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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2E39AC55182 for ; Mon, 3 Aug 2026 21:05:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CC5D86B007B; Mon, 3 Aug 2026 17:05:28 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C77D26B0088; Mon, 3 Aug 2026 17:05:28 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B3E736B008A; Mon, 3 Aug 2026 17:05:28 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 823E06B007B for ; Mon, 3 Aug 2026 17:05:28 -0400 (EDT) Received: from smtpin08.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 0FDA71A080C for ; Mon, 3 Aug 2026 21:05:28 +0000 (UTC) X-FDA: 85061189136.08.964DBAC Received: from CY3PR05CU001.outbound.protection.outlook.com (mail-westcentralusazon11013044.outbound.protection.outlook.com [40.93.201.44]) by imf03.hostedemail.com (Postfix) with ESMTP id 284B220013 for ; Mon, 3 Aug 2026 21:05:25 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=okQQYAJn; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf03.hostedemail.com: domain of ziy@nvidia.com designates 40.93.201.44 as permitted sender) smtp.mailfrom=ziy@nvidia.com ARC-Message-Signature: i=2; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1785791125; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=XREpuZBe0n3lN7r7Qv8j0KvE4PoKPPmkt622YERMb9o=; b=WxaSJ74nUGDr1Hdr7Fy0raWYuItE8qTgcd5NOoaW1GpKXBwU/RbNCMeLKlwlIVXjKVF49C T1ZIuz2E9FuVBwCMy8za4sikWHv1r064KDd3a2QPujymeSwDIF6QvgubfhzNf1tvgyQoyP GFyZhgi+WvQ8KY8ANjvxcrBoPJ+Nkr8= ARC-Authentication-Results: i=2; imf03.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b=okQQYAJn; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector10001:i=1"); spf=pass (imf03.hostedemail.com: domain of ziy@nvidia.com designates 40.93.201.44 as permitted sender) smtp.mailfrom=ziy@nvidia.com ARC-Seal: i=2; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=pass; t=1785791125; b=DFaqb5u79/xf36SDihFra8+A5AXqtv6nynlcy/trqFXYApFbQbj16EuZlmhCwzTL3BAEo/ 24sd6QsrhkXHu9DnZNMamChzR/g6Z504TPOPZiZhX8fT8GvnfPbrYzijlOdYr/oA/52hyJ tsDHvzT/bEvvEORdGjPHQBNsxNWAVAA= ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=iRbqIDYTQckXuGlw1HQqIOepasaRaCLp/zES+D4zJ7faSFxvx+nr+GesT+3UxLAtbtJFid1Mu2aDOiCKreUX77HFqt6CCuShX2y6OEa2fTKf0qs4ZjDL1Q+RnHbSkyrVqj7iVX3zO62uloyUP4u6WArgwLnocRR3Nf4O9Z50ekG3st94SWLBSnoiR6f1KbaAL0vptSwoggZSTrT7gQISoqES2CA+p3UQAn6mZdp5j3PsmaiQiNmc4MzS3DB8m4RSWDsar9fH0L4f6ltpFy/UlU7ub4eznS80C7OYrEUvM2fuDYI7jDLyJ2P2i6xE5DzAjuI/+1eEqoDG+djvXswYYQ== 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=XREpuZBe0n3lN7r7Qv8j0KvE4PoKPPmkt622YERMb9o=; b=Acnk/q9/q+zOBPHJy/Ss3VuhU81yyjIxSMyYneDrCAwprbpVLDyQvXkk3iGhxvVPSQxZEd/aQPPRzitoG9bAtojD5oM9ON+Hiokq+Vy825ySJFD+vfWMAcA05yGLo69Cb/fUi9tsmOu+Fs8MQWrVnN6d4aUONB3ToaXQYLMfcod2FuoxYzMNW8S+lAYC/S1fkIhhcc7aIJBwJMz4uTokKzzgpOP8C0aPB5BfwGn5eOs+MhDSiTWWXXw0TkbRplb3N80tbfQz02y29C1ErcpdWQN4n63Ue/PFtU+LaV8TY9mVTS6U1ewLFJVMqjtmzIwSKn8Ygk/mlomx/z4tV1Awzw== 