Fixing smartd "Offline uncorrectable sectors"

You can mount a partition read only or unmount it.
Then you can run e2fsck with the following:

e2fsck -p -f -c -C 0
 -p  automatically repairs problems
 -f force the file system check
 -c run badblocks
 -C 0 display the progress bar

(clipped from http://lists.phillylinux.org/mailman/listinfo/plug)