From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 706201D63F7 for ; Mon, 6 Oct 2025 06:28:25 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759732107; cv=none; b=N2dKt0KixWiXuqyVP5LXCKlO01FnxjFFFuv1xmOfPn2+sBUsHFETjXU9OEZ8U+lkaLsLCzGrmeKy1KEwPpGiGu/mxZLShg2qLg3s8eggU5hUkmZX3X6hNXxf1roAvHNvkT9bM4EVuHKBR8+0IDtC9b2eo7pLbh93YLUdxIcENEs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1759732107; c=relaxed/simple; bh=p30WR1fRKfo4Zn9J5kvCerH+ZDGCiLDXfxdoaqlW1zE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=G5jHvm9Sf6AEqLtmPul54T1ItX144WcsEKNKPDcMo7vJ0RvBPQkJMZIGoawlS4Be344UqorVla/mw4mpEjUs8npIXgKcJ5eADNeAtxa45t8DDlH8vrIGg0Iuo8fOI6hsTzP0aqhyQKrzPoHCE/GqAvV9qkNUCpWLkGUnRbF//rI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B93451515; Sun, 5 Oct 2025 23:28:16 -0700 (PDT) Received: from [10.164.18.47] (unknown [10.164.18.47]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1F8013F59E; Sun, 5 Oct 2025 23:28:22 -0700 (PDT) Message-ID: <1c948262-e201-4473-b156-8b90fedc9ce7@arm.com> Date: Mon, 6 Oct 2025 11:58:20 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/dirty: Replace READ_ONCE() with pudp_get() To: Dev Jain , linux-mm@kvack.org Cc: Andrew Morton , David Hildenbrand , linux-kernel@vger.kernel.org References: <20251006055214.1845342-1-anshuman.khandual@arm.com> <4b513d32-7795-4998-98df-d398c3d5462a@arm.com> Content-Language: en-US From: Anshuman Khandual In-Reply-To: <4b513d32-7795-4998-98df-d398c3d5462a@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 06/10/25 11:37 AM, Dev Jain wrote: > > On 06/10/25 11:22 am, Anshuman Khandual wrote: >> Replace READ_ONCE() with a standard page table accessor i.e pudp_get() that >> anyways defaults into READ_ONCE() in cases where platform does not override >> >> Cc: Andrew Morton >> Cc: David Hildenbrand >> Cc: linux-mm@kvack.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Anshuman Khandual >> --- >>   mm/mapping_dirty_helpers.c | 2 +- >>   1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/mapping_dirty_helpers.c b/mm/mapping_dirty_helpers.c >> index c193de6cb23a..737c407f4081 100644 >> --- a/mm/mapping_dirty_helpers.c >> +++ b/mm/mapping_dirty_helpers.c >> @@ -149,7 +149,7 @@ static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end, >>                     struct mm_walk *walk) >>   { >>   #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD >> -    pud_t pudval = READ_ONCE(*pud); >> +    pud_t pudval = pudp_get(pud); >>         /* Do not split a huge pud */ >>       if (pud_trans_huge(pudval)) { > > Talking about mm, why not also make changes for these READ_ONCE accesses > in gup, hmm, memory, mprotect, sparse-vmemmap? > Right, could replace all mm/ READ_ONCE() for pxdp pointers with the pgtable helpers but that will create too much code churn in a single patch. Thought of doing these replacements per file will be much more contained which is easy both for review and testing.