Received-SPF: pass (google.com: domain of linux-kernel+bounces-18480-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Message-ID: <e98fd1bc-ab6a-4f6f-a2f3-29b68fa5b15f@intel.com>
Date: Sat, 6 Jan 2024 12:36:13 +0800
User-Agent: Mozilla Thunderbird
Subject: Re: [syzbot] [mm?] WARNING in __folio_rmap_sanity_checks
To: David Hildenbrand <david@redhat.com>, Ryan Roberts <ryan.roberts@arm.com>,
	syzbot <syzbot+50ef73537bbc393a25bb@syzkaller.appspotmail.com>,
	<akpm@linux-foundation.org>, <linux-kernel@vger.kernel.org>,
	<linux-mm@kvack.org>, <syzkaller-bugs@googlegroups.com>, Matthew Wilcox
	<willy@infradead.org>
References: <000000000000014174060e09316e@google.com>
 <c4e2e700-2d26-492f-8eb2-eb3ab14bc07a@redhat.com>
 <3feecbd6-b3bd-440c-a4f9-2a7dba3ff8f1@intel.com>
 <36ace74a-1de7-4224-8bc1-7f487764f6e2@redhat.com>
 <8bc02927-a0f0-490a-a014-0e100d30ffe4@intel.com>
 <1eb61435-c89c-4ca1-b1b6-aa00b3478cd2@arm.com>
 <556f8a4f-c739-41e0-85ec-643a0b32a2ce@redhat.com>
 <58e2fe0f-b198-4248-9ead-fb5bf4f3edee@intel.com>
 <d08a3e17-ea4d-40e4-b36c-031bf1f2a0a0@redhat.com>
Content-Language: en-US
From: "Yin, Fengwei" <fengwei.yin@intel.com>
In-Reply-To: <d08a3e17-ea4d-40e4-b36c-031bf1f2a0a0@redhat.com>
Content-Type: text/plain; charset="UTF-8"; format=flowed
Content-Transfer-Encoding: 8bit
Precedence: bulk
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?RUtaNmExelRMclcyNXYvZ2Yyd1NVUzYvVVlEUnNldC9FTUFYZ210K3M1RFBH?=
 =?utf-8?B?bVgzaVRxT0wybGpWL1RDT0FVeThpNzZ4eVcvS0ZCajVTZHp0VDhpYjk1QnE4?=
 =?utf-8?B?SUlLOFBaVnpvMVVzckdhNldFUWpYS1hkMWNXUFZqR1Rvc0cwZkNzcE5iOGpw?=
 =?utf-8?B?b3lmTTdhY05OejBydFR0SURXakVqNVE2bzBmV3BrbHgycVNkUFdENDVIdndF?=
 =?utf-8?B?Z1dnbnZXWkVwQnc5YWlxTzFsQXF0S0dMeXJmNnlXTGlZd29jcFZBOEU4cFFz?=
 =?utf-8?B?RlFlMnMzYmsxajhHYUdNTjdDUUdRTzF2K29TUHd0aXhQbkd5R3UyWDZIc2tP?=
 =?utf-8?B?ckR0NGdaLytlbmo5NWFhcTBvL0hwR2hiYXhpZ2FLWmtzZ2VMbmhXSHozdVlR?=
 =?utf-8?B?VEwxS0NNVnl4ODFwSUh6bUQrTFRqblhwaytSWmg1cmdBL1JsaFVaOFdpZGxB?=
 =?utf-8?B?YUpsMklEam9qajRoeCtZV1ROZmxtTnN2bXZBU1FhTGIvRUtXS05PbGtwUDJZ?=
 =?utf-8?B?MVJaYllRZWlkTmVYQm0xWVUrYjVJM295UUNVUThWaWtCZGN4enRsWmFtaW1z?=
 =?utf-8?B?UFUxLzVkL2JtcTRyaFRhSUg5MGpQS2JyclBDRXdBWkVvYTRpNkc5NGJVeEl5?=
 =?utf-8?B?ZHc0bVB6M0ZFZXFYYjdwMnhlOURCMzh3d2tQRnVHV2d1VTZVeDR1UzZqR2k4?=
 =?utf-8?B?ODk4VmZZQmpIclYxT01mK1JubkhPQWp0ZVdmYXJwUmJtZEJva2ZWdXRRVkR2?=
 =?utf-8?B?bDUwejFuL0kxTUNNcnhKWTVvQTkxRmNmVkRqeVF2UkJFeWt4ZkY0cTlQN2NZ?=
 =?utf-8?B?M3RPNzBUVzZXOW8wMEJPQ1NWQk1LdG1tWkM5R0FVVlBXaWdBZ3FnMXVacVNX?=
 =?utf-8?B?cUxIN3JsMGJsZ3ZWQThwcHdaZjV4Q3R2eUFNeVYyOWs2QWM0NXBKK2c5Ujgz?=
 =?utf-8?B?bWIxcmdVMGtzbkFnU2VMV3YvREc2cnFhRTdrZzh3enBLMUhENXd0NVNIMTM2?=
 =?utf-8?B?Z0ZDams4Rk4za2hncVlFeEVZdnBYTXgrTVQ0SmxwRVRDYlZTUmdybkxSTUJI?=
