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Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH] mm/memory_hotplug.c: don't fail hot unplug quite so eagerly Content-Language: en-US To: David Hildenbrand , Oscar Salvador CC: Andrew Morton , LKML , References: <20230620011719.155379-1-jhubbard@nvidia.com> <80e01fa9-28c0-37e8-57f8-5bb4ce9a9db7@nvidia.com> <83689f25-ca50-7ece-45f0-a936e704df7d@redhat.com> From: John Hubbard In-Reply-To: <83689f25-ca50-7ece-45f0-a936e704df7d@redhat.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.126.231.35] X-ClientProxiedBy: rnnvmail201.nvidia.com (10.129.68.8) To rnnvmail201.nvidia.com (10.129.68.8) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SN1PEPF0002636C:EE_|CY5PR12MB6034:EE_ X-MS-Office365-Filtering-Correlation-Id: 5d57c62a-ca5f-4be5-52e6-08db72c789c2 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:216.228.117.161;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:mail.nvidia.com;PTR:dc6edge2.nvidia.com;CAT:NONE;SFS:(13230028)(4636009)(376002)(136003)(39860400002)(346002)(396003)(451199021)(40470700004)(46966006)(36840700001)(356005)(53546011)(7636003)(82740400003)(336012)(186003)(2616005)(16526019)(26005)(36860700001)(47076005)(40480700001)(8936002)(8676002)(41300700001)(5660300002)(2906002)(36756003)(478600001)(70206006)(70586007)(83380400001)(40460700003)(110136005)(54906003)(316002)(426003)(31696002)(86362001)(16576012)(4326008)(31686004)(82310400005)(43740500002);DIR:OUT;SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Jun 2023 02:22:33.6923 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 5d57c62a-ca5f-4be5-52e6-08db72c789c2 X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a;Ip=[216.228.117.161];Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: SN1PEPF0002636C.namprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CY5PR12MB6034 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/21/23 01:11, David Hildenbrand wrote: >> ...what about discerning between "user initiated offline_pages" and >> "offline pages as part of a driver shutdown/unload"? > > Makes sense to me. > > There are two ways for triggering it directly from user space: > > 1) drivers/base/core.c:online_store() > 2) drivers/base/memory.c:state_store() > > We cannot easily hook into 2) to indicate "we're offlining directly > from user space". SO we might have to do it the other way around. > > > Something along the following lines should do the trick (expect whitespace damage): > > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 53ee7654f009..acd4b739505a 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -152,6 +152,13 @@ void put_online_mems(void) > >  bool movable_node_enabled = false; > > +/* > + * Protected by the device hotplug lock. Indicates whether device offlining > + * is triggered from try_offline_memory_block() such that we don't fail memory > + * offlining if a signal is pending. > + */ > +static bool mhp_in_try_offline_memory_block; > + >  #ifndef CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE >  int mhp_default_online_type = MMOP_OFFLINE; >  #else > @@ -1860,7 +1867,8 @@ int __ref offline_pages(unsigned long start_pfn, unsigned long nr_pages, >         do { >                 pfn = start_pfn; >                 do { > -                       if (signal_pending(current)) { > +                       if (!mhp_in_try_offline_memory_block && > +                           signal_pending(current)) { >                                 ret = -EINTR; >                                 reason = "signal backoff"; >                                 goto failed_removal_isolated; > @@ -2177,7 +2185,9 @@ static int try_offline_memory_block(struct memory_block *mem, void *arg) >         if (page && zone_idx(page_zone(page)) == ZONE_MOVABLE) >                 online_type = MMOP_ONLINE_MOVABLE; > > +       mhp_in_try_offline_memory_block = true; >         rc = device_offline(&mem->dev); > +       mhp_in_try_offline_memory_block = false; >         /* >          * Default is MMOP_OFFLINE - change it only if offlining succeeded, >          * so try_reonline_memory_block() can do the right thing. > > > > There is still arch/powerpc/platforms/pseries/hotplug-memory.c that calls > device_offline() and would fail on signals (not sure if relevant, like for virtio-mem it > shouldn't be that relevant). > > I guess dlpar_remove_lmb() can now simply call offline_and_remove_memory(). > [I might craft a patch later] > This direction looks good to me, I'd love to see a patch if you put something together. thanks, -- John Hubbard NVIDIA