent *cache;
+	int ret = 0;
+
+	rec = btrfs_new_block_group_record(leaf, key, slot);
+	if (!rec->cache.size)
+		goto free_out;
+again:
+	cache = lookup_cache_extent(&bg_cache->tree,
+				    rec->cache.start,
+				    rec->cache.size);
+	if (cache) {
+		exist = container_of(cache, struct block_group_record, cache);
+
+		/*check the generation and replace if needed*/
+		if (exist->generation > rec->generation)
+			goto free_out;
+		if (exist->generation == rec->generation) {
+			int offset = offsetof(struct block_group_record,
+					      generation);
+			/*
+			 * According to the current kernel code, the following
+			 * case is impossble, or there is something wrong in
+			 * the kernel code.
+			 */
+			if (memcmp(((void *)exist) + offset,
+				   ((void *)rec) + offset,
+				   sizeof(*rec) - offset))
+				ret = -EEXIST;
+			goto free_out;
+		}
+		remove_cache_extent(&bg_cache->tree, cache);
+		list_del_init(&exist->list);
+		free(exist);
+		/*
+		 * We must do seach again to avoid the following cache.
+		 * /--old bg 1--//--old bg 2--/
+		 *        /--new bg--/
+		 */
+		goto again;
+	}
+
+	ret = insert_block_group_record(bg_cache, rec);
+	BUG_ON(ret);
+out:
+	return ret;
+free_out:
+	free(rec);
+	goto out;
+}
+
+static int process_chunk_item(struct cache_tree *chunk_cache,
+			      struct extent_buffer *leaf, struct btrfs_key *key,
+			      int slot)
+{
+	struct chunk_record *rec;
+	struct chunk_record *exist;
+	struct cache_extent *cache;
+	int ret = 0;
+
+	rec = btrfs_new_chunk_record(leaf, key, slot);
+	if (!rec->cache.size)
+		goto free_out;
+again:
+	cache = lookup_cache_extent(chunk_cache, rec->offset, rec->length);
+	if (cache) {
+		exist = container_of(cache, struct chunk_record, cache);
+
+		if (exist->generation > rec->generation)
+			goto free_out;
+		if (exist->generation == rec->generation) {
+			int num_stripes = rec->num_stripes;
+			int rec_size = btrfs_chunk_record_size(num_stripes);
+			int offset = offsetof(struct chunk_record, generation);
+
+			if (exist->num_stripes != rec->num_stripes ||
+			    memcmp(((void *)exist) + offset,
+				   ((void *)rec) + offset,
+				   rec_size - offset))
+				ret = -EEXIST;
+			goto free_out;
+		}
+		remove_cache_extent(chunk_cache, cache);
+		free(exist);
+		goto again;
+	}
+	ret = insert_cache_extent(chunk_cache, &rec->cache);
+	BUG_ON(ret);
+out:
+	return ret;
+free_out:
+	free(rec);
+	goto out;
+}
+
+static int process_device_extent_item(struct device_extent_tree *devext_cache,
+				      struct extent_buffer *leaf,
+				      struct btrfs_key *key, int slot)
+{
+	struct device_extent_record *rec;
+	struct device_extent_record *exist;
+	struct cache_extent *cache;
+	int ret = 0;
+
+	rec = btrfs_new_device_extent_record(leaf, key, slot);
+	if (!rec->cache.size)
+		goto free_out;
+again:
+	cache = lookup_cache_extent2(&devext_cache->tree,
+				     rec->cache.objectid,
+				     rec->cache.start,
+				     rec->cache.size);
+	if (cache) {
+		exist = container_of(cache, struct device_extent_record, cache);
+		if (exist->generation > rec->generation)
+			goto free_out;
+		if (exist->generation == rec->generation) {
+			int offset = offsetof(struct device_extent_record,
+					      generation);
+			if (memcmp(((void *)exist) + offset,
+				   ((void *)rec) + offset,
+				   sizeof(*rec) - offset))
+				ret = -EEXIST;
+			goto free_out;
+		}
+		remove_cache_extent(&devext_cache->tree, cache);
+		list_del_init(&exist->chunk_list);
+		list_del_init(&exist->device_list);
+		free(exist);
+		goto again;
+	}
+
+	ret = insert_device_extent_record(devext_cache, rec);
+	BUG_ON(ret);
+out:
+	return ret;
+free_out:
+	free(rec);
+	goto out;
+}
+
+static void print_block_group_info(struct block_group_record *rec, char *prefix)
+{
+	if (prefix)
+		printf("%s", prefix);
+	printf("Block Group: start = %llu, len = %llu, flag = %llx\n",
+	       rec->objectid, rec->offset, rec->flags);
+}
+
+static void print_block_group_tree(struct block_group_tree *tree)
+{
+	struct cache_extent *cache;
+	struct block_group_record *rec;
+
+	printf("All Block Groups:\n");
+	for (cache = first_cache_extent(&tree->tree); cache;
+	     cache = next_cache_extent(cache)) {
+		rec = container_of(cache, struct block_group_record, cache);
+		print_block_group_info(rec, "\t");
+	}
+	printf("\n");
+}
+
+static void print_stripe_info(struct stripe *data, char *prefix1, char *prefix2,
+			      int index)
+{
+	if (prefix1)
+		printf("%s", prefix1);
+	if (prefix2)
+		printf("%s", prefix2);
+	printf("[%2d] Stripe: devid = %llu, offset = %llu\n",
+	       index, data->devid, data->offset);
+}
+
+static void print_chunk_self_info(struct chunk_record *rec, char *prefix)
+{
+	int i;
+
+	if (prefix)
+		printf("%s", prefix);
+	printf("Chunk: start = %llu, len = %llu, type = %llx, num_stripes = %u\n",
+	       rec->offset, rec->length, rec->type_flags, rec->num_stripes);
+	if (prefix)
+		printf("%s", prefix);
+	printf("    Stripes list:\n");
+	for (i = 0; i < rec->num_stripes; i++)
+		print_stripe_info(&rec->stripes[i], prefix, "    ", i);
+}
+
+static void print_chunk_tree(struct cache_tree *tree)
+{
+	struct cache_extent *n;
+	struct chunk_record *entry;
+
+	printf("All Chunks:\n");
+	for (n = first_cache_extent(tree); n;
+	     n = next_cache_extent(n)) {
+		entry = container_of(n, struct chunk_record, cache);
+		print_chunk_self_info(entry, "\t");
+	}
+	printf("\n");
+}
+
+static void print_device_extent_info(struct device_extent_record *rec,