 =?utf-8?B?UHhWZzlYUit0MTBvdm9GeGljSXRoZU1CbTF1RUVUNnV5ZEZHa2V5WEljWnlW?=
 =?utf-8?B?SkoyYzhLbCt3ZFRHWitVMnYxWlJFc1VBWkx1c3FFTHU3UlMyREIyTmJJZDM4?=
 =?utf-8?B?cDBMY2U1SUNjM0xaWSt4dUpYSkxrUCs1TDVyWWFzT0FkZ0dLOTRXdllMcnBh?=
 =?utf-8?B?dGhEVVdYK3Nsa1VlKzFhOTg0NXFIQjF1ZThWNSsrWjVKT3o4ZVk2Vmh5MzZY?=
 =?utf-8?B?bDZsNFh5SXNKdm9Fb0RSNmJBTXYxR2ZMT2U2Uk11Y29GdEhURVNTV3F1NFJz?=
 =?utf-8?B?N1Uya096cm1adHVOSlpDMHdQWHZvTzUxNFdHckxBeVFHSWZvK3dKaUhiWDFx?=
 =?utf-8?B?ZU9vRmpGdWd2R3FJVU1xVmZnbyt4Wmx1NU90Y25uTnF6QWtjcTU1b0p3V29k?=
 =?utf-8?B?azQydGg1a095NDVzT0RUdXVpVVQ0cWU5QmNLeG5qUGtCRU50cVlrRkpwSnZt?=
 =?utf-8?B?cHZNSnppalNnbWVOenMrZDJkQ3ZhaCtIcW5WQW9rZmluNTh3aWp0aHljbldC?=
 =?utf-8?B?SFd1NmtVb09xNlBJbm8rb01mNUJxdm5oeUpCRkNodEtXZ2g1cllvMUpLT2p2?=
 =?utf-8?B?OVEyaEltSDNYaGhWWVY1L0UzV2h0ZFZPOGI0VFNqTkVpVm84dnd5QThrVmNZ?=
 =?utf-8?B?TWZPT00vTS9NdlNUWkFDdkpPdXRjaWNTUXRLbk5SeGs2MitETytDR1d4TTZM?=
 =?utf-8?B?a2grSW04Y1l3dEFWSUtmT3R6M2lYVGp2cGxHdDkrOVJtL3JpTG1kVkg3b1R2?=
 =?utf-8?B?WmhKR0hjRkNnMEpBUHhyYmVtam9LMUV0MXBPL2FreTRRQnAvTVArb1dpQThQ?=
 =?utf-8?B?RXRjRDdJdDQ2Nkxybjd0dXVhbXhKS3BMdDROKy91dC9LNnp0a2twMHNUTjls?=
 =?utf-8?B?RDRYOHZiSUpObnFkL0FWNkVJMW9ENVNhbUFZZmNpejJ6SjlObXBIRnl4WUZU?=
 =?utf-8?B?T2ozTVFqTW1FN1hmNXB3TXhWUHZFSDRoOEpDbVFBTW9peUt5bzNhUFQyV1hS?=
 =?utf-8?Q?yYkKtiFqnI2IQqb8uQDKR9Mck?=
X-MS-Exchange-CrossTenant-Network-Message-Id: 1f505b80-2be4-42ed-351c-08dc0e7107a1
X-MS-Exchange-CrossTenant-AuthSource: CO1PR11MB4820.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Jan 2024 04:36:20.6572
 (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: A2QgFML211mZ0AC6BEVZwslOowuysNx5+TiXynAp2q1AWjqHaiXLFrYVQej83yUKjNXBe5Xd9wf3TGQ5lhYp5g==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS0PR11MB8020
X-OriginatorOrg: intel.com


On 1/5/2024 11:45 PM, David Hildenbrand wrote:
>>> vm_normal_page() works on these mappings, so we'd also have to skip rmap
>>> code when unmapping these pages etc. Maybe that's the whole reason we
>>> have the rmap handling here: to not special-case the unmap path.
>>
>> vm_insert_page() will set VM_MIXEDMAP and vm_normal_page() will skip
>> the page if CONFIG_ARCH_HAS_PTE_SPECIAL is enabled (it's enabled for
>> x86).  So the unmap path will skip these kind of folios?
> 
> I think we run into the
>      if (likely(!pte_special(pte)))
>          goto check_pfn;
> 
> first and return these folios. That also matches the comment of 
> vm_normal_page: "VM_MIXEDMAP mappings can likewise contain memory with 
> or without ... _all_ pages with a struct page (that is, those where 
> pfn_valid is true) are refcounted and considered normal pages by the VM."
Oh. Yes. This is the path. Thanks a lot for pointing it out to me.


Regards
Yin, Fengwei