diff --git a/mkfs/common.c b/mkfs/common.c
index e4785c5..f34c4eb 100644
--- a/mkfs/common.c
+++ b/mkfs/common.c
@@ -93,18 +93,18 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	uuid_generate(super.dev_item.uuid);
 	uuid_generate(chunk_tree_uuid);
 
-	cfg->blocks[0] = BTRFS_SUPER_INFO_OFFSET;
-	for (i = 1; i < 7; i++) {
+	cfg->blocks[SUPER_BLOCK] = BTRFS_SUPER_INFO_OFFSET;
+	for (i = 1; i < BLOCK_COUNT; i++) {
 		cfg->blocks[i] = BTRFS_SUPER_INFO_OFFSET + 1024 * 1024 +
 			cfg->nodesize * i;
 	}
 
-	btrfs_set_super_bytenr(&super, cfg->blocks[0]);
+	btrfs_set_super_bytenr(&super, cfg->blocks[SUPER_BLOCK]);
 	btrfs_set_super_num_devices(&super, 1);
 	btrfs_set_super_magic(&super, BTRFS_MAGIC_PARTIAL);
 	btrfs_set_super_generation(&super, 1);
-	btrfs_set_super_root(&super, cfg->blocks[1]);
-	btrfs_set_super_chunk_root(&super, cfg->blocks[3]);
+	btrfs_set_super_root(&super, cfg->blocks[ROOT_TREE]);
+	btrfs_set_super_chunk_root(&super, cfg->blocks[CHUNK_TREE]);
 	btrfs_set_super_total_bytes(&super, num_bytes);
 	btrfs_set_super_bytes_used(&super, 6 * cfg->nodesize);
 	btrfs_set_super_sectorsize(&super, cfg->sectorsize);
@@ -121,7 +121,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	/* create the tree of root objects */
 	memset(buf->data, 0, cfg->nodesize);
 	buf->len = cfg->nodesize;
-	btrfs_set_header_bytenr(buf, cfg->blocks[1]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[ROOT_TREE]);
 	btrfs_set_header_nritems(buf, 4);
 	btrfs_set_header_generation(buf, 1);
 	btrfs_set_header_backref_rev(buf, BTRFS_MIXED_BACKREF_REV);
@@ -151,7 +151,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	nritems = 0;
 
 	itemoff = __BTRFS_LEAF_DATA_SIZE(cfg->nodesize) - sizeof(root_item);
-	btrfs_set_root_bytenr(&root_item, cfg->blocks[2]);
+	btrfs_set_root_bytenr(&root_item, cfg->blocks[EXTENT_TREE]);
 	btrfs_set_disk_key_objectid(&disk_key, BTRFS_EXTENT_TREE_OBJECTID);
 	btrfs_set_item_key(buf, &disk_key, nritems);
 	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
@@ -162,7 +162,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	nritems++;
 
 	itemoff = itemoff - sizeof(root_item);
-	btrfs_set_root_bytenr(&root_item, cfg->blocks[4]);
+	btrfs_set_root_bytenr(&root_item, cfg->blocks[DEV_TREE]);
 	btrfs_set_disk_key_objectid(&disk_key, BTRFS_DEV_TREE_OBJECTID);
 	btrfs_set_item_key(buf, &disk_key, nritems);
 	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
@@ -174,7 +174,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	nritems++;
 
 	itemoff = itemoff - sizeof(root_item);
-	btrfs_set_root_bytenr(&root_item, cfg->blocks[5]);
+	btrfs_set_root_bytenr(&root_item, cfg->blocks[FS_TREE]);
 	btrfs_set_disk_key_objectid(&disk_key, BTRFS_FS_TREE_OBJECTID);
 	btrfs_set_item_key(buf, &disk_key, nritems);
 	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
@@ -186,7 +186,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	nritems++;
 
 	itemoff = itemoff - sizeof(root_item);
-	btrfs_set_root_bytenr(&root_item, cfg->blocks[6]);
+	btrfs_set_root_bytenr(&root_item, cfg->blocks[CSUM_TREE]);
 	btrfs_set_disk_key_objectid(&disk_key, BTRFS_CSUM_TREE_OBJECTID);
 	btrfs_set_item_key(buf, &disk_key, nritems);
 	btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
@@ -199,7 +199,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 
 
