From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 20BC7C2D0CD for ; Mon, 19 May 2025 19:26:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2CE766B0082; Mon, 19 May 2025 15:26:52 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 256F96B0083; Mon, 19 May 2025 15:26:52 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 05E066B0085; Mon, 19 May 2025 15:26:52 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id D31F16B0082 for ; Mon, 19 May 2025 15:26:51 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id D9F5FC065C for ; Mon, 19 May 2025 19:26:53 +0000 (UTC) X-FDA: 83460639906.10.AF91B2D Received: from mx0b-00069f02.pphosted.com (mx0b-00069f02.pphosted.com [205.220.177.32]) by imf11.hostedemail.com (Postfix) with ESMTP id 77A3940005 for ; Mon, 19 May 2025 19:26:50 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2025-04-25 header.b=rQtxcOVU; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=Oq9Db3iz; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf11.hostedemail.com: domain of lorenzo.stoakes@oracle.com designates 205.220.177.32 as permitted sender) smtp.mailfrom=lorenzo.stoakes@oracle.com; dmarc=pass (policy=reject) header.from=oracle.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1747682810; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=jRwM8km0nKNLW7lKrSnr9Lv2UlKnuqGyOUJF55w+0Vg=; b=OFLkvTKJ09fp68FRuts7TAhFjWNfUtjy8Qm0L03gx3oRq64DaeZ/tcmm68dYrpK+GkyVwH aEm218lnq0QAG10la7ppFHaNney3VKUflW8Gsj7zPYqplyv2Vs9/iBwCyR1JxEB+JIrvN5 qwgwPpK5w01TSySlyUv/1uwNa/WDUwY= ARC-Authentication-Results: i=2; imf11.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2025-04-25 header.b=rQtxcOVU; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=Oq9Db3iz; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf11.hostedemail.com: domain of lorenzo.stoakes@oracle.com designates 205.220.177.32 as permitted sender) smtp.mailfrom=lorenzo.stoakes@oracle.com; dmarc=pass (policy=reject) header.from=oracle.com ARC-Seal: i=2; s=arc-20220608; d=hostedemail.com; t=1747682810; a=rsa-sha256; cv=pass; b=eaRzSg6EuXobdWMFStzhhk+PbGONP6/Xk5aIiUwTz4RAIk7dvFfr0LQFXHTPdDU11UqoKs W9JyTkgh4EjNF3LMWnpA7V/dA0OjGRWFF4QjhQWJSD+dOk1Sjx9JqTjFMu7RM5/ECb5ZlQ /o3pAHbO9LFl6lqM6UIGZqgnmVHpYEc= Received: from pps.filterd (m0246631.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 54JGMoSB026232; Mon, 19 May 2025 19:26:46 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=cc :content-type:date:from:in-reply-to:message-id:mime-version :references:subject:to; s=corp-2025-04-25; bh=jRwM8km0nKNLW7lKrS nr9Lv2UlKnuqGyOUJF55w+0Vg=; b=rQtxcOVU7+x2XluminHhSDIXaMDh8jiSbU hPpCrvWkOOgXD1YE2QVivFoTvRdBd3XlIKbwrKleFIvGLhFZq1OyqjYcxdpTn+/l K2jxAYSRMLKM5TSTO0i7CsO/Zj+Qsofdhq8ZMihAprJL3zMamCOnGrOvk9yfvW0B ylKazmxBtb9RQKtxwXWwKel8741Jdlq1rewo9njFiLKGrUKXh8UiH23C3Au2mD8H eSD0dQg81Fxx9AG+uEjJPmhJgVv+nTxlYv8TbuipXrTp8WWlbND+a3IHBTnB4iw+ 8FFEULrDli6rPgWdDJ7StVT6TOHs5hVUyEOmz8OqeUxPrwhL5Akw== Received: from phxpaimrmta03.