From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from BN8PR05CU002.outbound.protection.outlook.com (mail-eastus2azon11011056.outbound.protection.outlook.com [52.101.57.56]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5288A2BE03C; Tue, 8 Sep 2026 02:56:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.57.56 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788836203; cv=fail; b=L5p3vrt9fzwd4vEeL+CkseESwi6n2v/Qx/fIR3aDzUfCcYV7/TwB1ovUO2wYvsIPdvrje7ndL4A1LHfXnsY/WDRLzn/aUxdqwDlAc74/zFFVVCFXM55PVNPY8QxvbLzujJgF5eacattSebA9RIMd/eZbabP7fGsBrNJBhwApPmE= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788836203; c=relaxed/simple; bh=Uh0ln4U4kGGNMEw2jFKEFqkhAhvENpu5gIdu/9eaBUg=; h=From:Subject:Date:Message-Id:Content-Type:To:Cc:MIME-Version; b=PybezJpEileb/uB9pZpLD3qoU1sCAQkb98f7H2WcxoNgbAtwXBU4TqweXD9X31M47GqBkA2+qTedkkEQc6qF+aU49LGsVnJ3nkGF1vs9aNjPJqT4xcMdH9cFWVhd+gXNQOtx2BwVeOTyk8X4VeLA1RtQu055L51aKFsduFNVTB0= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=O7zqGrJi; arc=fail smtp.client-ip=52.101.57.56 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="O7zqGrJi" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=FNLKY/TL9ihjVf2a51ONNvLPuDvfAHEdEwlp53OPvKoYISnQQCA1Pe3CuSbYICUW75wUwpeq4vqynBY714801xJh2vGx0V302o5ftHSglYgVDCUyLqlubRlMBRt3M/du4b95mEDv/WmKdIeRZxufODQNX0K/jxby0sWLM/+kSf4LndFxaTIVE44HayniZ9TespyJWKuOrV1dkjkGd7Binj3Nb2Y38hxDZwCAAoabkSD6wvnhgSwv0K2NlbS4hrf/ZCHMNqQsdvJd89lIjHxEUEbqG7xOR7CQ89JaQNBRfuM6GY33kpv5qRbsasVCoNQa5C7mihcg97TM+rEAj2xsxw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=0/+loFgTpB5WI64K9N4RnP70y5sRGMjPtenQs1tbBDA=; b=lTeeySTtb4b/YkEw9x3cLjYc0qImguU9uDMHWRKpgl+r3iioTtN2l5VS0TPf2FqB82Zw8VfxqaA8LnUnUMnEJEOXI40UVp7lobphhdoFnRRsTwiakI8PrpUn4VefNlAvMYTCK8vH4qXM5c3XxfuXO4zQor7tF/YNB2N8H2eZnH+Var5a6JLgL173TsC2Z8d7LBC3Pq1+VqdlkR3g62QHWBruGh7IkdaubyHRPPXGjl5d/TJnpodOEJToSHKRn4hJcOzAp9VdD6n+g7MtGBn6EhgLMKakXPsJzxrdCtTNzU1GfwdSWmnpxGJqfpJqwMIy1OPonfEY9IPzys26aoA3nw== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=0/+loFgTpB5WI64K9N4RnP70y5sRGMjPtenQs1tbBDA=; b=O7zqGrJipndOZP+iH4uMuHVRC/jFfGog+WpzDfJc48qIu1XEmMioqbdt1soIAjrJi9tD2laD1hutZUAdLf6QmmC8EWG8ZPJSGgIXVl/5ZzLy+XnpQJ4FXR6k+8e35lfIafxsS4BC/tKH/fwqoaWpcREealRy0eT0Ij2bKudWYOXRyl/wKtFIdQNhegY+kjBoCKrd7uYIJ87o5ts0MnRt2YEsUJ+RtX2KPa/+wz9rHaBBOpye4ptOGIkLndknWWTy2+oCBMqu1uC0rgV2A5hG4gm+HWonFtSV8vddbrmU/bBfTmLQ269DUCpZ8nZ592kK3WNDA6sPi/FZ5M0e/YMbgg== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) by DM6PR12MB4435.namprd12.prod.outlook.com (2603:10b6:5:2a6::23) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.382.15; Tue, 8 Sep 2026 02:56:27 +0000 Received: from IA0PR12MB8374.namprd12.prod.outlook.com ([fe80::d85f:4c87:ae84:3f16]) by IA0PR12MB8374.namprd12.prod.outlook.com ([fe80::d85f:4c87:ae84:3f16%5]) with mapi id 15.21.0382.014; Tue, 8 Sep 2026 02:56:27 +0000 From: Zi Yan Subject: [PATCH v3 00/14] Remove PG_private by using page/folio->private checks instead Date: Mon, 07 Sep 2026 22:56:07 -0400 Message-Id: <20260907-remove-pg_private-v3-0-6ae22f9d9272@nvidia.