From: Michal Hocko <mhocko@kernel.org>
To: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
Oleg Nesterov <oleg@redhat.com>,
Wenwei Tao <wenwei.tww@alibaba-inc.com>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/2] mm, oom: fix potential data corruption when oom_reaper races with writer
Date: Thu, 10 Aug 2017 15:33:38 +0200 [thread overview]
Message-ID: <20170810133338.GV23863@dhcp22.suse.cz> (raw)
In-Reply-To: <20170810082118.GH23863@dhcp22.suse.cz>
On Thu 10-08-17 10:21:18, Michal Hocko wrote:
> On Tue 08-08-17 19:48:55, Andrea Arcangeli wrote:
> [...]
> > The bug corrected by this patch 1/2 I pointed it out last week while
> > reviewing other oom reaper fixes so that looks fine.
> >
> > However I'd prefer to dump MMF_UNSTABLE for good instead of adding
> > more of it. It can be replaced with unmap_page_range in
> > __oom_reap_task_mm with a function that arms a special migration entry
> > so that no branchs are added to the fast paths and it's all hidden
> > inside is_migration_entry slow paths.
>
> This sounds like an interesting idea but I would like to address the
> _correctness_ issue first and optimize on top of it. If for nothing else
> backporting a follow up fix sounds easier than a complete rework. There
> are quite some callers of is_migration_entry and the patch won't be
> trivial either. So can we focus on the fix first please?
Btw, if the overhead is a concern then we can add a jump label and only
make the code active only while the OOM is in progress. We already do
count all oom victims so we have a clear entry and exit points. This
would still sound easier to do than teach every is_migration_entry a new
migration entry type and handle it properly, not to mention make
everybody aware of this for future callers of is_migration_entry.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-08-10 13:33 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-07 11:38 [PATCH 0/2] mm, oom: fix oom_reaper fallouts Michal Hocko
2017-08-07 11:38 ` [PATCH 1/2] mm: fix double mmap_sem unlock on MMF_UNSTABLE enforced SIGBUS Michal Hocko
2017-08-15 0:49 ` David Rientjes
2017-08-07 11:38 ` [PATCH 2/2] mm, oom: fix potential data corruption when oom_reaper races with writer Michal Hocko
2017-08-08 17:48 ` Andrea Arcangeli
2017-08-08 23:35 ` Tetsuo Handa
2017-08-09 18:36 ` Andrea Arcangeli
2017-08-10 8:21 ` Michal Hocko
2017-08-10 13:33 ` Michal Hocko [this message]
2017-08-11 2:28 ` Tetsuo Handa
2017-08-11 7:09 ` Michal Hocko
2017-08-11 7:54 ` Tetsuo Handa
2017-08-11 10:22 ` Andrea Arcangeli
2017-08-11 10:42 ` Andrea Arcangeli
2017-08-11 11:53 ` Tetsuo Handa
2017-08-11 12:08 ` Michal Hocko
2017-08-11 15:46 ` Tetsuo Handa
2017-08-14 13:59 ` Michal Hocko
[not found] ` <201708142251.v7EMp3j9081456@www262.sakura.ne.jp>
2017-08-15 6:55 ` Michal Hocko
2017-08-15 8:41 ` Michal Hocko
[not found] ` <201708151006.v7FA6SxD079619@www262.sakura.ne.jp>
2017-08-15 12:26 ` Michal Hocko
[not found] ` <201708151258.v7FCwTsV029946@www262.sakura.ne.jp>
2017-08-17 13:58 ` Michal Hocko
2017-08-07 13:28 ` [PATCH 0/2] mm, oom: fix oom_reaper fallouts Tetsuo Handa
2017-08-07 14:04 ` Michal Hocko
2017-08-07 15:23 ` Tetsuo Handa
2017-08-15 12:29 ` Michal Hocko
-- strict thread matches above, loose matches on Subject: below --
2017-08-04 8:32 Re: [PATCH] mm, oom: fix potential data corruption when oom_reaper races with writer Michal Hocko
2017-08-04 8:33 ` [PATCH 1/2] mm: fix double mmap_sem unlock on MMF_UNSTABLE enforced SIGBUS Michal Hocko
2017-08-04 8:33 ` [PATCH 2/2] mm, oom: fix potential data corruption when oom_reaper races with writer Michal Hocko
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