Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Received-SPF: Pass (protection.outlook.com: domain of arm.com designates
 63.35.35.123 as permitted sender) receiver=protection.outlook.com;
 client-ip=63.35.35.123; helo=64aa7808-outbound-1.mta.getcheckrecipient.com;
From:   Justin He <Justin.He@arm.com>
To:     Michal Hocko <mhocko@kernel.org>,
        David Hildenbrand <david@redhat.com>
CC:     Catalin Marinas <Catalin.Marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mike Rapoport <rppt@linux.ibm.com>,
        Baoquan He <bhe@redhat.com>,
        Chuhong Yuan <hslester96@gmail.com>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>,
        Kaly Xin <Kaly.Xin@arm.com>
Subject: RE: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as
 EXPORT_SYMBOL_GPL
Thread-Topic: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as
 EXPORT_SYMBOL_GPL
Thread-Index: AQHWVCPSGGxRNvjq20KjOcC2mjPWIqj8ApMAgADwVZA=
Date:   Wed, 8 Jul 2020 02:20:17 +0000
Message-ID: <AM6PR08MB406907F9F2B13DA6DC893AD9F7670@AM6PR08MB4069.eurprd08.prod.outlook.com>
References: <20200707055917.143653-1-justin.he@arm.com>
 <20200707055917.143653-2-justin.he@arm.com>
 <20200707115454.GN5913@dhcp22.suse.cz>
In-Reply-To: <20200707115454.GN5913@dhcp22.suse.cz>
Accept-Language: en-US, zh-CN
Content-Language: en-US
Authentication-Results-Original: kernel.org; dkim=none (message not signed)
 header.d=none;kernel.org; dmarc=none action=none header.from=arm.com;
nodisclaimer: true
X-Microsoft-Antispam-Message-Info-Original: iqokAUQL/G50BtDL2TuIGlrJOGKByIF5jzP6/fG59bN9ap4qwtLiTF9QLhexXvGftYT55H0jadEQrsOY4UUGxcMA1K2tLIGhMgFLvhm8STAIgB8lHdYjdVTKn24rFcxFyn4mV9QSX0wxlxyGgb8Uy7ezDH9dA+ULcgfOUQBOedv+LgtAWbnAyl1dSMnoTejIlROE7aFyqkQ9bQJJPN/fQiAGB666LYOkXz38XC57pErrUWZWId8DQFEPgMcDIAj3WI84B0asOWb37qev8lEceRKQMBHfOUYgGaMD9WE3AR8p+O+aYJtti5b4i/eLwS32LJZy/rr7BnhCRbdr4iuL6Q==
X-Forefront-Antispam-Report-Untrusted: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:AM6PR08MB4069.eurprd08.prod.outlook.com;PTR:;CAT:NONE;SFTY:;SFS:(4636009)(376002)(396003)(39850400004)(346002)(136003)(366004)(2906002)(52536014)(86362001)(5660300002)(76116006)(66476007)(66946007)(66446008)(66556008)(110136005)(64756008)(8676002)(6506007)(8936002)(53546011)(7696005)(54906003)(4326008)(316002)(33656002)(71200400001)(478600001)(55016002)(26005)(9686003)(7416002)(186003)(83380400001);DIR:OUT;SFP:1101;
x-ms-exchange-antispam-messagedata: zeR7jallz/SMaiTB4kHQ4s+nP0QXiKeVwrEscnB6Tbnd/Tp+3tc5/wG8lO+Yw0p80HYaEBkHhHnRaXll5rnNTi3j4cscNAUaLdDK88xwWFiHogPxCC04IeBA3CUQlfk/WcKwQc26kMHMHsHcy4vgW+LUaqFyRvqrnUEy490ady+7+UPjIyzkawbkL4aplrDBBUHSMKw054P/2yD51YX+LZO15PvM2FvUTAJzZJcW6uzdwEg8ClOQw8RNDmaoraO1exGorszFPisJFjYeZvYvWPDMX9gnXyxWlqibm5U4K9mSfpop3DD+ztnEDT9qcvvktQlDi/k4vgtxSmLq+2S31IXeQf78wB/BJ7n002Njqwvwcm/RXnZWbeCjQi7un8tPmOP6jfytKgjlFuD6KBV+rdTvJ+FJtotn6AoqMZ6ydS2TwfwCDnKPZGy6dUjFA2rcmO056RZuTFvMKCkzqDnYJFWVB0DtNHDaZZOn7AVxub0=
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR08MB4689
Original-Authentication-Results: kernel.org; dkim=none (message not signed)
 header.d=none;kernel.org; dmarc=none action=none header.from=arm.com;
X-EOPAttributedMessage: 0
X-MS-Exchange-Transport-CrossTenantHeadersStripped: DB5EUR03FT005.eop-EUR03.prod.protection.outlook.com
X-Forefront-Antispam-Report: CIP:63.35.35.123;CTRY:IE;LANG:en;SCL:1;SRV:;IPV:CAL;SFV:NSPM;H:64aa7808-outbound-1.mta.getcheckrecipient.com;PTR:ec2-63-35-35-123.eu-west-1.compute.amazonaws.com;CAT:NONE;SFTY:;SFS:(4636009)(136003)(39850400004)(376002)(346002)(396003)(46966005)(316002)(52536014)(4326008)(8936002)(8676002)(356005)(83380400001)(6506007)(81166007)(82310400002)(70586007)(26005)(53546011)(70206006)(5660300002)(186003)(7696005)(55016002)(2906002)(33656002)(478600001)(47076004)(336012)(54906003)(86362001)(9686003)(110136005)(82740400003);DIR:OUT;SFP:1101;
X-MS-Office365-Filtering-Correlation-Id-Prvs: 270ccc62-11ed-468f-0502-08d822e5752f
X-Forefront-PRVS: 04583CED1A
X-Microsoft-Antispam: BCL:0;
X-Microsoft-Antispam-Message-Info: ac+T9R5M3s5y4XHEqD4xUIID4+52qoyEDkHwLYQ2+wsv9t/ZOxbZJA5XwGCg+0/p0l7s/i/CacWG+vnjmkFpHvduXOA3XYUM8FfigzEmb9r/ZdHELzQl1RFsZr5yl1fS/8zHOKa+I7LdJpva5ttbZKX3VfqQzNvfGhfm3bnE8SwH5bIyGLniqaNHUTBx4JF6X2br55QR+qi0nAqEGg1T9aipYGPHpMpNQqxGH2tUT4e/9Z9yWO4RtutaOUDA6soC/1ZQ8Og2K0kFpf1hmrJd8oZ0rc06W+RlngENqyYaWEkSV42PpldEs+7Q7Cpa8lIz/01lQWWvXMX0/bdnjlnL9UmI6aOoVd/qqj81lgkeOw7NXfvp243IKYp0Rw+IUYFZEzPEFmoIk1VQbGdpQ9I6Wg==
X-OriginatorOrg: arm.com
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jul 2020 02:20:26.0517
 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 0d3d335a-5d0b-4d41-20a8-08d822e579e1
X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d
X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com]
X-MS-Exchange-CrossTenant-AuthSource: DB5EUR03FT005.eop-EUR03.prod.protection.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Anonymous
X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB8PR08MB5484
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Hi Michal and David