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta03.appoci.oracle.com [138.1.37.129]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 46ph84kthv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 19 May 2025 19:26:45 +0000 (GMT) Received: from pps.filterd (phxpaimrmta03.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by phxpaimrmta03.imrmtpd1.prodappphxaev1.oraclevcn.com (8.18.1.2/8.18.1.2) with ESMTP id 54JIvAYG028887; Mon, 19 May 2025 19:26:45 GMT Received: from nam11-bn8-obe.outbound.protection.outlook.com (mail-bn8nam11lp2170.outbound.protection.outlook.com [104.47.58.170]) by phxpaimrmta03.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 46pgw73bs6-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 19 May 2025 19:26:44 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=XWUDAtkYSuD3EPyb9Wxjvr1R+N13byMTZdyZtm6vClpnWE+0lxG6ggNhd3jTIl4D3MUkrFQ7pkCkeUjYU556ibu7sNUogb7+xTg5HgbidPu1Nmduq/u2P6e45XNOdCzp+m3x4yhkcZgoNNk/1oOyyxZhhmXGP2RVULcGYdUXoAsSqyItKIXYmbh6cuNiAjcHuXXJy+TrWRQjxg+tfQhe2b37KHqHf/FWJmWWwimwNX7X7fbAKCWulspo2xg8TXBiXpxXcentgzakoyH51j1a05nth4PCasQ9POBcOAUFo+wtsVyC5f01zyLpsZw3VxA1t6C8VSVDnzDjHnFNZjIspQ== 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=jRwM8km0nKNLW7lKrSnr9Lv2UlKnuqGyOUJF55w+0Vg=; b=XXZ8sJ6ix0Qm2zXegDJWzOCL1edYgbGsAawl2FuuMuniLedgMNPvUTuqlw/oVCDD95FXuq42lo7bTVDQtMdcJWOe8JT8mygtHdpGOybfs58R6rNv30IG7X40ROnHKdqrMsLYhVJHYLy9DPxdIwUMvdwZ58XvkH6xAX6lt9RdhObVdSBGUXu83thV8nPfqiG+bT2GGmuj9YUo0EEEErqu/N36JdfgoU54awFeyX3jn0CuEmHYM92ukJMbkgKEYsEISj9H9c/QtumoSduBRbS9i37loBvCvWVQqe8QCraUlYimSiI/3xde95K0X9tT4/pAENig9UXRGFk7WZV7Z6VokQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=oracle.com; dmarc=pass action=none header.from=oracle.com; dkim=pass header.d=oracle.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=jRwM8km0nKNLW7lKrSnr9Lv2UlKnuqGyOUJF55w+0Vg=; b=Oq9Db3izWymKmXD2GooVcQV9+6ZvwUnP4HUw9lj4Tw4FepoFa02nWzuZNXEp0qynk329QTO2FUgJbTUhHicUCK2+xhVOkDuZfAAmCojrqZ3m9P88hXQXy7Qa4Fw+evZ7lDqhOO4uNGpvdUtZ1fURxMV6pSq31MM3yimSh1mWvbQ= Received: from DM4PR10MB8218.namprd10.prod.outlook.com (2603:10b6:8:1cc::16) by LV3PR10MB8010.namprd10.prod.outlook.com (2603:10b6:408:282::5) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.8746.29; Mon, 19 May 2025 19:26:42 +0000 Received: from DM4PR10MB8218.namprd10.prod.outlook.com ([fe80::2650:55cf:2816:5f2]) by DM4PR10MB8218.namprd10.prod.outlook.com ([fe80::2650:55cf:2816:5f2%5]) with mapi id 15.20.8746.030; Mon, 19 May 2025 19:26:42 +0000 Date: Mon, 19 May 2025 20:26:40 +0100 From: Lorenzo Stoakes To: David Hildenbrand Cc: Andrew Morton , Alexander Viro , Christian Brauner , Jan Kara , "Liam R . Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , Xu Xin , Chengming Zhou , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 3/4] mm: prevent KSM from completely breaking VMA merging Message-ID: <36ea1ee7-bb6c-47ff-a6cf-18f43fb23493@lucifer.local> References: <418d3edbec3a718a7023f1beed5478f5952fc3df.1747431920.git.lorenzo.stoakes@oracle.com> <3e2d3bbb-8610-41d3-9aee-5a7bba3f2ce8@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: LO3P265CA0024.GBRP265.PROD.OUTLOOK.COM (2603:10a6:600:387::19) To DM4PR10MB8218.namprd10.prod.outlook.com (2603:10b6:8:1cc::16) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DM4PR10MB8218:EE_|LV3PR10MB8010:EE_ X-MS-Office365-Filtering-Correlation-Id: 2d04778e-81ef-4acc-ee65-08dd970b15bb X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014; X-Microsoft-Antispam-Message-Info: =?us-ascii?Q?sXS1dMmvnb1KTvk+5d/YggExtF6eIMb3wkKkmbFowSG6GjLRRb93G3g9q57r?= =?us-ascii?Q?zRgoCEzBpN2yWAqBVwdYlDnkwF7wY+LzPyYzDhnyXsEMB9iLKlO8zrIFraQE?= =?us-ascii?Q?1RGkSpj40ujvoc+ZikRPKaOHpZ7pT95AlQfCU/xdNh2/a6KZ4vYIw6+Zp3Lb?= =?us-ascii?Q?oW+sEy3q32KT7teiFglgavsk+LZyVh18yZFR7UDLvoRpfRH2ewSCep+pRupM?= =?us-ascii?Q?wJhGE2YhdGcm+9UqQe16B+KfVYo+u+3T3W4rAaer0yyHcsoTtNpVNQNM505l?= =?us-ascii?Q?aqJpAJK3S/Vz9doj6AOH7djLdWKxSr0JiwS39Ij+KPl8VbPduPxxNE+Qu/uF?= =?us-ascii?Q?VGXWHVKXnym3YypvNUHX4OcN/wr3dnrE21U2qsk0trbFaMVGaMrOgl95iFBw?= =?us-ascii?Q?evY98uCV7RFP0ZUrNes3Ar6aftR77uvr/i1kq7s+HdXebzx9v17Uwtmta/JZ?= =?us-ascii?Q?Ajz5gOZd1qnnbOmCF+bX0SDqDudDhCDW26PV5vozXSZp2tQikdHU+y1HLD9n?= =?us-ascii?Q?9Cs/ahmqAaTn9qQbSdx5QpfxuVYYXXk9vFtDkH4w0LysGdqIXUp2fm8yYYlc?= =?us-ascii?Q?a9eiVUFwzz+3iwdfgdYKEzSFbDFgLCNgQIL0htPCPYCHeAJhASoTDwx1rd/t?= =?us-ascii?Q?8F/2EDjMLYmT2gl7rA0v5SKs40VzFljDrti2eLuNZvaN9NV+ktVe8sVg+coX?= =?us-ascii?Q?ckQpxYhk2LHhwAzAFvfsArRXHsHlJJPUxYean6RarhmfISAb5PcXS7HYzcWy?= =?us-ascii?Q?3tEp09Y49YDhQKhNXzxr1qKy69ybZFvA0N3F5BI5kO5nnp6eFnLg/Hq80rCD?= =?us-ascii?Q?IiBEA4gIf2s7oqJuY7LaBwxIaAuc5d5hmIgCVVFFBoeUTZkdl/Ff0jk5zWw0?= =?us-ascii?Q?NUAKftlk2fFPmSshBnSV/VE3AqN6W4rPtkODNuqBhPKEAxiSoC8CkNAdK6Cp?= =?us-ascii?Q?rXDjO7GS4ALyAvvrXnVpOdOWPPOd38alFS+FEMTEuvU5LqWRBcxqFO95PEhg?= =?us-ascii?Q?ztgrhOjjZRdNFX7mi+n6gg/DGlb2tFM1NO3pYYkBAmE6m/28USnw5+6XMh+d?= =?us-ascii?Q?XJwEIDoIYcj9LxtmZETKa3nom8wyMCO4O+5BHpZIxx73snl/sxwUaoGFygki?= =?us-ascii?Q?KaZztkHmHIuCrQdufBzduhbnL6CVFaxtpCRWtMPo09Y7lxakPRZIgxKRMl/g?