Hi, there are two issues this patch series attempts to fix. First one is something that has been broken since MMF_UNSTABLE flag introduction and I guess we should backport it stable trees (patch 1). The other issue has been brought up by Wenwei Tao and Tetsuo Handa has created a test case to trigger it very reliably. I am not yet sure this is a stable material because the test case is rather artificial. If there is a demand for the stable backport I will prepare it, of course, though.
I hope I've done the second patch correctly but I would definitely appreciate some more eyes on it. Hence CCing Andrea and Kirill. My previous attempt with some more context was posted here http://lkml.kernel.org/r/20170803135902.31977-1-mho...@kernel.org My testing didn't show anything unusual with these two applied on top of the mmotm tree.