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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=no 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 41056C433ED for ; Tue, 27 Apr 2021 20:30:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 19DD46112F for ; Tue, 27 Apr 2021 20:30:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236995AbhD0Uah (ORCPT ); Tue, 27 Apr 2021 16:30:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235610AbhD0Uag (ORCPT ); Tue, 27 Apr 2021 16:30:36 -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 61300C061760 for ; Tue, 27 Apr 2021 13:29:52 -0700 (PDT) Received: by mail-io1-xd2f.google.com with SMTP id z14so8393306ioc.12 for ; Tue, 27 Apr 2021 13:29:52 -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=WzJWSS3LQ6tF0DgK++1lrPiC81dYzxiPck8oPTQIuQM=; b=gbNFD7FoTA7n8IPPyw2KHOylIt8tzudj0Lpkdgu7mzsab/vYDoCX8VQ2+pW2PafQbp JxR1XGRxzePWZg0k/lL8HrzfJX1SnDe5TpFzpooVXmvhCVtquqkAHffLdiPX/s4G6iTl 9ONp86hzSzE7P1p3W+LL5QOZ/CQ3Ze/kT8jGK0OwsPFtA9fF3Z8j93LJX1jAzWtovcFo wraUFwADLhrGc/ZRhKyMAE1vzcpZTFlKnS3wTfzLUX/OyuUTfXrJrtKvBZoyZWbDyJDM IGj8vWkjpL1dSCRy2ZHIBkB+wFNwbbCdZZCFIG8416YkWzweIhGhpxBxMpCiUWXMipAc 5UdQ== 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=WzJWSS3LQ6tF0DgK++1lrPiC81dYzxiPck8oPTQIuQM=; b=jpZLJQwwb5yy5rfA0BXltRDWf8hVRs5GO7kucQM/Le8fZXCVyZ4U9nVxAWgurPYilN j3O80YNSzOJUnBD2C/v8nm05wUeIIMnTffkhfktlTJmAOPSHcLgwjITFm370zbqSvZOC UTyCYoWZOQiu50ygyXRto/zlo7fWAKwM/AQgmVyodtWwB3qw25VMmQRo+Muh8xmBuDAX gR+jrhNvR1ec4h0Ak4vJEkdu7Q0V2Dpv5nyqTaswfBEaIXgL6eHFUqIawJbC8AmaxTGW 9WFha3Wx9Za2MpcB7i/0Z0U1vo0XQKxexC3+4ShPC6/+j26H/WN3/pYxM7qA31P5HytG n9Dg== X-Gm-Message-State: AOAM530lU/vWLSF4CMGlJVpkcChx9tKBLZu3giRrH6sU5lZdiEnxTI0C //7TyJRf4AoDTKB1p9zznmdgPVaIcNDG4Miotysz9g== X-Google-Smtp-Source: ABdhPJz7iNqaf7JHZFiCQ426WqlOiaRzxCMbG8Vk0qKa7/LDNoylh0febweO3CgkD2dvFe5U0B95hMpS/QZFyMb3tpE= X-Received: by 2002:a05:6638:3387:: with SMTP id h7mr12471126jav.96.1619555391579; Tue, 27 Apr 2021 13:29:51 -0700 (PDT) MIME-Version: 1.0 References: <20210420220804.486803-1-axelrasmussen@google.com> <20210420220804.486803-4-axelrasmussen@google.com> <20210427155414.GB6820@xz-x1> <20210427180314.GD6820@xz-x1> In-Reply-To: <20210427180314.GD6820@xz-x1> From: Axel Rasmussen Date: Tue, 27 Apr 2021 13:29:14 -0700 Message-ID: Subject: Re: [PATCH v4 03/10] userfaultfd/shmem: support UFFDIO_CONTINUE 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-kernel@vger.kernel.org On Tue, Apr 27, 2021 at 11:03 AM Peter Xu wrote: > > On Tue, Apr 27, 2021 at 09:57:16AM -0700, Axel Rasmussen wrote: > > I'd prefer to keep them separate, as they are not tiny patches (they > > are roughly +200/-150 each). And, they really are quite independent - > > at least in the sense that I can reorder them via rebase with no > > conflicts, and the code builds at each commit in either orientation. I > > think this implies they're easier to review separately, rather than > > squashed. > > > > I don't have a strong feeling about the order. I slightly prefer > > swapping them compared to this v4 series: first introduce minor > > faults, then introduce CONTINUE. > > > > Since Peter also has no strong opinion, and Hugh it sounds like you > > prefer it the other way around, I'll swap them as we had in some > > previous version of this series: first introduce minor faults, then > > introduce CONTINUE. > > Yes I have no strong opinion, but that's probably the least I prefer. :-) > > Because you'll declare UFFD_FEATURE_MINOR_SHMEM and enable this feature without > the feature being completely implemented (without UFFDIO_CONTINUE, it's not > complete since no one will be able to resolve that minor fault). > > Not a big deal anyway, but since we're at it... Basically I think three things > to do for minor shmem support: > > (1) UFFDIO_CONTINUE (resolving path) > (2) Handle fault path for shmem minor fault (faulting path) > (3) Enablement of UFFD_FEATURE_MINOR_SHMEM (from which point, user can detect > and enable it) > > I have no preference on how you'd like to merge these steps (right now you did > 1 first, then 2+3 later; or as Hugh suggested do 1+2+3 together), but I'd still > hope item 3 should always be the last, if possible... In that case, I'll split the patch which adds the faulting path in two: add the faulting path hook and registration mode, and then in a separate commit advertise the feature flag as available. Then I'll order them like so, which I think is the order Hugh finds more natural: 1. MInor fault registration / faulting path 2. CONTINUE ioctl to resolve the faults 3. Advertise the feature as supported Sound okay? > > Thanks, > > -- > Peter Xu >