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 BF5CDC982D8 for ; Fri, 18 Sep 2026 20:53:59 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 6DBAA6B0096; Fri, 18 Sep 2026 16:53:58 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6B35F6B0099; Fri, 18 Sep 2026 16:53:58 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5A1476B009B; Fri, 18 Sep 2026 16:53:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 321786B0096 for ; Fri, 18 Sep 2026 16:53:58 -0400 (EDT) Received: from smtpin01.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 6F07E1407B9 for ; Fri, 18 Sep 2026 20:53:57 +0000 (UTC) X-FDA: 85228084914.01.D20CA3F Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf06.hostedemail.com (Postfix) with ESMTP id 928A618000B for ; Fri, 18 Sep 2026 20:53:55 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=Kn6cunyI; spf=pass (imf06.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=1789764835; 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=xubuskVOjl35A2T8LbXWyaJic0HJ1gjUagG1E7uyg5k=; b=k3TRcYIHmRlzGoTZfFHUupogCkVBhditHN/320FvZ6+nNG7FmbP2m48bb3fUYNgriogh2W KiVH8xUgyibXPfT0SiwbxY1D63bu1gV2vjgOIZ5hfGip7u4/awD4G2fiwTrQqufKP/Iynj N5z51KtocewwdO6vUAlecdXUETyNG9Y= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=Kn6cunyI; spf=pass (imf06.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=1789764835; b=AYuWkLoMiVUyLpmF4A1qhg5DMrG41wVigwiVHi0Mjn9HvUN3JXcYUKeelG5O1LdkTygXhI hIsfR795BbjbHNCYznZctUBdFRGaZJ648QTId35bwy+Ko00SPr3PWiutkHX3Ex0vyEioBL XVSpW3ZzUUVmwIy2n55WCoZhaPHgZFA= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 7C6F740F1C; Fri, 18 Sep 2026 20:53:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 29BD21F000FF; Fri, 18 Sep 2026 20:53:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789764834; bh=xubuskVOjl35A2T8LbXWyaJic0HJ1gjUagG1E7uyg5k=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Kn6cunyIes7b/fgeRfTD/r8Fz5Dt/p48ZFG59t5T2b5RHLeaNgCTrqw7SoEvlPOI5 OvuHjFp9mBWp2eSxzlYCzHbBrSV8vl/DXuPzPJZsbYv0Xuqx3JThxg5gE7p21r47NM re8B0ycP+LBJEhifDZxmaPWvMaTdbkP9L8TH7qLJTIaTctBBzxc/RuD/7RF6jFkHb8 KWnVoWNdO0FqVgOZmWwuAtlvnO4A/sZK0V15/LeRJeHFJOPaq8+/KJ7WwXC3Fux/3b Sy/yzfOLjEbN8O91kS4uuktMUrONkl0khiUu0A6+wRjAt+8vW3dCgUQdRS96CC41GY RUB7RSuRPKQLg== Message-ID: <475ff6df-c8ef-4681-be83-2fbd7a68c417@kernel.org> Date: Fri, 18 Sep 2026 22:53:45 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 10/17] mm/huge_memory: move the racy refcount check into unmap_folio() To: kasong@tencent.com, linux-mm@kvack.org Cc: 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 , Yeoreum Yun , "Kiryl Shutsemau (Meta)" , Shivam Kalra , Kairui Song References: <20260915-swap-thp-cleanup-v5-0-39878b37dfb0@tencent.com> <20260915-swap-thp-cleanup-v5-10-39878b37dfb0@tencent.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: <20260915-swap-thp-cleanup-v5-10-39878b37dfb0@tencent.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: 7ctyuuuja4z6qed3swwbirkh7xxru98n X-Rspamd-Queue-Id: 928A618000B X-Rspamd-Server: rspam07 X-HE-Tag: 1789764835-273836 X-HE-Meta: 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 e8GvOfY0 LLIhm9j3e9Musi1CEPCpuJVuSbolKjDTopt+vD+tBlHHonQFaLn1DZ1MTNpqI87NToTakq1+4rhsQ7/xHA6IX3Hox3GdVeppa5TwVG5tHug73wDZ0yPkwcBEXEmI3CcFFDwpynwr2Zw1HIIRuUD6Gkql13+PZrSIj1IajmgtijpGQ4VCKrGp2j6CqDCgVOL3OkeL71+p0L6V3kzMlg9WxnZ88qNO1QKT9DgBHF+IrEGqU7YnEQcqhlPvbM+jAqxuJb1GlSq+qJZ7pzD8Zw20kW63v4WlR83KVSkTNiycfsPNLbPvkZz9GG74k3YHLTaXpy5qAtHALQc6CnFTSGX+ZM9fC7ciBSOUTQk2HOiVBRu9EvNQWKFRrbYYBDFsJibmPXnKB Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/14/26 19:14, Kairui Song via B4 Relay wrote: > From: Kairui Song > > The check only exists to avoid the expensive PMD-splitting unmap of a > folio that cannot be split anyway. Move it from __folio_split() into and folio_split_unmapped() > unmap_folio(), right before the PMD split, so both the anon and file > split helpers get the early check without repeating it. > > unmap_folio() now returns -EAGAIN if the check fails and the split > helpers propagate the error. folio_split_unmapped() drops its own > copy of the check: it works on already unmapped folios and the > definitive folio_ref_freeze() in __folio_freeze_split_anon() still > catches unexpected references. > > Reviewed-by: Zi Yan > Reviewed-by: Kiryl Shutsemau (Meta) > Signed-off-by: Kairui Song > --- > mm/huge_memory.c | 29 +++++++++++++---------------- > 1 file changed, 13 insertions(+), 16 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 77bf68c9b9af..859aefda7356 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3539,13 +3539,17 @@ void vma_adjust_trans_huge(struct vm_area_struct *vma, > split_huge_pmd_if_needed(next, end); > } > > -static void unmap_folio(struct folio *folio) > +static int unmap_folio(struct folio *folio) The semantics are special: a return value of 0 does not mean that unmapping succeeded. It might have still failed, but remap_anon_folio() must be called afterwards (for anon folios). Might be worth a quick comment. In general, LGTM. Acked-by: David Hildenbrand (Arm) -- Cheers, David