--- a/radix-tree.h
+++ b/radix-tree.h
@@ -43,6 +43,21 @@
 #include <btrfs/kerncompat.h>
 #endif /* BTRFS_FLAT_INCLUDES */
 
+/* no longer provided by the btrfs-progs 6.x kerncompat.h */
+#ifndef __GFP_BITS_SHIFT
+typedef int gfp_t;
+#define __GFP_BITS_SHIFT 20
+#define __GFP_BITS_MASK ((int)((1 << __GFP_BITS_SHIFT) - 1))
+#define GFP_KERNEL 0
+#endif
+#ifndef preempt_enable
+#define preempt_enable()	do { } while (0)
+#define preempt_disable()	do { } while (0)
+#endif
+#ifndef IS_ALIGNED
+#define IS_ALIGNED(x, a)	(((x) & ((typeof(x))(a) - 1)) == 0)
+#endif
+
 #define RADIX_TREE_MAX_TAGS 2
 
 /* root tags are stored in gfp_mask, shifted by __GFP_BITS_SHIFT */