+#define BL_WANTDEALLOC 0x00000010 /* buffer should be put on empty list when clean */
+#define BL_SHADOW 0x00000020
+#define BL_EXTERNAL 0x00000040
+#define BL_WAITSHADOW 0x00000080
+#define BL_IOBUF_ALLOC 0x00000100
+
+/*
+ * Parameters for buffer cache garbage collection
+ */
+#define BUF_STALE_THRESHHOLD 30 /* Collect if untouched in the last 30 seconds */
+#define BUF_MAX_GC_COUNT 1024 /* Generally 6-8 MB */
+#define BUF_MAX_GC_BATCH_SIZE 128 /* Under a single grab of the lock */