how to resize /usr on RHEL ES3 wit LVM1

Thu Mar 22 17:02:08 UTC 2007

hi,
I am running out of space on /usr. It's  a logical volume (LogVol00) under
LVM (Volume00). I do have free space on Volume00
I did Lvextend -L +500MB /dev/Volume00/LogVol00
Now how do I extend actual filesystem?
It's RHEL ES release 3. Filesystem is EXT3. LVM 1.0.3 Kernal 2.4.21

I tried resize2fs and but that is not working because I am unable unmount
/usr

Thanks
Patel