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit X-B4-Tracking: v=1; b=H4sIAAAAAAAC/23N0QqCMBTG8VeRXbdwZzm3rnqPiFjzqOciJ5uMQ nz3pgQRePn/4PzOzCIGwsjOxcwCJorkhxzyUDDX26FDTk1uBiWosgbNAz59Qj529zFQshNy16I B5epWS8fy3RiwpddmXm+5e4qTD+/tRRLr+tWk2NGS4CUXJ3CmflhZKbgMiRqyR+efbOUS/Ai9T 0AmpFJaVMY1BvUfsSzLB/oTPbj2AAAA X-Change-ID: 20260728-remove-pg_private-cfe926c7f83c To: David Hildenbrand , "Matthew Wilcox (Oracle)" , Andrew Morton , Muchun Song , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Gregory Price , Ying Huang , Alistair Popple , Johannes Weiner , Qi Zheng , Shakeel Butt , Kairui Song Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Zi Yan , Minchan Kim , Sergey Senozhatsky , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Thomas Gleixner , Borislav Petkov , Dave Hansen , x86@kernel.org, Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , James Clark , "H. Peter Anvin" , linux-perf-users@vger.kernel.org, Juergen Gross , Stefano Stabellini , Oleksandr Tyshchenko , xen-devel@lists.xenproject.org, Eric Biggers , "Theodore Y. Ts'o" , Jaegeuk Kim , linux-fscrypt@vger.kernel.org, Oscar Salvador , Chao Yu , linux-f2fs-devel@lists.sourceforge.net, Gao Xiang , Jan Kara , Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li , Chunhai Guo , linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org, Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Axel Rasmussen , Yuanchu Xie , Wei Xu , linux-trace-kernel@vger.kernel.org, Trond Myklebust , Anna Schumaker , linux-nfs@vger.kernel.org, Song Liu , Yu Kuai , Ilya Dryomov , Alex Markuze , Viacheslav Dubeyko , Li Nan , Xiao Ni , linux-raid@vger.kernel.org, ceph-devel@vger.kernel.org, Richard Weinberger , Zhihao Cheng , linux-mtd@lists.infradead.org, Baoquan He , Pasha Tatashin , Pratyush Yadav , Jonathan Corbet , Dave Young , Shuah Khan , kexec@lists.infradead.org, linux-doc@vger.kernel.org X-Mailer: b4 0.15.2 X-ClientProxiedBy: BL1PR13CA0376.namprd13.prod.outlook.com (2603:10b6:208:2c0::21) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA0PR12MB8374:EE_|DM6PR12MB4435:EE_ X-MS-Office365-Filtering-Correlation-Id: f5a43f69-1177-4e40-a343-08df0d54c6aa X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|366016|23010399003|1800799024|921020|6133799003|5023799004|10067099003|56012099006|11063799006|18002099003|3023799007; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:IA0PR12MB8374.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(376014)(7416014)(366016)(23010399003)(1800799024)(921020)(6133799003)(5023799004)(10067099003)(56012099006)(11063799006)(18002099003)(3023799007);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?c0ZkUmxZZjFYTzVXbExEWUhiMGkyWk9VWjc2aE1yTUl4UnVURW1lZWY2RGNW?= =?utf-8?B?S3ozbW9vV20xazBDUVFzNlFTRkRYVlJSQUhFS3pDTWVLZGNLQ0prd1M3R2k5?= =?utf-8?B?MlZoc0c3ZHFXMGRkSUFaejlWQTNLZm4xYUp5TjZPNGZEczRzUy9CdkdOa3o3?= =?utf-8?B?bStheEdaSGlQNnIxTjdZOXU5em0wekVoTjcyR2Q3TStmNWVWZldQSGRVRXRP?