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;
Message-ID: <9c5ccb75-c06a-e638-a83b-07c318a0d074@oracle.com>
Date:   Fri, 20 Jan 2023 14:05:57 -0800
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.6.0
Subject: Re: [PATCH 4/9] mm/rmap: change hugepage_add_new_anon_rmap to take in
 a folio
Content-Language: en-US
To:     Matthew Wilcox <willy@infradead.org>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        akpm@linux-foundation.org, songmuchun@bytedance.com,
        mike.kravetz@oracle.com, jhubbard@nvidia.com
References: <20230119211446.54165-1-sidhartha.kumar@oracle.com>
 <20230119211446.54165-5-sidhartha.kumar@oracle.com>
 <Y8ot5Y01TWmB4sBj@casper.infradead.org>
 <9c276d01-379f-9bd7-0a7a-6a831b7b4571@oracle.com>
 <Y8sE2l7EvBPnTCab@casper.infradead.org>
From:   Sidhartha Kumar <sidhartha.kumar@oracle.com>
In-Reply-To: <Y8sE2l7EvBPnTCab@casper.infradead.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?TjJEZXdVY01pdmZVMks5M25wRW1Xc24xbm1aWTJwbXBlWEUybXZpWGJjMWV4?=
 =?utf-8?B?RmMyV2Z4dXRudXA2TGJGaFk0WUVVbE9MeXB5U0d3R2R1UW1hU0x4U2grNk5h?=
 =?utf-8?B?YUtydjZDV3Q5TkVUNmpyd2JUMTI4ZjRVNW96cWpNNG8yWDhKNFBMS25oQnFr?=
 =?utf-8?B?VUxTR0o3ZVRFblpyTW9wSGwzTUZmSjFTSXBrRXk5OFN6QXdZdkowZ2lYU3RO?=
 =?utf-8?B?KzJjK2pBMFBlOUtURmwxOFJ2cVIzVTZWd0dFU3RaWDZlWnpudWpNNlJXdlhk?=
 =?utf-8?B?ZFd5dWYzbWhLRVVNcVJPMGloQzNzRFlYK0lxSzN6TEY5bjhWbndIdm1CdFlq?=
 =?utf-8?B?SHJ4TUxkTlBNdTB4Zkxza3AvKy9PSEgwVSszVGhscW1FckNaV2FnRnFHcGM3?=
 =?utf-8?B?SHExc0Q1c2l2c3FuenpzTGo2c2hLRFprd3JXRUh1WlVGTWUzL1ZTVStnSm9k?=
 =?utf-8?B?NlJOUWI2M05GaU56R2VLcHBPY1FDVlJyNkNYSDZrZ0RFLzdISmcwQkhIUnhW?=
 =?utf-8?B?aG05ZzRUNlZ3Ni9EUjBxVU1tVm41c3YzcjRUamNjQlZvNnljQW40Rm5sQ2VY?=
 =?utf-8?B?b0o3RWhLZHVUcSt6MmhIK2ZUSUNQYkE2YWZ5VE9VZU9LWDdRUE05c1FScjR6?=
 =?utf-8?B?a09uMEJQcElhWDd6cFRNTGppcVFrRFBOc3Rhbzk4QVVKN3JkN1JSY0ZyQm4v?=
 =?utf-8?B?VWRzVk41Z0hrNHp6SWt0eW9aWUhjZEtiL0dVMWlrY2grMUFFSmpxeVlraWJr?=
 =?utf-8?B?QkY0TURtY2hUTWpMeEJGakkwRjhBSm1RaCs3RmlCT2NMcVZBS1Z1bUlHWWlG?=
 =?utf-8?B?TW05eUkxeklqV2FqR3NXenJ3ZWg3UG4zOENYTVE1TXdyaWV6WnZRQzlmZWRv?=
 =?utf-8?B?Y0RsWDUyMUhGMlhCMFRxTENlMXlsejU3NDJlWVVPNUZwQlNTbGpMbXliUHIv?=
 =?utf-8?B?dEFjVlRyWHVKWjdRaDB2UDZLa3orYkNxR3dIenVDUFFqSXlyVXRIeW1HTUU5?=
 =?utf-8?B?TEZQRXBtZEN3RGRDOHlNU0pvOGJPWUJFcVBVMnJ5bUdocEh5NkJwQ1JzMTRP?=
 =?utf-8?B?R1cxL2VTQzMvT2EyaFlzQ3VqUXNoTVBCY09UZ0xFazZKK2V0bHRmZUZQKytB?=
 =?utf-8?B?RmtYalA0TmZ2amJ6NzlqT0xHSHptdHpMUTJJUUh2dVFFNnRoSlY2TjcxYmEr?=
 =?utf-8?B?QUpaMkQwODBKRVg5bmZnUGNzZ00wcmQ2emUxTkJieUdZOExvdy9BOEhzdWFz?=
 =?utf-8?B?VnNjcVMzYTMyYXB0VStMekVzc2RvYXR4TjNwTEhhaFYwMGVwajV6eURkZnJI?=
 =?utf-8?B?OXlLYzRmM2FGdTFuQ01qQTFvalpvaFhTc2RWTE9OYm5EemtTSVVLSHlYa3RZ?=
 =?utf-8?B?VGkyTTVjaGFBQ2hHSEpCYUFxSzdlR0wwOXhRR3ZLdE5ka0kzNVBjR0NNcDhm?=
 =?utf-8?B?d3JxUlZkMmd1bTBxNnBrZFJGS1pDQ2VNNGdIOFVOSXp4dUFtUDVJVkYwME1o?=
