On Thu, 25 Jun 2015 18:33:16 +0300
tlknv [off-list ref] wrote:

I have just discovered that I had 'discard' mount option even though I though it wasn't there :-(
After removing 'discard' and forcing 'repair' mismatch_cnt stays 0 even after a bunch of writes and deletes (the most importantly) to the partition.

I wouldn't recommend disabling discard 'for good' though, from your experiment
we can probably conclude the mismatch_cnt numbers you had previously are indeed
harmless. If you had no other issues due to discard being active, then what you
did now is disable a working and useful feature to fix what's only a cosmetic
problem.

-- 
With respect,
Roman