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=XREpuZBe0n3lN7r7Qv8j0KvE4PoKPPmkt622YERMb9o=; b=okQQYAJnam8O0eeLuY8Eu8qgZZv/ZkyPIW/Mkk9RHxETM2FklZ0Jjyc/SYbLYemd1zePuPK1soXGxUToHfyXtOikRgi08+MWKoGnWfhXpI3g2EZJ8EslIy8NdvaOvlGFPtHcRhIN/y0gkjcsB21LBAfVYv/pXCHpoel8UYvksFEGhmWYqbidnrC8kQOdbc/efyx1tNgvapHsjIh6QLuoRGfDWzboz3h4epBlw581LanjlmTShO6i/OelbzOuB6mHL8E0o4QRvFr9zcPQqa/uy1NZo5T9QDLLEm1Yj64W43TgOXA+S8VDU4lnndbn+ipnyS+P+YfNmC2oJHn03feZJQ== Received: from IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) by DM4PR12MB9735.namprd12.prod.outlook.com (2603:10b6:8:225::8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.270.17; Mon, 3 Aug 2026 21:05:17 +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 15.21.0270.017; Mon, 3 Aug 2026 21:05:17 +0000 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Mon, 03 Aug 2026 17:05:12 -0400 Message-Id: Cc: "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" , "Qi Zheng" , "Shakeel Butt" , "Kairui Song" , , , "Minchan Kim" , "Sergey Senozhatsky" To: "Johannes Weiner" From: "Zi Yan" Subject: Re: [PATCH RFC 01/14] mm/zsmalloc: replace PG_private with pointer comparison X-Mailer: aerc 0.21.0 References: <20260731-remove-pg_private-v1-0-142c97ba3562@nvidia.com> <20260731-remove-pg_private-v1-1-142c97ba3562@nvidia.com> In-Reply-To: X-ClientProxiedBy: CY5PR19CA0061.namprd19.prod.outlook.com (2603:10b6:930:69::7) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA0PR12MB8374:EE_|DM4PR12MB9735:EE_ X-MS-Office365-Filtering-Correlation-Id: 345d2414-cf16-4c92-732c-08def1a2eb95 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|23010399003|376014|7416014|18002099003|22082099003|5023799004|4143699003|11063799006|10067099003|56012099006; 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)(366016)(1800799024)(23010399003)(376014)(7416014)(18002099003)(22082099003)(5023799004)(4143699003)(11063799006)(10067099003)(56012099006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?R1E0Qzg5NEJiVENYck4vZTdxNHl5TlRYazNoTUZuOU80ai9NT2xDUnpoSjl3?= =?utf-8?B?Y1IrMVRRenVad1ZVbmhHZHVSUGlDczB3Vk1VNmdnRmtVMFFmbm5sN1dkM3Zu?= =?utf-8?B?Ri9mTlNNUUl5STV5cVloVVphekYyTjBZTjVmeGlYNDE4eEFGendJb0VwL2Iw?= =?utf-8?B?YmUzaWhhR3NYc1hyMGdpOWtIOElvS2hnZS9LcTQxb0tLQkNJcUhiYkNkbFA0?= =?utf-8?B?QlorQmROcENEaUlkUUVURXBoSit6UVhkampON1RWYndZOWZCeWlFUVliNC9n?= =?utf-8?B?ZnE0V3VvTU9yR2ZvajlnTnF3dTdJVk5BL0hkaGtaM3g3dHIxQzlOWXdoWDJu?= =?utf-8?B?Tk85bkhmTVdJZWVhWmNud1RWUlUyOVZBdFQvNFNrb0ZPb1JEYmRxbk91a3Fn?= =?utf-8?B?MnVkMWtxUWNkbFo3R053Wi9GT0xFcGV0WTh4NVArV2hUem9qcE0vaEI5T2x4?= =?utf-8?B?UDEvc3J6Yk9LZXdiVE9tQXB6dzFYd1dMUWI5aGVPOWk2bk13aU9xbVZpVCtQ?= =?utf-8?B?UDg3d0xwb2MxaFRnamxsbHI1Q2lNOVdCcE54U3EyOHhMYmtqN05XRmhMaTZU?= =?utf-8?B?MHFXM2FGdVFPaW41TXlSNnNheUpzaXVqTUtpVFJ3dGhSM09rMVlzMms1Ym1V?= =?utf-8?B?SWw5ajd3UlJpRkM4YlNValBKVGlCUXJLTUVuakxoWnZqeHhydXcvcXc4ci9t?