+/**
+ * File IDentifier.
+ *
+ * FID is a cluster-wide unique identifier of a file or an object (stripe).
+ * FIDs are never reused.
+ **/
+struct lu_fid {
+ /**
+ * FID sequence. Sequence is a unit of migration: all files (objects)
+ * with FIDs from a given sequence are stored on the same server.
+ * Lustre should support 2^64 objects, so even if each sequence
+ * has only a single object we can still enumerate 2^64 objects.
+ **/
+ __u64 f_seq;
+ /* FID number within sequence. */
+ __u32 f_oid;
+ /**
+ * FID version, used to distinguish different versions (in the sense
+ * of snapshots, etc.) of the same file system object. Not currently
+ * used.
+ **/
+ __u32 f_ver;
+};
+
+struct filter_fid {
+ struct lu_fid ff_parent; /* ff_parent.f_ver == file stripe number */
+ __u64 ff_objid;
+ __u64 ff_seq;
+};
+
+/* Userspace should treat lu_fid as opaque, and only use the following methods
+ * to print or parse them. Other functions (e.g. compare, swab) could be moved
+ * here from lustre_idl.h if needed. */
+typedef struct lu_fid lustre_fid;