xfs: scrub refcount btrees

Plumb in the pieces necessary to check the refcount btree.  If rmap is
available, check the reference count by performing an interval query
against the rmapbt.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
diff --git a/fs/xfs/scrub/common.h b/fs/xfs/scrub/common.h
index 7922775..610e956 100644
--- a/fs/xfs/scrub/common.h
+++ b/fs/xfs/scrub/common.h
@@ -85,6 +85,8 @@ int xfs_scrub_setup_ag_iallocbt(struct xfs_scrub_context *sc,
 				struct xfs_inode *ip);
 int xfs_scrub_setup_ag_rmapbt(struct xfs_scrub_context *sc,
 			      struct xfs_inode *ip);
+int xfs_scrub_setup_ag_refcountbt(struct xfs_scrub_context *sc,
+				  struct xfs_inode *ip);
 
 
 void xfs_scrub_ag_free(struct xfs_scrub_context *sc, struct xfs_scrub_ag *sa);