+				     char *prefix)
+{
+	if (prefix)
+		printf("%s", prefix);
+	printf("Device extent: devid = %llu, start = %llu, len = %llu, chunk offset = %llu\n",
+	       rec->objectid, rec->offset, rec->length, rec->chunk_offset);
+}
+
+static void print_device_extent_tree(struct device_extent_tree *tree)
+{
+	struct cache_extent *n;
+	struct device_extent_record *entry;
+
+	printf("All Device Extents:\n");
+	for (n = first_cache_extent(&tree->tree); n;
+	     n = next_cache_extent(n)) {
+		entry = container_of(n, struct device_extent_record, cache);
+		print_device_extent_info(entry, "\t");
+	}
+	printf("\n");
+}
+
+static void print_device_info(struct btrfs_device *device, char *prefix)
+{
+	if (prefix)
+		printf("%s", prefix);
+	printf("Device: id = %llu, name = %s\n",
+	       device->devid, device->name);
+}
+
+static void print_all_devices(struct list_head *devices)
+{
+	struct btrfs_device *dev;
+
+	printf("All Devices:\n");
+	list_for_each_entry(dev, devices, dev_list)
+		print_device_info(dev, "\t");
+	printf("\n");
+}
+
+static void print_scan_result(struct recover_control *rc)
+{
+	if (!rc->verbose)
+		return;
+
+	printf("DEVICE SCAN RESULT:\n");
+	printf("Filesystem Information:\n");
+	printf("\tsectorsize: %d\n", rc->sectorsize);
+	printf("\tleafsize: %d\n", rc->leafsize);
+	printf("\ttree root generation: %llu\n", rc->generation);
+	printf("\tchunk root generation: %llu\n", rc->chunk_root_generation);
+	printf("\n");
+
+	print_all_devices(&rc->fs_devices->devices);
+	print_block_group_tree(&rc->bg);
+	print_chunk_tree(&rc->chunk);
+	print_device_extent_tree(&rc->devext);
+}
+
+static void print_chunk_info(struct chunk_record *chunk, char *prefix)
+{
+	struct device_extent_record *devext;
+	int i;
+
+	print_chunk_self_info(chunk, prefix);
+	if (prefix)
+		printf("%s", prefix);
+	if (chunk->bg_rec)
+		print_block_group_info(chunk->bg_rec, "    ");
+	else
+		printf("    No block group.\n");
+	if (prefix)
+		printf("%s", prefix);
+	if (list_empty(&chunk->dextents)) {
+		printf("    No device extent.\n");
+	} else {
+		printf("    Device extent list:\n");
+		i = 0;
+		list_for_each_entry(devext, &chunk->dextents, chunk_list) {
+			if (prefix)
+				printf("%s", prefix);
+			printf("%s[%2d]", "        ", i);
+			print_device_extent_info(devext, NULL);
+			i++;
+		}
+	}
+}
+
+static void print_check_result(struct recover_control *rc)
+{
+	struct chunk_record *chunk;
+	struct block_group_record *bg;
+	struct device_extent_record *devext;
+	int total = 0;
+	int good = 0;
+	int bad = 0;
+
+	if (!rc->verbose)
+		return;
+
+	printf("CHECK RESULT:\n");
+	printf("Healthy Chunks:\n");
+	list_for_each_entry(chunk, &rc->good_chunks, list) {
+		print_chunk_info(chunk, "  ");
+		good++;
+		total++;
+	}
+	printf("Bad Chunks:\n");
+	list_for_each_entry(chunk, &rc->bad_chunks, list) {
+		print_chunk_info(chunk, "  ");
+		bad++;
+		total++;
+	}
+	printf("\n");
+	printf("Total Chunks:\t%d\n", total);
+	printf("  Heathy:\t%d\n", good);
+	printf("  Bad:\t%d\n", bad);
+
+	printf("\n");
+	printf("Orphan Block Groups:\n");
+	list_for_each_entry(bg, &rc->bg.block_groups, list)
+		print_block_group_info(bg, "  ");
+
+	printf("\n");
+	printf("Orphan Device Extents:\n");
+	list_for_each_entry(devext, &rc->devext.no_chunk_orphans, chunk_list)
+		print_device_extent_info(devext, "  ");
+}
+
+static int check_chunk_by_metadata(struct recover_control *rc,
+				   struct btrfs_root *root,
+				   struct chunk_record *chunk, int bg_only)
+{
+	int ret;
+	int i;
+	int slot;
+	struct btrfs_path path;
+	struct btrfs_key key;
+	struct btrfs_root *dev_root;
+	struct stripe *stripe;
+	struct btrfs_dev_extent *dev_extent;
+	struct btrfs_block_group_item *bg_ptr;
+	struct extent_buffer *l;
+
+	btrfs_init_path(&path);
+
+	if (bg_only)
+		goto bg_check;
+
+	dev_root = root->fs_info->dev_root;
+	for (i = 0; i < chunk->num_stripes; i++) {
+		stripe = &chunk->stripes[i];
+
+		key.objectid = stripe->devid;
+		key.offset = stripe->offset;
+		key.type = BTRFS_DEV_EXTENT_KEY;
+
+		ret = btrfs_search_slot(NULL, dev_root, &key, &path, 0, 0);
+		if (ret < 0) {
+			fprintf(stderr, "Search device extent failed(%d)\n",
+				ret);
+			btrfs_release_path(&path);
+			return ret;
+		} else if (ret > 0) {
+			if (rc->verbose)
+				fprintf(stderr,
+					"No device extent[%llu, %llu]\n",
+					stripe->devid, stripe->offset);
+			btrfs_release_path(&path);
+			return -ENOENT;
+		}
+		l = path.nodes[0];
+		slot = path.slots[0];
+		dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent);
+		if (chunk->offset !=
+		    btrfs_dev_extent_chunk_offset(l, dev_extent)) {
+			if (rc->verbose)
+				fprintf(stderr,
+					"Device tree unmatch with chunks dev_extent[%llu, %llu], chunk[%llu, %llu]\n",
+					btrfs_dev_extent_chunk_offset(l,
+								dev_extent),
+					btrfs_dev_extent_length(l, dev_extent),
+					chunk->offset, chunk->length);
+			btrfs_release_path(&path);
+			return -ENOENT;
+		}
+		btrfs_release_path(&path);
+	}
+
+bg_check:
+	key.objectid = chunk->offset;
+	key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
+	key.offset = chunk->length;
+
+	ret = btrfs_search_slot(NULL, root->fs_info->extent_root, &key, &path,
+				0, 0);
+	if (ret < 0) {
+		fprintf(stderr, "Search block group failed(%d)\n", ret);
+		btrfs_release_path(&path);
+		return ret;
+	} else if (ret > 0) {
+		if (rc->verbose)
+			fprintf(stderr, "No block group[%llu, %llu]\n",
