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=-3.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 99F3BC433E1 for ; Wed, 12 Aug 2020 10:04:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7435320639 for ; Wed, 12 Aug 2020 10:04:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=szeredi.hu header.i=@szeredi.hu header.b="meHCbgoh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727791AbgHLKE3 (ORCPT ); Wed, 12 Aug 2020 06:04:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33992 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727066AbgHLKE2 (ORCPT ); Wed, 12 Aug 2020 06:04:28 -0400 Received: from mail-ed1-x542.google.com (mail-ed1-x542.google.com [IPv6:2a00:1450:4864:20::542]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 59837C06178A for ; Wed, 12 Aug 2020 03:04:28 -0700 (PDT) Received: by mail-ed1-x542.google.com with SMTP id t15so1046766edq.13 for ; Wed, 12 Aug 2020 03:04:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=kveMn0CgVzgGdVO37SLre07hhA5DE1v0+4qD8NOY8tw=; b=meHCbgohoEeC4hc/3sMZ6QCAEA9FUFcIJ64vE/4XOtBGCJ8LFfjQFEgukMJIh2Pvot /fmUuiXKdoiBfNWEPbdJ4AkbQdQM3NmC8zm334GGtWtQYCqSraq0qRmdpMys765+69Pb tPGVyqcwlBQnoez3b76geaZ2Dtsd59vUcEg7M= 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=kveMn0CgVzgGdVO37SLre07hhA5DE1v0+4qD8NOY8tw=; b=n5Z/mRy2jFTkvxY3p81Oxad7jifzhHkd4lDuef1vf0jwtQ5GSqpSEmA5rScwEdZYTq paMV7yOfAKFCGyGSrwokqU+bHOeOkIXVDPkNTds0mQAJxqyIOW3WqEHJ3DuaQ69BxpKI 1oJoPsGjBps07zEYzbuFGdWL2r1lXWf2wdwV7dM9Q4+D8c9xFlJBanLsxCkxAhg9MV2N imMK0S9QF6xhdVIdCzc8bEQ54o4kHUe+v8ZYL58i38BNlCGRInFK4E0QgvMDRupNPWv4 8sR5qe/yK01EcxTs8vCmWL+SF3FBkTi9gs+lMqexdgZkiEdpX6Rk1er4C322G9KUU6Ob NhxA== X-Gm-Message-State: AOAM530o5ljEtK7qsylzk1pFnJ0olspswYV2LuwwTqAKSeGfOPm3rvQ0 hu2KX2SlaXP2YDFN3X/NiR5IHUEOCXZLDFUbqnX/gQ== X-Google-Smtp-Source: ABdhPJwfjFZ9rdnzWnYSUjRsmmzORGZKTAagxP8wu7SkP1m0JpqC5Md7Y+EUKS8tVWs1GLaPgrI/CGuiH4LIFXoeUG4= X-Received: by 2002:aa7:d688:: with SMTP id d8mr30572344edr.168.1597226666050; Wed, 12 Aug 2020 03:04:26 -0700 (PDT) MIME-Version: 1.0 References: <1842689.1596468469@warthog.procyon.org.uk> <1845353.1596469795@warthog.procyon.org.uk> <20200811135419.GA1263716@miu.piliscsaba.redhat.com> <52483.1597190733@warthog.procyon.org.uk> <98802.1597220949@warthog.procyon.org.uk> In-Reply-To: From: Miklos Szeredi Date: Wed, 12 Aug 2020 12:04:14 +0200 Message-ID: Subject: Re: file metadata via fs API To: Steven Whitehouse Cc: David Howells , Linus Torvalds , linux-fsdevel , Al Viro , Karel Zak , Jeff Layton , Miklos Szeredi , Nicolas Dichtel , Christian Brauner , Lennart Poettering , Linux API , Ian Kent , LSM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 12, 2020 at 11:43 AM Steven Whitehouse wrote: > > Hi, > > On 12/08/2020 09:37, Miklos Szeredi wrote: > [snip] > > > > b) The awarded performance boost is not warranted for the use cases it > > is designed for. > > This is a key point. One of the main drivers for this work is the > efficiency improvement for large numbers of mounts. Ian and Karel have > already provided performance measurements showing a significant benefit > compared with what we have today. If you want to propose this > alternative interface then you need to show that it can sustain similar > levels of performance, otherwise it doesn't solve the problem. So > performance numbers here would be helpful. Definitely. Will measure performance with the interface which Linus proposed. I'm not worried, though; the problem with the previous interface was that it resulted in the complete mount table being re-parsed on each individual event resulting in quadratic behavior. This doesn't affect any interface that can query individual mount/superblock objects. > Also - I may have missed this earlier in the discussion, what are the > atomicity guarantees with this proposal? This is the other key point for > the API, so it would be good to see that clearly stated (i.e. how does > one use it in combination with the notifications to provide an up to > date, consistent view of the kernel's mounts) fsinfo(2) provides version counters on mount and superblock objects to verify consistency of returned data, since not all data is returned in a single call. Same method could be used with the open/read based interface to verify consistency in case multiple attributes/attribute groups need to be queried. Thanks, Miklos