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=-3.0 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_NEOMUTT 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 BEA79C4360F for ; Wed, 20 Mar 2019 09:40:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E59021850 for ; Wed, 20 Mar 2019 09:40:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=shutemov-name.20150623.gappssmtp.com header.i=@shutemov-name.20150623.gappssmtp.com header.b="agGczCTy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727473AbfCTJkg (ORCPT ); Wed, 20 Mar 2019 05:40:36 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:35300 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727073AbfCTJkf (ORCPT ); Wed, 20 Mar 2019 05:40:35 -0400 Received: by mail-pg1-f194.google.com with SMTP id g8so1411981pgf.2 for ; Wed, 20 Mar 2019 02:40:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=shutemov-name.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=2ilZdXEgKQl8eu/If6oZwzfIDgI9nzN5u6h3xxR7k4I=; b=agGczCTyVX3YbxtbNXvXDU8mq3XwNWH9k0ijzWdCgnWmZ24E6MXUuKm4fIV2Q58fjO rOmnT42x6IFqOMRyniVzVvrcvEdFZuh29FVdN73buc2fLd6c9XSGSU4ekUwdIRP9w0jI TnG1CjqVJaKfsNBHua+/pXoacxpFw/skgnhdL+ii6OjDFsLZhdTCVeT8jAXx0g6s32ff uOpFM8zsMkWdQ3UMLwxog6cqiiP4a9Wn8JCr/Sm942GLxVQsp/kAULxiT5dKNnnH46Xj PRBqmL8qznxMJI3VqLWDQ45wB8rzfg+CagDnTAavLEuE4SvWjzHy/VzxJQpLMF3zACQ4 92wA== 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:user-agent; bh=2ilZdXEgKQl8eu/If6oZwzfIDgI9nzN5u6h3xxR7k4I=; b=QbClbMY+wk8BSgJDJukkvzClD6p6o4tUm+vsYKy3XLfTYN+vuTu2o5acaHOiIrUUDe ILYnMGoS7jIjb+s5jF9y1gcVlf1qpFAxUGZvVBDmzYfT+CDHaR5FW7ebzTufxz7r/BsD RRlv/bNsKfkw2+oIsr2oCzt/9j5kgtJ6uMnNJVrdwJoblFafohkTI7PAgqOfGnKLa4zF jsf2+jVZUKibUkstcwpDRy40UTTof9Lc65NrCX8fheecxwSemT57MM/Qwqxr9EWMbrDV BNfHJqC6upPcq1vXI3FE2aqj09jZuFFtP2P+xuLVFna4PSNtNt8pLHkmr9gMypOv2baN Hp/A== X-Gm-Message-State: APjAAAU+CQvH5SIa9zuQtFFwn90DMLFBMqZsfN3fa1ABysujPi6/8jia vt4amUF6TDnmeohwQyxMOc1qTg== X-Google-Smtp-Source: APXvYqyRZpQfbFJVEpRMID17XPrBgMkhW+bQ+/Tdq95pUIU9dvdMgO/DYyin4FL9ZRNXRc0CEIUHAw== X-Received: by 2002:a63:5515:: with SMTP id j21mr6551236pgb.244.1553074834713; Wed, 20 Mar 2019 02:40:34 -0700 (PDT) Received: from kshutemo-mobl1.localdomain ([134.134.139.82]) by smtp.gmail.com with ESMTPSA id 10sm2608365pft.83.2019.03.20.02.40.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 Mar 2019 02:40:34 -0700 (PDT) Received: by kshutemo-mobl1.localdomain (Postfix, from userid 1000) id 47B4C3011DB; Wed, 20 Mar 2019 12:40:29 +0300 (+03) Date: Wed, 20 Mar 2019 12:40:29 +0300 From: "Kirill A. Shutemov" To: John Hubbard Cc: Jerome Glisse , john.hubbard@gmail.com, Andrew Morton , linux-mm@kvack.org, Al Viro , Christian Benvenuti , Christoph Hellwig , Christopher Lameter , Dan Williams , Dave Chinner , Dennis Dalessandro , Doug Ledford , Ira Weiny , Jan Kara , Jason Gunthorpe , Matthew Wilcox , Michal Hocko , Mike Rapoport , Mike Marciniszyn , Ralph Campbell , Tom Talpey , LKML , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH v4 1/1] mm: introduce put_user_page*(), placeholder versions Message-ID: <20190320094029.ifweqx4wowyyr3wi@kshutemo-mobl1> References: <20190308213633.28978-1-jhubbard@nvidia.com> <20190308213633.28978-2-jhubbard@nvidia.com> <20190319120417.yzormwjhaeuu7jpp@kshutemo-mobl1> <20190319134724.GB3437@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 19, 2019 at 12:24:00PM -0700, John Hubbard wrote: > So, I could be persuaded either way. But given the lack of an visible perf > effects, and given that this could will get removed anyway because we'll > likely end up with set_page_dirty() called at GUP time instead...it seems > like it's probably OK to just leave it as is. Apart from ugly code generated, other argument might be Spectre-like attacks on these call. I would rather avoid indirect function calls whenever possible. And I don't think opencodded versions of these functions would look much worse. -- Kirill A. Shutemov