LVM and df

Hi, Obtained during installation a freespace problem on a LVM filesystem. Extended this filesystem with command lvextend from 300MB to 450MB lvdisplay shows file was extended to 450MB (so lvextend worked well). Yet still same problem when restarting the installation. df command shows the size is still 307184KB (same as before the lvextend command). What is blocking? François Vanderstucken