Btrfs: use BUG_ON

Use BUG_ON(x) rather than if(x) BUG();

The semantic patch that fixes this problem is as follows:

// <smpl>
@@ identifier x; @@
-if (x) BUG();
+BUG_ON(x);
// </smpl>

Signed-off-by: Himangi Saraogi <himangi774@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Chris Mason <clm@fb.com>

fs/btrfs/volumes.c

@@ -2677,8 +2677,8 @@ again:
 						   found_key.offset);
 			if (ret == -ENOSPC)
 				failed++;
-			else if (ret)
+			else
-				BUG();
+				BUG_ON(ret);
 		}
 
 		if (found_key.offset == 0)