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 F0027CAC5A5 for ; Wed, 24 Sep 2025 12:32:10 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 44AF68E0011; Wed, 24 Sep 2025 08:32:10 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 422418E0001; Wed, 24 Sep 2025 08:32:10 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 338028E0011; Wed, 24 Sep 2025 08:32:10 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 244248E0001 for ; Wed, 24 Sep 2025 08:32:10 -0400 (EDT) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id BEC8A11ACA3 for ; Wed, 24 Sep 2025 12:32:09 +0000 (UTC) X-FDA: 83924081178.03.1C4848A Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf29.hostedemail.com (Postfix) with ESMTP id 64CE0120011 for ; Wed, 24 Sep 2025 12:32:07 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Fq60GKxA; spf=pass (imf29.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1758717127; 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=nxDPC3N2WqjlWNs99FhY5LFBBOFWE7WmpuWkOT+s240=; b=lY4rBHBNeeASa4cen2epEcq7HYbWl7Ql+r+AJ9qJsF16e7dqv/Pvqwy/+zGtPrBOpBDqNK OBF8EiurYp3tXhE4Te69y9NQMf8YWJ8FtREne4ACXHHV8KCqPMfcn767G7J9mIGyhnDUmj Zq5bR8rZ1gVBIgwjWy8CIQoA712F2l8= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1758717127; a=rsa-sha256; cv=none; b=s0KWlbv8UGd0QfDODAN9il8G/0kGg5kV53b6T+wrsNHQ8XzenwmYqqzwzRI3IcXuF1yOBo Z9+OvbMSWpLioHEYQaxPsQwQE8ktQHSjBObQyh3sUq8ZBzV63ZjAbq0BClm18vYdg+v6b7 1LWwcWaJswa25G+pTR+DvBWQbqbB8P4= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Fq60GKxA; spf=pass (imf29.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758717126; h=from:from: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:autocrypt:autocrypt; bh=nxDPC3N2WqjlWNs99FhY5LFBBOFWE7WmpuWkOT+s240=; b=Fq60GKxAQwDNUv1kbt/VOGNx3B9hh073Cmb2bGNTdKNS6YE/CAc/gQBBcpU1sIquj/MsX6 5nHOFIAt0sLcssAow9i+eUiqSZCyI05WS6iCibT58G1gZarPPmnTaon6c3Qr7Ud5TR0rD0 U4Lolgx7YmbVo22U5BKgHx5Rw07a7s0= Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-604-7J5pFT4iMlKgsA-7jeabtg-1; Wed, 24 Sep 2025 08:32:03 -0400 X-MC-Unique: 7J5pFT4iMlKgsA-7jeabtg-1 X-Mimecast-MFC-AGG-ID: 7J5pFT4iMlKgsA-7jeabtg_1758717123 Received: by mail-qk1-f199.google.com with SMTP id af79cd13be357-7e870614b86so1758432785a.2 for ; Wed, 24 Sep 2025 05:32:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1758717123; x=1759321923; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=nxDPC3N2WqjlWNs99FhY5LFBBOFWE7WmpuWkOT+s240=; b=dMD35JL7wCHFb4j++m+2OQztfqaKYW3t0Jf7Vpa0b9JefBdPPjO6IZm10lruwckkNV /1/OEyMqsSUeBzaxzNMqy8mhqaPmWpV4KFPH/+gdVlUTP6j4SM06vmQFe179UKtklKow O4z7cktVEsQDnyAR1DVYDXAAiARzf7lSNofVh1y01n1bTfCLIhyoHK11rDw6sgpq9ZGF +uiu2mPBCM0NRDMurSFBLH0Tj/pIOCcwHXFAkPfLBR0evp0etIAHIIJfcTgPzHBh5qe2 puXXmcqt9Y/iYQBT12WTZUzES3Nymu+i9aSo855R2+uzrSBkCofDAERaT9Y6wQmdbP4j v0Xg== X-Gm-Message-State: AOJu0YzEDPOfcU8ZQDmc7CiD9KXeGObL3GxvjYUV+nmSUPrNcMwMOvnH 5GA5qqEj3pdZSwe5+h9TOaF4tUTwpHabLs20+kkPxuAHkvM+IlN/sZVvuzXQczvXYJrLTIVNw8y Wr6tXGRQ6eihII9eGEkE4rB/1qzTmDWXhKnHY933zM3XWfUYZ6qTD X-Gm-Gg: ASbGncuEH6BQSfvVHvs3s3H+7GmkPOr0waGD3cua0IUoPLn2y+Dnrl0dJmhUEldH/+r OXW7S0I6hvLI0LpbJHMmUnmlwapVbN9mpZcWq+Y9kH2ef96R6BCsN59zGAj3KRjMfhwJ/s/bcGn qDzk9q0aov/MYl9QV2ggXfhYS9LFH/QvJah2JQ13XJwBEIr4lSY+4ZtU/5sb8mviO1/xdVAtB/g kRHusREy+5Hw8jy9azVhCKfJ3wA5siReQ++gtOfVScVK+tV595hKSH5AUC2LDvEpfzStJ/6j8bO Zea1bWRU5+UBODrcA2zWXWYRhsZVkLNaOvVDkCAdnJCebX2GA2R6fUlLCGXjq6zhfPQHNEfxM9O nQKBFL1US28tHblDcoCgh8Qeu/u2dwK/oHT+bbjFXuOqtMo+pUPfw6y7NxhXt2ZrPrg== X-Received: by 