+				key.objectid, key.offset);
+		btrfs_release_path(&path);
+		return -ENOENT;
+	}
+
+	l = path.nodes[0];
+	slot = path.slots[0];
+	bg_ptr = btrfs_item_ptr(l, slot, struct btrfs_block_group_item);
+	if (chunk->type_flags != btrfs_disk_block_group_flags(l, bg_ptr)) {
+		if (rc->verbose)
+			fprintf(stderr,
+				"Chunk[%llu, %llu]'s type(%llu) is differemt with Block Group's type(%llu)\n",
+				chunk->offset, chunk->length, chunk->type_flags,
+				btrfs_disk_block_group_flags(l, bg_ptr));
+		btrfs_release_path(&path);
+		return -ENOENT;
+	}
+	btrfs_release_path(&path);
+	return 0;
+}
+
+static int check_all_chunks_by_metadata(struct recover_control *rc,
+					struct btrfs_root *root)
+{
+	struct chunk_record *chunk;
+	struct chunk_record *next;
+	LIST_HEAD(orphan_chunks);
+	int ret = 0;
+	int err;
+
+	list_for_each_entry_safe(chunk, next, &rc->good_chunks, list) {
+		err = check_chunk_by_metadata(rc, root, chunk, 0);
+		if (err) {
+			if (err == -ENOENT)
+				list_move_tail(&chunk->list, &orphan_chunks);
+			else if (err && !ret)
+				ret = err;
+		}
+	}
+
+	list_for_each_entry_safe(chunk, next, &rc->unrepaired_chunks, list) {
+		err = check_chunk_by_metadata(rc, root, chunk, 1);
+		if (err == -ENOENT)
+			list_move_tail(&chunk->list, &orphan_chunks);
+		else if (err && !ret)
+			ret = err;
+	}
+
+	list_for_each_entry(chunk, &rc->bad_chunks, list) {
+		err = check_chunk_by_metadata(rc, root, chunk, 1);
+		if (err != -ENOENT && !ret)
+			ret = err ? err : -EINVAL;
+	}
+	list_splice(&orphan_chunks, &rc->bad_chunks);
+	return ret;
+}
+
+static int extract_metadata_record(struct recover_control *rc,
+				   struct extent_buffer *leaf)
+{
+	struct btrfs_key key;
+	int ret = 0;
+	int i;
+	u32 nritems;
+
+	nritems = btrfs_header_nritems(leaf);
+	for (i = 0; i < nritems; i++) {
+		btrfs_item_key_to_cpu(leaf, &key, i);
+		switch (key.type) {
+		case BTRFS_BLOCK_GROUP_ITEM_KEY:
+			ret = process_block_group_item(&rc->bg, leaf, &key, i);
+			break;
+		case BTRFS_CHUNK_ITEM_KEY:
+			ret = process_chunk_item(&rc->chunk, leaf, &key, i);
+			break;
+		case BTRFS_DEV_EXTENT_KEY:
+			ret = process_device_extent_item(&rc->devext, leaf,
+							 &key, i);
+			break;
+		}
+		if (ret)
+			break;
+	}
+	return ret;
+}
+
+static inline int is_super_block_address(u64 offset)
+{
+	int i;
+
+	for (i = 0; i < BTRFS_SUPER_MIRROR_MAX; i++) {
+		if (offset == btrfs_sb_offset(i))
+			return 1;
+	}
+	return 0;
+}
+
+static int scan_one_device(struct recover_control *rc, int fd,
+			   struct btrfs_device *device)
+{
+	struct extent_buffer *buf;
+	u64 bytenr;
+	int ret = 0;
+
+	buf = malloc(sizeof(*buf) + rc->leafsize);
+	if (!buf)
+		return -ENOMEM;
+	buf->len = rc->leafsize;
+
+	bytenr = 0;
+	while (1) {
+		if (is_super_block_address(bytenr))
+			bytenr += rc->sectorsize;
+
+		if (pread64(fd, buf->data, rc->leafsize, bytenr) <
+		    rc->leafsize)
+			break;
+
+		if (memcmp_extent_buffer(buf, rc->fs_devices->fsid,
+					 (unsigned long)btrfs_header_fsid(buf),
+					 BTRFS_FSID_SIZE)) {
+			bytenr += rc->sectorsize;
+			continue;
+		}
+
+		if (verify_tree_block_csum_silent(buf, rc->csum_size)) {
+			bytenr += rc->sectorsize;
+			continue;
+		}
+
+		ret = process_extent_buffer(&rc->eb_cache, buf, device, bytenr);
+		if (ret)
+			goto out;
+
+		if (btrfs_header_level(buf) != 0)
+			goto next_node;
+
+		switch (btrfs_header_owner(buf)) {
+		case BTRFS_EXTENT_TREE_OBJECTID:
+		case BTRFS_DEV_TREE_OBJECTID:
+			/* different tree use different generation */
+			if (btrfs_header_generation(buf) > rc->generation)
+				break;
+			ret = extract_metadata_record(rc, buf);
+			if (ret)
+				goto out;
+			break;
+		case BTRFS_CHUNK_TREE_OBJECTID:
+			if (btrfs_header_generation(buf) >
+			    rc->chunk_root_generation)
+				break;
+			ret = extract_metadata_record(rc, buf);
+			if (ret)
+				goto out;
+			break;
+		}
+next_node:
+		bytenr += rc->leafsize;
+	}
+out:
+	free(buf);
+	return ret;
+}
+
+static int scan_devices(struct recover_control *rc)
+{
+	int ret = 0;
+	int fd;
+	struct btrfs_device *dev;
+
+	list_for_each_entry(dev, &rc->fs_devices->devices, dev_list) {
+		fd = open(dev->name, O_RDONLY);
+		if (fd < 0) {
+			fprintf(stderr, "Failed to open device %s\n",
+				dev->name);
+			return -1;
+		}
+		ret = scan_one_device(rc, fd, dev);
+		close(fd);
+		if (ret)
+			return ret;
+	}
+	return ret;
+}
+
+static int build_device_map_by_chunk_record(struct btrfs_root *root,
+					    struct chunk_record *chunk)
+{
+	int ret = 0;
+	int i;
+	u64 devid;
+	u8 uuid[BTRFS_UUID_SIZE];
+	u16 num_stripes;
+	struct btrfs_mapping_tree *map_tree;
+	struct map_lookup *map;
+	struct stripe *stripe;
+
+	map_tree = &root->fs_info->mapping_tree;
+	num_stripes = chunk->num_stripes;
+	map = malloc(btrfs_map_lookup_size(num_stripes));
+	if (!map)
+		return -ENOMEM;
+	map->ce.start = chunk->offset;
+	map->ce.size = chunk->length;
+	map->num_stripes = num_stripes;
+	map->io_width = chunk->io_width;
+	map->io_align = chunk->io_align;
+	map->sector_size = chunk->sector_size;
+	map->stripe_len = chunk->stripe_len;
+	map->type = chunk->type_flags;
+	map->sub_stripes = chunk->sub_stripes;
+
+	for (i = 0, stripe = chunk->stripes; i < num_stripes; i++, stripe++) {
+		devid = stripe->devid;
+		memcpy(uuid, stripe->dev_uuid, BTRFS_UUID_SIZE);
+		map->stripes[i].physical = stripe->offset;
+		map->stripes[i].dev = btrfs_find_device(root, devid,
+							uuid, NULL);
+		if (!map->stripes[i].dev) {
