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 90593C433F5 for ; Mon, 24 Jan 2022 09:13:35 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 263356B0081; Mon, 24 Jan 2022 04:13:35 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2132E6B0083; Mon, 24 Jan 2022 04:13:35 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 103706B0085; Mon, 24 Jan 2022 04:13:35 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0172.hostedemail.com [216.40.44.172]) by kanga.kvack.org (Postfix) with ESMTP id 026B46B0081 for ; Mon, 24 Jan 2022 04:13:34 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id A7FDC8249980 for ; Mon, 24 Jan 2022 09:13:34 +0000 (UTC) X-FDA: 79064617548.07.3EDE6F8 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf27.hostedemail.com (Postfix) with ESMTP id 3F5504004D for ; Mon, 24 Jan 2022 09:13:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643015613; 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=q/cJ3iWSzk/L9pl1h0bSd2z9dkOZnVgBJiwkxutziMY=; b=bLYUGthLDw0J6KPgMwTXhUG+U5kWqjSGd5PFODJc1yfBukcbUwIlwIT4LauUhgZAJqSmSq Orl57qKLuMO6JkvoQSUUSWz3ojVftsL+arR63s8UkO8iYOiYTuyppWOvAX0/9Jm9WG82UM RWyTePmqrQjzV8ajtdCUjuux2n4MWoM= Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-453-YjDMX_58M3COkOgc9Xxz_g-1; Mon, 24 Jan 2022 04:13:32 -0500 X-MC-Unique: YjDMX_58M3COkOgc9Xxz_g-1 Received: by mail-pf1-f197.google.com with SMTP id j21-20020aa78d15000000b004c82d9c2977so1991173pfe.21 for ; Mon, 24 Jan 2022 01:13:32 -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=q/cJ3iWSzk/L9pl1h0bSd2z9dkOZnVgBJiwkxutziMY=; b=crOd4G8y+IW2TSc9Tr34JAgBwdcf3eH0ucglUZxIaEBVufulP8KDjQPrn/L9X8OrN7 yeJqubXvRxvlWIPQRdO3ZoUSRy2Ow83Pp3L2pH66JO6tuo5NHIWeIc+hfUhp+2kOgq9c gXXmE9HEDb9U1KY1hN1BJnpmmyvLZLDR4KC/6DE4Yt4rxm//RtVUAVIaRtzJWKJW6bE0 /3RlrHj7gdx+24r5qhWdrau2eoUt5qhsnar+Lo+9Z90zcHGxnuanQ4CY9yqKwOiFtr0J 7IZd7RtAqNbOT+iWScRSMCp6PX1TQT4IE9dIoBDkxzL7wk0uFbrZiPQ6Kwnvib0V9L+d NHnA== X-Gm-Message-State: AOAM53229Z8mPKgnaTCH1g65Gr4bvRhS9wr5MCaDQoPaqMTEH8MVRF2K UB4NkrSFfGOYfvm7niR7ed3dRNpYgFeJIqQ/q4EVKlFlLxWPbixErsVbyKXPx/BgIOb+z1U9Tl8 MI+NgQRfn9XA= X-Received: by 2002:a17:90b:2406:: with SMTP id nr6mr966732pjb.99.1643015611589; Mon, 24 Jan 2022 01:13:31 -0800 (PST) X-Google-Smtp-Source: ABdhPJwWqTwByq4KaLiWEW35f6vhZ1leVAu4fEBkDJOyuZh7qPP+hPn4AmTAz6+a6+60W4DPgrTBcA== X-Received: by 2002:a17:90b:2406:: with SMTP id nr6mr966711pjb.99.1643015611367; Mon, 24 Jan 2022 01:13:31 -0800 (PST) Received: from xz-m1.local ([94.177.118.73]) by smtp.gmail.com with ESMTPSA id s13sm4719075pfk.174.2022.01.24.01.13.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Jan 2022 01:13:30 -0800 (PST) Date: Mon, 24 Jan 2022 17:13:23 +0800 From: Peter Xu To: Hugh Dickins Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand , Andrea Arcangeli , Yang Shi , Vlastimil Babka , Andrew Morton , Alistair Popple , "Kirill A . Shutemov" , Matthew Wilcox Subject: Re: [PATCH RFC v2 1/2] mm: Don't skip swap entry even if zap_details specified Message-ID: References: <20211115134951.85286-1-peterx@redhat.com> <20211115134951.85286-2-peterx@redhat.com> <9937aaa-d9ab-2839-b0b7-691d85c9141@google.com> <391aa58d-ce84-9d4-d68d-d98a9c533255@google.com> <56e33192-965d-691a-afc-f77f5856afd@google.com> MIME-Version: 1.0 In-Reply-To: <56e33192-965d-691a-afc-f77f5856afd@google.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3F5504004D X-Stat-Signature: w4cr6sjzakoqm171z84whgok4xxkpjdo Authentication-Results: imf27.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=bLYUGthL; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf27.hostedemail.com: domain of peterx@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=peterx@redhat.com X-HE-Tag: 1643015614-140316 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 Sun, Jan 23, 2022 at 10:51:57PM -0800, Hugh Dickins wrote: > I don't know of any problem that needs fixing with the zero page: > how do you suppose the zero page gets into a truncatable or hole-punchable > mapping? We use it for read faults in anonymous mappings. And I told the > story of how once-upon-a-time it could get inserted into any mapping by > reading from /dev/zero, but that odd case was dropped years ago. And I > am open to (even encouraging) a change to make use of zero page for read > faults of holes in shmem: but that's potential future work, which would > require some changes elsewhere (though perhaps none here: the zero page > could never be used for the result of a COW). > > Please explain the zero page problem you hope to fix here. After I tried to learn the old/new worlds of zero page somehow I thought there can be zero pfns installed, but it seems not at all.. Please ignore above, sorry for the noise. -- Peter Xu