= =?utf-8?B?ZTVtWkcvVnZ0aDcyU05tQnVvemZCTUxqazVOUm1oUEh0Y2Nwc1YvWk9Tdk9I?= =?utf-8?B?cnFwVVlYQmlXZU9Ea2Y4L3RDQUZ1ckJmbzlyeFRuVC9lNEpycGRYTllYWlo1?= =?utf-8?B?czNjMjJGKzR5MFNRNmlCVmFJSk1jRTFJRHFYelF5OXZsNy93ODVEU1UwRnhn?= =?utf-8?B?QjFPQmRyTnVCeVl4dTdxYzQ2cW5vYm1VRWR1SlIzRk1zTFlmZU52SmNOMDhh?= =?utf-8?B?aFBFTURhUGQ1MDlqZDZSVWF0MEZaWWdic2xpZFFLNkl0QUhMZXduTm5OelVW?= =?utf-8?B?UFRGSi9PejZ5cmx2SGRhM3VFK082Q2g4TlgrZWgxc255bjRBMFZ1QThlM0sw?= =?utf-8?B?YXJVeThzUENRRG81MGQvVXF1bU5vRUVBcEN4KzBPdnVDTzJLZ3ByU25UKzcr?= =?utf-8?B?dHFMd0RscmtPaG1PWWtJZ3g0UmJnMmkrQnFTc2VKL0I0bjRLUnovNUJ6YUpn?= =?utf-8?B?YjZyb2tWLzhJUmJTcThlZkZnem9lQmV6NmZDdTdRdnRIanE4VlhkdGtjQ01p?= =?utf-8?B?WXdDZ1hVTzlOeVBNQm9ZOVZSUTRMRFJzY3pSVWVBY004OGpVWW1Ra0xpV2k1?= =?utf-8?B?NkF1d3hIcUFhWkdyWDdaTjBaQUNGV1NpQWM4ME1LL1ZBMjZJM0NEUDlTT2dM?= =?utf-8?B?YlgrOUkxUXFwZDhhZTN3NzFFRUVJVmwvcGhTbVl6VTY3a3lNZUxqVzJHb2Yv?= =?utf-8?B?YmZ3cjVKd3B3UTdhUkF5VFlZT1VmbjFsT3RNckh2VnMxZUtYaWVTSW1HOWtK?= =?utf-8?B?enUzNTFLV2ZFM1FwQUJWaCtJRUxRQzdqVGxFV2pQaXBWWWtHTlhCeFI1K0NT?= =?utf-8?B?V3MxQitmU0xEbUtnUTdLUndscHM1b0RvR2F6QTZ0MXU5a0lzQkp1a3oyWU1V?= =?utf-8?B?WGIvVTk3NWl3aDI3Wktzbk9JcVlQb0EraVFxMFdwemRqZ3MvcnFrZm1yUWRN?= =?utf-8?B?UGZKakxzNnJYak1yN2VNcHdtRnl2SU5UVkZuOXhmeno2RFZjdVNISThLaWts?= =?utf-8?B?Q0J5UW5hM1dzcFBSUDJ2NkVxaGlhTFVyOXJGQ0g4eUlYZjdrQXFzL2dZbXN5?= =?utf-8?B?T0Ircjd6QmFucHZLSkc4NlFRL1I1bHpTZm83L2krTVptaU4yMUlETzZhTmw3?= =?utf-8?B?eXI1TVExNDN6bEtPWjBycFk2bTZ1MXh2aWovYXdBMC9obzBNQW84bDV6RlFa?= =?utf-8?B?RW50anRnRFVWTGxNSmkzcHBERzFxVTJlZHR0L0VzUGRpVXgyNGhrYlJONGdJ?= =?utf-8?B?WnpuSnNYckE1ZzdYOUxCeHZxRnFiVXlpZFBXSUMyTVdOY1FjQmI2NW9SejBj?= =?utf-8?B?bldDWERKUi9MWXdGdDAzeUw4emE2V3FjdklMcURrQWxydzN4K1pSb0JBeFJN?= =?utf-8?B?UmdvelpLMFlsRHRlQkZwRFFBTUpSaTRINGQ3UXdWeFNsY3ZyZk40MXN2VWk5?= =?utf-8?B?cW0ydGNlaGZmYWcraldkbk8xdTB6TUJqQUpWaER0RVBTSzJmYUlucG9DTGto?= =?utf-8?B?VzFxcEJnQjdFellZWUd5bkF5bk1YempsRjN3ODdFTEFUSlByZWQ3UmZQcTNE?= =?utf-8?Q?pYH0bG2+wR08arRE8B?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 345d2414-cf16-4c92-732c-08def1a2eb95 X-MS-Exchange-CrossTenant-AuthSource: IA0PR12MB8374.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 03 Aug 2026 21:05:17.4566 (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: eFM3iVQk3BUJTZKA5I94XWwBcEB83owOnF4bp3XOOEbRpzMszk6j7fcUH8U9j1Xd X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB9735 X-Stat-Signature: uyzeegm46xqm7n7xm51skku5t6nm365g X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 284B220013 X-HE-Tag: 1785791125-90112 X-HE-Meta: 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 DQapC/j+ 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon Aug 3, 2026 at 12:53 PM EDT, Johannes Weiner wrote: > On Mon, Aug 03, 2026 at 11:34:35AM -0400, Zi Yan wrote: >> On Mon Aug 3, 2026 at 11:04 AM EDT, Johannes Weiner wrote: >> > On Fri, Jul 31, 2026 at 10:13:24PM -0400, Zi Yan wrote: >> >> zsmalloc uses PG_private to indicate first zpdesc in the zspage chain= . >> >> Replace