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

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Message-ID: <87o7wmcj7q.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Mon, 15 Aug 2022 10:51:37 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     "Wang, Haiyue" <haiyue.wang@...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

"Wang, Haiyue" <haiyue.wang@...el.com> writes:

>> -----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."

Looks good to me.  Thanks!

Best Regards,
Huang, Ying

>>
>> >
>> > 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]