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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kefeng Wang , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Ron Economos Subject: Re: [PATCH v2] mm/cma: move put_page_testzero() out of VM_WARN_ON in cma_release() Date: Tue, 24 Feb 2026 22:04:15 -0500 X-Mailer: MailMate (2.0r6290) Message-ID: <7AAE3B00-627F-4F40-A383-7F5FDCBAC8F5@nvidia.com> In-Reply-To: <20260225025440.63897-1-sj@kernel.org> References: <20260225025440.63897-1-sj@kernel.org> Content-Type: text/plain Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: MN2PR22CA0007.namprd22.prod.outlook.com (2603:10b6:208:238::12) To DS7PR12MB9473.namprd12.prod.outlook.com (2603:10b6:8:252::5) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR12MB9473:EE_|EAYPR12MB999155:EE_ X-MS-Office365-Filtering-Correlation-Id: dab899ac-2b5b-4295-48e6-08de741a90ea X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|7416014|376014|366016; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?jLUvPlg6uj6KTthpOTqwHPsNbOM6rFdTBhdmtipSdh6LToOhhv2lsklbwnoK?= =?us-ascii?Q?uJBNfpCv7EPQ8OCmgf1+3JzBusARqrhcEsZa3R3D9dohjuC/swJFuxCqT8Bs?= =?us-ascii?Q?mUwYm2S7cAHn391Aw7Bb8y51azliZFmZ9HLaC//zK4QKbEyRLhPOjyfYU2PJ?= =?us-ascii?Q?Fy8E47SQCRVChphiAjpUGbUWkybktVxu19jQyTFpMCsyeMhRidggaWWUWl0V?= =?us-ascii?Q?sgttMAaeXMq4e49GjGUyDAKtLYBdMMj0r2E+qBipBZC7cAEcWxH5oI24+q5f?= =?us-ascii?Q?vAuzhTj+rCTXMB/c+3Cb4oQ+8REDYyROXXUIuMlPkDBSyvpFhThVjjJxO7Ga?= =?us-ascii?Q?SVXGAXzQWJE8UOzSWb2xQioC3aJim/0UBHxr02Eym7lXptokHRWyo/SzFvbw?= =?us-ascii?Q?XTPwdllovTWZgq5DSGr8bMA0KxG5q921mP3ktHJ2ejL0dw0uSjBbFF7othE1?= =?us-ascii?Q?i6Uvs1xqEwpe7laBJQsqrEKqAPFpSk7S8jUoOdd+H6jfiBJdOZGC06aTXXqr?= =?us-ascii?Q?wvCKwS53zbC1rJjE7aeeGkm6vWbr7z4vbPfCC+rPJ3rlliMIbE1SIQu13DU0?= =?us-ascii?Q?17gt4eYnUhj21Gk9trLuD5tQ/pRndMPX7NvUj9U9YQEtcUItnWPqpLsQg57M?= =?us-ascii?Q?kw39INF897WQzI3VHy/Ju5Z5wsB5pELkOBTTYwkDiCJAQTSRhJSPoIXQyQjd?= =?us-ascii?Q?UBmyMlhajhsyGVxmQotNWcRfkTsRFtxNMbLCbqucODKfQ87TnY5NusIu4Edg?= =?us-ascii?Q?d/3ZS2vCsZM51Xg/5haF6F8pwuBcsAMUDQA/cwB2/xW7rDuZZijKWPRkAhUD?= =?us-ascii?Q?JB0A/dQdsGG3lExIFoE+RX94zzZnNVvmg49Yu+kgxHcknNOYU20iwHqTR0oN?= =?us-ascii?Q?pXtGkspp4I1MMlbvjaw9G7o1dpWqvzi8PwB1S7ylwlIw57WRVgiWXMwrF+n0?= =?us-ascii?Q?xKwxioBxT6KG4JWlol5zBEJT1ES4eP1j70Ry+k8nOWJkh9oV9H5OvQ7p8o/2?= =?us-ascii?Q?LgT/k/G2wiFkPTrOS+tEEvzlKQ0XtnLxV07tD/cPnExqznEeBHwoqzZDzMBE?= =?us-ascii?Q?Tj3aP4HQfsxGZmFl8v2Ii0oHzB6q0OupOOIa/VLFJTzZaR8+SLMYdXybi+bE?= =?us-ascii?Q?WUiMpxBwuJDcLekMAKinyg6wEwehfs3pNmpsdNTlvN2yrdazw3pTH33kPraz?= =?us-ascii?Q?OAESEhLXiEexhldap9OIr/uLLNTHNnKeuyQOMH7Y6EqevLsCab2SWHpOexCD?= =?us-ascii?Q?n2y+naBKr7gB4QT0QzwKcem4N/BBTULJvUw2mlijUIvJ2dx3QgM20O0VNAYC?= =?us-ascii?Q?HqLfDAGk4wVlQTwN+iJ2tqOyhX5LNdjhBXbUxqQbXTc4hccOIRVqb90lx+9O?= =?us-ascii?Q?ew+TCJaTXhZwY1mOiKNOFVvY4mmTe5pGW70fSSopRJhfQDe0hy2tRu8dScNa?