linux-kernel - RE: [PATCH v3 1/2] mm: migration: fix the FOLL

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Message-ID: <BYAPR11MB34959E47398000C2430E7188F7689@BYAPR11MB3495.namprd11.prod.outlook.com>
Date:   Mon, 15 Aug 2022 02:15:41 +0000
From:   "Wang, Haiyue" <haiyue.wang@...el.com>
To:     "Huang, Ying" <ying.huang@...el.com>
CC:     "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "david@...hat.com" <david@...hat.com>,
        "linmiaohe@...wei.com" <linmiaohe@...wei.com>,
        "songmuchun@...edance.com" <songmuchun@...edance.com>,
        "naoya.horiguchi@...ux.dev" <naoya.horiguchi@...ux.dev>,
        "alex.sierra@....com" <alex.sierra@....com>
Subject: RE: [PATCH v3 1/2] mm: migration: fix the FOLL_GET failure on
 following huge page

> -----Original Message-----
> From: Wang, Haiyue
> Sent: Monday, August 15, 2022 10:11
> To: Huang, Ying <ying.huang@...el.com>
> Cc: linux-mm@...ck.org; linux-kernel@...r.kernel.org; akpm@...ux-foundation.org; david@...hat.com;
> linmiaohe@...wei.com; songmuchun@...edance.com; naoya.horiguchi@...ux.dev; alex.sierra@....com
> Subject: RE: [PATCH v3 1/2] mm: migration: fix the FOLL_GET failure on following huge page
> 
> > -----Original Message-----
> > From: Huang, Ying <ying.huang@...el.com>
> > Sent: Monday, August 15, 2022 09:59
> > To: Wang, Haiyue <haiyue.wang@...el.com>
> > Cc: linux-mm@...ck.org; linux-kernel@...r.kernel.org; akpm@...ux-foundation.org; david@...hat.com;
> > linmiaohe@...wei.com; songmuchun@...edance.com; naoya.horiguchi@...ux.dev; alex.sierra@....com
> > Subject: Re: [PATCH v3 1/2] mm: migration: fix the FOLL_GET failure on following huge page
> >
> > Haiyue Wang <haiyue.wang@...el.com> writes:
> >


> >
> > > This is an temporary solution to mitigate the racing fix.
> >
> > Why is it "racing fix"?  This isn't a race condition fix.
> 
> The 'Fixes' commit is about race condition fix.
> 
> How about " his is an temporary solution to mitigate the side effect
> Of the race condition fix"

Try to add more words to make things clean:

"This is an temporary solution to mitigate the side effect of the race
condition fix by calling follow_page() with FOLL_GET set."

> 
> >
> > Best Regards,
> > Huang, Ying
> >
> > > After supporting follow huge page by FOLL_GET is done, this fix can be
> > > reverted safely.
> > >
> > > Fixes: 4cd614841c06 ("mm: migration: fix possible do_pages_stat_array racing with memory offline")
> > > Signed-off-by: Haiyue Wang <haiyue.wang@...el.com>
> >
> > [snip]