= =?utf-8?B?VkNHWHdMZFU2ZFBzOEpQNURzYm13dXVBQU5wSmtQQXc4dHBmc0lTeVJKbGJo?= =?utf-8?B?TkxMYW5uNnZRUWlweDFORE5sUERQeUtlcTdLeGEyU0RNbTltWndwR3l4L2ZO?= =?utf-8?B?V1MybllhMUtlYlY4Z2ZlT0VtOHpkTktwLzJEaFdnVE1lMVdtR3BMT0dlaGly?= =?utf-8?B?NXdGWUl0cHR1anRVcy9MV3M4dWNVSWx0QmtmSVZ6NEdYcmVCbUJQaDY4QmRk?= =?utf-8?B?alRQOUZYU09PZ2pva2c4YW1FeXhBSDVGMFRzM0ZyYnVtQ2dWemx0bCs5dW5u?= =?utf-8?B?eEorTENjbnRKU3ZIWDZKcldBR0p1R2dTV3ZZTVdPUHJuWjZRUUUxWXNlRXJj?= =?utf-8?B?eTA2VzFtRjFSMGk0OEZLcDc4QTJIa21hZmJTNUoxZlpzQ1d5V3FvQWxxWWVO?= =?utf-8?B?Qi9sczVsU2Z5K0p1TW5GTnJldUtjc0hEOWdSbWtWcGV3RnhtSGlaOUdQWW9x?= =?utf-8?B?enhzRWsrMU04bDJzSlUvNm5HY1M0OE1GY29VRjk1Z1FsNDZscVJIMFIyVHBr?= =?utf-8?B?bloxSUNCRXJLWnVQMHduZVdEZ2EvVzVvUDJva3Z3UXhaSmpUU1hsZG53aG1D?= =?utf-8?B?Tmt0ZmNJQjY4WkpMdng4TWt1MmFHZG1QQi9Wa2dXNzc5NEdWdnNqY09QbUw4?= =?utf-8?B?SzJPbUcycVpvQmtiS1c1QmlWRUEzMGM0OGhJVWR6RDh2ZTZNbWppSjlBWGdi?= =?utf-8?B?dTkrdmFja25tekpnYXROSFJRK3FtNWU2WFA4TkE2MFBPeTZsak5ZTVkvS0h5?= =?utf-8?B?dVZheFRqSUxJSXZSSHc0dG95RXVVVnMyYytBUTNoQ1QrZUZ4M2xuRVZ6Y2F3?= =?utf-8?B?T0VGcFprY3lmbkNVSksrUEVBSDkrNTdzS21MSzB2VEVRUFNQNTgzcVQ4S2Nl?= =?utf-8?B?Q0VGUEVOTk9MZS9Ebk02azhaQkNrQTM2ZVFWazNBUjBtS3gzdlovR1lGMk1r?= =?utf-8?B?V0NKaytEQzMvNlE1UGJJTEFnK01GQ0J0d2lCNkxRM3ZGRWJFUGw0UERDdVEx?= =?utf-8?B?UVFMaWV4NERCU1MvZlhIbEJuN1psWXBvSWJvNGIrdW9ZRXlhemZuckltOFVr?= =?utf-8?B?NHUvSGp6Y2psbWRhcVdZTkFsSDhWMkJHNEc0eUtESldzRkNmb3NiSFR6akk5?= =?utf-8?B?UGRzcHNTaGpFRVMzVUlnSmJ1dzRuL0NkaHVTWk1OSC9qNU5IVk9CQWhvQ3dZ?= =?utf-8?B?Sy9aUHJRNWtxWlkza0RqSFVOL0FYRTVINXF1YS9vVTRyM2l4RkZBVXFpSzlk?= =?utf-8?B?c0pNTGtVOGRobTBkWHZCeUc0YTFybUt6U3c3UlpObWpoRWlKd3k5MzVXdjZM?= =?utf-8?B?cHNFSzFRL0JpV0ZOUzlRY09ldE94Vkg2RzJOZFJ3Y2IyTUVjNURyRzZMNlNw?= =?utf-8?B?MStzSG1nZHIvdEZLdVJVQ25FYi8yTkRKaFF1OTVQUlNINXJOVXZJM0JuczhN?= =?utf-8?B?SjRIVFJNUEpqNFlsc3FlTWUvaVBodTN0ZVZBb01zYk5YdkJzUDdGNVVtd3RV?= =?utf-8?B?eFpKY0g5MTN4NkhxM2ZnZUlpeTBvMTQ1WTg0emFadi9heTRORGF3Y2pqU2do?= =?utf-8?B?US9PaTN3VnJTYSt3MHA4R3FsN1JYS0dqTWRpdFdwU0ozNEJKUHd3djNVMzlt?= =?utf-8?B?cmRjN2htTDRTajVxc3JhYi9xeHg1WTlzeXc1SU9jWmxTeTNoRW1IWjRRMVBR?= =?utf-8?B?VVJCYVRaSVdiL3JYaVplWnJmNjFFUW5zclArN3J4WTF6YUx6WFdDYmdrNlVt?= =?utf-8?B?c1krOGFHcVlNblRFUkFESDBEb2tHc2VXNTBVTUY5eTh4dmZieHJpUGQ2K01n?= =?utf-8?B?UVlRUWdUOUVSNmhiRmYyU3dLSnJIZ05vRjVCM0RpZWtPRTUwT3NaRHFQQXJL?= =?utf-8?B?cGQ4MzAxQ0tPRVhBa3A4dC85bVlNRElEd1JMUUJObkNqRStQeHdzMm1uNThS?= =?utf-8?B?c3pQTXNIUCtxS3lKRURaUU9BUDV3TlBhVGxXZHNmZzZHUFczVWFGMjdUN1R3?= =?utf-8?B?MDRBZzd4T1VsM0wrTzY1M0hUem5zR0pJRDE2SU1IcS8wVG81TUkzNS9aYzhx?= =?utf-8?Q?tqOmrccOv/+NYgACkW?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: f5a43f69-1177-4e40-a343-08df0d54c6aa X-MS-Exchange-CrossTenant-AuthSource: IA0PR12MB8374.