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 3ED87C79FA0 for ; Mon, 7 Sep 2026 19:56:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 43B476B0098; Mon, 7 Sep 2026 15:56:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3FAD16B0099; Mon, 7 Sep 2026 15:56:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2EA2D6B009B; Mon, 7 Sep 2026 15:56:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 04B696B0098 for ; Mon, 7 Sep 2026 15:56:22 -0400 (EDT) Received: from smtpin09.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 8329C1202B1 for ; Mon, 7 Sep 2026 19:56:22 +0000 (UTC) X-FDA: 85188023004.09.C884E86 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf23.hostedemail.com (Postfix) with ESMTP id A0FFA140008 for ; Mon, 7 Sep 2026 19:56:20 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=WCOXS26t; spf=pass (imf23.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; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788810980; b=YKs0dH2cx10SEivU0HBPSBu3/0Esra9+9XlOlbUyZR0p0v7FjmozG8ZpImnTRexlJflHDt Fn1QvuRkRvC+B5QwBPVcwan/NBsxCV2WQMptfgJSpvL1e4w7gPloU1u9vY0Yn6kBayTl6Q 4MlvaursZHyQnXOH4Lv5BELNpmsYW1w= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788810980; 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=C3Pz/iR4GmFSYdm+nHFH7X5f2zkT5Cx1Ic044VaYKjQ=; b=iIdkOmznrghbENC5vMuShVMQkZEauby/GAKnoNgOycMLQTpiEx/gh/gikpE2FMGkn5voMk 25Uif/cOfX/vqSbTx9EcVD9ClcwT5lOJjnuDm6AVG+XwNj8LYkP18QsQTCG5aeU16M3Fgx QxYftxYu8l7N1TbHl8y0HmFyfbY41qQ= ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=WCOXS26t; spf=pass (imf23.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 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id C44BB43C18; Mon, 7 Sep 2026 19:56:19 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C24391F00A3A; Mon, 7 Sep 2026 19:56:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788810979; bh=C3Pz/iR4GmFSYdm+nHFH7X5f2zkT5Cx1Ic044VaYKjQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=WCOXS26toUTLJFI73Th2e5DBWd9pznJ5zigCpkMzAlpc6EvgsoUrsMEgN0bmtUve/ Qb2LNffAKzQHuIp0Bk7LDdvW2qNZx88XIAiwsSlgIKhBkSMFsQF+hYi0b2agZOWFB2 DZF3bfWkA31yxJ+fb5okPc74s/ctN4KGAscjKVCClPO1DZ3qdeYkgZlLT6VQgvXgjK c13zCIll1Dzcb6Rn4TAT0xuSHHVmzz7KPYv0P9VxQtrYDAGIIoRvd4OJKPoxI0Ysxx ggNnYmtmWDkUOZeLeOHGfXAGypwRvKGVkwRerQ4wiMc6kHH+sKE6d07CW4seXVfD5Y +o6968+qyF0LQ== Message-ID: <9ab052f8-510d-4d45-be56-f49efca595dd@kernel.org> Date: Mon, 7 Sep 2026 21:56:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 09/18] mm/huge_memory: move anon_vma and filemap management into split helpers To: Kairui Song Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Lorenzo Stoakes , Zi Yan , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Lance Yang , Usama Arif , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Chris Li , Kemeng Shi , Nhat Pham , Baoquan He , Barry Song , Youngjun Park , Shivam Kalra References: <20260821-swap-thp-cleanup-v3-0-9b43f5163238@tencent.com> <20260821-swap-thp-cleanup-v3-9-9b43f5163238@tencent.com> <6e85fde9-9314-4854-99fb-3582b13486fd@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: 8bit X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: A0FFA140008 X-Stat-Signature: 6rj1d6zhd3f6wu6rqd61nd4tw1946y7d X-HE-Tag: 1788810980-173 X-HE-Meta: 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 iV/6Xy97 qNKKgpNC4t3PpWHOp/AE6kzRTQN3T+tUh61KTEP4KA3axLsWScE/+yQvwtAtheNfr5yYUyzt1xUSicaaKb/ltlc2A4yB0hO5VZj6AG4rj+mrcs5QBudd6Tc74HsIo6SwGQVieHOnNJFGtwgqtXZ1/LXUsKN3NaJNUL8lB4sjIZPgUD+UVGH86DKNDplUjBVlnYGs0Zal8Y7vtrpm5ocpxaapGdSmJPEr2piKP6ix0m3GE1npBGCQ/aa62p5aDuE6zvHpgZzjBj6xJLJLMKdg1BY34HaPfVrjoCy5r3uzJCIbqw0UpMMWm3prXhDqjTtYw21+nvlbk7DRTEe7/RN+7L/aUFzdiay+lbe03 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/7/26 19:55, Kairui Song wrote: > On Mon, Sep 7, 2026 at 8:36 PM David Hildenbrand (Arm) wrote: >> >> On 8/30/26 17:23, Kairui Song wrote: >>> >>> We can keep it where it is right now, but this patch is moving the >>> anon_vma_lock_write and i_mmap_lock_read into the two anon / file >>> helpers seperately, so keeping the folio_expected_ref_count check >>> outside and before the helper call will cause a potential higher >>> false positive / negative rate of this check? Leads to unnecessary >>> call to unmap_folio. >>> >>> How about moving the folio_expected_ref_count check into >>> unmap_folio since the purpose of the ref check is to avoid >>> unnecessary unmap? No more duplication that way. >> >> I think the crucial part (for anon folios) is to also check after we unmapped. >> >> See __folio_migrate_mapping(), where we don't do the !folio_ref_freeze() in case >> we tun into the !mapping scenario. > > If I understand you correctly, I think we are fine as is? The > folio_expected_ref_count() check here is just a racy check to avoid > the PMD split for a folio that cannot be split anyway, not a gate. > > The gate is the folio_ref_freeze() immediately after unmap_folio() in > __folio_freeze_split_anon() (only a local_irq_disable() in between). > For an unmapped anon folio folio_expected_ref_count() is uses > folio_swapcache_ref_count(). It might be worth optimizing, but that > could be done later. > > Or did you mean something else for the anon case? I thought for anon folios during migration it actually serves the purpose *after unmap* to detect any remaining GUP references (etc). But I might be wrong. I'll look at v4. -- Cheers, David