linux-kernel - Re: [PATCH v2 0/2] mm: soft-offline: fix race against page allocation

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Date:   Fri, 26 Oct 2018 10:46:36 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "xishi.qiuxishi@...baba-inc.com" <xishi.qiuxishi@...baba-inc.com>,
        "zy.zhengyi@...baba-inc.com" <zy.zhengyi@...baba-inc.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mike Kravetz <mike.kravetz@...cle.com>
Subject: Re: [PATCH v2 0/2] mm: soft-offline: fix race against page allocation

On Wed 22-08-18 10:00:25, Michal Hocko wrote:
> On Wed 22-08-18 01:37:48, Naoya Horiguchi wrote:
> > On Wed, Aug 15, 2018 at 03:43:34PM -0700, Andrew Morton wrote:
> > > On Tue, 17 Jul 2018 14:32:30 +0900 Naoya Horiguchi <n-horiguchi@...jp.nec.com> wrote:
> > > 
> > > > I've updated the patchset based on feedbacks:
> > > > 
> > > > - updated comments (from Andrew),
> > > > - moved calling set_hwpoison_free_buddy_page() from mm/migrate.c to mm/memory-failure.c,
> > > >   which is necessary to check the return code of set_hwpoison_free_buddy_page(),
> > > > - lkp bot reported a build error when only 1/2 is applied.
> > > > 
> > > >   >    mm/memory-failure.c: In function 'soft_offline_huge_page':
> > > >   > >> mm/memory-failure.c:1610:8: error: implicit declaration of function
> > > >   > 'set_hwpoison_free_buddy_page'; did you mean 'is_free_buddy_page'?
> > > >   > [-Werror=implicit-function-declaration]
> > > >   >        if (set_hwpoison_free_buddy_page(page))
> > > >   >            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > >   >            is_free_buddy_page
> > > >   >    cc1: some warnings being treated as errors
> > > > 
> > > >   set_hwpoison_free_buddy_page() is defined in 2/2, so we can't use it
> > > >   in 1/2. Simply doing s/set_hwpoison_free_buddy_page/!TestSetPageHWPoison/
> > > >   will fix this.
> > > > 
> > > > v1: https://lkml.org/lkml/2018/7/12/968
> > > > 
> > > 
> > > Quite a bit of discussion on these two, but no actual acks or
> > > review-by's?
> > 
> > Really sorry for late response.
> > Xishi provided feedback on previous version, but no final ack/reviewed-by.
> > This fix should work on the reported issue, but rewriting soft-offlining
> > without PageHWPoison flag would be the better fix (no actual patch yet.)
> 
> If we can go with the later the I would obviously prefer that. I cannot
> promise to work on the patch though. I can help with reviewing of
> course.
> 
> If this is important enough that people are hitting the issue in normal
> workloads then sure, let's go with the simple fix and continue on top of
> that.

Naoya, did you have any chance to look at this or have any plans to look?
I am willing to review and help with the overal design but I cannot
really promise to work on the code.
-- 
Michal Hocko
SUSE Labs