diff --git a/disk-io.c b/disk-io.c
index d49f2cea..8150d73b 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -38,12 +38,12 @@
 static int check_tree_block(struct btrfs_root *root, struct extent_buffer *buf)
 {
 	if (buf->start != btrfs_header_bytenr(buf))
-		BUG();
+		return 1;
 
 	if (memcmp_extent_buffer(buf, root->fs_info->fsid,
 				 (unsigned long)btrfs_header_fsid(buf),
 				 BTRFS_FSID_SIZE))
-		BUG();
+		return 1;
 	return 0;
 }
 
@@ -57,8 +57,8 @@ void btrfs_csum_final(u32 crc, char *result)
 	*(__le32 *)result = ~cpu_to_le32(crc);
 }
 
-static int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
-			   int verify)
+int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
+		    int verify)
 {
 	char result[BTRFS_CRC32_SIZE];
 	u32 len;
@@ -70,8 +70,9 @@ static int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
 
 	if (verify) {
 		if (memcmp_extent_buffer(buf, result, 0, BTRFS_CRC32_SIZE)) {
-			printk("checksum verify failed on %llu\n",
-				(unsigned long long)buf->start);
+			printk("checksum verify failed on %llu wanted %X "
+			       "found %X\n", (unsigned long long)buf->start,
+			       *((int *)result), *((int *)buf));
 			return 1;
 		}
 	} else {
@@ -112,7 +113,7 @@ int readahead_tree_block(struct btrfs_root *root, u64 bytenr, u32 blocksize)
 	dev_nr = 0;
 	length = blocksize;
 	ret = btrfs_map_block(&root->fs_info->mapping_tree, READ,
-			      bytenr, &length, &multi);
+			      bytenr, &length, &multi, 0);
 	BUG_ON(ret);
 	device = multi->stripes[0].dev;
 	device->total_ios++;
@@ -131,6 +132,8 @@ struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
 	u64 length;
 	struct btrfs_multi_bio *multi = NULL;
 	struct btrfs_device *device;
+	int mirror_num = 0;
+	int num_copies;
 
 	eb = btrfs_find_create_tree_block(root, bytenr, blocksize);
 	if (!eb)
@@ -141,21 +144,35 @@ struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
 
 	dev_nr = 0;
 	length = blocksize;
-	ret = btrfs_map_block(&root->fs_info->mapping_tree, READ,
-			      eb->start, &length, &multi);
-	BUG_ON(ret);
-	device = multi->stripes[0].dev;
-	eb->fd = device->fd;
-	device->total_ios++;
-	eb->dev_bytenr = multi->stripes[0].physical;
-	ret = read_extent_from_disk(eb);
-	if (ret) {
-		free_extent_buffer(eb);
-		return NULL;
+	while (1) {
+		ret = btrfs_map_block(&root->fs_info->mapping_tree, READ,
+				      eb->start, &length, &multi, mirror_num);
+		BUG_ON(ret);
+		device = multi->stripes[0].dev;
+		eb->fd = device->fd;
+		device->total_ios++;
+		eb->dev_bytenr = multi->stripes[0].physical;
+		kfree(multi);
+		ret = read_extent_from_disk(eb);
+		if (ret == 0 && check_tree_block(root, eb) == 0 &&
+		    csum_tree_block(root, eb, 1) == 0) {
+			btrfs_set_buffer_uptodate(eb);
+			return eb;
+		}
+		num_copies = btrfs_num_copies(&root->fs_info->mapping_tree,
+					      eb->start, eb->len);
+		if (num_copies == 1) {
+printk("reading %Lu failed only one copy\n", eb->start);
+			break;
+		}
+		mirror_num++;
+		if (mirror_num > num_copies) {
+printk("bailing at mirror %d of %d\n", mirror_num, num_copies);
+			break;
+		}
 	}
-	btrfs_set_buffer_uptodate(eb);
-	kfree(multi);
-	return eb;
+	free_extent_buffer(eb);
+	return NULL;
 }
 
 int write_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root *root,
@@ -177,7 +194,7 @@ int write_tree_block(struct btrfs_trans_handle *trans, struct btrfs_root *root,
 	dev_nr = 0;
 	length = eb->len;
 	ret = btrfs_map_block(&root->fs_info->mapping_tree, WRITE,
-			      eb->start, &length, &multi);
+			      eb->start, &length, &multi, 0);
 	while(dev_nr < multi->num_stripes) {
 		BUG_ON(ret);
 		eb->fd = multi->stripes[dev_nr].dev->fd;
diff --git a/disk-io.h b/disk-io.h
index f680721a..1b5cbdfb 100644
--- a/disk-io.h
+++ b/disk-io.h
@@ -52,4 +52,6 @@ void btrfs_csum_final(u32 crc, char *result);
 int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
 			     struct btrfs_root *root);
 int btrfs_open_device(struct btrfs_device *dev);
+int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
+		    int verify);
 #endif
diff --git a/utils.c b/utils.c
index 55d3f5f1..9d162da7 100644
--- a/utils.c
+++ b/utils.c
@@ -106,6 +106,7 @@ int make_btrfs(int fd, char *device_name,
 
 	/* create the tree of root objects */
 	memset(buf->data, 0, leafsize);
+	buf->len = leafsize;
 	btrfs_set_header_bytenr(buf, blocks[1]);
 	btrfs_set_header_nritems(buf, 3);
 	btrfs_set_header_generation(buf, 1);
@@ -165,6 +166,7 @@ int make_btrfs(int fd, char *device_name,
 	nritems++;
 
