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 2C014CD5BC8 for ; Tue, 26 May 2026 11:05:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 83DFE6B0088; Tue, 26 May 2026 07:05:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 815DE6B008A; Tue, 26 May 2026 07:05:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 72BAB6B008C; Tue, 26 May 2026 07:05:25 -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 617D66B0088 for ; Tue, 26 May 2026 07:05:25 -0400 (EDT) Received: from smtpin11.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id F2A8F1203CA for ; Tue, 26 May 2026 11:05:24 +0000 (UTC) X-FDA: 84809289768.11.95625F1 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf04.hostedemail.com (Postfix) with ESMTP id 66D8340018 for ; Tue, 26 May 2026 11:05:23 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=i+2Dh7MF; spf=pass (imf04.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@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=1779793523; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=qk40xgulls2bsEySJ0d4/5IyTPrAc0LfClUBUzlGCjE=; b=7Qs5I5oXrSWPYLew8l6iT6pRVESpHy+bRPiowfHLVjFp0GSnWwW7UV7Di6hAO1fSlJYDWP gHHCdmQA09KKtaGkBu1Beb5m6EOeE7YAuFoDg33QSMM4PRzpZuJE+wpk6wSBZdLYouzyJt 6Z0DWRFFNMVzEYWCbXd9/hxJ0gpVVYs= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=i+2Dh7MF; spf=pass (imf04.hostedemail.com: domain of ljs@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=ljs@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1779793523; a=rsa-sha256; cv=none; b=YjzyLdqcG0aunZfynDZC5S2mbUd7dTlvzTzFovRFXuveYMRT6My+zGBCMyQmYMQ3oMbzWW sl5ibjz6tRLWHBQW2h9yrC72qivcmBdiVLUQsMzF7yj16gBr/6CbOlRY0WfYOsxzr35RQK tY9hDLfjAPaj9sZoxQ6h6X4GN36b85Y= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id CBD32600AB; Tue, 26 May 2026 11:05:22 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 55E4B1F000E9; Tue, 26 May 2026 11:05:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779793522; bh=qk40xgulls2bsEySJ0d4/5IyTPrAc0LfClUBUzlGCjE=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=i+2Dh7MFEtK74+pZLmmNLDVqGWGe2BE+kd3pDCqQXGbpTjL7Logl9E6fmQ0ubku+1 nyOjwqL+o0m5Ts5cROkskSsx8BBovl9L8IyPmf5m4cF5bkx26ThEevbfbn5KNW9ygl yXWTAuQX9CmIwRFZUksstdZwplvejzDeV1LunwDhE+WlkkWABJoU4quxu4Aa6r1l9s EKOxiCJ0cQvS3yULxl9RIkuNSKc0fB5rcyvNUYLxymB/EWdGPLZ09F6aUnfWem9QML xeIJ6Kzi3M/GWTMKKHZ0SypcJlgX7NGSp7a2OopiPU5ihCB+0KREcp481g6H5y5p9w 2mUtT7NpMbH4A== Date: Tue, 26 May 2026 12:05:15 +0100 From: Lorenzo Stoakes To: Yin Tirui Cc: Andrew Morton , David Hildenbrand , Zi Yan , Baolin Wang , "Liam R . Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Vlastimil Babka , Yang Shi , wangkefeng.wang@huawei.com, chenjun102@huawei.