+			kfree(map);
+			return -EIO;
+		}
+	}
+
+	ret = insert_cache_extent(&map_tree->cache_tree, &map->ce);
+	return ret;
+}
+
+static int build_device_maps_by_chunk_records(struct recover_control *rc,
+					      struct btrfs_root *root)
+{
+	int ret = 0;
+	struct chunk_record *chunk;
+
+	list_for_each_entry(chunk, &rc->good_chunks, list) {
+		ret = build_device_map_by_chunk_record(root, chunk);
+		if (ret)
+			return ret;
+	}
+	return ret;
+}
+
+static int block_group_remove_all_extent_items(struct btrfs_trans_handle *trans,
+					       struct btrfs_root *root,
+					       struct block_group_record *bg)
+{
+	struct btrfs_fs_info *fs_info = root->fs_info;
+	struct btrfs_key key;
+	struct btrfs_path path;
+	struct extent_buffer *leaf;
+	u64 start = bg->objectid;
+	u64 end = bg->objectid + bg->offset;
+	u64 old_val;
+	int nitems;
+	int ret;
+	int i;
+	int del_s, del_nr;
+
+	btrfs_init_path(&path);
+	root = root->fs_info->extent_root;
+
+	key.objectid = start;
+	key.offset = 0;
+	key.type = BTRFS_EXTENT_ITEM_KEY;
+again:
+	ret = btrfs_search_slot(trans, root, &key, &path, -1, 1);
+	if (ret < 0)
+		goto err;
+	else if (ret > 0)
+		ret = 0;
+
+	leaf = path.nodes[0];
+	nitems = btrfs_header_nritems(leaf);
+	if (!nitems) {
+		/* The tree is empty. */
+		ret = 0;
+		goto err;
+	}
+
+	if (path.slots[0] >= nitems) {
+		ret = btrfs_next_leaf(root, &path);
+		if (ret < 0)
+			goto err;
+		if (ret > 0) {
+			ret = 0;
+			goto err;
+		}
+		leaf = path.nodes[0];
+		btrfs_item_key_to_cpu(leaf, &key, 0);
+		if (key.objectid >= end)
+			goto err;
+		btrfs_release_path(&path);
+		goto again;
+	}
+
+	del_nr = 0;
+	del_s = -1;
+	for (i = path.slots[0]; i < nitems; i++) {
+		btrfs_item_key_to_cpu(leaf, &key, i);
+		if (key.objectid >= end)
+			break;
+
+		if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
+			if (del_nr == 0)
+				continue;
+			else
+				break;
+		}
+
+		if (del_s == -1)
+			del_s = i;
+		del_nr++;
+		if (key.type == BTRFS_EXTENT_ITEM_KEY ||
+		    key.type == BTRFS_METADATA_ITEM_KEY) {
+			old_val = btrfs_super_bytes_used(fs_info->super_copy);
+			if (key.type == BTRFS_METADATA_ITEM_KEY)
+				old_val += root->leafsize;
+			else
+				old_val += key.offset;
+			btrfs_set_super_bytes_used(fs_info->super_copy,
+						   old_val);
+		}
+	}
+
+	if (del_nr) {
+		ret = btrfs_del_items(trans, root, &path, del_s, del_nr);
+		if (ret)
+			goto err;
+	}
+
+	if (key.objectid < end) {
+		if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
+			key.objectid += root->sectorsize;
+			key.type = BTRFS_EXTENT_ITEM_KEY;
+			key.offset = 0;
+		}
+		btrfs_release_path(&path);
+		goto again;
+	}
+err:
+	btrfs_release_path(&path);
+	return ret;
+}
+
+static int block_group_free_all_extent(struct btrfs_trans_handle *trans,
+				       struct btrfs_root *root,
+				       struct block_group_record *bg)
+{
+	struct btrfs_block_group_cache *cache;
+	struct btrfs_fs_info *info;
+	u64 start;
+	u64 end;
+
+	info = root->fs_info;
+	cache = btrfs_lookup_block_group(info, bg->objectid);
+	if (!cache)
+		return -ENOENT;
+
+	start = cache->key.objectid;
+	end = start + cache->key.offset - 1;
+
+	set_extent_bits(&info->block_group_cache, start, end,
+			BLOCK_GROUP_DIRTY, GFP_NOFS);
+	set_extent_dirty(&info->free_space_cache, start, end, GFP_NOFS);
+
+	btrfs_set_block_group_used(&cache->item, 0);
+
+	return 0;
+}
+
+static int remove_chunk_extent_item(struct btrfs_trans_handle *trans,
+				    struct recover_control *rc,
+				    struct btrfs_root *root)
+{
+	struct chunk_record *chunk;
+	int ret = 0;
+
+	list_for_each_entry(chunk, &rc->good_chunks, list) {
+		if (!(chunk->type_flags & BTRFS_BLOCK_GROUP_SYSTEM))
+			continue;
+		ret = block_group_remove_all_extent_items(trans, root,
+							  chunk->bg_rec);
+		if (ret)
+			return ret;
+
+		ret = block_group_free_all_extent(trans, root, chunk->bg_rec);
+		if (ret)
+			return ret;
+	}
+	return ret;
+}
+
+static int __rebuild_chunk_root(struct btrfs_trans_handle *trans,
+				struct recover_control *rc,
+				struct btrfs_root *root)
+{
+	u64 min_devid = -1;
+	struct btrfs_device *dev;
+	struct extent_buffer *cow;
+	struct btrfs_disk_key disk_key;
+	int ret = 0;
+
+	list_for_each_entry(dev, &rc->fs_devices->devices, dev_list) {
+		if (min_devid > dev->devid)
+			min_devid = dev->devid;
+	}
+	disk_key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
+	disk_key.type = BTRFS_DEV_ITEM_KEY;
+	disk_key.offset = min_devid;
+
+	cow = btrfs_alloc_free_block(trans, root, root->sectorsize,
+				     BTRFS_CHUNK_TREE_OBJECTID,
+				     &disk_key, 0, 0, 0);
+	btrfs_set_header_bytenr(cow, cow->start);
+	btrfs_set_header_generation(cow, trans->transid);
+	btrfs_set_header_nritems(cow, 0);
+	btrfs_set_header_level(cow, 0);
+	btrfs_set_header_backref_rev(cow, BTRFS_MIXED_BACKREF_REV);
+	btrfs_set_header_owner(cow, BTRFS_CHUNK_TREE_OBJECTID);
+	write_extent_buffer(cow, root->fs_info->fsid,
+			(unsigned long)btrfs_header_fsid(cow),
+			BTRFS_FSID_SIZE);
+
+	write_extent_buffer(cow, root->fs_info->chunk_tree_uuid,
+			(unsigned long)btrfs_header_chunk_tree_uuid(cow),
+			BTRFS_UUID_SIZE);
+
+	root->node = cow;
+	btrfs_mark_buffer_dirty(cow);
+
+	return ret;
+}
+
+static int __rebuild_device_items(struct btrfs_trans_handle *trans,
+				  struct recover_control *rc,
+				  struct btrfs_root *root)
+{
+	struct btrfs_device *dev;
+	struct btrfs_key key;
+	struct btrfs_dev_item *dev_item;
+	int ret = 0;
+