= =?us-ascii?Q?rsKP/GbOHZJeG9pR9JjQH6tBFN6bdurOGIeSdpo6MFUscBPAXTPbS9qRrMxX?= =?us-ascii?Q?p/9/Y8oD+t3Fc3Axz/hMnHld08MYY72pOjNiXNUFc98GGUtsbYRF947myfTr?= =?us-ascii?Q?uzQgTIWnEshbmu6UkVAjCED+go8K+Y1JW9uA4Vw+5vck8pjLx0BR5EDuxy2u?= =?us-ascii?Q?sr4SSd3PZ5uqV4M0DgHi6lxzcup5NM3hKG4WckH+NEao4dEuCYp09kueI0n9?= =?us-ascii?Q?5uuVs+djH8E=3D?= X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:DM4PR10MB8218.namprd10.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(7416014)(376014);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?eiSyG/Gs9u44pEpsFD6OPie5HD19SvkjCLF4lAvmAsW0kGEtfSogWEBMAKC5?= =?us-ascii?Q?BeLdbXP2EQ6neEXJZqUzI+f2YWrIBWOIYmjcdDH76bXyZ5kmClkGq9qmuSJt?= =?us-ascii?Q?VcCZaJxePPoDM6MFD1pY5gwAu/FcozOWPcguV9fjmSwXPURhZ6nIn8f6wIq5?= =?us-ascii?Q?hcMKJFQtXmlYzK7j7XeTDbUXzjqlJdu2QrK/dSTpstGt6vqguv1hDJ+IRG8n?= =?us-ascii?Q?OkUKeY8eY+wm+aam0OaUFU9to8fFGtxmlx4KdZXclDGZiiyQwlXlYy0xo5m0?= =?us-ascii?Q?KUK46PGtn7s85zdNWwVDVMPlwyDCfU9da/3Hlu2QqOh8y8gZ8xkYb9eYMFKo?= =?us-ascii?Q?dZ719pRvs92zhmrgYCKmIhRxkkJ5rZKP6wNsEtg7yz61ITDmZcypDNL/Kzas?= =?us-ascii?Q?096v7YYdnUevXrrcSKx+1XAz+1144va2g84ycT0GMYcuANkWk8jWvOnWSY/4?= =?us-ascii?Q?UPJCGdwo5A/o9h1kOppKRcH3ZVZEkwu+bLvbttNGIMTVu54cuompsYViceIC?= =?us-ascii?Q?pH+0YVPzFiMsG5zzI98Hx23dS3509BV+00WGKob/SyCoG3nuVfyTluwSCsD0?= =?us-ascii?Q?9BqYNbTr5vCVpxaTZlcFkpdenyFPtttAKSgteurxdJDTC4guJR2gA7mceW7f?= =?us-ascii?Q?8cJUvP3P000peKC9QnA4nmdSvQMy1wzO4EF7G8MUdNGo36ShJGGOIX6o1A3Y?= =?us-ascii?Q?nV/cFu1Ps56CKMF1KQXcULzJ5falDOgGpMF2Lr/omS6dAc9v7Nk1c+alq1by?= =?us-ascii?Q?8cZLHBMS9ba5qN+UYsQ6q35zG0H9SDlz1iLbqH2RI7ctkkYisJLM4nySi0KD?= =?us-ascii?Q?OeVi5ctvGL+E5jU3beUdgM14jJPlKpDvwiknuGpl4cXxe5qmGisDVglxFshv?= =?us-ascii?Q?K5UYVrENugwXt0mO4WNiZZb2P2H6FtF9hUt6+N26PgmPd8DFlUjgyQ8F7nUz?= =?us-ascii?Q?7Na+9HBW9wB8omhh8fV3hUO+H3dUQykNB5hz8K8WlKBgKkwglMTmb3lWtmF1?= =?us-ascii?Q?sDBrxaciDyBlahtXDVT+/THvORZ6ntfnnQkMpM3b/mWI02ioWIY69j0lOnND?= =?us-ascii?Q?5XbG32H6ik7ZEHefTp8b+eWxYg/DyvsMOuIYBchaepH3XT9DSTsmtUvexL36?= =?us-ascii?Q?AfIwSabmjsbD2hq2j4unpzitC0BEToMSh1TR//U+mdNIr6gXt20XzXSsq7ms?= =?us-ascii?Q?uqxVnbYdv5tInIV57TSXX7l6cy5ffIAF1dzNoB41XIoRW5Vhxpw7B8Bpc8ru?= =?us-ascii?Q?CCFoVg9An37uFrV7S+6SOE9CzOUuhHbpWgozeE3EpqbW7iG4KPRKVHMsWT09?= =?us-ascii?Q?gDZi4C0V4QRFxwo0rpNpbpUKERqDKsGi7ySabFH2ymElC5ssNHzJVM1ujJnc?= =?us-ascii?Q?pQt+jpLThk4mN4p5OKuOmhLJD228mUcuOfSJ7qBkXyPrbMz26NFinOc819R0?= =?us-ascii?Q?uqfZJXxqBBNgK5LjcFJAmVpn1Ao9PP0PlrhMaTpB/AbJ8LNc86br5Rz5S2Ig?= =?us-ascii?Q?aAOCm0Qb6ev2JGcgbhi1XMc0KDBhQ14ZS2aY0PiVt0N67z4jNG6R7EVaeFJa?= =?us-ascii?Q?tF/hd7PNcFjrFez4kv76ggq1LohixuAEUfyi9o6mCGK9j5SEvmSIPGBb0JdS?= =?us-ascii?Q?kw=3D=3D?