it with zpdesc->zspage->first_zpdesc =3D=3D zpdesc. The check= , >> >> is_first_zpdesc(), is only used in VM_BUG_ON(), so performance impact >> >> should be negligible. >> >>=20 >> >> It prepares for a future commit that remove PG_private. >> >>=20 >> >> No functional change intended. >> >>=20 >> >> Assisted-by: Claude:claude-opus-4-8 >> >> Assisted-by: Codex:gpt-5 >> >> Signed-off-by: Zi Yan >> >> To: Minchan Kim >> >> To: Sergey Senozhatsky >> >> To: Andrew Morton >> >> Cc: linux-mm@kvack.org >> >> Cc: linux-kernel@vger.kernel.org >> >> --- >> >> mm/zpdesc.h | 2 +- >> >> mm/zsmalloc.c | 15 +++------------ >> >> 2 files changed, 4 insertions(+), 13 deletions(-) >> >>=20 >> >> diff --git a/mm/zpdesc.h b/mm/zpdesc.h >> >> index b8258dc78548d..4fd81c2e80769 100644 >> >> --- a/mm/zpdesc.h >> >> +++ b/mm/zpdesc.h >> >> @@ -26,8 +26,8 @@ >> >> * with memcg_data. >> >> * >> >> * Page flags used: >> >> - * * PG_private identifies the first component page. >> >> * * PG_locked is used by page migration code. >> >> + * The first component page has zpdesc->zspage->first_zpdesc =3D=3D = zpdesc >> >> */ >> >> struct zpdesc { >> >> unsigned long flags; >> >> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c >> >> index 8204b76f78308..e8ef227624efa 100644 >> >> --- a/mm/zsmalloc.c >> >> +++ b/mm/zsmalloc.c >> >> @@ -290,11 +290,6 @@ struct zs_pool { >> >> atomic_t compaction_in_progress; >> >> }; >> >> =20 >> >> -static inline void zpdesc_set_first(struct zpdesc *zpdesc) >> >> -{ >> >> - SetPagePrivate(zpdesc_page(zpdesc)); >> >> -} >> >> - >> >> static inline void zpdesc_inc_zone_page_state(struct zpdesc *zpdesc) >> >> { >> >> inc_zone_page_state(zpdesc_page(zpdesc), NR_ZSPAGES); >> >> @@ -478,7 +473,7 @@ static void record_obj(unsigned long handle, unsi= gned long obj) >> >> =20 >> >> static inline bool __maybe_unused is_first_zpdesc(struct zpdesc *zpd= esc) >> >> { >> >> - return PagePrivate(zpdesc_page(zpdesc)); >> >> + return zpdesc->zspage->first_zpdesc =3D=3D zpdesc; >> >> } >> > >> > There are two checks: get_first_zpdesc() and obj_allocated(). >> > >> > static struct zpdesc *get_first_zpdesc(struct zspage *zspage) >> > { >> > struct zpdesc *first_zpdesc =3D zspage->first_zpdesc; >> > >> > VM_BUG_ON_PAGE(is_first_zpdesc(first_zpdesc), zpdesc_page(first_zpdes= c)); >> > return first_zpdesc; >> > } >> > >> > If you expand the helper, this seems kind of pointless now: >> > >> > first_zpdesc =3D zspage->first_zpdesc; >> > VM_BUG_ON_PAGE(first_zpdesc !=3D first_zpdesc->zspage->first_zpdesc, = ...); >> > >> > Mayyybe it could make sense to assert first_zpdesc->zspage !