I don't think this is new to 3.18. I have had a lockup issue in every version since 3.2
I use ZFS where I can, but for root filesystems on linux machines reiser still seems like the best tradeoff.
I can't say I'd trust my data on it these days.
I heard they fixed it in 2012. Actually there have been a lot of developments in XFS since 2011, I'm not really interested in filesystems but you should have a look at it again if you're interested.