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=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 0E1DFC6377A for ; Thu, 22 Jul 2021 01:04:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E689D610D2 for ; Thu, 22 Jul 2021 01:04:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230153AbhGVAYB (ORCPT ); Wed, 21 Jul 2021 20:24:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60874 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229783AbhGVAYA (ORCPT ); Wed, 21 Jul 2021 20:24:00 -0400 Received: from mail-lj1-x236.google.com (mail-lj1-x236.google.com [IPv6:2a00:1450:4864:20::236]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 74110C061575 for ; Wed, 21 Jul 2021 18:04:35 -0700 (PDT) Received: by mail-lj1-x236.google.com with SMTP id b29so5272505ljf.11 for ; Wed, 21 Jul 2021 18:04:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=tdVcgyFrt783lScdfhCI3lPMqTnUeK9ABSA/mH1ibjA=; b=sDr7Rqiv2gHMiCoRQZiZO9pNAnwQF16sUvpKjdVJH0Bs24fQr9AU2Mv3v0hhZAlY6Z 8GTMv3YdfjExVAEMDk8Zm9SCBDeFJM5oVhyfr4Iqrf0J/9mRQH7aHRJq3qEWgUf2SgVn jPy+0bTF5vfNU7DBfMulckGN7g7nV9Fl1NpGrfOnTWBUHDS+UWyodtJyltQAD2+i54oj rNgHcLz/XyfVnoe26X2cehEIwB7CGRmzhaF4EILnrYuSrtqWx/coCNJWNkHjkRvdI3aW dNeItESvKhgTI6HIgYTSRPvEg9BrHhIxj+Nd8+yIWgbRHSHrQ4XJCP9Wk3v9xsd/NqLC W4mw== 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=tdVcgyFrt783lScdfhCI3lPMqTnUeK9ABSA/mH1ibjA=; b=G/+AConNENujU5xPfNqIkB4wKwQsuSs0qY2DyRRj8lwoqyLHpNghA497+gnuFDYvjP hDsVkDGzyYGPMhSFitBFlZgbrtB75sIfAoyGnj9YHwDdjQeWWZ6yvCPc/dfvKE4nAmYj 8+paeWILcdVXQBu0RN7vhwZQmlX7ZtjWVnMTw8zv5f0j7Ht8stvqnw13I8vQZpGM3Dhj 05ol1F6Z80ekJzV85aWh20exEerIwd128qj2y+Zv7CTMj90X2umOsKt/Thy+48uaAfLP 6kIsoE6T6CW825nDK2GfOvOifcaXzopMXSxYmu7gU8H9H9PIhtLoFr6YaTPk1wYnZeto IMbg== X-Gm-Message-State: AOAM531KqU+8VFDdQiDnNhtR63/l9PZ8FnlXwBiS2K1bJJto1K4HLotL IKIhSfmEJuPPSOJ3e1D1ERyDRbS8Zat7mMAbo2o= X-Google-Smtp-Source: ABdhPJx6C1BNH+dXBtZGhfH7IpQO10Bys3xuxRePvkRl3kG+SS2EgsEpLMT1bFABsd4JrLjCtuYKWGMBZvd6/yXFCLI= X-Received: by 2002:a2e:92c8:: with SMTP id k8mr15788610ljh.136.1626915873774; Wed, 21 Jul 2021 18:04:33 -0700 (PDT) MIME-Version: 1.0 References: <20210721072048.3035928-1-daeho43@gmail.com> In-Reply-To: From: Daeho Jeong Date: Wed, 21 Jul 2021 18:04:22 -0700 Message-ID: Subject: Re: [f2fs-dev] [PATCH] f2fs: change fiemap way in printing compression chunk To: Eric Biggers Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, kernel-team@android.com, Daeho Jeong Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 21, 2021 at 5:15 PM Eric Biggers wrote: > > On Wed, Jul 21, 2021 at 03:30:46PM -0700, Daeho Jeong wrote: > > Hi Eric, > > > > On Wed, Jul 21, 2021 at 2:35 PM Eric Biggers wrote: > > > > > > On Wed, Jul 21, 2021 at 12:20:48AM -0700, Daeho Jeong wrote: > > > > From: Daeho Jeong > > > > > > > > When we print out a discontinuous compression chunk, it shows like a > > > > continuous chunk now. To show it more correctly, I've changed the way of > > > > printing fiemap info like below. Plus, eliminated NEW_ADDR(-1) in fiemap > > > > info, since it is not in fiemap user api manual. > > > > > > > > 0: 0000000000000000 0000000000000000 0000000000001000 1008 (M/E) > > > > 1: 0000000000001000 0000000f15c0f000 0000000000001000 1008 (M/E) > > > > 2: 0000000000002000 0000000000000000 0000000000002000 1808 (M/U/E) > > > > 3: 