+	dev_item = malloc(sizeof(struct btrfs_dev_item));
+	if (!dev_item)
+		return -ENOMEM;
+
+	list_for_each_entry(dev, &rc->fs_devices->devices, dev_list) {
+		key.objectid = BTRFS_DEV_ITEMS_OBJECTID;
+		key.type = BTRFS_DEV_ITEM_KEY;
+		key.offset = dev->devid;
+
+		btrfs_set_stack_device_generation(dev_item, 0);
+		btrfs_set_stack_device_type(dev_item, dev->type);
+		btrfs_set_stack_device_id(dev_item, dev->devid);
+		btrfs_set_stack_device_total_bytes(dev_item, dev->total_bytes);
+		btrfs_set_stack_device_bytes_used(dev_item, dev->bytes_used);
+		btrfs_set_stack_device_io_align(dev_item, dev->io_align);
+		btrfs_set_stack_device_io_width(dev_item, dev->io_width);
+		btrfs_set_stack_device_sector_size(dev_item, dev->sector_size);
+		memcpy(dev_item->uuid, dev->uuid, BTRFS_UUID_SIZE);
+		memcpy(dev_item->fsid, dev->fs_devices->fsid, BTRFS_UUID_SIZE);
+
+		ret = btrfs_insert_item(trans, root, &key,
+					dev_item, sizeof(*dev_item));
+	}
+
+	free(dev_item);
+	return ret;
+}
+
+static int __rebuild_chunk_items(struct btrfs_trans_handle *trans,
+				 struct recover_control *rc,
+				 struct btrfs_root *root)
+{
+	struct btrfs_key key;
+	struct btrfs_chunk *chunk = NULL;
+	struct btrfs_root *chunk_root;
+	struct chunk_record *chunk_rec;
+	int ret;
+
+	chunk_root = root->fs_info->chunk_root;
+
+	list_for_each_entry(chunk_rec, &rc->good_chunks, list) {
+		chunk = create_chunk_item(chunk_rec);
+		if (!chunk)
+			return -ENOMEM;
+
+		key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
+		key.type = BTRFS_CHUNK_ITEM_KEY;
+		key.offset = chunk_rec->offset;
+
+		ret = btrfs_insert_item(trans, chunk_root, &key, chunk,
+				btrfs_chunk_item_size(chunk->num_stripes));
+		free(chunk);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static int rebuild_chunk_tree(struct btrfs_trans_handle *trans,
+			      struct recover_control *rc,
+			      struct btrfs_root *root)
+{
+	int ret = 0;
+
+	root = root->fs_info->chunk_root;
+
+	ret = __rebuild_chunk_root(trans, rc, root);
+	if (ret)
+		return ret;
+
+	ret = __rebuild_device_items(trans, rc, root);
+	if (ret)
+		return ret;
+
+	ret = __rebuild_chunk_items(trans, rc, root);
+
+	return ret;
+}
+
+static int rebuild_sys_array(struct recover_control *rc,
+			     struct btrfs_root *root)
+{
+	struct btrfs_chunk *chunk;
+	struct btrfs_key key;
+	struct chunk_record *chunk_rec;
+	int ret = 0;
+	u16 num_stripes;
+
+	btrfs_set_super_sys_array_size(root->fs_info->super_copy, 0);
+
+	list_for_each_entry(chunk_rec, &rc->good_chunks, list) {
+		if (!(chunk_rec->type_flags & BTRFS_BLOCK_GROUP_SYSTEM))
+			continue;
+
+		num_stripes = chunk_rec->num_stripes;
+		chunk = create_chunk_item(chunk_rec);
+		if (!chunk) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		key.objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
+		key.type = BTRFS_CHUNK_ITEM_KEY;
+		key.offset = chunk_rec->offset;
+
+		ret = btrfs_add_system_chunk(NULL, root, &key, chunk,
+				btrfs_chunk_item_size(num_stripes));
+		free(chunk);
+		if (ret)
+			break;
+	}
+	return ret;
+
+}
+
+static struct btrfs_root *
+open_ctree_with_broken_chunk(struct recover_control *rc)
+{
+	struct btrfs_fs_info *fs_info;
+	struct btrfs_super_block *disk_super;
+	struct extent_buffer *eb;
+	u32 sectorsize;
+	u32 nodesize;
+	u32 leafsize;
+	u32 stripesize;
+	int ret;
+
+	fs_info = btrfs_new_fs_info(1, BTRFS_SUPER_INFO_OFFSET);
+	if (!fs_info) {
+		fprintf(stderr, "Failed to allocate memory for fs_info\n");
+		return ERR_PTR(-ENOMEM);
+	}
+
+	fs_info->fs_devices = rc->fs_devices;
+	ret = btrfs_open_devices(fs_info->fs_devices, O_RDWR);
+	if (ret)
+		goto out;
+
+	disk_super = fs_info->super_copy;
+	ret = btrfs_read_dev_super(fs_info->fs_devices->latest_bdev,
+				   disk_super, fs_info->super_bytenr);
+	if (ret) {
+		fprintf(stderr, "No valid btrfs found\n");
+		goto out_devices;
+	}
+
+	memcpy(fs_info->fsid, &disk_super->fsid, BTRFS_FSID_SIZE);
+
+	ret = btrfs_check_fs_compatibility(disk_super, 1);
+	if (ret)
+		goto out_devices;
+
+	nodesize = btrfs_super_nodesize(disk_super);
+	leafsize = btrfs_super_leafsize(disk_super);
+	sectorsize = btrfs_super_sectorsize(disk_super);
+	stripesize = btrfs_super_stripesize(disk_super);
+
+	__setup_root(nodesize, leafsize, sectorsize, stripesize,
+		     fs_info->chunk_root, fs_info, BTRFS_CHUNK_TREE_OBJECTID);
+
+	ret = build_device_maps_by_chunk_records(rc, fs_info->chunk_root);
+	if (ret)
+		goto out_cleanup;
+
+	ret = btrfs_setup_all_roots(fs_info, 0, 0);
+	if (ret)
+		goto out_failed;
+
+	eb = fs_info->tree_root->node;
+	read_extent_buffer(eb, fs_info->chunk_tree_uuid,
+			   (unsigned long)btrfs_header_chunk_tree_uuid(eb),
+			   BTRFS_UUID_SIZE);
+
+	return fs_info->fs_root;
+out_failed:
+	btrfs_release_all_roots(fs_info);
+out_cleanup:
+	btrfs_cleanup_all_caches(fs_info);
+out_devices:
+	btrfs_close_devices(fs_info->fs_devices);
+out:
+	btrfs_free_fs_info(fs_info);
+	return ERR_PTR(ret);
+}
+
+static int recover_prepare(struct recover_control *rc, char *path)
+{
+	int ret;
+	int fd;
+	struct btrfs_super_block *sb;
+	struct btrfs_fs_devices *fs_devices;
+
+	ret = 0;
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		fprintf(stderr, "open %s\n error.\n", path);
+		return -1;
+	}
+
+	sb = malloc(sizeof(struct btrfs_super_block));
+	if (!sb) {
+		fprintf(stderr, "allocating memory for sb failed.\n");
+		ret = -ENOMEM;
+		goto fail_close_fd;
+	}
+
+	ret = btrfs_read_dev_super(fd, sb, BTRFS_SUPER_INFO_OFFSET);