> -----Original Message-----
> From: Michal Hocko <mhocko@kernel.org>
> Sent: Tuesday, July 7, 2020 7:55 PM
> To: Justin He <Justin.He@arm.com>
> Cc: Catalin Marinas <Catalin.Marinas@arm.com>; Will Deacon
> <will@kernel.org>; Dan Williams <dan.j.williams@intel.com>; Vishal Verma
> <vishal.l.verma@intel.com>; Dave Jiang <dave.jiang@intel.com>; Andrew
> Morton <akpm@linux-foundation.org>; Mike Rapoport <rppt@linux.ibm.com>;
> Baoquan He <bhe@redhat.com>; Chuhong Yuan <hslester96@gmail.com>; linux-
> arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; linux-
> mm@kvack.org; linux-nvdimm@lists.01.org; Kaly Xin <Kaly.Xin@arm.com>
> Subject: Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid
> as EXPORT_SYMBOL_GPL
>=20
> On Tue 07-07-20 13:59:15, Jia He wrote:
> > This exports memory_add_physaddr_to_nid() for module driver to use.
> >
> > memory_add_physaddr_to_nid() is a fallback option to get the nid in cas=
e
> > NUMA_NO_NID is detected.
> >
> > Suggested-by: David Hildenbrand <david@redhat.com>
> > Signed-off-by: Jia He <justin.he@arm.com>
> > ---
> >  arch/arm64/mm/numa.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
> > index aafcee3e3f7e..7eeb31740248 100644
> > --- a/arch/arm64/mm/numa.c
> > +++ b/arch/arm64/mm/numa.c
> > @@ -464,10 +464,11 @@ void __init arm64_numa_init(void)
> >
> >  /*
> >   * We hope that we will be hotplugging memory on nodes we already know
> about,
> > - * such that acpi_get_node() succeeds and we never fall back to this..=
.
> > + * such that acpi_get_node() succeeds. But when SRAT is not present,
> the node
> > + * id may be probed as NUMA_NO_NODE by acpi, Here provide a fallback
> option.
> >   */
> >  int memory_add_physaddr_to_nid(u64 addr)
> >  {
> > -	pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n",
> addr);
> >  	return 0;
> >  }
> > +EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
>=20
> Does it make sense to export a noop function? Wouldn't make more sense
> to simply make it static inline somewhere in a header? I haven't checked
> whether there is an easy way to do that sanely bu this just hit my eyes.

Okay, I can make a change in memory_hotplug.h, sth like:
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -149,13 +149,13 @@ int add_pages(int nid, unsigned long start_pfn, unsig=
ned long nr_pages,
              struct mhp_params *params);
 #endif /* ARCH_HAS_ADD_PAGES */
=20
-#ifdef CONFIG_NUMA
-extern int memory_add_physaddr_to_nid(u64 start);
-#else
+#if !defined(CONFIG_NUMA) || !defined(memory_add_physaddr_to_nid)
 static inline int memory_add_physaddr_to_nid(u64 start)
 {
        return 0;
 }
+#else
+extern int memory_add_physaddr_to_nid(u64 start);
 #endif

And then check the memory_add_physaddr_to_nid() helper on all arches,
if it is noop(return 0), I can simply remove it.
if it is not noop, after the helper,=20
#define memory_add_physaddr_to_nid

What do you think of this proposal?

--
Cheers,
Justin (Jia He)