= =?us-ascii?Q?/My5NQ1EscIZAFOtVva69b7UVFJAd59UrqDDESXf4ycWLPM2goh0Qh2TiGwg?= =?us-ascii?Q?rT01zdX0nwrP4w5Brh2EjpgKvP2Jy8t+cNMGwqtEkIQkXdozpOBJoKlo4VWQ?= =?us-ascii?Q?jsGjhK6tZpnFTWkTgQnvqztkMVfErapxBKexXkFoPElgJGCtxMNpCdOfKyzR?= =?us-ascii?Q?pGIl2h/3zGoh47nhCla58ucyEVlAQDodCiecfCHkx5Rl576ryMK+HSJcPvFz?= =?us-ascii?Q?LjDK+nA44MzxlThhJjIKHrn6YCx58XbTPS3fur4MKVFJ55B6ooHqGpVmq1tj?= =?us-ascii?Q?qv/6USCAng=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: dab899ac-2b5b-4295-48e6-08de741a90ea X-MS-Exchange-CrossTenant-AuthSource: DS7PR12MB9473.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 25 Feb 2026 03:04:18.3881 (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: orNL6EXAlfCn2K9asFZTim8OL5VrY8BZ0ytCBbS/e+GmiZiVZkb+9bjK30TX0wma X-MS-Exchange-Transport-CrossTenantHeadersStamped: EAYPR12MB999155 On 24 Feb 2026, at 21:54, SeongJae Park wrote: > On Tue, 24 Feb 2026 21:28:52 -0500 Zi Yan wrote: > >> When CONFIG_DEBUG_VM is not set, VM_WARN_ON is a NOP. Putting any stat= ement >> with side effect inside it is incorrect. Collect all put_page_testzero= () >> results and check the sum using WARN instead after the loop. >> >> Fixes: 9bda131c6093 ("mm: cma: add cma_alloc_frozen{_compound}()") >> Reported-by: Ron Economos >> Closes: https://lore.kernel.org/all/1b17c38f-30d3-4bb4-a7e1-e74b19ada8= 85@w6rz.net/ >> Suggested-by: Kefeng Wang >> Signed-off-by: Zi Yan >> --- >>> From V1: >> - Collect all put_page_testzero() results and do a single WARN after t= he >> loop. >> >> mm/cma.c | 5 ++++- >> 1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/mm/cma.c b/mm/cma.c >> index 94b5da468a7d..ea540d3f473c 100644 >> --- a/mm/cma.c >> +++ b/mm/cma.c >> @@ -1013,6 +1013,7 @@ bool cma_release(struct cma *cma, const struct p= age *pages, >> unsigned long count) >> { >> struct cma_memrange *cmr; >> + unsigned long ret =3D 0; >> unsigned long i, pfn; >> >> cmr =3D find_cma_memrange(cma, pages, count); >> @@ -1021,7 +1022,9 @@ bool cma_release(struct cma *cma, const struct p= age *pages, >> >> pfn =3D page_to_pfn(pages); >> for (i =3D 0; i < count; i++, pfn++) >> - VM_WARN_ON(!put_page_testzero(pfn_to_page(pfn))); >> + ret +=3D put_page_testzero(pfn_to_page(pfn)); > > So, 'ret' will be incremented when put_page_testzero() returns 'true', = right? > Shouldn't 'ret' be inceremented only when put_page_testzero() returns '= false'? Good catch. Let me fix it. Thanks. > >> + >> + WARN(ret, "%lu pages are still in use!\n", ret); > > This will trigger the warning even if CONFIG_DEBUG_VM is unset. I'm fi= ne with > the changed behavior, but I'm curious if that is the real intention of = this > revision. It was in free_contig_range()[1], which was called by cma_release() befor= e. [1] https://elixir.bootlin.com/linux/v6.19/source/mm/page_alloc.c#L7238 -- Best Regards, Yan, Zi