On Mon, 11 Nov 2013 13:52:23 -0500 Justin Piszcz [off-list ref]
wrote:

quoted

4- Linux or SSD bug on trim, such as trimming wrong offsets killing live
data
5- MD does not lock regions during check so returns erroneous mismatches for
areas being written. This would be harmless but your mismatches number seems
to high to me for this.

I wonder if this could be it.

I cannot promise that my code is bug free, but if it wasn't getting this
locking correct, that would be a very serious bug.  I think this possibility
is quite unlikely.

NeilBrown