return 0;
}
+/**
+ * whether the requestion IO contains older layout version than that on the
+ * disk.
+ */
+static inline bool ofd_layout_version_less(__u32 req_version,
+ __u32 ondisk_version)
+{
+ __u32 req = req_version & ~LU_LAYOUT_RESYNC;
+ __u32 ondisk = ondisk_version & ~LU_LAYOUT_RESYNC;
+
+ /**
+ * request layout version could be circularly increased to the samllest
+ * value, in that case @req < @ondisk but @req does not have the high
+ * end bit set while @ondisk does.
+ */
+ return (req < ondisk) &&
+ ((req & LU_LAYOUT_HIGEN) == (ondisk & LU_LAYOUT_HIGEN));
+}
+
#endif /* _OFD_INTERNAL_H */