diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 3f3a23f52a3b..01310de2bf4a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -13,10 +13,11 @@ extern struct kmem_cache *btrfs_path_cachep;
 #define BTRFS_MAGIC "_BtRfS_M"
 
 #define BTRFS_ROOT_TREE_OBJECTID 1ULL
-#define BTRFS_EXTENT_TREE_OBJECTID 2ULL
-#define BTRFS_FS_TREE_OBJECTID 3ULL
-#define BTRFS_ROOT_TREE_DIR_OBJECTID 4ULL
-#define BTRFS_FIRST_FREE_OBJECTID 5ULL
+#define BTRFS_DEV_TREE_OBJECTID 2ULL
+#define BTRFS_EXTENT_TREE_OBJECTID 3ULL
+#define BTRFS_FS_TREE_OBJECTID 4ULL
+#define BTRFS_ROOT_TREE_DIR_OBJECTID 5ULL
+#define BTRFS_FIRST_FREE_OBJECTID 6ULL
 
 /*
  * we can actually store much bigger names, but lets not confuse the rest
@@ -90,6 +91,10 @@ struct btrfs_super_block {
 	__le64 total_blocks;
 	__le64 blocks_used;
 	__le64 root_dir_objectid;
+	/* fields below here vary with the underlying disk */
+	__le64 device_block_start;
+	__le64 device_num_blocks;
+	__le64 device_root;
 } __attribute__ ((__packed__));
 
 /*
@@ -223,10 +228,15 @@ struct btrfs_csum_item {
 	u8 csum[BTRFS_CSUM_SIZE];
 } __attribute__ ((__packed__));
 
+struct btrfs_device_item {
+	__le16 pathlen;
+} __attribute__ ((__packed__));
+
 struct crypto_hash;
 struct btrfs_fs_info {
 	struct btrfs_root *extent_root;
 	struct btrfs_root *tree_root;
+	struct btrfs_root *dev_root;
 	struct btrfs_key current_insert;
 	struct btrfs_key last_insert;
 	struct radix_tree_root fs_roots_radix;
@@ -312,11 +322,16 @@ struct btrfs_root {
  */
 #define BTRFS_EXTENT_ITEM_KEY	8
 
+/*
+ * dev items list the devices that make up the FS
+ */
+#define BTRFS_DEV_ITEM_KEY	9
+
 /*
  * string items are for debugging.  They just store a short string of
  * data in the FS
  */
-#define BTRFS_STRING_ITEM_KEY	9
+#define BTRFS_STRING_ITEM_KEY	10
 
 static inline u64 btrfs_inode_generation(struct btrfs_inode_item *i)
 {
@@ -782,6 +797,40 @@ static inline void btrfs_set_super_root_dir(struct btrfs_super_block *s, u64
 	s->root_dir_objectid = cpu_to_le64(val);
 }
 
+static inline u64 btrfs_super_device_block_start(struct btrfs_super_block *s)
+{
+	return le64_to_cpu(s->device_block_start);
+}
+
+static inline void btrfs_set_super_device_block_start(struct btrfs_super_block
+						      *s, u64 val)
+{
+	s->device_block_start = cpu_to_le64(val);
+}
+
+static inline u64 btrfs_super_device_num_blocks(struct btrfs_super_block *s)
+{
+	return le64_to_cpu(s->device_num_blocks);
+}
+
+static inline void btrfs_set_super_device_num_blocks(struct btrfs_super_block
+						     *s, u64 val)
+{
+	s->device_num_blocks = cpu_to_le64(val);
+}
+
+static inline u64 btrfs_super_device_root(struct btrfs_super_block *s)
+{
+	return le64_to_cpu(s->device_root);
+}
+
+static inline void btrfs_set_super_device_root(struct btrfs_super_block
+						      *s, u64 val)
+{
+	s->device_root = cpu_to_le64(val);
+}
+
+
 static inline u8 *btrfs_leaf_data(struct btrfs_leaf *l)
 {
 	return (u8 *)l->items;
@@ -849,6 +898,17 @@ static inline void btrfs_set_file_extent_num_blocks(struct
 	e->num_blocks = cpu_to_le64(val);
 }
 
+static inline u16 btrfs_device_pathlen(struct btrfs_device_item *d)
+{
+	return le16_to_cpu(d->pathlen);
+}
+
+static inline void btrfs_set_device_pathlen(struct btrfs_device_item *d,
+						u16 val)
+{
+	d->pathlen = cpu_to_le16(val);
+}
+
 static inline struct btrfs_root *btrfs_sb(struct super_block *sb)
 {
 	return sb->s_fs_info;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index ff69162829b3..e09233262af6 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -378,6 +378,8 @@ struct btrfs_root *open_ctree(struct super_block *sb)
 {
 	struct btrfs_root *extent_root = kmalloc(sizeof(struct btrfs_root),
 						 GFP_NOFS);
+	struct btrfs_root *dev_root = kmalloc(sizeof(struct btrfs_root),
+						 GFP_NOFS);
 	struct btrfs_root *tree_root = kmalloc(sizeof(struct btrfs_root),
 					       GFP_NOFS);
 	struct btrfs_fs_info *fs_info = kmalloc(sizeof(*fs_info),
@@ -392,6 +394,7 @@ struct btrfs_root *open_ctree(struct super_block *sb)
 	fs_info->running_transaction = NULL;
 	fs_info->tree_root = tree_root;
 	fs_info->extent_root = extent_root;
+	fs_info->dev_root = dev_root;
 	fs_info->sb = sb;
 	fs_info->btree_inode = new_inode(sb);
 	fs_info->btree_inode->i_ino = 1;
@@ -414,6 +417,9 @@ struct btrfs_root *open_ctree(struct super_block *sb)
 	memset(&fs_info->current_insert, 0, sizeof(fs_info->current_insert));
 	memset(&fs_info->last_insert, 0, sizeof(fs_info->last_insert));
 
+	__setup_root(sb->s_blocksize, dev_root,
+		     fs_info, BTRFS_DEV_TREE_OBJECTID);
+
 	__setup_root(sb->s_blocksize, tree_root,
 		     fs_info, BTRFS_ROOT_TREE_OBJECTID);
 	fs_info->sb_buffer = read_tree_block(tree_root,
@@ -427,6 +433,8 @@ struct btrfs_root *open_ctree(struct super_block *sb)
 		return NULL;
 
 	fs_info->disk_super = disk_super;
+	dev_root->node = read_tree_block(tree_root,
+					  btrfs_super_device_root(disk_super));
 	tree_root->node = read_tree_block(tree_root,
 					  btrfs_super_root(disk_super));
 	BUG_ON(!tree_root->node);
@@ -519,6 +527,9 @@ int close_ctree(struct btrfs_root *root)
 	if (fs_info->extent_root->node)
 		btrfs_block_release(fs_info->extent_root,
 				    fs_info->extent_root->node);
+	if (fs_info->dev_root->node)
+		btrfs_block_release(fs_info->dev_root,
+				    fs_info->dev_root->node);
 	if (fs_info->tree_root->node)
 		btrfs_block_release(fs_info->tree_root,
 				    fs_info->tree_root->node);