+	if (ret) {
+		fprintf(stderr, "read super block error\n");
+		goto fail_free_sb;
+	}
+
+	rc->sectorsize = btrfs_super_sectorsize(sb);
+	rc->leafsize = btrfs_super_leafsize(sb);
+	rc->generation = btrfs_super_generation(sb);
+	rc->chunk_root_generation = btrfs_super_chunk_root_generation(sb);
+	rc->csum_size = btrfs_super_csum_size(sb);
+
+	/* if seed, the result of scanning below will be partial */
+	if (btrfs_super_flags(sb) & BTRFS_SUPER_FLAG_SEEDING) {
+		fprintf(stderr, "this device is seed device\n");
+		ret = -1;
+		goto fail_free_sb;
+	}
+
+	ret = btrfs_scan_fs_devices(fd, path, &fs_devices, 0);
+	if (ret)
+		goto fail_free_sb;
+
+	rc->fs_devices = fs_devices;
+
+	if (rc->verbose)
+		print_all_devices(&rc->fs_devices->devices);
+
+fail_free_sb:
+	free(sb);
+fail_close_fd:
+	close(fd);
+	return ret;
+}
+
+/*
+ * This reads a line from the stdin and only returns non-zero if the
+ * first whitespace delimited token is a case insensitive match with yes
+ * or y.
+ */
+static int ask_user(char *question)
+{
+	char buf[30] = {0,};
+	char *saveptr = NULL;
+	char *answer;
+
+	printf("%s [y/N]: ", question);
+
+	return fgets(buf, sizeof(buf) - 1, stdin) &&
+	       (answer = strtok_r(buf, " \t\n\r", &saveptr)) &&
+	       (!strcasecmp(answer, "yes") || !strcasecmp(answer, "y"));
+}
+
+static int btrfs_get_device_extents(u64 chunk_object,
+				    struct list_head *orphan_devexts,
+				    struct list_head *ret_list)
+{
+	struct device_extent_record *devext;
+	struct device_extent_record *next;
+	int count = 0;
+
+	list_for_each_entry_safe(devext, next, orphan_devexts, chunk_list) {
+		if (devext->chunk_offset == chunk_object) {
+			list_move_tail(&devext->chunk_list, ret_list);
+			count++;
+		}
+	}
+	return count;
+}
+
+static int calc_num_stripes(u64 type)
+{
+	if (type & (BTRFS_BLOCK_GROUP_RAID0 |
+		    BTRFS_BLOCK_GROUP_RAID10 |
+		    BTRFS_BLOCK_GROUP_RAID5 |
+		    BTRFS_BLOCK_GROUP_RAID6))
+		return 0;
+	else if (type & (BTRFS_BLOCK_GROUP_RAID1 |
+			 BTRFS_BLOCK_GROUP_DUP))
+		return 2;
+	else
+		return 1;
+}
+
+static inline int calc_sub_nstripes(u64 type)
+{
+	if (type & BTRFS_BLOCK_GROUP_RAID10)
+		return 2;
+	else
+		return 1;
+}
+
+static int btrfs_verify_device_extents(struct block_group_record *bg,
+				       struct list_head *devexts, int ndevexts)
+{
+	struct device_extent_record *devext;
+	u64 strpie_length;
+	int expected_num_stripes;
+
+	expected_num_stripes = calc_num_stripes(bg->flags);
+	if (expected_num_stripes && expected_num_stripes != ndevexts)
+		return 1;
+
+	strpie_length = calc_stripe_length(bg->flags, bg->offset, ndevexts);
+	list_for_each_entry(devext, devexts, chunk_list) {
+		if (devext->length != strpie_length)
+			return 1;
+	}
+	return 0;
+}
+
+static int btrfs_rebuild_unordered_chunk_stripes(struct recover_control *rc,
+						 struct chunk_record *chunk)
+{
+	struct device_extent_record *devext;
+	struct btrfs_device *device;
+	int i;
+
+	devext = list_first_entry(&chunk->dextents, struct device_extent_record,
+				  chunk_list);
+	for (i = 0; i < chunk->num_stripes; i++) {
+		chunk->stripes[i].devid = devext->objectid;
+		chunk->stripes[i].offset = devext->offset;
+		device = btrfs_find_device_by_devid(rc->fs_devices,
+						    devext->objectid,
+						    0);
+		if (!device)
+			return -ENOENT;
+		BUG_ON(btrfs_find_device_by_devid(rc->fs_devices,
+						  devext->objectid,
+						  1));
+		memcpy(chunk->stripes[i].dev_uuid, device->uuid,
+		       BTRFS_UUID_SIZE);
+		devext = list_next_entry(devext, chunk_list);
+	}
+	return 0;
+}
+
+static int btrfs_calc_stripe_index(struct chunk_record *chunk, u64 logical)
+{
+	u64 offset = logical - chunk->offset;
+	int stripe_nr;
+	int nr_data_stripes;
+	int index;
+
+	stripe_nr = offset / chunk->stripe_len;
+	if (chunk->type_flags & BTRFS_BLOCK_GROUP_RAID0) {
+		index = stripe_nr % chunk->num_stripes;
+	} else if (chunk->type_flags & BTRFS_BLOCK_GROUP_RAID10) {
+		index = stripe_nr % (chunk->num_stripes / chunk->sub_stripes);
+		index *= chunk->sub_stripes;
+	} else if (chunk->type_flags & BTRFS_BLOCK_GROUP_RAID5) {
+		nr_data_stripes = chunk->num_stripes - 1;
+		index = stripe_nr % nr_data_stripes;
+		stripe_nr /= nr_data_stripes;
+		index = (index + stripe_nr) % chunk->num_stripes;
+	} else if (chunk->type_flags & BTRFS_BLOCK_GROUP_RAID6) {
+		nr_data_stripes = chunk->num_stripes - 2;
+		index = stripe_nr % nr_data_stripes;
+		stripe_nr /= nr_data_stripes;
+		index = (index + stripe_nr) % chunk->num_stripes;
+	} else {
+		BUG_ON(1);
+	}
+	return index;
+}
+
+/* calc the logical offset which is the start of the next stripe. */
+static inline u64 btrfs_next_stripe_logical_offset(struct chunk_record *chunk,
+						   u64 logical)
+{
+	u64 offset = logical - chunk->offset;
+
+	offset /= chunk->stripe_len;
+	offset *= chunk->stripe_len;
+	offset += chunk->stripe_len;
+
+	return offset + chunk->offset;
+}
+
+static int is_extent_record_in_device_extent(struct extent_record *er,
+					     struct device_extent_record *dext,
+					     int *mirror)
+{
+	int i;
+
+	for (i = 0; i < er->nmirrors; i++) {
+		if (er->devices[i]->devid == dext->objectid &&
+		    er->offsets[i] >= dext->offset &&
+		    er->offsets[i] < dext->offset + dext->length) {
+			*mirror = i;
+			return 1;
+		}
+	}
+	return 0;
+}
+
+static int
+btrfs_rebuild_ordered_meta_chunk_stripes(struct recover_control *rc,
+					 struct chunk_record *chunk)
+{
+	u64 start = chunk->offset;