0000000000004000 0000000000000000 0000000000001000 1008 (M/E) > > > > 4: 0000000000005000 0000000f15c10000 0000000000001000 1008 (M/E) > > > > 5: 0000000000006000 0000000000000000 0000000000002000 1808 (M/U/E) > > > > 6: 0000000000008000 0000000000000000 0000000000001000 1008 (M/E) > > > > > > Please label these columns. > > > > > > Anyway, this doesn't appear to work quite in the way I had in mind. With this > > > patch, what I'm seeing is: > > > > > > $ head -c 16384 /dev/zero > file; xfs_io -c "fiemap -v" file > > > file: > > > EXT: FILE-OFFSET BLOCK-RANGE TOTAL FLAGS > > > 0: [0..7]: 0..7 8 0x1008 > > > 1: [8..15]: 2683128..2683135 8 0x1008 > > > 2: [16..31]: 0..15 16 0x1809 > > > > > > So, working in 512-byte sectors, the logical sectors 0-31 are stored as one > > > compressed cluster in the 8 physical sectors 2683128-2683135. > > > > > > The problem is, with this patch these physical sectors are reported at logical > > > sectors 8-15 instead of 0-7. Obviously, this isn't particularly well-defined, > > > but I thought it was logical for the physical blocks to be associated with the > > > first logical blocks. That is what the tests I've written (xfstest f2fs/002, > > > and the Android vts_kernel_encryption_test) assume. > > > > > > Is there any particular reason why you wouldn't report instead: > > > > > > 0: [0..7]: 2683128..2683135 8 0x1008 > > > 1: [8..31]: 0..23 8 0x1809 > > > > > > - Eric > > > > The reason is related to how F2FS stores the mapping information in > > the mapping table. > > Actually, the mapping inside of the table is like this. > > [0..7]: COMPR_ADDR flag(0x1008) -> merged, encoded > > [8..15]: 2683128..2683135 flag(0x1008) -> merged, encoded > > [16..31]: NEW_ADDR flag(0x1809) -> merged, unwritten(!), last_extent > > > > I understand what you mean. > > But, if we adapt to your way, how do you think we can print out when > > we ask for f2fs to print out only the [8..15] area? Zero address? How > > about flags? > > I think the current way explains the layout of the f2fs metadata more exactly. > > > > How f2fs stores the mapping information doesn't matter. That's an > implementation detail that shouldn't be exposed to userspace. The only thing > that should be exposed is the actual mapping, and for that it seems natural to > report the physical blocks first. > > There is no perfect solution for how to handle the remaining logical blocks, > given that the fiemap API was not designed for compressed files, but I think we > should just go with extending the length of the last compressed extent in the > cluster to cover the remaining logical blocks, i.e.: > > [0..31]: 2683128..2683159 flag(0x1009) -> merged, encoded, last_extent > > That's what btrfs does on compressed files. > > - Eric I also agree that that's an implementation detail that shouldn't be exposed to userspace. I want to make it more clear for better appearance. Do you think we have to remove "unwritten" information below? I also think it might be unnecessary information for the user. [0..31]: 2683128..2683159 flag(0x1009) -> merged, encoded, last_extent (unwritten?) Do you want f2fs to print out the info on a cluster basis, even when the user asks for one block information? Like If the user asks for the info of [8..15], f2fs will return the info of [0..31]? Thank you,