linux-kernel - Re: [mm-unstable PATCH v4 2/9] mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page

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Message-ID: <20220704020428.GA2466683@hori.linux.bs1.fc.nec.co.jp>
Date:   Mon, 4 Jul 2022 02:04:50 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        David Hildenbrand <david@...hat.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [mm-unstable PATCH v4 2/9] mm/hugetlb: separate path for hwpoison
 entry in copy_hugetlb_page_range()

On Sun, Jul 03, 2022 at 06:42:59PM -0700, Andrew Morton wrote:
> On Mon,  4 Jul 2022 10:33:05 +0900 Naoya Horiguchi <naoya.horiguchi@...ux.dev> wrote:
> 
> > Originally copy_hugetlb_page_range() handles migration entries and hwpoisoned
> > entries in similar manner.  But recently the related code path has more code
> > for migration entries, and when is_writable_migration_entry() was converted
> > to !is_readable_migration_entry(), hwpoison entries on source processes got
> > to be unexpectedly updated (which is legitimate for migration entries, but
> > not for hwpoison entries).  This results in unexpected serious issues like
> > kernel panic when forking processes with hwpoison entries in pmd.
> > 
> > Separate the if branch into one for hwpoison entries and one for migration
> > entries.
> > 
> > ...
> >
> > Cc: <stable@...r.kernel.org> # 5.18
> 
> It's unusual to have a cc:stable patch in the middle of a series like
> this.  One would expect the fix to be a standalone thing against
> current -linus.

Ah, OK, I should've submit this seperately.

> 
> As presented, this patch won't get into mainline until after 5.20-rc1. 
> If that's OK then OK.  Otherwise I can shuffle things around and stage
> this patch in mm-hotfixes?

Yes, I'd like to ask you to do it. Thank you for the arrangement.

- Naoya Horiguchi