linux-kernel - Re: [v3 PATCH 2/5] mm: filemap: check if THP has hwpoisoned subpage for PMD page fault

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Message-ID: <CAHbLzkrOsNygu5x8vbMHedv+P3dEqOxOC6=O6ACSm1qKzmoCng@mail.gmail.com>
Date:   Tue, 12 Oct 2021 11:02:09 -0700
From:   Yang Shi <shy828301@...il.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>, Hugh Dickins <hughd@...gle.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        Oscar Salvador <osalvador@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linux MM <linux-mm@...ck.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [v3 PATCH 2/5] mm: filemap: check if THP has hwpoisoned subpage
 for PMD page fault

On Mon, Oct 11, 2021 at 6:44 PM Peter Xu <peterx@...hat.com> wrote:
>
> On Mon, Oct 11, 2021 at 08:55:26PM -0400, Peter Xu wrote:
> > Another thing is I noticed soft_offline_in_use_page() will still ignore file
> > backed split.  I'm not sure whether it means we'd better also handle that case
> > as well, so shmem thp can be split there too?
>
> Please ignore this paragraph - I somehow read "!PageHuge(page)" as
> "PageAnon(page)"...  So I think patch 5 handles soft offline too.

Yes, exactly. And even though the split is failed (or file THP didn't
get split before patch 5/5), soft offline would just return -EBUSY
instead of calling __soft_offline_page->page_handle_poison(). So
page_handle_poison() should not see THP at all.

>
> --
> Peter Xu
>