= X-MS-Exchange-AntiSpam-ExternalHop-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-ExternalHop-MessageData-0: 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 X-OriginatorOrg: oracle.com X-MS-Exchange-CrossTenant-Network-Message-Id: 2d04778e-81ef-4acc-ee65-08dd970b15bb X-MS-Exchange-CrossTenant-AuthSource: DM4PR10MB8218.namprd10.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 19 May 2025 19:26:42.2309 (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: 3qPLYieL+smi4z1DsXOjAEvn+Mequla4ESWNaERj1+Bz0Ojq8HNFTyobk/j6aRBCIQncEmQGwn8o/tqURtDzzyqCj4e/5HgM2HOmEU14X20= X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV3PR10MB8010 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-05-19_07,2025-05-16_03,2025-03-28_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=622 mlxscore=0 adultscore=0 phishscore=0 malwarescore=0 suspectscore=0 spamscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2505070000 definitions=main-2505190181 X-Proofpoint-GUID: v8rR5W4CYmk2A6qqOE0donkmTSVXk7GB X-Authority-Analysis: v=2.4 cv=YPSfyQGx c=1 sm=1 tr=0 ts=682b85f6 b=1 cx=c_pps a=WeWmnZmh0fydH62SvGsd2A==:117 a=WeWmnZmh0fydH62SvGsd2A==:17 a=lCpzRmAYbLLaTzLvsPZ7Mbvzbb8=:19 a=wKuvFiaSGQ0qltdbU6+NXLB8nM8=:19 a=Ol13hO9ccFRV9qXi2t6ftBPywas=:19 a=xqWC_Br6kY4A:10 a=kj9zAlcOel0A:10 a=dt9VzEwgFbYA:10 a=GoEa3M9JfhUA:10 a=TkEz_1ESsawaIVgwL8gA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-ORIG-GUID: v8rR5W4CYmk2A6qqOE0donkmTSVXk7GB X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNTE5MDE4MiBTYWx0ZWRfX3iKtum+dA9Nr BLbepXLqwpSWs5AmdavwNRNGLJtJrgkd2uwRwPEeMe/0Hvii21S+tJa1myFsC21rCYjQGn0BNsQ LczGfCWMaoNHjsVoInUVRpLNj4H10nK0uc6VLnzm8NMSiLtilsC520upRsP0hLPZAdYpBbnP5FX KTOzL3lJkZj5xI3/aNDXtA2Tx2nZN0yOnW1MgGMoxlN4JkAV7pHMhFeB6udK3TG2eXpY9+C6r/K w6tVNNhmsn1HzQB5OzO+ofrHYaiY6z8BkUyDl2OIWIOyU2DRHJ80HDSbwG4hlWuKJREwh31Um5N lBBC3PAs22w4ktzphJZwPUIIOwezbBdkPSA7kJiPt9hxw8yzLeernbUCU5iNNn5wzBHJZvUjlDU I2WCzKRBpd6imJqCk/DBlfUqWhnO4Z8Se/G5Yn1RqIhmbz2WOfhHQgGpVUL7Jo7f3PE7Vmun X-Rspamd-Queue-Id: 77A3940005 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 1rrnmfmddh54otxau4t9msqynjkn6u93 X-HE-Tag: 1747682810-791422 X-HE-Meta: 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 Yk99vpx8 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, May 19, 2025 at 09:11:10PM +0200, David Hildenbrand wrote: > On 19.05.25 21:02, Lorenzo Stoakes wrote: > > On Mon, May 19, 2025 at 08:04:22PM +0200, David Hildenbrand wrote: > > > > > > > > +/* > > > > > + * Are we guaranteed no driver can change state such as to preclude KSM merging? > > > > > + * If so, let's set the KSM mergeable flag early so we don't break VMA merging. > > > > > + * > > > > > + * This is applicable when PR_SET_MEMORY_MERGE has been set on the mm_struct via > > > > > + * prctl() causing newly mapped VMAs to have the KSM mergeable VMA flag set. > > > > > + * > > > > > + * If this is not the case, then we set the flag after considering mergeability, > > > > > + * which will prevent mergeability as, when PR_SET_MEMORY_MERGE is set, a new > > > > > + * VMA will not have the KSM mergeability VMA flag set, but all other VMAs will, > > > > > + * preventing any merge. > > > > > > > > Hmmm, so an ordinary MAP_PRIVATE of any file (executable etc.) will get > > > > VM_MERGEABLE set but not be able to merge? > > > > > > > > Probably these are not often expected to be merged ... > > > > > > > > Preventing merging should really only happen because of VMA flags that > > > > are getting set: VM_PFNMAP, VM_MIXEDMAP, VM_DONTEXPAND, VM_IO. > > > > > > > > > > > > I am not 100% sure why we bail out on special mappings: all we have to > > > > do is reliably identify anon pages, and we should be able to do that. > > > > > > > > GUP does currently refuses any VM_PFNMAP | VM_IO, and KSM uses GUP, > > > > which might need a tweak then (maybe the solution could be to ... not > > > > use GUP but a folio_walk). > > > > > > Oh, someone called "David" already did that. Nice :) > > > > > > So we *should* be able to drop > > > > > > * VM_PFNMAP: we correctly identify CoWed pages > > > * VM_MIXEDMAP: we correctly identify CoWed pages > > > * VM_IO: should not affect CoWed pages > > > * VM_DONTEXPAND: no idea why that should even matter here > > > > I objected in the other thread but now realise I forgot we're talking about > > MAP_PRIVATE... So we can do the CoW etc. Right. > > > > Then we just need to be able to copy the thing on CoW... but what about > > write-through etc. cache settings? I suppose we don't care once CoW'd... > > Yes. It's ordinary kernel-managed memory. Yeah, it's the CoW'd bit right? So it's fine. > > > > > But is this common enough of a use case to be worth the hassle of checking this > > is all ok? > > The reason I bring it up is because > > 1) Just because some drivers do weird mmap() things, we cannot merge any > MAP_PRIVATE file mappings (except shmem ;) and mmap_prepare). > > 2) The whole "early_ksm" checks/handling would go away, making this patch > significantly simpler :) OK you're starting to convince me... Maybe this isn't such a big deal if the KSM code handles it already anwyay. If you're sure GUP isn't relying on this... it could be an additional patch like: 'remove VM_SPECIAL limitation, KSM can already handle this' And probably we _should_ let any insane driver blow up if they change stupid things they must not change. > > -- > Cheers, > > David / dhildenb >