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] mm/huge_memory: update file PMD counter before folio_put() Message-ID: References: <20260526101337.1984081-1-yintirui@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260526101337.1984081-1-yintirui@huawei.com> X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 66D8340018 X-Stat-Signature: hzhem89ai3a6jw4je4snqfits1d4uh3z X-HE-Tag: 1779793523-246964 X-HE-Meta: U2FsdGVkX1+r3NyfRUQx79wOJqO2CfGUJ6uIYei0+ND/cgdcmk7aca3d/FMvrnvQga3uZaCrT+y4kCs629xoDCITuVhL7w08uzNfVftpZ9LTI9kbX+UxO9kZCmQHZR0Iv6aZrdeS1oXmFhf2IOIJOJYYMYrGFx7ZkPHzdrLfT1HyomyNMDHyLX6MvaJfvhbybK/M8U+93qz4xC5SEm+fr1+TbwAxw26vyp4x9o0SSfmuFT1rdaEAIozNkYf1tb1CMI5A52bcU8x6Nkf1NH3L+J+CaQoyap7REQXikzAo7VtfpurJ/fbP7cK1V6crybF97yF/oc7i07FHPQI+rnyGRCnSEQBcagahdleBi/D/jTgwiIHkStUJf9mI3eMN/xHpsgSa2uOi346MF6UvXItjVSaJ80DGmvV1duM+lpo7j5LQfLXHbXY42N4DVTddY+c3cyunb0FRXbRJmU/+7XQDiemIl/Axz6V8fNjo27E6acttROOhhQGDNqrwWPf1B2X+k2xvM4Qwb+d1UcHPm5VRxbZo+Lv0OuPdaTOjV1ZqOC4PGvtgCuaCd1jtTkHJdzygtsRjpk/oY4C7lHsPdBqqIg8wEVdfnwVC3qrfHD5zCmNm8msuxGWnmLf7GGKZw3BZnF3tI0VdPjtBGo3SNExUmrhkfEqZUZyTBgpJTouAQFJTPDXBXlMIASsdhR+PyX/piJPU4NAutCk66eiiZ1NxsgwzsQ0CS66bhqTOxIPjtqieGpq1qzOEB4GhbfBayxJ7GQyv+Puko0M0oGEHy48DeS7bWQHe0nMAUA4fTgNTVksoOwpe4v+tipQXdcrKvDIQp/ZROrML27DphL4Y97JU6s9HeOTGUpJjW/YEUtCZrGT+Sdjg16AVnVwNb/t2T3rpwe5N2mBM4JslNxswqLj+LQeTFd3hZkX2JhbWnN44xberUBweA1f7Vqpg/KQ6lSz8tpkPoX+NQDnNr7IL5EA fExQIeMZ xmwrD1MeILy+bQNvZdPwbTuSspN3Q0V1BRMpC5hjs+auYovjfygf495b2MuXXUyhV0z1228yihbZuud7RO/SPiCQWD4z04TGPsxgDs5/RmNdKrg4VMkMKGyJb0NAT2/cmvpyjJX5idDbm+k/2hpxsM6vfIMc8XNz0Cm/k7ASLBJlEnuvNbnq0sn6mrnCGxvf74ZQ6ctD7VRH0OzGR7zX3B/3Km95MnyiPXup301MGOGeeP2DSJeQQc5fftlXXXedjS/0YQRn1AL4WJGQIiealaIqyRFm+VaEbawnDTLlWTx5swzghfF9KMDULy7jQQ7iwWNdnPQaA+Ao/RJUe0vreDROtOg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, May 26, 2026 at 06:13:37PM +0800, Yin Tirui wrote: > __split_huge_pmd_locked() updates the file/shmem RSS counter after > dropping the PMD mapping's folio reference. If folio_put() drops the > last reference, mm_counter_file() can later read freed folio state via > folio_test_swapbacked(). > > Move the counter update before folio_put(). > > Fixes: fadae2953072 ("thp: use mm_file_counter to determine update which rss counter") That's an old commit :) I mean I suspect we're probably not actually ever dropping the folio ref to 0 here since we never had a report since ~2018. The page cache keeping a reference I guess? But doesn't mean we shouldn't fix this on principal/there being some way this could happen. > Cc: > Signed-off-by: Yin Tirui LGTM, so: Reviewed-by: Lorenzo Stoakes > --- > mm/huge_memory.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index 0135c29a4372..a5f4a48b7b77 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3145,7 +3145,9 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd, > if (!folio_test_referenced(folio) && pmd_young(old_pmd)) > folio_set_referenced(folio); > folio_remove_rmap_pmd(folio, page, vma); > + add_mm_counter(mm, mm_counter_file(folio), -HPAGE_PMD_NR); > folio_put(folio); > + return; Hmm, sucks to duplicate like this, but for purposes of backport and getting this resolved fine, we can clean it up later. > } > add_mm_counter(mm, mm_counter_file(folio), -HPAGE_PMD_NR); > return; > -- > 2.43.0 > Cheers, Lorenzo