In testing with SEL port to the 2.12 branch, Grev found an data corruption issue.
I checked it with last master on client side and issue still present.
example of it
current step of investigation, KMS don't valid in some cases and ll_prepare_partial_page fill a full page with zero, while part of them already send to the OST.
this quick and dirty fix resolves an issue but KMS problem needs invested.
it not a problem with offset on same page, I tries to fix this check against real offset - but sometimes KMS result is very strange like KMS = 3G while offset point is 5G, so it's something like a more complex problem.