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 5F23F1125823 for ; Wed, 11 Mar 2026 13:57:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 58ADA6B0005; Wed, 11 Mar 2026 09:57:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 538F96B0089; Wed, 11 Mar 2026 09:57:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 419E36B008A; Wed, 11 Mar 2026 09:57:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 205AF6B0005 for ; Wed, 11 Mar 2026 09:57:24 -0400 (EDT) Received: from smtpin07.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id AD61E139688 for ; Wed, 11 Mar 2026 13:57:23 +0000 (UTC) X-FDA: 84533934366.07.D2EB2E9 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf18.hostedemail.com (Postfix) with ESMTP id AA1241C0011 for ; Wed, 11 Mar 2026 13:57:21 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ThdfCY7u; spf=pass (imf18.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 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=1773237441; 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=9X+P6xh1RRwRS0BS6v9pl8/dn7CGCNu57hnaPYTTGMI=; b=QShRb5TFwuqrHDQSBRkR3xzQBYUlF2Ubj2Kn/LHNV2Usl0aNlxuXIPxeL/g7iCJ3h9yI4R mT5mfP23zoARXv5ky3/PGxszThUS9TuXyF1O9zAtX3HwSSB8PLE8h8lzrRpLkjvkMQbiqj yc7Tq9JR25bcSXTXFs8WKLPoRPh3bvM= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ThdfCY7u; spf=pass (imf18.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1773237441; a=rsa-sha256; cv=none; b=0hGylXDaIor6tZeeHohXBhwhVfiOIbIWr1649GdfJsYh1Hefl6QP3u+TZF4V6IUY+Gr8Qi AEEFpSTQYqueOF/29S5jqbokr6NInG5XXMgS1IC2feie/c/uHiuDM3IaFE6KEGp+4Eny2S J9SFyMOmz5ekQ9lOW6Rh+vKn982opKw= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 4AD68439D6; Wed, 11 Mar 2026 13:57:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 453AFC4CEF7; Wed, 11 Mar 2026 13:57:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1773237440; bh=FufJY4hvTCH40qFLkuAK2NFVy71xbnZqN98KKnD052s=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ThdfCY7uv+bCmSMV0tDzf6VHVA6Jdq9XCJ+RRUYsmyC8OV3SYwg2agPWYsoJkT1hs NXctXTMpjZMDBVaWzYrLsQc6ibzOn3JMEYneFHA4YJQXdbpwuAj8iW7a9mRHJCZENv ycv8hQgqpCPRxCUIVE1fi+2sQs0DVfe8+4gGTt1JfujcfyT41J/2E9fkU/74c9cRk2 iYjH1+abmn4GcSECttN30LIj2KDjX030XG6Gh6z2GWivGTXlCcRH6+3oaCkAjF258i +cWKoMyEugZ2xSLLklhvgVw5kze4EAvzLhM4NZSxN2F5zgg5B42A3x0Qj7ThFMNhOY MnAtuI1Wr829g== Message-ID: <6678200f-92dc-4ab4-8bc0-d956bcea528a@kernel.org> Date: Wed, 11 Mar 2026 14:57:15 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: migrate: transfer large_rmappable flag in folio_migrate_flags() To: Zi Yan Cc: Usama Arif , Andrew Morton , npache@redhat.com, willy@infradead.org, linux-mm@kvack.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, hannes@cmpxchg.org, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, linux-kernel@vger.kernel.org, kernel-team@meta.com References: <20260311132342.3193160-1-usama.arif@linux.dev> <46edc7f1-f97e-4ff3-bf11-a56feb8e33b4@kernel.org> <1DA53E52-795E-4057-81F5-E39B85D7CF05@nvidia.com> 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: <1DA53E52-795E-4057-81F5-E39B85D7CF05@nvidia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: pe7bbht8cenyuqfer5g9xt9b673uia8q X-Rspamd-Server: rspam09 X-Rspam-User: X-Rspamd-Queue-Id: AA1241C0011 X-HE-Tag: 1773237441-508203 X-HE-Meta: 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 MvOFEkl7 gQOgC4175xHtpvSwKq7At9m2OLPEwxilXPCWzZs2ymKgw2yJEXhH8KlzTxQJO+tMyfFKg0JlInA3IiF9PtMbS07ssXTY/7YgTge3fVJxUM+/HIkxL5RJlxuh+56JHQLmUgYn2VJQveZ+UDqraREMcwy1HixyUnsjucq2g4w2VNy9efOiEc+JIQuaivYbU+d3zBePphMeNXQm7BkDzb8n/p26rQUOIQdzRH7W67D2ML6PtAKCSgLVM96zM9jcHhthTGAkbXPL6hUrhNFC/np502iIrppn4tx5KpbDQVmOHwgrIEwQC/8yayajtuT2SvHqIz+Ki0g03EMVazy1rud1M/d0nRUJRW/czylH6hmRvIQVzzAmK/x2PDx4KnlqT3qdWbf5X Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/11/26 14:38, Zi Yan wrote: > On 11 Mar 2026, at 9:33, David Hildenbrand (Arm) wrote: > >> On 3/11/26 14:23, Usama Arif wrote: >>> folio_migrate_flags() transfers folio state from source to destination >>> during migration, but does not transfer the large_rmappable flag. >>> >>> Migration allocators like alloc_migration_target() and >>> alloc_misplaced_dst_folio() use __folio_alloc() directly without >>> wrapping the result in page_rmappable_folio(), so the destination folio >>> never gets large_rmappable set. >>> >>> This becomes a problem when a folio on the deferred split queue is >>> migrated: the destination folio can be added to the deferred split queue >>> via deferred_split_folio() (which does not check large_rmappable), but >>> when the folio is later freed, folio_unqueue_deferred_split() bails out >>> early because large_rmappable is not set: >>> >>> if (folio_order(folio) <= 1 || !folio_test_large_rmappable(folio)) >>> return false; >>> >>> This leaves a stale entry on the deferred split queue, leading to >>> use-after-free when the shrinker walks the list. >>> >>> Fix this by transferring large_rmappable in folio_migrate_flags(), >>> consistent with how all other folio flags are handled. >>> >>> Fixes: dafff3f4c850 ("mm: split underused THPs") >>> Signed-off-by: Usama Arif >>> --- >>> mm/migrate.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/mm/migrate.c b/mm/migrate.c >>> index 3380021fd3db..ee1c7bc851dd 100644 >>> --- a/mm/migrate.c >>> +++ b/mm/migrate.c >>> @@ -846,6 +846,9 @@ void folio_migrate_flags(struct folio *newfolio, struct folio *folio) >>> folio_copy_owner(newfolio, folio); >>> pgalloc_tag_swap(newfolio, folio); >>> >>> + if (folio_test_large_rmappable(folio)) >>> + folio_set_large_rmappable(newfolio); >>> + >>> mem_cgroup_migrate(folio, newfolio); >>> } >>> EXPORT_SYMBOL(folio_migrate_flags); >> >> compaction_alloc_noprof() does the page_rmappable_folio() at the end. >> >> I'd assume that all migration allocation functions must take care of that. >> >> It's a responsibility of the folio allocation code, not folio migration >> code. > > I agree. The migration allocation function needs to give a folio or other > types of page matching the original one. Do we want to turn this into > a WARN to make sure newfolio matches folio's large_rmappable state? VM_WARN, sounds reasonable. -- Cheers, David