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Sep 2026 02:56:27.2502 (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: INmokXrarh8Yoor8WTq7CLfba+LlxdubfXkWLLcIL40rtSGcfkO9FCQhfhZ4OJUH X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB4435 Hi all, This patchset removes PG_private to make space for upcoming PG_folio (reserved as __PG_folio) for identifying pages from a folio (more details in Note below). Instead of checking PG_private, all code is changed to check page/folio->private != NULL instead. MM people are cc'd on all patches and subsystem people are cc'd on the cover letter and corresponding patches. Patch 6 is picked up separately in f2fs tree, but since mm-new does not have it yet, it is sent for MM testing. Overview === Most code uses folio_attach/detach/change_private() functions, so folio refcount is increased and decreased when folio->private is set and reset, respectively. There is no need to change them. Changes are needed for exceptional users: 1. zsmalloc uses PG_private to indicate first component zpdesc page and page->private is used to store zspage in zpdesc. To remove PG_private, is_first_zpdesc() is replaced by pointer comparison. 2. kernel/events/ring_buffer.c stores page order in page->private. Replacing PG_private with page->private != NULL works. 3. drivers/xen/grant-table.c stores xen_page_foreign in page->private, where on 32-bit, a pointer to xen_page_foreign is stored; on 64-bit, page->private is used as xen_page_foreign. PG_private check is replaced by page->private != NULL on 32-bit for xen_page_foreign deallocation. On 64-bit, page->private is cleared unconditionally since {domid=0, gref=0} (xen_page_foreign can be 0) is valid. 4. fs/crypto/crypto.c stores a folio pointer in page->private, PG_private checks are replaced by page->private != NULL. 5. fs/erofs has two different uses: 5a. folio->private is used to form a reversed list of the outputs of readahead_folio(). readahead_folio_last() is added to output folios in reversed order, so that ->private is no longer needed. 5b. folio->private is used as an in-flight I/O counter. Convert the code to use folio_attach/detach/get_private() and add bias==1 to the counter to avoid folio->private being zero. 6. fs/nfs/write.c: folio refcount maintenance is in a bigger scope than folio->private. So folio_attach/detach/get_private() is not used. Nothing to change. 7. fs/f2fs uses attach_page_private() to first reset folio->private then immediately sets PAGE_PRIVATE_NOT_POINTER bit on it. Change it to use attach_page_private() to set PAGE_PRIVATE_NOT_POINTER bit directly to avoid folio->private == NULL gap inside set_page_private_##name(). 8. hugetlb uses folio_change_private(folio, NULL) without folio refcount maintenance. Change it to folio->private = NULL. After the above changes, PG_private ops are converted to page/folio->private ops. folio_test_fs_private() is added to check filesystem-only private data by excluding swapcache and hugetlb folios, because swapcache folios overlap swp_entry_t swap with ->private and hugetlb sets its own flags in ->private. Note === 1. KPF_PRIVATE is removed after PG_private is removed. 2. Documentation/mm/hugetlbfs_reserv.rst is outdated, so I did not remove PG_private related text. It should be rewritten. 