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 X-Spam-Level: X-Spam-Status: No, score=-11.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A24C2C47083 for ; Fri, 4 Jun 2021 15:10:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 820AB613BF for ; Fri, 4 Jun 2021 15:10:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230083AbhFDPM0 (ORCPT ); Fri, 4 Jun 2021 11:12:26 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:55749 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229778AbhFDPMZ (ORCPT ); Fri, 4 Jun 2021 11:12:25 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622819438; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=rY04b6/ZRmaZK8r9pldsFNxxxfCAPomp4y4kXbJNY2s=; b=G46XFy8SLgZQm3OnIDfb8npzmhcgfqn5J8VmAyt/RMZYEN/CyvmUpHks+MxrbFdFMFUkK5 k2fkHCQadjpr7Zla/YaFERYz5S2eGSSPolj37uqU0OFAuttjc5vDXfirtNIZL+ruc2X++R pMPLQcPJa+tA5OGpt8B++eWJnjvr37Q= Received: from mail-qv1-f72.google.com (mail-qv1-f72.google.com [209.85.219.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-550-C2UGg3LDMxGByiTwhmPJBw-1; Fri, 04 Jun 2021 11:10:34 -0400 X-MC-Unique: C2UGg3LDMxGByiTwhmPJBw-1 Received: by mail-qv1-f72.google.com with SMTP id bl11-20020ad4564b0000b029021d1fdffd5aso6932747qvb.1 for ; Fri, 04 Jun 2021 08:10:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=rY04b6/ZRmaZK8r9pldsFNxxxfCAPomp4y4kXbJNY2s=; b=Eme8K9nipVtfVSYNESMWKPSKTUj/zUDsKSGibJG+7YZoIsdZmAy+wZVoUzk9HtLuBE SFP1uiWXiXngFq72Sc7ZZEX94UhdytqUsfE/LuhqPsvEilVIG/SdBsagYI6Edcfi/CAJ VJpzBOc/IAY9V0EF53FuRUmGH7Y+ZzYRIDWBzaCXytqEAoGltT/UInDcsHCtSzaTxkDr c1F6kVFd6kawBbTgZYfi8s8920bJmBx6Wq7iGZQS7nHrYaNK9ktEqOqeMhEpIjt/1/U5 AH0HMfyewc044aT46mP/N4/1Bk3oyABAYY4dbW/z2nDwfJwf12sN4IqEGIZ8NA1Li8ti S3Kg== X-Gm-Message-State: AOAM532i+Ch6zZIyaRZNhaQ/hDKdmbTn7JYBbaDX3ZPDHo7Fsjo1eVkS TEknW4XmFRjqRbqVMilRS1BEHVyWxu1+NIQutxk/EUvLUwjyZ/pC9MVJJeH14RCcsWfwoKXpXnG Y061M426ij1h1psbmvJ5TYh0q X-Received: by 2002:a05:620a:4410:: with SMTP id v16mr4841404qkp.387.1622819433549; Fri, 04 Jun 2021 08:10:33 -0700 (PDT) X-Google-Smtp-Source: ABdhPJz6+UagA80qzlImEErke2pvQrrl+/pEnQY+1T+0ccLCf3Gk/r95MsHbFPJ5TR5FuCtMgSGDLg== X-Received: by 2002:a05:620a:4410:: with SMTP id v16mr4841381qkp.387.1622819433348; Fri, 04 Jun 2021 08:10:33 -0700 (PDT) Received: from t490s (bras-base-toroon474qw-grc-61-184-147-118-108.dsl.bell.ca. [184.147.118.108]) by smtp.gmail.com with ESMTPSA id y1sm4320510qkp.21.2021.06.04.08.10.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Jun 2021 08:10:32 -0700 (PDT) Date: Fri, 4 Jun 2021 11:10:31 -0400 From: Peter Xu To: Hugh Dickins Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Andrea Arcangeli Subject: Re: [PATCH] mm/swap: Fix pte_same_as_swp() not removing uffd-wp bit when compare Message-ID: References: <20210603180546.9083-1-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 03, 2021 at 08:26:02PM -0700, Hugh Dickins wrote: > On Thu, 3 Jun 2021, Peter Xu wrote: > > > I found it by pure code review, that pte_same_as_swp() of unuse_vma() didn't > > Yes, that is an odd corner, easily missed. > > > take uffd-wp bit into account when comparing ptes. pte_same_as_swp() returning > > false negative could cause failure to swapoff swap ptes that was wr-protected > > by userfaultfd. > > > > Cc: Hugh Dickins > > Cc: Andrea Arcangeli > > Cc: Andrew Morton > > Signed-off-by: Peter Xu > > I expect you're right: swapoff used to hang forever (but interruptibly) > when this went wrong on powerpc originally. I don't know the uffd_wp > (nor the soft_dirty) end of it, but treating uffd_wp and soft_dirty > together looks a very good approach, so I'll venture an > > Acked-by: Hugh Dickins Thanks! > > But I think it should have a uffd_wp Fixes tag and be Cc stable. Yes, should be: Cc: stable@vger.kernel.org # v5.7+ Fixes: f45ec5ff16a7 ("userfaultfd: wp: support swap and page migration") -- Peter Xu