Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Thu, 4 Aug 2022 05:08:34 +0800
From:   Feng Tang <feng.tang@intel.com>
To:     Michal Hocko <mhocko@suse.com>
CC:     Muchun Song <songmuchun@bytedance.com>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "bwidawsk@kernel.org" <bwidawsk@kernel.org>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH] mm: mempolicy: fix policy_nodemask() for
 MPOL_PREFERRED_MANY case
Message-ID: <Yurj0sOXgGf40AJE@feng-clx>
References: <Yui7hWZYMX31ktOr@feng-skl>
 <YujGy8EIeZc1Avc7@FVFYT0MHHV2J>
 <YujUyCIBjFj+FzX5@feng-skl>
 <YujoLQt09Js/sSQL@dhcp22.suse.cz>
 <YuoYkPk+YzdPNvmN@feng-snb>
 <YuolieBmdaIzoS3t@dhcp22.suse.cz>
 <Yuqs+BTpfh9/PjtP@feng-clx>
 <Yupb+1mmn9sQ/G8K@dhcp22.suse.cz>
 <Yurd2iYp4XMIYM7T@feng-clx>
 <YupwjN6K6e6V3y+Q@dhcp22.suse.cz>
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <YupwjN6K6e6V3y+Q@dhcp22.suse.cz>
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?3Ys3Tb8R/GfgNyWjoa+i5qrTbMqu0q5/2DyU3oH+29aScY4uDvCjj9JpLE0b?=
 =?us-ascii?Q?+SyhAkgrdzDZ85+K3fln1posxeH01Z+ombHuXoIXyLmCGS8S21pQGK0HVDAB?=
 =?us-ascii?Q?ti4GDDDMdaiIh7GdXf3VZ8olMfCXgHkTNSMVwRt3n8Z9LylqHbH6boqD2v2f?=
 =?us-ascii?Q?M+qZzC5PIWVierR00TvrAHwcQI4FZJhKeBfHn0pCWjuU6T23UKLPs0IQCrSY?=
 =?us-ascii?Q?NMZ63OsKMEwhYHVQHh4DI/FHXcQEuUzwMSX1WOoM8/Ad+gvDNmWOfrxyO/RB?=
 =?us-ascii?Q?f0zqhXUGTpE8y262wV0x2bYmuTbjhlJOTNtNu4DE/4EsEZNSFWIIv+Uz1A0V?=
 =?us-ascii?Q?t6dlMo1J5YaaSlZmyyCnOaTBzCkNIm6sInaMCZdSYg7WZfFk5Lt0jbaGi7U2?=
 =?us-ascii?Q?ANYJFH7VxWf/YTzJGMtPlcPMbSvU2IDZr1dAhtOXAx8MHXIOWbEKXCzVgWU+?=
 =?us-ascii?Q?JwJKM/AazdIkNgwRNPwhDQLB4SMDCMF3HXxKlSpRKTdmakAkeMu2QjQ3+Nix?=
 =?us-ascii?Q?hzYjxWkkYUPAY4t3zS2Yb5BrC+LDfmcDOqufJL4rSGsWjwC+Z4yfu94+wxA/?=
 =?us-ascii?Q?MJDuz2c12wBydFNVcZsa6t0TlBSZSPGl7yh5V1IHEkuNas8AtQxTrhqqdKJF?=
 =?us-ascii?Q?deDmoWz/6PuWsjzyuJgL7PFG956kszN0ky+7ZF+z+H+FpaQoI3MYnrPCM39U?=
 =?us-ascii?Q?4vkEjehO9n9PVojDXFjcsKG7EXc8XXjIHxlvtfzk4bTIWachUIGg20MxEVC6?=
 =?us-ascii?Q?zipNs0E4FEH+Mg/ZCO5n4GOT6xXVGavmQkzF+hmfygre7guahrR95cliCMy2?=
 =?us-ascii?Q?roq70FBZYIRDTkf+Lisl/N3gPnr1vrPFqndXvuHtBp2bummrObrsVZl4XARY?=
 =?us-ascii?Q?xeJpo7UD/AaY17Nndw9iZMssblqUe9J6NF4QaYXY+a3bIJEAvXYPPV463NYh?=
 =?us-ascii?Q?8pn2yp5tnR2E1EY3o/09DMXb+nDjuguBeTtDZmvbgBVVOwEHFiV3wEnP3Afa?=
 =?us-ascii?Q?jjY8APqb64dygTCFr9qxN/4aOIV+Bajb5iAi1xr7UQdh3rxTgmNbfCEpsnZh?=
 =?us-ascii?Q?Ez3cn40ux7HRMmoZehnalqfnJTVUyxT1vGjs0mb9jdjbkeMliSCnTIfZBCk+?=
 =?us-ascii?Q?qX7mYWvfzTv/KZPjX4T1mk6ovmulqiCkYsAxhsi8V3cRs63BchADtFd4iPFA?=
 =?us-ascii?Q?SYYc54Pn9uQmAHLWl9UT8VK5sqdUPKaA8Jv26E6akb1UNdIyNmVttJ7CIgGf?=
 =?us-ascii?Q?bweIXQY+GS6ZtIM7Jtes5Zpek6MOje64L+hZoGiD9vSOHrUUW+QQovBTBnBK?=
 =?us-ascii?Q?f/MrZAmAFK9WyK3SIcvWKdJlOVzS/kARBWzMwXTZFN9ADiOAdunE5XNuNSt4?=
 =?us-ascii?Q?bUtWhPZIn4EqWHtnEEAfeVKLIdrCMr+vh+rBmFbLCcEew5LvJmsXebHBPwSd?=
 =?us-ascii?Q?n1bjj/wLlNoZwBHtJheQ0jAIJMbGmSv3/NlqZkHxfD9zeXofVhvAeKdDEIb7?=
 =?us-ascii?Q?OvP8gfmmwCEkrt7QddYQ8tvqLAy/c6QLAMRwbmuAoJ6zpwuqFMOqayVb3OKQ?=
 =?us-ascii?Q?edFYqWF3FqxDD5dxkmA7bHSN+qqUXUF16pcpKKCj?=
X-MS-Exchange-CrossTenant-Network-Message-Id: b96cafcb-75b2-4a88-062c-08da75519019
X-MS-Exchange-CrossTenant-AuthSource: MN0PR11MB6304.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Aug 2022 13:10:39.8893
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: ROmWV9yCbCmC8jMQJm2IgjC2V37Pgs83VStUgy1xmHBPrVLeTumTG2HXQY5U+hgEpk6YIHCsUgc/vgBbHED+/A==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH0PR11MB5830
X-OriginatorOrg: intel.com
X-Spam-Status: No, score=-5.7 required=5.0 tests=BAYES_00,DATE_IN_FUTURE_06_12,
        DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,
        RCVD_IN_DNSWL_HI,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,
        SPF_NONE autolearn=ham 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

