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 1101AC61DBE for ; Tue, 25 Aug 2026 11:26:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1FA356B00B4; Tue, 25 Aug 2026 07:26:53 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1D1D86B00B5; Tue, 25 Aug 2026 07:26:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0E7F16B00B6; Tue, 25 Aug 2026 07:26:53 -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 DC6F66B00B4 for ; Tue, 25 Aug 2026 07:26:52 -0400 (EDT) Received: from smtpin17.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 4BB51A3647 for ; Tue, 25 Aug 2026 11:26:52 +0000 (UTC) X-FDA: 85139564664.17.57C2FD4 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf24.hostedemail.com (Postfix) with ESMTP id A4A9618000D for ; Tue, 25 Aug 2026 11:26:50 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=GoXlgVdV; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf24.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1787657210; 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=+Kwg1vlmpiXfsrVuG+kXUemOecdCeye6XceIRD4GCkc=; b=xfls9lM9IFy6TV/9ohgPliMq3UP47PQWoWi5oM9BL7RzHotJt+XYBY3Djx0SNH8wIbjJk1 X+UZ25KgSQaSLQ6I589EBCbClU1OIX465OAXVyGbd8H5N4uw8JoEWIRVAyZCWxv6fHaEL9 h7NvsvlKCgd3hBIUKc4FVSVTHbiiLs4= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=GoXlgVdV; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf24.hostedemail.com: domain of ljs@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=ljs@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1787657210; b=EQ/9yW/8aMqVWLf23hSr9M//ZW3PwGVIxlvnwLcB7lM3i/PxuFes6zsME7RpQr4mzRE8PR 3Seyutkn/DcUnzm2hjOVmbXd2z0MMdjQpzAV38la991M602E+8p75LQ/kJRaKt5x6clOym Il/EiGdyVWh+gYmj2DRhJpn7ZEffh+I= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id BD31C43DD4; Tue, 25 Aug 2026 11:26:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F260C1F000E9; Tue, 25 Aug 2026 11:26:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787657209; bh=+Kwg1vlmpiXfsrVuG+kXUemOecdCeye6XceIRD4GCkc=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=GoXlgVdVnQB3UIKDtlCK2MeqgMCYQLVg5a+xp6sO3+cbWgVd5+A/I2aV1BFeUM7k6 BVHc7H3QnM5OAstm5ICZF1F8UtUkOy4StSrkX8dng+bSYclRRQOkGUeYGNXJIH+4/P l6uMBxScbiacbX2oODUOkqBBoDvwqh6gu0SouefX1HJd802b3VnwzhSPutCafbEAgU 8TdZqHlqFtDqM86XjkQzIPwG4CoL+2UmnlHJLOG1je/70VJB/I7p+JYvsI646XL6a8 Mci0t5DOw3pDjpm/SEMAL6Qcu0JDgf8r4KMhu5L88J2MrpMu0jWyZHq0dsDmDpecvY UJWoV4aI7U0Kg== Date: Tue, 25 Aug 2026 12:26:39 +0100 From: "Lorenzo Stoakes (ARM)" To: Mike Rapoport Cc: Andrew Morton , David Hildenbrand , Baolin Wang , Barry Song , Dev Jain , Hugh Dickins , Jann Horn , Jason Gunthorpe , John Hubbard , Jonathan Corbet , Lance Yang , "Liam R. Howlett" , Masami Hiramatsu , Mathieu Desnoyers , Michal Hocko , Muchun Song , Nico Pache , Oscar Salvador , Pedro Falcato , Peter Xu , Ryan Roberts , Shakeel Butt , Shuah Khan , Steven Rostedt , Suren Baghdasaryan , Usama Arif , Vlastimil Babka , Zi Yan , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: Re: [PATCH 3/6] userfaultfd: use userfaultfd_*() helpers instead of open coded flag tests Message-ID: References: <20260823-uffd-vm-flags-v1-v1-0-3086981b33cf@kernel.org> <20260823-uffd-vm-flags-v1-v1-3-3086981b33cf@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: A4A9618000D X-Stat-Signature: 9jpkeff54kihafha9s6aeyptznun9ypn X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1787657210-312938 X-HE-Meta: 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 ylDMmUsz FQQzbym/Aq3LX7fNVCLchOdUlLE7IUesGKYL437Bsgh4fURPqyU6NGq4FYNPhl37qS/N9CoU3+qGaHLpYkB2iELUHQmD06L/wLDGPIe7dFFrlcFWhrST3oNWVxb173Fc7SiGCtv4MQawlvonEJhP6SEtL1PqZ9JSDhT+GjzVAI/Cfs7KipCXukXaqj7LoBlYP0daNa6duTdFzvhWVpAaF+N182iScHC7NhEtV0/nWgd7F89rQ5HKcnkaz1OmY0nE9XrFw1nWmgTFvF1/C1Cqe27e2UEIPLtqwWp5KD6itBJv6bQs= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Aug 25, 2026 at 02:19:52PM +0300, Mike Rapoport wrote: > > > +/* > > > + * Don't do fault around for WP, RWP or MINOR registered uffd range. For > > > + * MINOR registered range, fault around will be a total disaster and ptes can > > > + * be installed without notifications; for WP it should mostly be fine as long > > > + * as the fault around checks for pte_none() before the installation, however > > > + * to be super safe we just forbid it; for RWP, pre-faulted neighbours would > > > + * be indistinguishable from accessed pages in PAGEMAP_SCAN (PAGE_IS_ACCESSED) > > > + * and pollute the tracked working set, so each page must be populated by its > > > + * own fault. > > > + */ > > > +static inline bool uffd_disable_fault_around(struct vm_area_struct *vma) > > > +{ > > > + return userfaultfd_minor(vma) || userfaultfd_wp(vma) || > > > + userfaultfd_rwp(vma); > > > > This is changing the logic. > > > > Before we were testing only the flags, now we have: > > > > static inline bool userfaultfd_rwp(const struct vm_area_struct *vma) > > { > > /* > > * Callers gate PAGE_NONE usage on this; PAGE_NONE is a BUILD_BUG() > > * without CONFIG_ARCH_HAS_PTE_PROTNONE, so fold to false. > > */ > > if (!IS_ENABLED(CONFIG_ARCH_HAS_PTE_PROTNONE)) > > return false; > > return vma_test_single_mask(vma, VMA_UFFD_RWP); > > } > > > > I.e. adding in a CONFIG_ARCH_HAS_PTE_PROTNONE check. > > Without CONFIG_ARCH_HAS_PTE_PROTNONE VMA_UFFD_RWP is hardwired to VM_NONE > so it's functionally the same ;-) Well then you're explicitly removing logic and not mentioning it anywhere with a NFC commit. So please say so in the commit message. > > > BTW side-note these: > > > > static inline bool userfaultfd_missing(const struct vm_area_struct *vma) > > { > > return vma_test_any_mask(vma, VMA_UFFD_MISSING); > > } > > > > static inline bool userfaultfd_wp(const struct vm_area_struct *vma) > > { > > return vma_test_any_mask(vma, VMA_UFFD_WP); > > } > > > > static inline bool userfaultfd_minor(const struct vm_area_struct *vma) > > { > > return vma_test_any_mask(vma, VMA_UFFD_MINOR); > > } > > > > Should all use vma_test_single_mask() really :) > > These are changed anyway in a later patch. Yup, but you (potentially) break one of them. Will comment there. > > > -- > > Cheers, Lorenzo > > -- > Sincerely yours, > Mike. -- Cheers, Lorenzo