xfs: cross-reference with the bnobt

When we're scrubbing various btrees, cross-reference the records with
the bnobt to ensure that we don't also think the space is free.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/scrub/scrub.h

@@ -123,4 +123,8 @@ xfs_scrub_quota(struct xfs_scrub_context *sc)
 }
 #endif
 
+/* cross-referencing helpers */
+void xfs_scrub_xref_is_used_space(struct xfs_scrub_context *sc,
+		xfs_agblock_t agbno, xfs_extlen_t len);
+
 #endif	/* __XFS_SCRUB_SCRUB_H__ */