+	u64 end = chunk->offset + chunk->length;
+	struct cache_extent *cache;
+	struct extent_record *er;
+	struct device_extent_record *devext;
+	struct device_extent_record *next;
+	struct btrfs_device *device;
+	LIST_HEAD(devexts);
+	int index;
+	int mirror;
+	int ret;
+
+	cache = lookup_cache_extent(&rc->eb_cache,
+				    start, chunk->length);
+	if (!cache) {
+		/* No used space, we can reorder the stripes freely. */
+		ret = btrfs_rebuild_unordered_chunk_stripes(rc, chunk);
+		return ret;
+	}
+
+	list_splice_init(&chunk->dextents, &devexts);
+again:
+	er = container_of(cache, struct extent_record, cache);
+	index = btrfs_calc_stripe_index(chunk, er->cache.start);
+	if (chunk->stripes[index].devid)
+		goto next;
+	list_for_each_entry_safe(devext, next, &devexts, chunk_list) {
+		if (is_extent_record_in_device_extent(er, devext, &mirror)) {
+			chunk->stripes[index].devid = devext->objectid;
+			chunk->stripes[index].offset = devext->offset;
+			memcpy(chunk->stripes[index].dev_uuid,
+			       er->devices[mirror]->uuid,
+			       BTRFS_UUID_SIZE);
+			index++;
+			list_move(&devext->chunk_list, &chunk->dextents);
+		}
+	}
+next:
+	start = btrfs_next_stripe_logical_offset(chunk, er->cache.start);
+	if (start >= end)
+		goto no_extent_record;
+
+	cache = lookup_cache_extent(&rc->eb_cache, start, end - start);
+	if (cache)
+		goto again;
+no_extent_record:
+	if (list_empty(&devexts))
+		return 0;
+
+	if (chunk->type_flags & (BTRFS_BLOCK_GROUP_RAID5 |
+				 BTRFS_BLOCK_GROUP_RAID6)) {
+		/* Fixme: try to recover the order by the parity block. */
+		list_splice_tail(&devexts, &chunk->dextents);
+		return -EINVAL;
+	}
+
+	/* There is no data on the lost stripes, we can reorder them freely. */
+	for (index = 0; index < chunk->num_stripes; index++) {
+		if (chunk->stripes[index].devid)
+			continue;
+
+		devext = list_first_entry(&devexts,
+					  struct device_extent_record,
+					   chunk_list);
+		list_move(&devext->chunk_list, &chunk->dextents);
+
+		chunk->stripes[index].devid = devext->objectid;
+		chunk->stripes[index].offset = devext->offset;
+		device = btrfs_find_device_by_devid(rc->fs_devices,
+						    devext->objectid,
+						    0);
+		if (!device) {
+			list_splice_tail(&devexts, &chunk->dextents);
+			return -EINVAL;
+		}
+		BUG_ON(btrfs_find_device_by_devid(rc->fs_devices,
+						  devext->objectid,
+						  1));
+		memcpy(chunk->stripes[index].dev_uuid, device->uuid,
+		       BTRFS_UUID_SIZE);
+	}
+	return 0;
+}
+
+#define BTRFS_ORDERED_RAID	(BTRFS_BLOCK_GROUP_RAID0 |	\
+				 BTRFS_BLOCK_GROUP_RAID10 |	\
+				 BTRFS_BLOCK_GROUP_RAID5 |	\
+				 BTRFS_BLOCK_GROUP_RAID6)
+
+static int btrfs_rebuild_chunk_stripes(struct recover_control *rc,
+				       struct chunk_record *chunk)
+{
+	int ret;
+
+	/*
+	 * All the data in the system metadata chunk will be dropped,
+	 * so we need not guarantee that the data is right or not, that
+	 * is we can reorder the stripes in the system metadata chunk.
+	 */
+	if ((chunk->type_flags & BTRFS_BLOCK_GROUP_METADATA) &&
+	    (chunk->type_flags & BTRFS_ORDERED_RAID))
+		ret =btrfs_rebuild_ordered_meta_chunk_stripes(rc, chunk);
+	else if ((chunk->type_flags & BTRFS_BLOCK_GROUP_DATA) &&
+		 (chunk->type_flags & BTRFS_ORDERED_RAID))
+		ret = 1;	/* Be handled after the fs is opened. */
+	else
+		ret = btrfs_rebuild_unordered_chunk_stripes(rc, chunk);
+
+	return ret;
+}
+
+static int btrfs_recover_chunks(struct recover_control *rc)
+{
+	struct chunk_record *chunk;
+	struct block_group_record *bg;
+	struct block_group_record *next;
+	LIST_HEAD(new_chunks);
+	LIST_HEAD(devexts);
+	int nstripes;
+	int ret;
+
+	/* create the chunk by block group */
+	list_for_each_entry_safe(bg, next, &rc->bg.block_groups, list) {
+		nstripes = btrfs_get_device_extents(bg->objectid,
+						    &rc->devext.no_chunk_orphans,
+						    &devexts);
+		chunk = malloc(btrfs_chunk_record_size(nstripes));
+		if (!chunk)
+			return -ENOMEM;
+		memset(chunk, 0, btrfs_chunk_record_size(nstripes));
+		INIT_LIST_HEAD(&chunk->dextents);
+		chunk->bg_rec = bg;
+		chunk->cache.start = bg->objectid;
+		chunk->cache.size = bg->offset;
+		chunk->objectid = BTRFS_FIRST_CHUNK_TREE_OBJECTID;
+		chunk->type = BTRFS_CHUNK_ITEM_KEY;
+		chunk->offset = bg->objectid;
+		chunk->generation = bg->generation;
+		chunk->length = bg->offset;
+		chunk->owner = BTRFS_CHUNK_TREE_OBJECTID;
+		chunk->stripe_len = BTRFS_STRIPE_LEN;
+		chunk->type_flags = bg->flags;
+		chunk->io_width = BTRFS_STRIPE_LEN;
+		chunk->io_align = BTRFS_STRIPE_LEN;
+		chunk->sector_size = rc->sectorsize;
+		chunk->sub_stripes = calc_sub_nstripes(bg->flags);
+
+		ret = insert_cache_extent(&rc->chunk, &chunk->cache);
+		BUG_ON(ret);
+
+		if (!nstripes) {
+			list_add_tail(&chunk->list, &rc->bad_chunks);
+			continue;
+		}
+
+		list_splice_init(&devexts, &chunk->dextents);
+
+		ret = btrfs_verify_device_extents(bg, &devexts, nstripes);
+		if (ret) {
+			list_add_tail(&chunk->list, &rc->bad_chunks);
+			continue;
+		}
+
+		chunk->num_stripes = nstripes;
+		ret = btrfs_rebuild_chunk_stripes(rc, chunk);
+		if (ret > 0)
+			list_add_tail(&chunk->list, &rc->unrepaired_chunks);
+		else if (ret < 0)
+			list_add_tail(&chunk->list, &rc->bad_chunks);
+		else
+			list_add_tail(&chunk->list, &rc->good_chunks);
+	}
+	/*
+	 * Don't worry about the lost orphan device extents, they don't
+	 * have its chunk and block group, they must be the old ones that
+	 * we have dropped.
