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=-18.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_IN_DEF_DKIM_WL autolearn=ham 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 32994C433ED for ; Tue, 27 Apr 2021 17:03:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 062B4613D0 for ; Tue, 27 Apr 2021 17:03:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236332AbhD0REk (ORCPT ); Tue, 27 Apr 2021 13:04:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33016 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235842AbhD0REj (ORCPT ); Tue, 27 Apr 2021 13:04:39 -0400 Received: from mail-io1-xd2f.google.com (mail-io1-xd2f.google.com [IPv6:2607:f8b0:4864:20::d2f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 787A8C061760 for ; Tue, 27 Apr 2021 10:03:56 -0700 (PDT) Received: by mail-io1-xd2f.google.com with SMTP id q25so16851882iog.5 for ; Tue, 27 Apr 2021 10:03:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=GR5JD0ns+pkMtnVUKEORcsBQhRfif8pxVKBIY8qVHxA=; b=QmLHoLcsn+BCVDfzUQrjwg8Xy2xVvUXFxBBU5ft+H64o4TFVvBIXxXHuqOMECGEcTO dtvozDEMUp4GFivPJePB0PbkV52eNybLkucfQwmJgQrhAYuEEpl8ey6u5rr7froL9831 wYVyAxisrA82rOkudABuC3U8PenfOlk7D+S7mAqWQheynJuG+L6t550RQN2xH3AtQmcj YZOVPtow4jaHCIeBDjTYIj5/8GSNps1Fuw/jToYXPcH3cgKCRyqq/rZVHA/3bXXQ2Nve 2ueglmp/SjvnojiN9svPkpekJLSz97FI7Aop3wlrKzIy55Bwfsy6mB/auPJu3BpBHN4P BL/A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=GR5JD0ns+pkMtnVUKEORcsBQhRfif8pxVKBIY8qVHxA=; b=cmic8jOB1PhMjkDre88UevVGbarzp7RoWJ6Sz+Fo3C+OSsqlAPJrPPVCI9FxVUXG6h Q8GOk8TgITK/P8iv3FVWQcTjAsFbuA7UnswB/vOPtkA5XVk62nsWsr8d1+Xil3rS/QbA FiCgQsRG+rZ1XAVtOQc4l3fRwFWET7/3AyA9HUDkdOhRiz3b8bR4uthavfT8MRQL7JK+ ZBOu08EZJG23TR0r+rKcK2q1WpMKK9+Sz8GmpWa7UYbtQlqbf9WnhhtnApImJPiDYarz FadW8K9oHg+VFEO5O9fls999f5Y74QhQMWXN3E0+W1H9z0U1TlDkt9p/zEYzqDqnoGXU KgNw== X-Gm-Message-State: AOAM531BWt5OqKo3iz7pK4Nx1wDxFLirB+KP6sDcEXl5rjR/9PL7TvHW LOMi9p9J0U+LxpFmNsWP4KLMdN3V35mz7ieueUniVQ== X-Google-Smtp-Source: ABdhPJwulj3vaxVO0sHbkW6fF/E/7qJzf+HEs1+HRhzpNXwno9kM3bLiLURQiT9BXMHQwBaFd9a8rHY/eeZXQQ4/jXo= X-Received: by 2002:a5d:9682:: with SMTP id m2mr20925814ion.20.1619543035845; Tue, 27 Apr 2021 10:03:55 -0700 (PDT) MIME-Version: 1.0 References: <20210420220804.486803-1-axelrasmussen@google.com> <20210420220804.486803-5-axelrasmussen@google.com> <20210427155713.GC6820@xz-x1> In-Reply-To: <20210427155713.GC6820@xz-x1> From: Axel Rasmussen Date: Tue, 27 Apr 2021 10:03:20 -0700 Message-ID: Subject: Re: [PATCH v4 04/10] userfaultfd/shmem: support minor fault registration for shmem To: Peter Xu Cc: Hugh Dickins , Alexander Viro , Andrea Arcangeli , Andrew Morton , Jerome Glisse , Joe Perches , Lokesh Gidra , Mike Kravetz , Mike Rapoport , Shaohua Li , Shuah Khan , Stephen Rothwell , Wang Qing , linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, LKML , linux-kselftest@vger.kernel.org, Linux MM , Brian Geffon , "Dr . David Alan Gilbert" , Mina Almasry , Oliver Upton Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org Ah yes, I should have modified the commit message when I swapped them the first time - sorry for overlooking it. As I said in the other thread, unless someone strongly objects I'll just re-order them the other way around, minor faults first and then CONTINUE, which resolves this concern at least. I'm not too worried about leaving them split. Clearly we'll never release a kernel with one but not the other. So the only scenario I can imagine is, bisecting. But, bisecting across the range where UFFD shmem minor faults were introduced, if you're using that feature, won't really work out well no matter what we do. If you aren't using this feature explicitly, then any of the configurations we've talked about are fine. On Tue, Apr 27, 2021 at 8:57 AM Peter Xu wrote: > > On Mon, Apr 26, 2021 at 07:23:57PM -0700, Hugh Dickins wrote: > > On Tue, 20 Apr 2021, Axel Rasmussen wrote: > > > > > This patch allows shmem-backed VMAs to be registered for minor faults. > > > Minor faults are appropriately relayed to userspace in the fault path, > > > for VMAs with the relevant flag. > > > > > > This commit doesn't hook up the UFFDIO_CONTINUE ioctl for shmem-backed > > > minor faults, though, so userspace doesn't yet have a way to resolve > > > such faults. > > > > > > Acked-by: Peter Xu > > > Signed-off-by: Axel Rasmussen > > > > And if this "04/10" had been numbered 03/10, I would have said > > Acked-by: Hugh Dickins > > > > Just read the comment above: "so userspace doesn't yet have a way to > > resolve such faults" - if it doesn't by this stage, we're in trouble. > > Right, so merging the two patches might be easier. Even if we don't merge > them, we'll need to touch up the commit message since at least above paragraph > is not true anymore as we've already have UFFDIO_CONTINUE. Thanks, > > -- > Peter Xu >