Comment 2 for bug 691726

Apparently it has something to do with this filesystem as I can resize a freshly created one mounted or not:

root@server:/usr/share/doc/e2fsprogs# lvcreate -L1G -n lvtest vg
  Logical volume "lvtest" created
root@server:/usr/share/doc/e2fsprogs# mkfs.ext4 /dev/vg/lvtest
mke2fs 1.41.11 (14-Mar-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
65536 inodes, 262144 blocks
13107 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=268435456
8 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376

Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 29 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
root@server:/usr/share/doc/e2fsprogs# lvextend -L+1G /dev/vg/lvtest
  Extending logical volume lvtest to 2.00 GiB
  Logical volume lvtest successfully resized
root@server:/usr/share/doc/e2fsprogs# resize2fs /dev/vg/lvtest
resize2fs 1.41.11 (14-Mar-2010)
Resizing the filesystem on /dev/vg/lvtest to 524288 (4k) blocks.
The filesystem on /dev/vg/lvtest is now 524288 blocks long.

root@server:/usr/share/doc/e2fsprogs# mkdir /mnt/test
root@server:/usr/share/doc/e2fsprogs# mount /dev/vg/lvtest /mnt/test/
root@server:/usr/share/doc/e2fsprogs# lvextend -L+1G /dev/vg/lvtest
  Extending logical volume lvtest to 3.00 GiB
  Logical volume lvtest successfully resized
root@server:/usr/share/doc/e2fsprogs# resize2fs /dev/vg/lvtest
resize2fs 1.41.11 (14-Mar-2010)
Filesystem at /dev/vg/lvtest is mounted on /mnt/test; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/vg/lvtest to 786432 (4k) blocks.
The filesystem on /dev/vg/lvtest is now 786432 blocks long.