Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH 1/2] mm/memory-failure.c: PageHuge is handled at the
 beginning of memory_failure
To:     Wei Yang <richardw.yang@linux.intel.com>,
        n-horiguchi@ah.jp.nec.com, akpm@linux-foundation.org
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org
References: <20191118082003.26240-1-richardw.yang@linux.intel.com>
From:   David Hildenbrand <david@redhat.com>
Organization: Red Hat GmbH
Message-ID: <1e61c115-5787-9ef4-a449-2e490c53fca7@redhat.com>
Date:   Tue, 19 Nov 2019 13:23:54 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.1.1
MIME-Version: 1.0
In-Reply-To: <20191118082003.26240-1-richardw.yang@linux.intel.com>
Content-Language: en-US
Content-Type: text/plain; charset=WINDOWS-1252; format=flowed
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 18.11.19 09:20, Wei Yang wrote:
> PageHuge is handled by memory_failure_hugetlb(), so this case could be
> removed.
>=20
> Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
> ---
>   mm/memory-failure.c | 5 +----
>   1 file changed, 1 insertion(+), 4 deletions(-)
>=20
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index 3151c87dff73..392ac277b17d 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1359,10 +1359,7 @@ int memory_failure(unsigned long pfn, int flags)
>   =09 * page_remove_rmap() in try_to_unmap_one(). So to determine page st=
atus
>   =09 * correctly, we save a copy of the page flags at this time.
>   =09 */
> -=09if (PageHuge(p))
> -=09=09page_flags =3D hpage->flags;
> -=09else
> -=09=09page_flags =3D p->flags;
> +=09page_flags =3D p->flags;
>  =20
>   =09/*
>   =09 * unpoison always clear PG_hwpoison inside page lock
>=20

I somewhat miss a proper explanation why this is safe to do. We access=20
page flags here, so why is it safe to refer to the ones of the sub-page?

--=20

Thanks,

David / dhildenb