 =?utf-8?B?WG1LeERJWnR5TjAxREMrQ1d6a2hZNDhHKzd1bGFSOU1odFV5WTdYMVVqbjR6?=
 =?utf-8?B?MGlWL0NXaVFWMTB6YmgzamVsVmMwUytVbkdZbG9kcGlyVVg0ck02WjJNY1BZ?=
 =?utf-8?B?VFdyaldQa1podnVQTEplQnhDRDRDdVZpSmZHNmRrM2lxNXovay9LbVdsMWRm?=
 =?utf-8?B?NTl1ZDUvcFgvcERwbHBjWVVDOFF0blpOc28yMTF4eDQ2VEZKMW9TQ3NvNmwr?=
 =?utf-8?B?N2lmdzFpM01LaEp4Rk1sVEZjN1c0dXVYdmg5TXJld1pBQVl1OEN1Mzd4cURu?=
 =?utf-8?B?bDBDdVBjS1B1bzhqcXVhWTMwVkErU205RW5pUkd4cEZJZEQxZWJEQzFwbUh0?=
 =?utf-8?B?cldCakNRM3RnYnFDZGxNK0wrcmw2T1ppNzhiZStKZGh3a29sbW5hci9oVGwy?=
 =?utf-8?B?ckc3bUxCdEJGTEY0Y3lwbGV0Z2Vwa3U5R0tmOWFFK3VKT3FTeTZXZ2JQaDFY?=
 =?utf-8?B?N29oWlR0Vnk3WHRjeTk1emRWTVBIQ0tVZll0RGZ2Q1pOWDFJUTYyT1ZNZG0z?=
 =?utf-8?B?Qm0wcFppVW5mQnQ0SDZFNmdhM3JZSG5IZzJBdGd1M3c2Qi8xOFM1d0ZkcXlH?=
 =?utf-8?B?ZUJhb1J5ODhoV2MyQW1qYUNMVzd6aVVoRm5EaGQ1cTZuUWhqUlVZUENoZ3RU?=
 =?utf-8?B?V0E9PQ==?=
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: =?utf-8?B?TWtkOVFLYll5Y05UbXhNcWJwNWRNN0IxLzFhWUptRG82K2ViTEhvZGFyWVVm?=
 =?utf-8?B?REhidHpIcUp2NFd4QVY4b1JtK01yYkRTNXpBd3FSZEFCNlBGaTJxZlU0S3Mz?=
 =?utf-8?B?QnV2ZC9rUGhwTmNUWVFsRzU2UXdhYTdkVVdQNG1tT2dzakludWlwTnhaUnh1?=
 =?utf-8?B?UkZ3ZlpWclZNYjB6SFVidjNmMWJYUms5eGFqZVhiQ2pId2ZOT21kUFVBSDBG?=
 =?utf-8?B?bUp5c096a2JSZm5yd0hHTHA1SnFONWJic0tTMVV3NmRoaGRvSzJ1SVZkMk1r?=
 =?utf-8?B?OWt2d3Q0TlNEYXEvd2RJdzJTa1MybytOVUpTWTRIeGRhajJ6Smo3MEhFb3pw?=
 =?utf-8?B?YUhTUVZHbEhjSkdFdmFEV0FldHNkUjBXQTRuUDhNRTVNY1IvL2lYelBVbjhp?=
 =?utf-8?B?TXlpYVRKSEZTdVJBd0hlYlc1WXhwaWQ4Ym03ckQ2SGQwRXFhbkhEUW1sSk05?=
 =?utf-8?B?QVlmeXJicUVWSmhFa3RUeGY5eCtUa1RMczdoK2FxNVRjK3ZWcllSYTYvNmJ2?=
 =?utf-8?B?dTN1ZlRiSWFMa21kQnN5U0g3aDhGRVhUeGxtaWRkd092aVZ1VGdPbnplOXRy?=
 =?utf-8?B?QndsMTVMbUxlZ05ON0dkcGJzcWdIbW9jbExHc0RvVkplV3hiUHRmR3FyNTNj?=
 =?utf-8?B?N2dnVFR4YjlwSUtGS3IyelZYck5PUUtXdTRGSEY4MTk0UXBjTGtIbjJYVU52?=
 =?utf-8?B?SVNqbDBYditrNW5sdGFjWHVUYmdFMDRRYXhzMlRoRVdtck52WmkwL1pCUlAx?=
 =?utf-8?B?R3MveE9vZHlvTVJ6OVdTbUNjbm8zZ0thVXd0UXFROU9LVTQ1S2lQZXpNUG5r?=
 =?utf-8?B?R3dudDg1d0JKZVRQa3JIYkY2cVI2dlRKMHBXVkdUK1JTMGNBOUdabjVyS0ds?=
 =?utf-8?B?NmsydE9zRjh1WHoyY1kwQ2dYTHBiRFJaNlJwTjE2djExMU5TUDR3b2J2SmZM?=
 =?utf-8?B?OGNnKzVuRitWS25IVUwvL0plREQza0FuM21ZY2k0RXBQWTZVd3h5QkhWenJr?=
 =?utf-8?B?a1RXdHh6TWxMUFl1TTB3SGlMNFpqOXFFaDJ0d0RhOElwOXQra2VnTk9oS1Nw?=
 =?utf-8?B?REhaT25hVE42cUs2L3I3QWJITnRDWjM0Q0crMGQ4WDZ0aWMxTEpkUGdDdkRC?=
 =?utf-8?B?cVFzOXVIeld4b2FKdnN0MkZUclkwRXJobkRqZzdHOHFseXB5aEQ2M3Q4c3Zo?=
 =?utf-8?B?R3RnMzNHeGNEejkvdDAzQjZ4REVZeTRPY1RIWHMzcGRodmo0ekZTM3BjWkJ5?=
 =?utf-8?Q?ujE0zbwxk4Rqd0e?=
X-OriginatorOrg: oracle.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 7abbcbbe-8faf-4ccc-6610-08dafb328388
X-MS-Exchange-CrossTenant-AuthSource: DS7PR10MB5117.namprd10.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 20 Jan 2023 22:06:00.2068
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 4e2c6054-71cb-48f1-bd6c-3a9705aca71b