On Wed, Aug 03, 2022 at 08:56:44PM +0800, Michal Hocko wrote:
> On Thu 04-08-22 04:43:06, Feng Tang wrote:
> > On Wed, Aug 03, 2022 at 07:28:59PM +0800, Michal Hocko wrote:
> [...]
> > > +struct mempolicy *policy_mbind_nodemask(gfp_t gfp)
> > > +{
> > > +#ifdef CONFIG_MEMPOLICY
> > > +	struct mempolicy *mpol = get_task_policy(current);
> > > +
> > > +	/*
> > > +	 * only enforce MBIND which overlaps with cpuset policy (from policy_nodemask)
> > > +	 * specifically for hugetlb case
> > > +	 */
> > > +	if (mpol->mode == MPOL_BIND &&
> > > +		(apply_policy_zone(mpol, gfp_zone(gfp)) &&
> > > +		 cpuset_nodemask_valid_mems_allowed(&policy->nodes))
> > > +		return &mpol->nodes;
> > > +#endif
> > > +	return NULL;
> > 
> > I saw the logic is not changed, and it confused me that if there is
> > no qualified node, it will still return NULL which effectively equals
> > node_states[N_MEMORY], while I think it should return a all zero
> > nodemasks.
> 
> This is a separate thing and I have to admit that the existing code is
> rather non-intuitive or even broken. I guess we do not care all that
> much because MBIND with completely non-overlapping cpusets is just a
> broken configuration. I am not sure this case is interesting or even
> supported.

Fair enough, and moving the policy_mbind_nodemask() into hugetlb.c for
one single caller make it much less severe.

Do we still need the other nodemask API I proposed earlier which has
no parameter of gfp_flag, and used for __nr_hugepages_store_common?

Thanks,
Feng


> -- 
> Michal Hocko
> SUSE Labs
>