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 1FAD4FF8875 for ; Thu, 30 Apr 2026 11:32:00 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 19B286B0088; Thu, 30 Apr 2026 07:31:59 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1253C6B008A; Thu, 30 Apr 2026 07:31:59 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F2EA96B008C; Thu, 30 Apr 2026 07:31:58 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id DD4776B0088 for ; Thu, 30 Apr 2026 07:31:58 -0400 (EDT) Received: from smtpin04.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 9FF75A0161 for ; Thu, 30 Apr 2026 11:31:58 +0000 (UTC) X-FDA: 84715007916.04.931EA25 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf18.hostedemail.com (Postfix) with ESMTP id C9CD51C0009 for ; Thu, 30 Apr 2026 11:31:56 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=PO7A+Z6C; spf=pass (imf18.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 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=1777548716; 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: references:dkim-signature; bh=7rgaagdvk5X+BPhver7PNTAkTh2XjtdqtERugOJknd4=; b=ZQmVTfWEZVW+98GrlvwzXI819wg+0FSylbKPoYpj2mA3PR2UP3qQbqxSchacQRdfl5o5Xm vMz/XslVG1jB0yX3lg1PiNT/aQH4GL63dfW7MnVBANp+yM7vDmFH/zSSOXoCiyPVQfV3WQ ypXiu6+hJQ2FwrjhXtQ3+Ki8y3DgUR8= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=PO7A+Z6C; spf=pass (imf18.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1777548716; a=rsa-sha256; cv=none; b=WiYGJ38PUcjnIR1f/Igt8M67p6sR5hFA+4NSFgyLzzsQ83YYOajA29AenzATTdqhr+mRvU oegqYs+mD0evPSIVIMc0wvQ90y8A5/5cK+h+aCQPygBQCBSQW+FBiZ8t/5cnXuwfD9faYa CMR9tvA5WFDMTxkgMAKXWGEG0kNNHqs= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 1C5756057A; Thu, 30 Apr 2026 11:31:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 68341C2BCB3; Thu, 30 Apr 2026 11:31:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777548715; bh=GAVeUYrfD81Vgxhl/4MJAOtYKmr0cjXk10/5oQ2nEDM=; h=From:Date:Subject:To:Cc:From; b=PO7A+Z6CSYSyfV7aQwYqp2SRHmj4kkRrsddLZMzbjtkDjEPu33pdvOLXg1x/cq7Ro tVFeT6roiky4eZBekVtFBAkyN+CpbWOyix2h/s5uO9+He9dYFBy4MhMgso2xGA9nnC z+2VpX4usUvmrArf3ScDgAmL0hh+fukLQ/dfr0SctDhJoRagc2mPhDok1GVJI5Zvbb hM96Jg//w7p6me4AW8RaKiO33otuDKipcx8MzGsI44vVitn8C/mdcvK9NFLnH28ADM QUFx638NESL+SkYYaF4pWrVrk/viM6e2oe6zL9ngteF0RcmTybjp6H0wkODsxZ6Pdj vQKkm8itzQPLw== From: "David Hildenbrand (Arm)" Date: Thu, 30 Apr 2026 13:31:22 +0200 Subject: [PATCH] mm: fix __vm_normal_page() to handle missing support for pmd_special()/pud_special() MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260430-pmd_special-v1-1-dbcbcfd72c20@kernel.org> X-B4-Tracking: v=1; b=H4sIAIk982kC/6tWKk4tykwtVrJSqFYqSi3LLM7MzwNyDHUUlJIzE vPSU3UzU4B8JSMDIzMDE2MD3YLclPjigtTkzMQcXTNDg5SklBSLxGTjZCWgjoKi1LTMCrBp0bG 1tQDlEi9iXQAAAA== To: 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, "David Hildenbrand (Arm)" X-Mailer: b4 0.13.0 X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: C9CD51C0009 X-Stat-Signature: ymkc89tmayoazzaw8byrunc5as4o6wmy X-HE-Tag: 1777548716-260605 X-HE-Meta: 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 SthUupN2 CSA+wsEQVa2WRFKXz2/qgfGmttbl/snT8OYqd7rcuBsdClhu5wZzchHDLsBlSifRnIzUrTA28pguCXWb7678LGAxg6g5Ry3Ilb1l7g087qHShVu86HrFKtSf0d7Hfm+gCCeVEwSDH3qi5DfX1xTbhlPqZua9E0feMgDZnYkCxaWh3NxOFjt1N3Z12kTC8Jk0VOib6YkhxDUBO7nDud5AeW7ZWGEAusM9FgLwa3sm+EJsOgw6nErB3w5A3EWOGK8vDthLXVji7tCFE0/5E9fybY1p4BLmweR+FjjN5AwsY4dES9SdmWVafW830DA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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) --- This is an alternative to Hugh's patch, whereby we leave pmd_special() be a NOP and instead teach __vm_normal_page() about lack of support for pmd_special/pud_special. --- mm/memory.c | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) diff --git a/mm/memory.c b/mm/memory.c index 7322a40e73b9..4d84976fc7f4 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -612,6 +612,21 @@ static void print_bad_page_map(struct vm_area_struct *vma, dump_stack(); add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE); } + +static inline bool pgtable_level_has_pxx_special(enum pgtable_level level) +{ + switch (level) { + case PGTABLE_LEVEL_PTE: + return IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL); + case PGTABLE_LEVEL_PMD: + return IS_ENABLED(CONFIG_ARCH_SUPPORTS_PMD_PFNMAP); + case PGTABLE_LEVEL_PUD: + return IS_ENABLED(CONFIG_ARCH_SUPPORTS_PUD_PFNMAP); + default: + return false; + } +} + #define print_bad_pte(vma, addr, pte, page) \ print_bad_page_map(vma, addr, pte_val(pte), page, PGTABLE_LEVEL_PTE) @@ -684,7 +699,7 @@ static inline struct page *__vm_normal_page(struct vm_area_struct *vma, unsigned long addr, unsigned long pfn, bool special, unsigned long long entry, enum pgtable_level level) { - if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) { + if (pgtable_level_has_pxx_special(level)) { if (unlikely(special)) { #ifdef CONFIG_FIND_NORMAL_PAGE if (vma->vm_ops && vma->vm_ops->find_normal_page) @@ -699,8 +714,9 @@ static inline struct page *__vm_normal_page(struct vm_area_struct *vma, return NULL; } /* - * With CONFIG_ARCH_HAS_PTE_SPECIAL, any special page table - * mappings (incl. shared zero folios) are marked accordingly. + * With working pte_special()/pmd_special()..., any special page + * table mappings (incl. shared zero folios) are marked + * accordingly. */ } else { if (unlikely(vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))) { --- base-commit: d94322006a51b522dd361128a450bf9e75aad889 change-id: 20260430-pmd_special-610dbdd8ac3c -- Cheers, David