-int gfs2_revoke_add(struct gfs2_sbd *sdp, u64 blkno, unsigned int where);
-int gfs2_revoke_check(struct gfs2_sbd *sdp, u64 blkno, unsigned int where);
-void gfs2_revoke_clean(struct gfs2_sbd *sdp);
+extern int gfs2_revoke_add(struct gfs2_sbd *sdp, u64 blkno, unsigned int where);
+extern int gfs2_revoke_check(struct gfs2_sbd *sdp, u64 blkno, unsigned int where);
+extern void gfs2_revoke_clean(struct gfs2_sbd *sdp);