Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
From:   Zi Yan <ziy@nvidia.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Linux-MM <linux-mm@kvack.org>,
        Steven Rostedt <rostedt@goodmis.org>,
        David Hildenbrand <david@redhat.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Mel Gorman <mgorman@techsingularity.net>,
        Mike Rapoport <rppt@kernel.org>,
        Oscar Salvador <osalvador@suse.de>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 2/2] mm: wrap __find_buddy_pfn() with a necessary buddy page validation.
Date:   Fri, 01 Apr 2022 15:25:44 -0400
Message-ID: <C8ADDC89-FE41-4DA1-A820-E3F7CE818955@nvidia.com>
In-Reply-To: <CAHk-=wgNxEq9BaxBSjC+RvKPsc5zuRwc1PGEvXqqX9vb1UALyA@mail.gmail.com>
References: <20220401181109.1477354-1-zi.yan@sent.com>
 <20220401181109.1477354-2-zi.yan@sent.com>
 <CAHk-=wifQimj2d6npq-wCi5onYPjzQg4vyO4tFcPJJZr268cRw@mail.gmail.com>
 <ADC113C0-F731-4835-AE3E-87C2302877B5@nvidia.com>
 <CAHk-=wgNxEq9BaxBSjC+RvKPsc5zuRwc1PGEvXqqX9vb1UALyA@mail.gmail.com>
Content-Type: multipart/signed;
 boundary="=_MailMate_69019D90-B67C-40E6-99F6-195971470BFC_=";
 micalg=pgp-sha512; protocol="application/pgp-signature"
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?uEanB9Db4rxq8Xio7tmKystVOHoKZm98S9aPLcGXoApS8xJK5AcUuCM6lws3?=
 =?us-ascii?Q?RoGnZBao+bPKO5CgNZGerpBYUDEoAO1pz6qi3suP4bMUKqOmAaolnkAybib6?=
 =?us-ascii?Q?f4hn1/uGt5Uq/CfFOwea0cmn6X6G2F3H3/lfv1/2buD/EvY3tTU3N7UEbbNV?=
 =?us-ascii?Q?MOzz6uEfiIcP/hxzZDxJU2TSd2NUv4P7/v/m7uLCktPpmfNcEF+TTULPOA/V?=
 =?us-ascii?Q?ia1Mkxj0Hb83fYBLFJ5rEMOhKcB13DjrGwlm2NPlHBsUuV+1K2lWgrZBQ+wk?=
 =?us-ascii?Q?sBkzyALSreXrx9awUKit6sSuQL/wiqqViMh24u7NqwO9/T8suWv0ryNi9B9n?=
 =?us-ascii?Q?FhFZ0fWJ4DT4jFHduj0hLDM5SRbzL2dZjUamz3+QrpRpuDbxXl9CKrdIxxqX?=
 =?us-ascii?Q?xhXrJBpEhGZ24Vts45QqVCQUVHWXoBstFm/0zkaD9StoWxMNaTAOAfqG/kgJ?=
 =?us-ascii?Q?K9x0XpiKxap2nfl90R0d16S54LKs1gvuTa1byqN5KGzPH4MAEPKoJQb43QmS?=
 =?us-ascii?Q?I4GFL2ZFOuJUEg7+UpAJo0KsOMo3EvU6yLUbPPhbaeB4ZOMvI+sY3QBJCaA4?=
 =?us-ascii?Q?l/xSzbAJk6WmsrgrvXHN5PeiIJM9WjpedraJQKHPK8Q/jDEHV+s5x0G9Crwk?=
 =?us-ascii?Q?jGJJ8J4jeSxfjXr6t6V1X8F4ocdFIU4uYCTS8bqM8xWI8rhiUyWCjnEutEVI?=
 =?us-ascii?Q?2qT/3Edr4b6wy23NgPwCAvHAvejqrWzBo9GcYQAh1UknceXalvIh5lzTOUNu?=
 =?us-ascii?Q?fZVP2w30tyya/BZC4k+7XazUy506s02RxEH51d8wyV4UbiCr7ATaTdHwQbgs?=
 =?us-ascii?Q?7CYYf9CXP07A+Ft0sYo/wTk3RdyfwPlyA9mRcZi7jue+v7cHHFsdkYsUk1mv?=
 =?us-ascii?Q?9wZ/Bw9Yxo2mjJ6vfT6iRsJig/52cJ6K87Bh3Nbk1iHUqJncAdb6ay0BON7W?=
 =?us-ascii?Q?ETLfaP3w0RsCLMml2WcigAspzLV4Xqn1/wfpX3Hm9L0fhh/GowhXqzNDIyBq?=
 =?us-ascii?Q?XrmlHXdg2mnTrgmIjfpDc/xyhM8xAF12WdgMSwZgI5mjDaWIViVWR1jGJ7R/?=
 =?us-ascii?Q?CZmzDhCNZJMn/f20XBAI+kiA5PfmuP4OSs9T5dxOquQxJ4QDuzlay6xXIoE3?=
 =?us-ascii?Q?3Zf1WN83YXcc4ud33gfQWur1bV0iFzzJ0OxovWAuv/T2otY+A89Ra5uTBe7N?=
 =?us-ascii?Q?r1G8t3zznEwxgKu89BOj5d5irVFfFSzaL5H7n8qw4pJE3efUQmCLmCJ2Wxei?=
 =?us-ascii?Q?EPjcaMLotRn0ErhGwzMSoTROaEilIY4DuRijUkMi4zJTqikWGHUzX7QK+3WN?=
 =?us-ascii?Q?9QyvFPbpilQxeooQPAgZo16s8jrxLoZUj2XLvxJNdOME5I/QAsiuDmnEhg2v?=
 =?us-ascii?Q?hvc7T4Gq5P31WFAPdaRiPc9sQ2N5mvnOGyNFNWZvE9WOw4GAwnMY8qOqNUwY?=
 =?us-ascii?Q?jNaIpmgRyTzH/NutGhlSocuBJg4Zms/6em32ahkZYUlX6QEdLQ4gsYtNC+iT?=
 =?us-ascii?Q?NifKBjBfnPMQ8vGTRZcj19Gf1UgP+e49mzbd5O5bnoH5cR3s1DjC7DSu0lxg?=
 =?us-ascii?Q?zCaS3X5q2eT1mcfe1O0y88uNIk0uZCCQv5xSIjJHxGBd5mQQPhXLx5WlWkaY?=
 =?us-ascii?Q?alHBxNOYlwOOcM1UDKo2JfbdTmyq7rcwiCpNW2ffQ4rQXliTLHc7EH3NzwI7?=
 =?us-ascii?Q?x6DdRukA5Fl1q9Rq7rBpPvcRsu5xsDXBTYkpbcHDrYz4U0QydthfC5/f2Zwo?=
 =?us-ascii?Q?6bvqo9DanQ=3D=3D?=
X-OriginatorOrg: Nvidia.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 051f68bb-1a82-4e5b-73a0-08da14156bb8
X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB3823.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 01 Apr 2022 19:25:46.1559
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: 7eoAdrolQ3fz8XCozBTczCt0wDYAYHYagu6Mpx3ejV2Yu+tLJMlySZrZk2sG1Kat
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN0PR12MB5979
X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,
	DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,
	MAILING_LIST_MULTI,RDNS_NONE,SPF_HELO_NONE,T_SCC_BODY_TEXT_LINE
	autolearn=no autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

