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 6CCBFCD3424 for ; Wed, 6 May 2026 05:12:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 917AC6B0005; Wed, 6 May 2026 01:11:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8C8B66B0088; Wed, 6 May 2026 01:11:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7DE4A6B008A; Wed, 6 May 2026 01:11:59 -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 6DC286B0005 for ; Wed, 6 May 2026 01:11:59 -0400 (EDT) Received: from smtpin25.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 0019EC25E9 for ; Wed, 6 May 2026 05:11:58 +0000 (UTC) X-FDA: 84735823116.25.6E315B0 Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com [115.124.30.130]) by imf19.hostedemail.com (Postfix) with ESMTP id 0230D1A0004 for ; Wed, 6 May 2026 05:11:55 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=linux.alibaba.com header.s=default header.b=vRPeqtKi; spf=pass (imf19.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.130 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=linux.alibaba.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1778044317; 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=Yjv1YwoUlV3YcbGhSBZo4j1p+egaq8G4dSfMBztXKz4=; b=JTMu/EE/s6uOgFBQ/ZZJ109W264am5FZ4N4t3TiU6p7hZ4RFqw5JaKO+lWTxJZr9QNsjvW IdahDmhL+/9qJ3eTQvjPU8zHmrxl5ZU925fRfiBBumALYUOiLMS8Z7wqi1WpbpFHg239oJ XWHNP0Pk0D6aA7iiQ3nFL+S683oHYGw= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=linux.alibaba.com header.s=default header.b=vRPeqtKi; spf=pass (imf19.hostedemail.com: domain of baolin.wang@linux.alibaba.com designates 115.124.30.130 as permitted sender) smtp.mailfrom=baolin.wang@linux.alibaba.com; dmarc=pass (policy=none) header.from=linux.alibaba.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1778044317; a=rsa-sha256; cv=none; b=4V6UX7Pyu/ONOa62z58DG/Ry4PW2T/v0KVdN9jEtROblLe81ChFMufJIn36mHb1qHC+8iR BVD8up6vllQnC90xnY+z9IHK98uDvFK18lgB75lN68h+Sq6pqSX/5V1v6WnVDriLcMzgh8 KUBLmINLDFrtdk1TWJgl3pIATUwQza4= DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1778044309; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=Yjv1YwoUlV3YcbGhSBZo4j1p+egaq8G4dSfMBztXKz4=; b=vRPeqtKi40CfXuQctLCccjheYhEbuCq7JvDrWSlgynnQ+uwVBE8ljukxKWrP1i5izmzcyyWuDJVIdF8URWvPW3+Wulo2DpCbSsEJS69mpTHYsobtR/JHkmPeCym3suJDWZmTRcVY2Pgg8+DFCHF/0xNAQc+xzdo6dzj+DK7fPoY= X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R141e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=maildocker-contentspam033045133197;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=15;SR=0;TI=SMTPD_---0X2L9Eve_1778044305; Received: from 30.221.149.158(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X2L9Eve_1778044305 cluster:ay36) by smtp.aliyun-inc.com; Wed, 06 May 2026 13:11:46 +0800 Message-ID: <1a5c8084-c244-455b-b999-f110fc9e4749@linux.alibaba.com> Date: Wed, 6 May 2026 13:11:44 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: fix __vm_normal_page() to handle missing support for pmd_special()/pud_special() To: "David Hildenbrand (Arm)" , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Oscar Salvador , Hugh Dickins , Lance Yang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Bibo Mao , stable@vger.kernel.org References: <20260430-pmd_special-v1-1-dbcbcfd72c20@kernel.org> From: Baolin Wang In-Reply-To: <20260430-pmd_special-v1-1-dbcbcfd72c20@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 0230D1A0004 X-Stat-Signature: muac6go8sqo4ttht1urpxem1x488aek1 X-HE-Tag: 1778044315-287933 X-HE-Meta: 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 5NzauEFk dDUlkeNFaB2b7DHdln55nkLydeTa0c5u4x103nuBw/uN7Hutg0duztySeDseVy+j3MazBimY/L6pBddCNLFLXRViOHnWadgufArxwxZWSOQwiHxowTH1LxGVMKU6E4x0tjzR5Yf/tSG1AY8j6bxZB+IWmKyq6q9wq8TmkTSJxbXkQoUQyl8rM5QWHCI9G8BP9AN51jDgJdMlutXClspew3PFvdSzaohXgTBwNRF7pOkmyfvBK3DXTK0PImqd1tiM9HbWJRwBLBAQ9RrrLMjpZ3KEube3HlXnrEuLQt2S4+kpGDDv/mqtIy4Q7fAukC/XrgRXECECzeVBYAAMu7iRKtOSz3xep4tgPL9+lcRI3llNx2pW18NV8sk2Bg7ULj7NYE3yIklPwcYTLRvk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/30/26 7:31 PM, David Hildenbrand (Arm) wrote: > On x86 32-bit with THP enabled, zap_huge_pmd() is seen to generate a > "WARNING: mm/memory.c:735 at __vm_normal_page+0x6a/0x7d", from the > VM_WARN_ON_ONCE(is_zero_pfn(pfn) || is_huge_zero_pfn(pfn)); followed > by "BUG: Bad rss-counter state"s, then later "BUG: Bad page state"s > when reclaim gets to call shrink_huge_zero_folio_scan(). > > It's as if the _PAGE_SPECIAL bit never got set in the huge_zero pmd: > and indeed, whereas pte_special() and pte_mkspecial() are subject to a > dedicated CONFIG_ARCH_HAS_PTE_SPECIAL, pmd_special() and pmd_mkspecial() > are subject to CONFIG_ARCH_SUPPORTS_PMD_PFNMAP, which is never enabled > on any 32-bit architecture. > > While the problem was exposed through commit d80a9cb1a64a ("mm/huge_memory: > add and use normal_or_softleaf_folio_pmd()"), it was an oversight in commit > af38538801c6 ("mm/memory: factor out common code from vm_normal_page_*()") > and would result in other problems: > * huge zero folio accounted in smaps, pagemap (PAGE_IS_FILE) and > numamaps as file-backed THP > * folio_walk_start() returning the folio even without FW_ZEROPAGE set. > Callers seem to tolerate that, though. > > ... and triggering the VM_WARN_ON_ONE(), although never reported so far. > > To fix it, teach vm_normal_page_pmd()/vm_normal_page_pud() to consider > whether pmd_special/pud_special is actually implemented. > > Fixes: af38538801c6 ("mm/memory: factor out common code from vm_normal_page_*()") > Reported-by: Hugh Dickins > Closes: https://lore.kernel.org/r/74a75b59-2e13-3985-ee99-d5521f39df2a@google.com > Reported-by: Bibo Mao > Closes: https://lore.kernel.org/r/20260430041121.2839350-1-maobibo@loongson.cn > Debugged-by: Hugh Dickins > Reviewed-by: Lance Yang > Tested-by: Bibo Mao > Cc: stable@vger.kernel.org > Signed-off-by: David Hildenbrand (Arm) > --- LGTM. Feel free to add: Reviewed-by: Baolin Wang