2002:a05:620a:319b:b0:84a:568:b7d3 with SMTP id af79cd13be357-8517370024bmr640303785a.74.1758717122870; Wed, 24 Sep 2025 05:32:02 -0700 (PDT) X-Google-Smtp-Source: AGHT+IGU15mmr+4FrFEuvbHzmbfHN1dEwcBROdLoWHPYj5RplChD/U2Nd74SiOjXAk6SjarpxJnJ8Q== X-Received: by 2002:a05:620a:319b:b0:84a:568:b7d3 with SMTP id af79cd13be357-8517370024bmr640299285a.74.1758717122380; Wed, 24 Sep 2025 05:32:02 -0700 (PDT) Received: from ?IPV6:2003:d8:2f14:2400:afc:9797:137c:a25b? (p200300d82f1424000afc9797137ca25b.dip0.t-ipconnect.de. [2003:d8:2f14:2400:afc:9797:137c:a25b]) by smtp.gmail.com with ESMTPSA id d75a77b69052e-4cc0b7734d8sm45780151cf.53.2025.09.24.05.31.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Sep 2025 05:32:01 -0700 (PDT) Message-ID: <3ffda308-1210-4760-bac0-ba5b019c0e2a@redhat.com> Date: Wed, 24 Sep 2025 14:31:57 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 3/4] mm: thp: use folio_batch to handle THP splitting in deferred_split_scan() To: Qi Zheng , hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song References: <782da2d3eca63d9bf152c58c6733c4e16b06b740.1758618527.git.zhengqi.arch@bytedance.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+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: <782da2d3eca63d9bf152c58c6733c4e16b06b740.1758618527.git.zhengqi.arch@bytedance.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 36YvyLuDvbDkSDYqOxpCkrdetKAvFdxQZI620pka-JE_1758717123 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 64CE0120011 X-Stat-Signature: 7e3chxq6bgirrf31s7n1mx1q7r6597pg X-Rspam-User: X-HE-Tag: 1758717127-254630 X-HE-Meta: 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 /aaajj5D 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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 23.09.25 11:16, Qi Zheng wrote: > From: Muchun Song > > The maintenance of the folio->_deferred_list is intricate because it's > reused in a local list. > > Here are some peculiarities: > > 1) When a folio is removed from its split queue and added to a local > on-stack list in deferred_split_scan(), the ->split_queue_len isn't > updated, leading to an inconsistency between it and the actual > number of folios in the split queue. > > 2) When the folio is split via split_folio() later, it's removed from > the local list while holding the split queue lock. At this time, > this lock protects the local list, not the split queue. > > 3) To handle the race condition with a third-party freeing or migrating > the preceding folio, we must ensure there's always one safe (with > raised refcount) folio before by delaying its folio_put(). More > details can be found in commit e66f3185fa04 ("mm/thp: fix deferred > split queue not partially_mapped"). It's rather tricky. > > We can use the folio_batch infrastructure to handle this clearly. In this > case, ->split_queue_len will be consistent with the real number of folios > in the split queue. If list_empty(&folio->_deferred_list) returns false, > it's clear the folio must be in its split queue (not in a local list > anymore). > > In the future, we will reparent LRU folios during memcg offline to > eliminate dying memory cgroups, which requires reparenting the split queue > to its parent first. So this patch prepares for using > folio_split_queue_lock_irqsave() as the memcg may change then. > > Signed-off-by: Muchun Song > Signed-off-by: Qi Zheng > --- Nothing jumped at me Acked-by: David Hildenbrand -- Cheers David / dhildenb