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[1]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[ROOT_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -210,7 +210,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 		cfg->nodesize - sizeof(struct btrfs_header));
 	nritems = 0;
 	itemoff = __BTRFS_LEAF_DATA_SIZE(cfg->nodesize);
-	for (i = 1; i < 7; i++) {
+	for (i = 1; i < BLOCK_COUNT; i++) {
 		item_size = sizeof(struct btrfs_extent_item);
 		if (!skinny_metadata)
 			item_size += sizeof(struct btrfs_tree_block_info);
@@ -267,11 +267,11 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 		btrfs_set_item_size(buf, btrfs_item_nr(nritems), 0);
 		nritems++;
 	}
-	btrfs_set_header_bytenr(buf, cfg->blocks[2]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[EXTENT_TREE]);
 	btrfs_set_header_owner(buf, BTRFS_EXTENT_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, nritems);
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[2]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[EXTENT_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -354,11 +354,11 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	ptr += item_size;
 	btrfs_set_super_sys_array_size(&super, array_size);
 
-	btrfs_set_header_bytenr(buf, cfg->blocks[3]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[CHUNK_TREE]);
 	btrfs_set_header_owner(buf, BTRFS_CHUNK_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, nritems);
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[3]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[CHUNK_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -393,11 +393,11 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 				    BTRFS_MKFS_SYSTEM_GROUP_SIZE);
 	nritems++;
 
-	btrfs_set_header_bytenr(buf, cfg->blocks[4]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[DEV_TREE]);
 	btrfs_set_header_owner(buf, BTRFS_DEV_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, nritems);
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[4]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[DEV_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -406,11 +406,11 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	/* create the FS root */
 	memset(buf->data + sizeof(struct btrfs_header), 0,
 		cfg->nodesize - sizeof(struct btrfs_header));
-	btrfs_set_header_bytenr(buf, cfg->blocks[5]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[FS_TREE]);
 	btrfs_set_header_owner(buf, BTRFS_FS_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, 0);
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[5]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[FS_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -418,11 +418,11 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	/* finally create the csum root */
 	memset(buf->data + sizeof(struct btrfs_header), 0,
 		cfg->nodesize - sizeof(struct btrfs_header));
-	btrfs_set_header_bytenr(buf, cfg->blocks[6]);
+	btrfs_set_header_bytenr(buf, cfg->blocks[CSUM_TREE]);
 	btrfs_set_header_owner(buf, BTRFS_CSUM_TREE_OBJECTID);
 	btrfs_set_header_nritems(buf, 0);
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[6]);
+	ret = pwrite(fd, buf->data, cfg->nodesize, cfg->blocks[CSUM_TREE]);
 	if (ret != cfg->nodesize) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
@@ -433,7 +433,8 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
 	memcpy(buf->data, &super, sizeof(super));
 	buf->len = BTRFS_SUPER_INFO_SIZE;
 	csum_tree_block_size(buf, BTRFS_CRC32_SIZE, 0);
-	ret = pwrite(fd, buf->data, BTRFS_SUPER_INFO_SIZE, cfg->blocks[0]);
+	ret = pwrite(fd, buf->data, BTRFS_SUPER_INFO_SIZE,
+			cfg->blocks[SUPER_BLOCK]);
 	if (ret != BTRFS_SUPER_INFO_SIZE) {
 		ret = (ret < 0 ? -errno : -EIO);
 		goto out;
diff --git a/mkfs/common.h b/mkfs/common.h
index 666a75b..4d8a314 100644
--- a/mkfs/common.h
+++ b/mkfs/common.h
@@ -28,6 +28,18 @@
 #define BTRFS_MKFS_SYSTEM_GROUP_SIZE SZ_4M
 #define BTRFS_MKFS_SMALL_VOLUME_SIZE SZ_1G
 
+/* roots: root tree, extent tree, chunk tree, dev tree, fs tree, csum tree */
+enum btrfs_mkfs_block {
+	SUPER_BLOCK = 0,
+	ROOT_TREE,
+	EXTENT_TREE,
+	CHUNK_TREE,
+	DEV_TREE,
+	FS_TREE,
+	CSUM_TREE,
+	BLOCK_COUNT
+};
+
 struct btrfs_mkfs_config {
 	/* Label of the new filesystem */
 	const char *label;
@@ -43,7 +55,7 @@ struct btrfs_mkfs_config {
 	/* Output fields, set during creation */
 
 	/* Logical addresses of superblock [0] and other tree roots */
-	u64 blocks[8];
+	u64 blocks[BLOCK_COUNT];
 	char fs_uuid[BTRFS_UUID_UNPARSED_SIZE];
 	char chunk_uuid[BTRFS_UUID_UNPARSED_SIZE];
 
