Btrfs: Add support for mirroring across drives

Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 67d533c..0a20786 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -418,6 +418,7 @@
 #define BTRFS_BLOCK_GROUP_SYSTEM   (1 << 1)
 #define BTRFS_BLOCK_GROUP_METADATA (1 << 2)
 #define BTRFS_BLOCK_GROUP_RAID0    (1 << 3)
+#define BTRFS_BLOCK_GROUP_RAID1    (1 << 4)
 
 
 struct btrfs_block_group_item {
@@ -504,8 +505,12 @@
 	u64 delalloc_bytes;
 	u64 last_alloc;
 	u64 last_data_alloc;
-	int extra_data_alloc_bits;
-	int extra_alloc_bits;
+	int avail_data_alloc_bits;
+	int avail_metadata_alloc_bits;
+	int avail_system_alloc_bits;
+	int data_alloc_profile;
+	int metadata_alloc_profile;
+	int system_alloc_profile;
 };
 
 /*