Comment # 16 on bug 1222429 from David Sterba

(In reply to Lukas Ocilka from comment #14)
> The point of r-o mounting is to keep the FS "as is" (also/or ideally
> with noatime as that may also change something).

Please note that the 'ro' mount option semantics does not prevent writes to
happen before the mount is finished, the writes are prevented from user space.
IOW, log replay can still happen with 'ro' mount so you need some sort of log
replay preventing option, or to temporarily make the block device read-only
(blockdev --setro).