+	 */
+	return 0;
+}
+
+/*
+ * Return 0 when succesful, < 0 on error and > 0 if aborted by user
+ */
+int btrfs_recover_chunk_tree(char *path, int verbose, int yes)
+{
+	int ret = 0;
+	struct btrfs_root *root = NULL;
+	struct btrfs_trans_handle *trans;
+	struct recover_control rc;
+
+	init_recover_control(&rc, verbose, yes);
+
+	ret = recover_prepare(&rc, path);
+	if (ret) {
+		fprintf(stderr, "recover prepare error\n");
+		return ret;
+	}
+
+	ret = scan_devices(&rc);
+	if (ret) {
+		fprintf(stderr, "scan chunk headers error\n");
+		goto fail_rc;
+	}
+
+	if (cache_tree_empty(&rc.chunk) &&
+	    cache_tree_empty(&rc.bg.tree) &&
+	    cache_tree_empty(&rc.devext.tree)) {
+		fprintf(stderr, "no recoverable chunk\n");
+		goto fail_rc;
+	}
+
+	print_scan_result(&rc);
+
+	ret = check_chunks(&rc.chunk, &rc.bg, &rc.devext, &rc.good_chunks,
+			   &rc.bad_chunks, 1);
+	print_check_result(&rc);
+	if (ret) {
+		if (!list_empty(&rc.bg.block_groups) ||
+		    !list_empty(&rc.devext.no_chunk_orphans)) {
+			ret = btrfs_recover_chunks(&rc);
+			if (ret)
+				goto fail_rc;
+		}
+		/*
+		 * If the chunk is healthy, its block group item and device
+		 * extent item should be written on the disks. So, it is very
+		 * likely that the bad chunk is a old one that has been
+		 * droppped from the fs. Don't deal with them now, we will
+		 * check it after the fs is opened.
+		 */
+	}
+
+	root = open_ctree_with_broken_chunk(&rc);
+	if (IS_ERR(root)) {
+		fprintf(stderr, "open with broken chunk error\n");
+		ret = PTR_ERR(root);
+		goto fail_rc;
+	}
+
+	ret = check_all_chunks_by_metadata(&rc, root);
+	if (ret) {
+		fprintf(stderr, "The chunks in memory can not match the metadata of the fs. Repair failed.\n");
+		goto fail_close_ctree;
+	}
+
+	if (!rc.yes) {
+		ret = ask_user("We are going to rebuild the chunk tree on disk, it might destroy the old metadata on the disk, Are you sure?");
+		if (!ret) {
+			ret = 1;
+			goto fail_close_ctree;
+		}
+	}
+
+	trans = btrfs_start_transaction(root, 1);
+	ret = remove_chunk_extent_item(trans, &rc, root);
+	BUG_ON(ret);
+
+	ret = rebuild_chunk_tree(trans, &rc, root);
+	BUG_ON(ret);
+
+	ret = rebuild_sys_array(&rc, root);
+	BUG_ON(ret);
+
+	btrfs_commit_transaction(trans, root);
+fail_close_ctree:
+	close_ctree(root);
+fail_rc:
+	free_recover_control(&rc);
+	return ret;
+}
diff --git a/cmds-rescue.c b/cmds-rescue.c
index 35b3bb1..cfbc198 100644
--- a/cmds-rescue.c
+++ b/cmds-rescue.c
@@ -18,13 +18,75 @@
 
 #include "kerncompat.h"
 
+#include <getopt.h>
 #include "commands.h"
+#include "utils.h"
 
 static const char * const rescue_cmd_group_usage[] = {
 	"btrfs rescue <command> [options] <path>",
 	NULL
 };
 
+int btrfs_recover_chunk_tree(char *path, int verbose, int yes);
+
+const char * const cmd_chunk_recover_usage[] = {
+	"btrfs rescue chunk-recover [options] <device>",
+	"Recover the chunk tree by scanning the devices one by one.",
+	"",
+	"-y	Assume an answer of `yes' to all questions",
+	"-v	Verbose mode",
+	"-h	Help",
+	NULL
+};
+
+int cmd_chunk_recover(int argc, char *argv[])
+{
+	int ret = 0;
+	char *file;
+	int yes = 0;
+	int verbose = 0;
+
+	while (1) {
+		int c = getopt(argc, argv, "yvh");
+		if (c < 0)
+			break;
+		switch (c) {
+		case 'y':
+			yes = 1;
+			break;
+		case 'v':
+			verbose = 1;
+			break;
+		case 'h':
+		default:
+			usage(cmd_chunk_recover_usage);
+		}
+	}
+
+	argc = argc - optind;
+	if (argc == 0)
+		usage(cmd_chunk_recover_usage);
+
+	file = argv[optind];
+
+	ret = check_mounted(file);
+	if (ret) {
+		fprintf(stderr, "the device is busy\n");
+		return ret;
+	}
+
+	ret = btrfs_recover_chunk_tree(file, verbose, yes);
+	if (!ret) {
+		fprintf(stdout, "Recover the chunk tree successfully.\n");
+	} else if (ret > 0) {
+		ret = 0;
+		fprintf(stdout, "Abort to rebuild the on-disk chunk tree.\n");
+	} else {
+		fprintf(stdout, "Fail to recover the chunk tree.\n");
+	}
+	return ret;
+}
+
 const struct cmd_group rescue_cmd_group = {
 	rescue_cmd_group_usage, NULL, {
 		{ "chunk-recover", cmd_chunk_recover, cmd_chunk_recover_usage, NULL, 0},
