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]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9558C433EF for ; Thu, 16 Dec 2021 05:39:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 193836B0071; Thu, 16 Dec 2021 00:38:59 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 143D06B0073; Thu, 16 Dec 2021 00:38:59 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F063F6B0074; Thu, 16 Dec 2021 00:38:58 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0032.hostedemail.com [216.40.44.32]) by kanga.kvack.org (Postfix) with ESMTP id DC7FD6B0071 for ; Thu, 16 Dec 2021 00:38:58 -0500 (EST) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 21BE2886C4 for ; Thu, 16 Dec 2021 05:38:47 +0000 (UTC) X-FDA: 78922553094.09.C8D8C7E Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf01.hostedemail.com (Postfix) with ESMTP id 1757240010 for ; Thu, 16 Dec 2021 05:38:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1639633126; 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=qrBEElh5/4hAbc/6jTGVDH5c4ghjYxLIGLQd5AjrjwY=; b=gki/y18i+zVRzLTT8mFqAlJg7eRlmR4THLdRsWwF2ntIUTjo73v5yhrwZwiZz9fnFcB6y1 I4Z9JRbnNqAHKrq41cYCojyJlBgTrNm6qtMwLF5RFaLmG13jJycYE7myO/QsgW6l6HVV7H 9bCE2KryMnqNQJatDxni+Gu9E4jPTL0= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-428-wnp0qtSjNw2jEiWkbWGdzA-1; Thu, 16 Dec 2021 00:38:43 -0500 X-MC-Unique: wnp0qtSjNw2jEiWkbWGdzA-1 Received: by mail-wm1-f71.google.com with SMTP id j71-20020a1c234a000000b00342f418ae7cso770485wmj.1 for ; Wed, 15 Dec 2021 21:38:43 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=qrBEElh5/4hAbc/6jTGVDH5c4ghjYxLIGLQd5AjrjwY=; b=SdhRqtqAvDxzluwtOcVwISxwAdR06Du3jq8yP6Hmcxpk1YNnj4Ye9ZNyjX+z4DNyzk Y0IM9o7FFNMFkrvjPlmmMRcXiOBpU6jTRhM/Ejc9B1HY9D1IIakPO3huTE9BzxqE3Q7R KhiSqhD6uuvTuN+5+X5zAnuE+v/6Mfdeomnr44kqWpQXfLpdadzUTGRXko2esFUTGm7y C30B3cograwcOPubP3UdtwXMMLjEQQgYt971oCAOECJjRWDXe5E5QNYDDiPKbHkjk/w/ zlmTt7C6xkz4oqGGAJc7o0i+nZ6Cbw2lgTP5ZYqdWRhl6JcCA/9bz9JOJ0mDCDSP9C3I 4D0w== X-Gm-Message-State: AOAM530u7XR11OqLZvz/TLTJFpVYnIRtcRfthDiqdon41zoo/+BJbCEQ A1FlVJqPnnoxdc9dvIwopH4FLNYDqCv41V45pAoy/QmuA41iAqnH0581zZbb/jVO0ked2aBUHF6 smWeLeqyKJQA= X-Received: by 2002:a5d:47a4:: with SMTP id 4mr1205807wrb.180.1639633122494; Wed, 15 Dec 2021 21:38:42 -0800 (PST) X-Google-Smtp-Source: ABdhPJwqQ37OdEvGxFLS+2BX/bA8SD4YT3AcsowKwMM8wl7jpWe3zWiGOeyYUH+9wrL53x86/SZLbw== X-Received: by 2002:a5d:47a4:: with SMTP id 4mr1205778wrb.180.1639633122061; Wed, 15 Dec 2021 21:38:42 -0800 (PST) Received: from xz-m1.local ([64.64.123.12]) by smtp.gmail.com with ESMTPSA id h5sm3426758wrz.63.2021.12.15.21.38.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Dec 2021 21:38:41 -0800 (PST) Date: Thu, 16 Dec 2021 13:38:33 +0800 From: Peter Xu To: Alistair Popple Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Axel Rasmussen , Nadav Amit , Mike Rapoport , Hugh Dickins , Mike Kravetz , "Kirill A . Shutemov" , Jerome Glisse , Matthew Wilcox , Andrew Morton , David Hildenbrand , Andrea Arcangeli Subject: Re: [PATCH v6 03/23] mm: Check against orig_pte for finish_fault() Message-ID: References: <20211115075522.73795-1-peterx@redhat.com> <20211115075522.73795-4-peterx@redhat.com> <6260997.DYpkEd5BTb@nvdebian> MIME-Version: 1.0 In-Reply-To: <6260997.DYpkEd5BTb@nvdebian> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 1757240010 X-Stat-Signature: 531a39d7quecay5jarj8pyqbcq6ftzr1 Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="gki/y18i"; spf=none (imf01.hostedemail.com: domain of peterx@redhat.com has no SPF policy when checking 170.10.133.124) smtp.mailfrom=peterx@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-HE-Tag: 1639633121-536698 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Dec 16, 2021 at 04:01:47PM +1100, Alistair Popple wrote: > On Monday, 15 November 2021 6:55:02 PM AEDT Peter Xu wrote: > > We used to check against none pte and in those cases orig_pte should always be > > none pte anyway. > > Is that always true? From what I can see in handle_pte_fault() orig_pte only > gets initialised in the !pmd_none() case so might not be pte_none. I believe it's true, otherwise I must have overlooked. IMHO it's not "when we set orig_pte" that matters - note that finish_fault() (that this patch modifies) is only called for file-backed memories, and it's only called in do_fault() where the pte is not mapped at all. DAX seems to call it too, but still DAX comes from do_fault() too, afaict. The pte will not be mapped in two cases in handle_pte_fault(): - When pmd_none - When !pmd_none, however if we find that pte_none==true, that's: if (pte_none(vmf->orig_pte)) { pte_unmap(vmf->pte); vmf->pte = NULL; } So when we're already in do_fault(), afaict, orig_pte must be pte_none(). Another side note is that, IIUC pte_none() is a looser check than the pte_val()==0 and it should be arch dependent. Thanks, > > > This change prepares us to be able to call do_fault() on !none ptes. For > > example, we should allow that to happen for pte marker so that we can restore > > information out of the pte markers. > > > > Signed-off-by: Peter Xu > > --- > > mm/memory.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/mm/memory.c b/mm/memory.c > > index 04662b010005..d5966d9e24c3 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -4052,7 +4052,7 @@ vm_fault_t finish_fault(struct vm_fault *vmf) > > vmf->address, &vmf->ptl); > > ret = 0; > > /* Re-check under ptl */ > > - if (likely(pte_none(*vmf->pte))) > > + if (likely(pte_same(*vmf->pte, vmf->orig_pte))) > > do_set_pte(vmf, page, vmf->address); > > else > > ret = VM_FAULT_NOPAGE; > > > > > > -- Peter Xu