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=-6.5 required=3.0 tests=FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS 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 25367C43441 for ; Fri, 12 Oct 2018 08:46:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C2BF020868 for ; Fri, 12 Oct 2018 08:46:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C2BF020868 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=gmx.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-btrfs-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727819AbeJLQRX (ORCPT ); Fri, 12 Oct 2018 12:17:23 -0400 Received: from mout.gmx.net ([212.227.15.19]:47867 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727524AbeJLQRX (ORCPT ); Fri, 12 Oct 2018 12:17:23 -0400 Received: from [0.0.0.0] ([210.140.77.29]) by mail.gmx.com (mrgmx003 [212.227.17.184]) with ESMTPSA (Nemesis) id 0MMShK-1gJ6YZ0I3S-008Lok; Fri, 12 Oct 2018 10:45:54 +0200 Received: from [0.0.0.0] ([210.140.77.29]) by mail.gmx.com (mrgmx003 [212.227.17.184]) with ESMTPSA (Nemesis) id 0MMShK-1gJ6YZ0I3S-008Lok; Fri, 12 Oct 2018 10:45:54 +0200 Subject: Re: [PATCH v2] btrfs: Deprecate unused super block member, log_root_transid To: Nikolay Borisov , Qu Wenruo , linux-btrfs@vger.kernel.org References: <20181012063720.25659-1-wqu@suse.com> <9584982b-ac47-1b99-cb6f-7c0c68804b94@suse.com> From: Qu Wenruo Openpgp: preference=signencrypt Autocrypt: addr=quwenruo.btrfs@gmx.com; prefer-encrypt=mutual; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCWdWCnQUJCWYC bgAKCRDCPZHzoSX+qAR8B/94VAsSNygx1C6dhb1u1Wp1Jr/lfO7QIOK/nf1PF0VpYjTQ2au8 ihf/RApTna31sVjBx3jzlmpy+lDoPdXwbI3Czx1PwDbdhAAjdRbvBmwM6cUWyqD+zjVm4RTG rFTPi3E7828YJ71Vpda2qghOYdnC45xCcjmHh8FwReLzsV2A6FtXsvd87bq6Iw2axOHVUax2 FGSbardMsHrya1dC2jF2R6n0uxaIc1bWGweYsq0LXvLcvjWH+zDgzYCUB0cfb+6Ib/ipSCYp 3i8BevMsTs62MOBmKz7til6Zdz0kkqDdSNOq8LgWGLOwUTqBh71+lqN2XBpTDu1eLZaNbxSI ilaVzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCWdWBrwIbDAUJA8JnAAAK CRDCPZHzoSX+qA3xB/4zS8zYh3Cbm3FllKz7+RKBw/ETBibFSKedQkbJzRlZhBc+XRwF61mi f0SXSdqKMbM1a98fEg8H5kV6GTo62BzvynVrf/FyT+zWbIVEuuZttMk2gWLIvbmWNyrQnzPl mnjK4AEvZGIt1pk+3+N/CMEfAZH5Aqnp0PaoytRZ/1vtMXNgMxlfNnb96giC3KMR6U0E+siA 4V7biIoyNoaN33t8m5FwEwd2FQDG9dAXWhG13zcm9gnk63BN3wyCQR+X5+jsfBaS4dvNzvQv h8Uq/YGjCoV1ofKYh3WKMY8avjq25nlrhzD/Nto9jHp8niwr21K//pXVA81R2qaXqGbql+zo Message-ID: <1ceba3fb-f84a-7b5d-0fed-f06997806b74@gmx.com> Date: Fri, 12 Oct 2018 16:45:49 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <9584982b-ac47-1b99-cb6f-7c0c68804b94@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Provags-ID: V03:K1:91wcFtaTYAdNp4Bau0Vi8UqMWObvCbreakxntSE3OHtNC/du/Cd YFYAjTiVox1lfsNbyyRxTHdLmxt2xAgsdvpHS0NBSycAngSHf5Va+uh/KxOS4T2FenNb8vq KdHMTIoAh/XZVhMd9HnPfNXtL7jGceWmrQxjEi3KybKC4+tczzRrCnCrDPlVf3fzoOOKBQA Bu+qVgp6naN6MiBhd40Ew== X-UI-Out-Filterresults: notjunk:1;V01:K0:scd2VTfoesk=:yJiiFauypGmt/UBNCKtzGA