This bug has been copied from bug #660661 and has been proposed to be backported to 5.6 z-stream (EUS).
in kernel-2.6.18-238.1.1.el5 linux-2.6-fs-gfs2-fix-statfs-error-after-gfs2_grow.patch
An advisory has been issued which should help the problem described in this bug report. This report is therefore being closed with a resolution of ERRATA. For more information on therefore solution and/or where to find the updated files, please follow the link below. You may reopen this bug report if the solution does not work for you. http://rhn.redhat.com/errata/RHSA-2011-0163.html
Technical note added. If any revisions are required, please edit the "Technical Notes" field accordingly. All revisions will be proofread by the Engineering Content Services team. New Contents: Due to an off-by-one error, gfs2_grow failed to take the very last "rgrp" parameter into account when adding up the new free space. With this update, the GFS2 kernel properly counts all the new resource groups and fixes the "statfs" file correctly.