linux-kernel - Re: [PATCH 1/2] mm, oom: introduce oom reaper

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Date:	Thu, 24 Dec 2015 13:39:51 -0700
From:	Ross Zwisler <zwisler@...il.com>
To:	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:	Michal Hocko <mhocko@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	Andrea Argangeli <andrea@...nel.org>,
	Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [PATCH 1/2] mm, oom: introduce oom reaper

On Thu, Dec 24, 2015 at 4:06 AM, Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
> 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.)

No, DAX was not turned on, and while my fsync/msync patches were the initial
reason I was testing (hence the new_fsync_v6 kernel name) they were not
applied during the bisect, so I'm sure they are not related to this issue.

I will retest with the patch referenced above, but it probably won't
happen until
the new year.
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