 
+	csum_tree_block(NULL, buf, 0);
 	ret = pwrite(fd, buf->data, leafsize, blocks[1]);
 	BUG_ON(ret != leafsize);
 
@@ -229,6 +231,7 @@ int make_btrfs(int fd, char *device_name,
 	btrfs_set_header_bytenr(buf, blocks[2]);
 	btrfs_set_header_owner(buf, BTRFS_EXTENT_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, nritems);
+	csum_tree_block(NULL, buf, 0);
 	ret = pwrite(fd, buf->data, leafsize, blocks[2]);
 	BUG_ON(ret != leafsize);
 
@@ -302,6 +305,7 @@ int make_btrfs(int fd, char *device_name,
 	btrfs_set_header_bytenr(buf, blocks[3]);
 	btrfs_set_header_owner(buf, BTRFS_CHUNK_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, nritems);
+	csum_tree_block(NULL, buf, 0);
 	ret = pwrite(fd, buf->data, leafsize, blocks[3]);
 
 	/* create the device tree */
@@ -325,12 +329,14 @@ int make_btrfs(int fd, char *device_name,
 	btrfs_set_header_bytenr(buf, blocks[4]);
 	btrfs_set_header_owner(buf, BTRFS_DEV_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, nritems);
+	csum_tree_block(NULL, buf, 0);
 	ret = pwrite(fd, buf->data, leafsize, blocks[4]);
 
 	/* finally create the FS root */
 	btrfs_set_header_bytenr(buf, blocks[5]);
 	btrfs_set_header_owner(buf, BTRFS_FS_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, 0);
+	csum_tree_block(NULL, buf, 0);
 	ret = pwrite(fd, buf->data, leafsize, blocks[5]);
 	BUG_ON(ret != leafsize);
 
@@ -338,6 +344,8 @@ int make_btrfs(int fd, char *device_name,
 	BUG_ON(sizeof(super) > sectorsize);
 	memset(buf->data, 0, sectorsize);
 	memcpy(buf->data, &super, sizeof(super));
+	buf->len = sectorsize;
+	csum_tree_block(NULL, buf, 0);
 	ret = pwrite(fd, buf->data, sectorsize, blocks[0]);
 	BUG_ON(ret != sectorsize);
 
diff --git a/volumes.c b/volumes.c
index ef2f59ca..44e67291 100644
--- a/volumes.c
+++ b/volumes.c
@@ -732,9 +732,29 @@ void btrfs_mapping_init(struct btrfs_mapping_tree *tree)
 	cache_tree_init(&tree->cache_tree);
 }
 
+int btrfs_num_copies(struct btrfs_mapping_tree *map_tree, u64 logical, u64 len)
+{
+	struct cache_extent *ce;
+	struct map_lookup *map;
+	int ret;
+	u64 offset;
+
+	ce = find_first_cache_extent(&map_tree->cache_tree, logical);
+	BUG_ON(!ce);
+	BUG_ON(ce->start > logical || ce->start + ce->size < logical);
+	map = container_of(ce, struct map_lookup, ce);
+
+	offset = logical - ce->start;
+	if (map->type & (BTRFS_BLOCK_GROUP_DUP | BTRFS_BLOCK_GROUP_RAID1))
+		ret = map->num_stripes;
+	else
+		ret = 1;
+	return ret;
+}
+
 int btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
 		    u64 logical, u64 *length,
-		    struct btrfs_multi_bio **multi_ret)
+		    struct btrfs_multi_bio **multi_ret, int mirror_num)
 {
 	struct cache_extent *ce;
 	struct map_lookup *map;
@@ -802,11 +822,15 @@ again:
 	if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
 		if (rw == WRITE)
 			multi->num_stripes = map->num_stripes;
+		else if (mirror_num)
+			stripe_index = mirror_num - 1;
 		else
 			stripe_index = stripe_nr % map->num_stripes;
 	} else if (map->type & BTRFS_BLOCK_GROUP_DUP) {
 		if (rw == WRITE)
 			multi->num_stripes = map->num_stripes;
+		else if (mirror_num)
+			stripe_index = mirror_num - 1;
 	} else {
 		/*
 		 * after this do_div call, stripe_nr is the number of stripes
diff --git a/volumes.h b/volumes.h
index 9928c1f9..be543163 100644
--- a/volumes.h
+++ b/volumes.h
@@ -85,7 +85,7 @@ int btrfs_alloc_dev_extent(struct btrfs_trans_handle *trans,
 			   u64 owner, u64 num_bytes, u64 *start);
 int btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
 		    u64 logical, u64 *length,
-		    struct btrfs_multi_bio **multi_ret);
+		    struct btrfs_multi_bio **multi_ret, int mirror_num);
 int btrfs_read_sys_array(struct btrfs_root *root);
 int btrfs_read_chunk_tree(struct btrfs_root *root);
 int btrfs_alloc_chunk(struct btrfs_trans_handle *trans,
@@ -104,4 +104,5 @@ int btrfs_add_device(struct btrfs_trans_handle *trans,
 int btrfs_scan_one_device(int fd, const char *path,
 			  struct btrfs_fs_devices **fs_devices_ret,
 			  u64 *total_devs, u64 super_offset);
+int btrfs_num_copies(struct btrfs_mapping_tree *map_tree, u64 logical, u64 len);
 #endif