I had a SAN which went into emergency mode the other day which caused running VM's in vSphere to either pause or to mark disks in read only mode. Most problematic to this was the actual vSphere guest VM and the Platform Services Controller VM. Both of these marked /dev/sda3 as read only and on a forced reboot they entered Recovery Mode.

Luckily for me running a fsck successfully recovered the disk. I used the details from here which worked perfectly. For brevity all it was was:

e2fsck -y /dev/sda3