Yup. Boot into rescue mode, the make sure the sysimage root is not mounted and then resize2fs && lvm resize. Since you're presumably talking about FC2test, not FC1, you may have to lvm vgcfgbackup && lvm vgcfgrestore to get the free PE count in the PV fixed (bug 112089, fixed in LVM2 CVS but not yet in rawhide).