--=_MailMate_69019D90-B67C-40E6-99F6-195971470BFC_=
Content-Type: text/plain

On 1 Apr 2022, at 15:01, Linus Torvalds wrote:

> On Fri, Apr 1, 2022 at 11:56 AM Zi Yan <ziy@nvidia.com> wrote:
>>
>> How about the patch below? If it looks good, I will send v3.
>
> I can't see anything worrisome, but by now I've looked at several
> versions and who knows what I'm missing.
>
> Making it inline and allowing a NULL 'buddy_pfn' pointer for the cases
> that don't care might be an option, but I don't think it matters
> hugely.

What do you mean by inlining it? Moving the function and __find_buddy_pfn()
to mm/internal.h and mark both inline?

Something like below to allow a NULL 'buddy_pfn'? buddy_pfn is needed
to store the result of __find_buddy_pfn(). The code does not look
as nice as before.

struct page *find_buddy_page_pfn(struct page *page, unsigned long pfn,
                        unsigned int order, unsigned long *buddy_pfn)
{
        struct page *buddy;

        if (buddy_pfn) {
                *buddy_pfn = __find_buddy_pfn(pfn, order);
                buddy = page + (*buddy_pfn - pfn);
        } else
                buddy = page + (__find_buddy_pfn(pfn, order) - pfn);

        if (page_is_buddy(page, buddy, order))
                return buddy;
        return NULL;
}

or

struct page *find_buddy_page_pfn(struct page *page, unsigned long pfn,
                        unsigned int order, unsigned long *buddy_pfn)
{
        struct page *buddy;
        unsigned long local_buddy_pfn = __find_buddy_pfn(pfn, order);

        buddy = page + (local_buddy_pfn - pfn);
        if (buddy_pfn)
                *buddy_pfn = local_buddy_pfn;

        if (page_is_buddy(page, buddy, order))
                return buddy;
        return NULL;
}

--
Best Regards,
Yan, Zi

--=_MailMate_69019D90-B67C-40E6-99F6-195971470BFC_=
Content-Description: OpenPGP digital signature
Content-Disposition: attachment; filename="signature.asc"
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----
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=4QJu
-----END PGP SIGNATURE-----

--=_MailMate_69019D90-B67C-40E6-99F6-195971470BFC_=--