[CentOS] Need resize a partition LVM2

Hi all..
On my little test server I have 40GB hard disk.
I use LVM2, with 4 partitons: /boot, /home, /usr, /var
I set Apache to work in /var/www.
Now I added a 30GB hard disk to extend /var.
I regularly extended my volume group and the logical volume where /var stay.
Now I need to umount /var to run a resize2fs to extend the /var 
partiton, but I see ever the same message: "device is busy"
I tried to switch to runlevel 1, but no luck.
My var uses quota, and the fs is ext3.

Someone can help me?
Thank you a lot guys!

Nando

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