Ubuntu – FS mounted as RO on boot after upgrade to 15.04

Just upgraded from 14.10 to 15.04.
Couldn't get the system to boot ok.
I could boot using (upstart) option – not using default systemd.
When in default mode the lightdm terminal was stuck before login screen.
I could switch to TTY though.
I found out finally that in TTY i can run:
$ mount -rw -o remount /

This causes the lightdm service to continue to login screen and I can work normally.
However I now have to do that manually each reboot…

Also I tryed checing the FS using fsck and everything is OK.

Any thoughts?

EDIT – This is the content of my /etc/fstab:

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
# / was on /dev/sda1 during installation

/dev/disk/by-label/data /mnt/data ext4 nosuid,nodev,nofail 0 0
/dev/disk/by-label/backup /mnt/backup ext4 nosuid,nodev,nofail 0 0