Btrfs: fix df regression

The new ENOSPC stuff breaks out the raid types which breaks the way we were
reporting df to the system.  This fixes it back so that Available is the total
space available to data and used is the actual bytes used by the filesystem.
This means that Available is Total - data used - all of the metadata space.
Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 29c2009..014fd52 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -675,7 +675,8 @@
 struct btrfs_space_info {
 	u64 flags;
 
-	u64 total_bytes;	/* total bytes in the space */
+	u64 total_bytes;	/* total bytes in the space,
+				   this doesn't take mirrors into account */
 	u64 bytes_used;		/* total bytes used,
 				   this does't take mirrors into account */
 	u64 bytes_pinned;	/* total bytes pinned, will be freed when the
@@ -687,6 +688,8 @@
 	u64 bytes_may_use;	/* number of bytes that may be used for
 				   delalloc/allocations */
 	u64 disk_used;		/* total bytes used on disk */
+	u64 disk_total;		/* total bytes on disk, takes mirrors into
+				   account */
 
 	int full;		/* indicates that we cannot allocate any more
 				   chunks for this space */