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To: mhocko@kernel.org, zwisler@gmail.com
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Subject: Re: [PATCH 1/2] mm, oom: introduce oom reaper
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
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Michal Hocko wrote:
> This is VM_BUG_ON_PAGE(page_mapped(page), page), right? Could you attach
> the full kernel log? It all smells like a race when OOM reaper tears
> down the mapping and there is a truncate still in progress. But hitting
> the BUG_ON just because of that doesn't make much sense to me. OOM
> reaper is essentially MADV_DONTNEED. I have to think about this some
> more, though, but I am in a holiday mode until early next year so please
> bear with me.

I don't know whether the OOM killer was invoked just before this
VM_BUG_ON_PAGE().

> Is this somehow DAX related?

4.4.0-rc6-next-20151223_new_fsync_v6+ suggests that this kernel
has "[PATCH v6 0/7] DAX fsync/msync support" applied. But I think
http://marc.info/?l=linux-mm&m=145068666428057 should be applied
when retesting. (20151223 does not have this fix.)

[  235.768779]  [<ffffffff811feba4>] ? unmap_mapping_range+0x64/0x130
[  235.769385]  [<ffffffff811febb4>] ? unmap_mapping_range+0x74/0x130
[  235.770010]  [<ffffffff810f5c3f>] ? up_write+0x1f/0x40
[  235.770501]  [<ffffffff811febb4>] ? unmap_mapping_range+0x74/0x130
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