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 657C2C55822 for ; Wed, 5 Aug 2026 05:58:15 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 387E66B0088; Wed, 5 Aug 2026 01:58:14 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 35FCE6B008A; Wed, 5 Aug 2026 01:58:14 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 276276B0092; Wed, 5 Aug 2026 01:58:14 -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 06A626B0088 for ; Wed, 5 Aug 2026 01:58:13 -0400 (EDT) Received: from smtpin02.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 76D0E1403C2 for ; Wed, 5 Aug 2026 05:58:13 +0000 (UTC) X-FDA: 85066160466.02.3CA5F29 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf29.hostedemail.com (Postfix) with ESMTP id B980512000D for ; Wed, 5 Aug 2026 05:58:11 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=WpTfVY+g; spf=pass (imf29.hostedemail.com: domain of chleroy@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=chleroy@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=1785909491; 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=v7zCWK++jNfxfhEt8Y8jIgML8WXQN15ZQy6uHyDnBnc=; b=SkuYZbD5xtrNPwcxXV8pLEuA/tQQsGgSzlmnZfOsQI6u8Ofefw4XOrrZnjw0Zmn6dSCsD/ fICGg7QPUZcQEZWygVk2C5+61xA2px2necK5k2e6oPOl+vNzCTflyqAldu6cSKzfuXKyoq TPVA9RLnj1w0jRGx2+QhKVaG9DbgXu0= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=WpTfVY+g; spf=pass (imf29.hostedemail.com: domain of chleroy@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=chleroy@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=1785909491; b=EC/KND3tWEBEDuaGkHfUCVhBHAb5wA5+5Q84H3xFyr4NmC/5MXHs4KoIeY8N2p7FoLKicQ 0PMSgchd8AZmYtlGAmMX59o06PoynKum1BjpqELN71CB/E5aykDGWiH3nWUx7YsBNIz9Dq 8UD3UZtvI/WRxg7PPCqeKsuAIXWTObg= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 12245403D2; Wed, 5 Aug 2026 05:58:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 574631F000E9; Wed, 5 Aug 2026 05:58:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785909490; bh=v7zCWK++jNfxfhEt8Y8jIgML8WXQN15ZQy6uHyDnBnc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=WpTfVY+gis0GaZ8Ilij2iuNXtip1yECYuuQNUlYVo6jVc87VSMT30kmNOwPl/ZTao 7oJbpElLKRYZM/H9E3uzPA0m2dDs7qxBrWfUSWeNQgVusyFJAB0zhgsb3CndB3eLBl oVx+8kJVKo/dvCnEjFd77EC7hbxP5rQoI682riTb93MQ9TfiRSWCb3g5JOckn0oZli 58e+xTR7r2M3llPSRy5MrzI9rSBdgu2K2JYrZI3FiSOydblbfVLAtbSKgrhbcozdEM SIQIBRN5owC9lJ1/5UdzSc5P9So3/Y8YL+DvqEaETnFE51wJndUFjamNuiFbFR2lzb lLGJvpl87Db5A== Message-ID: <595fe323-59d3-4f4a-92a3-ac5d67b7461b@kernel.org> Date: Wed, 5 Aug 2026 07:58:02 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 6/6] mm: constify the pte_offset_map_ro_nolock() return value To: Pedro Falcato , "Lorenzo Stoakes (ARM)" Cc: David Hildenbrand , Andrew Morton , Catalin Marinas , Will Deacon , "James E.J. Bottomley" , Helge Deller , Madhavan Srinivasan , Michael Ellerman , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Kevin Brodsky , Muhammad Usama Anjum , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org References: <20260803164400.531199-1-pfalcato@suse.de> <20260803164400.531199-7-pfalcato@suse.de> Content-Language: fr-FR From: "Christophe Leroy (CS GROUP)" In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: B980512000D X-Stat-Signature: 3kcx9j15do86t8ho9mrjz5ahde13ahm1 X-HE-Tag: 1785909491-676205 X-HE-Meta: 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 mkQ2O1S4 ZqN2XFUnUkEB70uBMlQn7ny3vMgkS7vqu4qBvgXjnym1K83oNmI6aHpsWMI4Q84h3cG+CfvpuJrTEYJglrVmws6JAR2H5UaBFah4oTqbAvOXHHiS/CT6oKoHiN7nCc52oxIQsayipCDvpkd/5DxYuZu9Erro3pROUd2zwgigB6C3lGde0oWCd1mc8WVFDN7GZdGuiUpkVc32JQ6g2dNXbTqaiwaGzzD2GTFkFBW/xEE3lKtRUgz8vfvaCcuWOpLPPRlO/EHYSngmo/gZ0ABG7TwIXYiNgzzCkDuHaBuIbMJw7gDDD178MnQUmHAEwjb+LMFPsHOZH65L+TcEOZ+bZD/FN5jSPeEx50TQ6Rgci93UkiOFv7jesZ4Jg8ir+83JMOgnCSiK1fePSuXqek+6boFg36w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Le 04/08/2026 à 21:22, Pedro Falcato a écrit : > On Tue, Aug 04, 2026 at 12:22:19PM +0100, Lorenzo Stoakes (ARM) wrote: > >> >>> if (!pte) { >>> mmap_read_unlock(mm); >>> result = SCAN_NO_PTE_TABLE; >>> diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c >>> index b91b1a98029c..2cfc6e608ef4 100644 >>> --- a/mm/pgtable-generic.c >>> +++ b/mm/pgtable-generic.c >>> @@ -308,8 +308,8 @@ pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp) >>> return NULL; >>> } >>> >>> -pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd, >>> - unsigned long addr, spinlock_t **ptlp) >>> +const pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd, >> >> Can pmd be const too? > > I was going to say "yes but then pmdp_get() also needs to be constfified" but > actually no, it can't: > > pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp) { > if (unlikely(pmd_bad(pmdval))) { > pmd_clear_bad(pmd); > goto nomap; > } > } > > so PTE mapping actually needs to write to the pmdp if the pmd looks bad. > Tricky stuff :) But if pmd is const, can it be bad at all ? Christophe