=3D >> > zspage. But that's a separate issue that the previous check didn't >>=20 >> Usama has the same comment about this. >>=20 >> > necessarily catch. And might not be worth checking, considering how >> > trivial create_page_chain() is. >> > >> > In any case, it doesn't seem worth keeping the check as-is. >> > >> > And with one caller remaining, you could delete the helper and inline >> > that expression into the check in obj_allocated(). What it does now is >> > self-explanatory; it doesn't need another name like that PagePrivate() >> > check before did. >>=20 >> How about the version below? Basically, I made is_first_zpdesc() more >> straightforward for backpointer checking and first_zpdesc checking. >>=20 >> 1. get_first_zpdesc() needs the backpointer check; the first_zpdesc chec= k is >> meaningless, since the assignment is done above. >>=20 >> 2. obj_allocated() needs the first_zpdesc check; the backpointer check >> is meaningless, since the zspage is from get_zspage(). > > Personally, I'm not a fan of "super predicates" where individual > conditions are only useful for only some of the callsites. They tend > to become obstacles to understanding the code and lead to subtle bugs > when developers misunderstand context requirements. > > IMO it's better to just precisely express what each callsite > needs. Only factor a common helper if it's actually the same. OK. The below is what I come up with like you suggested. I realize that there are actually two things to check for a zspage chain: 1. all zpdescs point to the same zspage, 2. for a ZsHugePage, handle is only in the first zpdesc. get_first_zpdesc() checks 1 and obj_allocated() checks 2. So I added comments to them. >From 4567d7d9cc8c84d5c05de92ee8905f4c5e5cf67f Mon Sep 17 00:00:00 2001 From: Zi Yan Date: Tue, 28 Jul 2026 22:41:23 -0400 Subject: [PATCH] mm/zsmalloc: replace PG_private with pointer comparison zsmalloc uses PG_private to indicate first zpdesc in a zspage chain. It is equivalent to check zpdesc =3D=3D zspage->first_zpdesc. Replace is_first_zpdesc() with zpdesc =3D=3D zspage->first_zpdesc in obj_allocated(= ). For get_first_zpdesc(), first_zpdesc is from zspage->first_zpdesc, so replace is_first_zpdesc() with first_zpdesc->zspage =3D=3D zspage, the seco= nd requirement of a zspage chain, where all zpdescs point to the same zspage. is_first_zpdesc(), is only used in VM_BUG_ON_PAGE(), so performance impact should be negligible. While at it, change VM_BUG_ON() to VM_WARN_ON_ONCE_PAGE(). It prepares for a future commit that remove PG_private. No functional change intended. Assisted-by: Claude:claude-opus-4-8 Assisted-by: Codex:gpt-5 Signed-off-by: Zi Yan To: Minchan Kim To: Sergey Senozhatsky To: Andrew Morton Cc: linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org --- mm/zpdesc.h | 2 +- mm/zsmalloc.c | 24 ++++++------------------ 2 files changed, 7 insertions(+), 19 deletions(-) diff --git a/mm/zpdesc.h b/mm/zpdesc.h index b8258dc78548d..4fd81c2e80769 100644 --- a/mm/zpdesc.h +++ b/mm/zpdesc.h @@ -26,8 +26,8 @@ * with memcg_data. * * Page flags used: - * * PG_private identifies the first component page. * * PG_locked is used by page migration