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 957CDC79FB7 for ; Wed, 9 Sep 2026 13:27:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id AE93A6B0093; Wed, 9 Sep 2026 09:27:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AC0A46B0095; Wed, 9 Sep 2026 09:27:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 98BB66B0096; Wed, 9 Sep 2026 09:27:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 65CCE6B0093 for ; Wed, 9 Sep 2026 09:27:16 -0400 (EDT) Received: from smtpin13.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 76A7EC0205 for ; Wed, 9 Sep 2026 13:27:15 +0000 (UTC) X-FDA: 85194300030.13.F1A93BA Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf06.hostedemail.com (Postfix) with ESMTP id B006218000D for ; Wed, 9 Sep 2026 13:27:13 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=R6GXnFu8; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788960433; b=r/kC2qvSgw4FZPzKM2A/jCp2Hsly7xXRNX9k0LwE8DoGjFHtP+s+p5EP9PBUVJvfxy5mxx rMsFaK9SxMo92KcpyTwPS1yxSVCuDTwAXXdweT0lTx7SWfiBmjfKdyRcPyRf/uKUsWaTZY oMcKUPBhjNJsAv2/PVNZsYHMyh+nRMk= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=R6GXnFu8; spf=pass (imf06.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788960433; 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=RS94z3rEAyu0Bjc7OED+9UH7pawFKgmuE2czeP57phU=; b=JmXIdY+cDIVuuwJ5CvHfEoAARqs4VIQqe++kFZ7l4ZPbseA2QjCvyK00V79pp8nBAjjB0U GRQoY7vYtj1erLpQnFDlSJdA7sFePQkVHh+vZIk3KYkqttZRAxr/BoZ/SLeZNUbU45txRA giFrHuW3LXqiQSY5YSKQMq3kF0dXEKY= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id EB9CB60216; Wed, 9 Sep 2026 13:27:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E3F461F00A3A; Wed, 9 Sep 2026 13:27:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788960432; bh=RS94z3rEAyu0Bjc7OED+9UH7pawFKgmuE2czeP57phU=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=R6GXnFu8mwOitVsLDqixKEjX05Dbn1yn80ABydAZ+iG2csBdc8qLDLiGZms52yQeR Qo+SJ0uhkIYEpcfkw04tMaGvcHiDQVghyck05icc7KQfuX9Es4+6ioM9vooN+FEKQQ d+YN4rgalDXNOhmnUS5K9vdKMQe6bEnBQ4Z7n3LZifCPT9hJpV/znd3fhrBwxMAOQL aPZom5TZTUdifDvkaRiU0X2HGDEnKKe49JnL8wsqRi7XQqHbewo9yN7iEUERXgPTKQ FFw9nlGfN21z/sYGUGQ0m8lqNHXt7GR/TqZoVXo0il69z8Io36XBvjmmg76H0dDpy7 MFkQJM7oq/52A== Message-ID: <6a465ff3-21ff-435d-963b-385e7e5174fa@kernel.org> Date: Wed, 9 Sep 2026 15:27:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 08/14] erofs: use folio_attach/detach_private() instead of direct assignment To: Zi Yan , "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, Gao Xiang , Chao Yu , Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li , Chunhai Guo , linux-erofs@lists.ozlabs.org References: <20260907-remove-pg_private-v3-0-6ae22f9d9272@nvidia.com> <20260907-remove-pg_private-v3-8-6ae22f9d9272@nvidia.com> <5b02f5de-00b6-4f8e-9e30-6d0acedafaf4@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: B006218000D X-Rspam-User: X-Stat-Signature: 4dihiueii8bgecjhdzm4gu6qi9o4ok3b X-HE-Tag: 1788960433-471953 X-HE-Meta: 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 /emBzW26 REsbGQlAt0cdGffUOcjnTUPxiq1agjFHFRo/KEvuVFX/le6tZi3XB91+jtqa3YgD5gTBWQAFaAA8lNTKPiKaabv73RXxEU4Ffl90lCoreC0uS1AKDGt/fxNZOJznYRH2WV4uPAuTtB8/yjYuZhv8TY+sHZV7DKk/kBWnTSceKlJRar81rWgSDzGtmwdoWv6HYSoVmGX865byrYjf3k2jva5kxw55LoKy8l9joV2Nxv9WY8XV0VfgkRujt33iIL8iTyj5Fs0EpyLYWQQiQr0m6OVWdfYiQLlbUnw2exh8h/cddShjBlOq/MV483Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/8/26 19:19, Zi Yan wrote: > On Tue Sep 8, 2026 at 12:13 PM EDT, David Hildenbrand (Arm) wrote: >> On 9/8/26 04:56, Zi Yan wrote: >>> erofs_onlinefolio_init/split/end() use folio->private without setting >>> PG_private or increasing folio refcount and it works. But after PG_private >>> is replaced by checking folio->private in a future commit, it can break >>> folio_expected_ref_count(), since the folio has private data without >>> elevated refcount. Change them to use folio_attach/detach_private(). >> >> Freezing the folio will properly work I assume, as we'd always freeze with that >> refcount in mind or remove the reference (detach private) early? > > Yes. > >> >> I'm thinking of folio_ref_freeze() in __folio_freeze_and_split_unmapped(). >> >> Or is the ref only very short-lived either way such that we don't care? > > The folios here are locked since they are in the process of > readahead, which requires all folios locked. So they are not reachable > from folio split code. In additio, the private is deatched and ref is > decreased before the folio lock is dropped. It would be great to summarize this interaction with core-mm (migration/split) in the patch description. -- Cheers, David