c9+VSnw+z3PKAiEAjsSNALx1uRGj4zUVBWAa2WRlHCQ7UECw3ELiaHP8/NhPg9oCwyc8li7RL Zk8VIHAnFl4xUz/jAkb4GMrZt8Oym4UBKQastIEkC5TMHNZ2yafZ+HCqyHW4KOuA04l81p/ZI WL9SO9l8w42GknRyZllWA7dZlfikoUWEpMEpx7gzWbWQo+kEw8btq0Y0y+x4KklczyF4XiVtg TFFlprQUwDRb6V4UbIAzlk/h+Tjfm1pN2PUK09xkv773k7IVoulTiskqIv/pG20xeqSEMiiKt X+zExQBWy1svZ4as15Nghah0U0O7WQ73HDFu6pYI1I/UDRHRY6VEBabd2rCgaeWmme2oxF8rm Ls7zJgFcXdPDQUNVdHHyS0PsLGBeIeMoYxk03FgmAXJQT3YunEItimywy1TSH3+XvLmGQfxlR EcNiHtOSuXdpxVDWxYIa5CQcUPqLTJe+CoLdx7jt+6MAnBeAN45BF54rYjdcFiDXmpp0dGJq3 EfkaSvt+U3RDGnlh9anUbmZdSwmjLZqXFkOWwbKKfDUczMEKvOpkln87OXy/QW4sCDUysQcDz dWhBx4YeHqn3qKLKo++Uafx8Y6L+dJTiJNjXBZVAbQswa07hapDCMV7V2EfmVh5tfFFRLge/O gG26OfXdccHn06bWsEDUrAnuOul4J0bBIRhjTtHfqjBoKtPVdkdRfWWZS4bqs5clUGwlgIa53 5fArpyApi7Hd0bqqWMMpPjEDX8+ko2+JtO4GqSyEaGLFFz8JKM7hUGwCyMi5j+UmwVnroEm2D Xhag8L4+PLBEHHdtILMyotyudJPKkj6hfz8QMwWFB+rkPu+qRg= Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 2018/10/12 下午2:52, Nikolay Borisov wrote: > > > On 12.10.2018 09:37, Qu Wenruo wrote: >> The member log_root_transid is never used. >> It's always kept untouched even when updating log tree root. >> >> And populating it without introducing new incompat flags could easily >> cause back-compatibility problems. >> So just mark it unused. >> >> Signed-off-by: Qu Wenruo >> --- >> changelog: >> v2: >> Remove the redundant comment. >> --- >> fs/btrfs/ctree.h | 5 +---- >> 1 file changed, 1 insertion(+), 4 deletions(-) >> >> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h >> index 53af9f5253f4..7adf5f4dcda4 100644 >> --- a/fs/btrfs/ctree.h >> +++ b/fs/btrfs/ctree.h >> @@ -214,8 +214,7 @@ struct btrfs_super_block { >> __le64 chunk_root; >> __le64 log_root; >> >> - /* this will help find the new super based on the log root */ >> - __le64 log_root_transid; >> + __le64 __unused_log_root_transid; > > why do you keep insisting on having "log_root_transid" in the name of > this member? It was never used on-disk so for all intents and purposes > log_root_transid doesn't mean anything? No need to resend, I'm sure > David will change it on commit, nut I'm just curious. We have a similar case, leaf_size. Although it differs from this case and it's still used, I prefer to have something showing that we at least planned to use this member. Just in case one day we tries to use it again. Thanks, Qu > > >> __le64 total_bytes; >> __le64 bytes_used; >> __le64 root_dir_objectid; >> @@ -2317,8 +2316,6 @@ BTRFS_SETGET_STACK_FUNCS(super_chunk_root_level, struct btrfs_super_block, >> chunk_root_level, 8); >> BTRFS_SETGET_STACK_FUNCS(super_log_root, struct btrfs_super_block, >> log_root, 64); >> -BTRFS_SETGET_STACK_FUNCS(super_log_root_transid, struct btrfs_super_block, >> - log_root_transid, 64); >> BTRFS_SETGET_STACK_FUNCS(super_log_root_level, struct btrfs_super_block, >> log_root_level, 8); >> BTRFS_SETGET_STACK_FUNCS(super_total_bytes, struct btrfs_super_block, >>