3. PG_folio is planned to be set on every page from a folio in page_rmappable_folio(), so folios with any order (currently PG_large_rmappable is used to identify >0 order folios, but not order-0 folios) can be identified. Then vm_insert_*() can correctly reject all folios and rmap code will only see folios. Eventually, page_folio() will return NULL for non-folio pages by checking PG_folio, but before that all existing users that treat compound pages as folios will need to be converted. Tests === 1. allmodconfig build passed. 2. zsmalloc is tested using ext4 on a 1GB lz4 zram: 2a. zram load + zsmalloc compaction; 2b. concurrent zspage migration via memory compaction; 2c. confirmed that multi-page zspages actually formed. Details: https://github.com/x-y-z/linux-dev/blob/b4/remove-pg_private/test_zsmalloc.md 3. erofs is tested on images created with -C4096 and lz4hc, lzma, deflate, and zstd algorithms: 3a. cold read of all files, verify checksums match source; 3b. readahead + reclaim/migration race. Details: https://github.com/x-y-z/linux-dev/blob/b4/remove-pg_private/test_erofs.md 4. fscrypt is tested on software-encrypted ext4 with writes to exercise bounce pages. Details: https://github.com/x-y-z/linux-dev/blob/b4/remove-pg_private/test_fscrypt.md 5. f2fs is tested on an image with inline_data,compress_algorithm=lz4: 5a. INLINE_INODE — lots of tiny files; 5b. REF_RESOURCE + general writeback — buffered write churn with fsync; 5c. ONGOING_MIGRATION — force GC / page migration; 5d. ATOMIC_WRITE — atomic-write ioctl path. Details: https://github.com/x-y-z/linux-dev/blob/b4/remove-pg_private/test_f2fs.md (I did not run xfstests) 6. MM selftests passed. LLM use === Claude was used to form a concrete plan on what code needs to be changed and how to change them. The plan was reviewed by Codex until no issue was spotted. Plan is at: https://github.com/x-y-z/linux-dev/blob/b4/remove-pg_private/plan.md I then followed the plan to make code changes. I did bounce ideas with Claude how to change fs/erofs, since I did not like the original idea. After each change, I asked Claude to review my code and git commit message. I also asked Claude to give me test plans (see above). At last, Codex was used to review all patches. Comments and suggestions are welcome. Thanks. Assisted-by: Claude:claude-opus-4-8 Assisted-by: Codex:gpt-5 Signed-off-by: Zi Yan --- Changes in v3: 1. changed folio_test_fs_private() to check PG_swapbacked instead of PG_swapcache for excluding swapcache folios. Because folio->private and PG_swapcache are not set as a whole, making folio_test_fs_private() give false positive, whereas PG_swapbacked is always set for swapcache folios. 2. added __DEF_PAGEFLAG_NAME() to show __PG_folio instead of open code. 3. f2fs change is picked up at https://git.kernel.org/jaegeuk/f2fs/c/5ad9409a9533, mm-new currently does not have it, so the patch is sent for MM testing purpose. - Link to v2: https://patch.msgid.link/20260831-remove-pg_private-v2-0-3668159cd9e8@nvidia.com Changes in v2: 1. removed is_first_zpdesc() in patch 1 and open coded the checks. 