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: IRosi0MB36iTlZZJXTXXT7DljmpGjcC8/GvaYBgugwZk5qQv2vgGjQUCKbKbKdCaELodQH8pOedOh8/4vFMBOpUJGcbRiBIjtFnFCoEjJs0=
X-MS-Exchange-Transport-CrossTenantHeadersStamped: IA0PR10MB7275
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.219,Aquarius:18.0.930,Hydra:6.0.562,FMLib:17.11.122.1
 definitions=2023-01-20_11,2023-01-20_01,2022-06-22_01
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 mlxlogscore=985
 malwarescore=0 mlxscore=0 phishscore=0 suspectscore=0 spamscore=0
 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1
 engine=8.12.0-2212070000 definitions=main-2301200211
X-Proofpoint-ORIG-GUID: dKTyG2LhKdD5_D929TAn6OHJjn5itNO7
X-Proofpoint-GUID: dKTyG2LhKdD5_D929TAn6OHJjn5itNO7
X-Spam-Status: No, score=-2.9 required=5.0 tests=BAYES_00,DKIM_SIGNED,
        DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,RCVD_IN_DNSWL_LOW,
        RCVD_IN_MSPIKE_H2,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 1/20/23 1:17 PM, Matthew Wilcox wrote:
> On Fri, Jan 20, 2023 at 12:45:38PM -0800, Sidhartha Kumar wrote:
>>>> @@ -6176,6 +6186,7 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
>>>>    	spinlock_t *ptl;
>>>>    	int ret = -ENOMEM;
>>>>    	struct page *page;
>>>> +	struct folio *folio = NULL;
>>>>    	int writable;
>>>>    	bool page_in_pagecache = false;
>>>> @@ -6251,12 +6262,15 @@ int hugetlb_mcopy_atomic_pte(struct mm_struct *dst_mm,
>>>>    		*pagep = NULL;
>>>>    	}
>>>> +	if (page)
>>>> +		folio = page_folio(page);
>>>> +
>>>>    	/*
>>>> -	 * The memory barrier inside __SetPageUptodate makes sure that
>>>> +	 * The memory barrier inside __folio_mark_uptodate makes sure that
>>>>    	 * preceding stores to the page contents become visible before
>>>>    	 * the set_pte_at() write.
>>>>    	 */
>>>> -	__SetPageUptodate(page);
>>>> +	__folio_mark_uptodate(folio);
>>>
>>
>> Hi Matthew,
>>
>> In the snippet:
>>
>> page = alloc_huge_page(dst_vma, dst_addr, 0);
>> if (IS_ERR(page)) {
>> 	put_page(*pagep);
>> 	ret = -ENOMEM;
>> 	*pagep = NULL;
>> 	goto out;
>> }
>> copy_user_huge_page(page, *pagep, dst_addr, dst_vma,
>> 		pages_per_huge_page(h));
>>
>> I thought the IS_ERR() call does not handle the NULL case and is a check for
>> high memory addresses, and copy_user_huge_page() path does not seem to
>> handle the NULL case as well but alloc_huge_page() can possibly return NULL
>> so I was unsure about how to handle the folio conversion.
> 
> I'm not sure how alloc_huge_page() can return NULL.  It seems like it
> returns ERR_PTR(-ENOSPC) or ERR_PTR(-ENOMEM) if it cannot allocate memory?
> 
I see now, I agree that page cannot be NULL at the return from 
alloc_huge_page, I will make that change in v2.

Thanks,
Sidhartha Kumar