code. + * The first component page has zpdesc->zspage->first_zpdesc =3D=3D zpdesc */ struct zpdesc { unsigned long flags; diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 8204b76f78308..b87679757e7b1 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -290,11 +290,6 @@ struct zs_pool { atomic_t compaction_in_progress; }; =20 -static inline void zpdesc_set_first(struct zpdesc *zpdesc) -{ - SetPagePrivate(zpdesc_page(zpdesc)); -} - static inline void zpdesc_inc_zone_page_state(struct zpdesc *zpdesc) { inc_zone_page_state(zpdesc_page(zpdesc), NR_ZSPAGES); @@ -476,11 +471,6 @@ static void record_obj(unsigned long handle, unsigned = long obj) WRITE_ONCE(*(unsigned long *)handle, obj); } =20 -static inline bool __maybe_unused is_first_zpdesc(struct zpdesc *zpdesc) -{ - return PagePrivate(zpdesc_page(zpdesc)); -} - /* Protected by class->lock */ static inline int get_zspage_inuse(struct zspage *zspage) { @@ -496,7 +486,8 @@ static struct zpdesc *get_first_zpdesc(struct zspage *z= spage) { struct zpdesc *first_zpdesc =3D zspage->first_zpdesc; =20 - VM_BUG_ON_PAGE(!is_first_zpdesc(first_zpdesc), zpdesc_page(first_zpdesc))= ; + /* the first zpdesc must point back to this zspage */ + VM_WARN_ON_ONCE_PAGE(first_zpdesc->zspage !=3D zspage, zpdesc_page(first_= zpdesc)); return first_zpdesc; } =20 @@ -833,7 +824,8 @@ static inline bool obj_allocated(struct zpdesc *zpdesc,= void *obj, struct zspage *zspage =3D get_zspage(zpdesc); =20 if (unlikely(ZsHugePage(zspage))) { - VM_BUG_ON_PAGE(!is_first_zpdesc(zpdesc), zpdesc_page(zpdesc)); + /* only first zpdesc holds the handle */ + VM_WARN_ON_ONCE_PAGE(zspage->first_zpdesc !=3D zpdesc, zpdesc_page(zpdes= c)); handle =3D zpdesc->handle; } else handle =3D *(unsigned long *)obj; @@ -848,9 +840,6 @@ static inline bool obj_allocated(struct zpdesc *zpdesc,= void *obj, =20 static void reset_zpdesc(struct zpdesc *zpdesc) { - struct page *page =3D zpdesc_page(zpdesc); - - ClearPagePrivate(page); zpdesc->zspage =3D NULL; zpdesc->next =3D NULL; /* PageZsmalloc is sticky until the page is freed to the buddy. */ @@ -1001,8 +990,8 @@ static void create_page_chain(struct size_class *class= , struct zspage *zspage, * 1. all pages are linked together using zpdesc->next * 2. each sub-page point to zspage using zpdesc->zspage * - * we set PG_private to identify the first zpdesc (i.e. no other zpdesc - * has this flag set). + * The first zpdesc has its zspage->first_zpdesc set to itself, no + * other zpdesc has this set. */ for (i =3D 0; i < nr_zpdescs; i++) { zpdesc =3D zpdescs[i]; @@ -1010,7 +999,6 @@ static void create_page_chain(struct size_class *class= , struct zspage *zspage, zpdesc->next =3D NULL; if (i =3D=3D 0) { zspage->first_zpdesc =3D zpdesc; - zpdesc_set_first(zpdesc); if (unlikely(class->objs_per_zspage =3D=3D 1 && class->pages_per_zspage =3D=3D 1)) SetZsHugePage(zspage); --=20 2.53.0 --=20 Best Regards, Yan, Zi