2. fixed wording in patch 2's commit message and clarified page_private() also works when ring buffer's AUX page order is 0. 3. removed the empty loop in 64-bit gnttab_pages_set_private(). 4. clarified folio->private will be reset to NULL by fscrypt_free_bounce_page() in the commit message. 5. clarified why hugetlb needs to restore hugetlb_vmemmap_optimized. 6. renamed readahead_folio_reverse() readahead_folio_last() and reimplemented readahead_folio_last() by adding a new readahead_control private member, _forward, and a new helper __readahead_advance(). 7. added a bias, 1, to erofs I/O counter, so that folio->private stays non NULL between folio_attach_private() and folio_detach_private(). 8. converted more call sites to use folio_test_fs_private(). - Link to v1: https://lore.kernel.org/r/20260731-remove-pg_private-v1-0-142c97ba3562@nvidia.com --- Zi Yan (14): mm/zsmalloc: replace PG_private with pointer comparison perf/ring_buffer: stop using PG_private as AUX page high-order marker xen/grant-table: stop setting PG_private on pages for grant mapping fscrypt: stop setting PG_private on bounce page mm/hugetlb: use direct assignment instead of folio_change_private() f2fs: stop using PG_private erofs: mm/pagemap: add readahead_folio_last() to avoid folio->private erofs: use folio_attach/detach_private() instead of direct assignment mm/page-flags: check page/folio->private instead of PG_private mm/page-flags: introduce folio_test_fs_private() treewide: remove folio_set/clear_private() treewide: replace PagePrivate() with page_private() treewide: adjust comments on PagePrivate and PG_private mm/page-flags: remove PG_private Documentation/admin-guide/kdump/vmcoreinfo.rst | 2 +- Documentation/filesystems/vfs.rst | 6 +-- arch/x86/events/intel/bts.c | 3 -- arch/x86/events/intel/pt.c | 6 +-- drivers/md/md-bitmap.c | 6 +-- drivers/xen/balloon.c | 5 +++ drivers/xen/grant-table.c | 11 +++-- fs/ceph/addr.c | 8 ++-- fs/crypto/crypto.c | 2 - fs/erofs/data.c | 16 ++++--- fs/erofs/zdata.c | 13 ++---- fs/f2fs/f2fs.h | 8 ++-- fs/nfs/file.c | 4 +- fs/nfs/write.c | 2 - fs/proc/page.c | 1 - fs/ubifs/file.c | 8 ++-- include/linux/buffer_head.h | 6 --- include/linux/kernel-page-flags.h | 1 - include/linux/mm.h | 35 +++++++++------ include/linux/mm_types.h | 4 +- include/linux/page-flags.h | 43 +++++++++++++----- include/linux/pagemap.h | 60 +++++++++++++++++++++----- include/trace/events/mmflags.h | 3 +- include/trace/events/pagemap.h | 3 +- kernel/events/ring_buffer.c | 7 ++- kernel/vmcore_info.c | 1 - mm/huge_memory.c | 3 +- mm/hugetlb.c | 6 +-- mm/migrate.c | 3 +- mm/page-writeback.c | 3 +- mm/vmscan.c | 2 +- mm/zpdesc.h | 2 +- mm/zsmalloc.c | 24 +++-------- tools/mm/page-types.c | 2 - 34 files changed, 172 insertions(+), 137 deletions(-) --- base-commit: 5f4c0999b2bde1fbbba3c499208b415447ca4c7a change-id: 20260728-remove-pg_private-cfe926c7f83c Best regards, -- Yan, Zi