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=-11.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 19ADEC433E0 for ; Wed, 15 Jul 2020 10:35:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F1AE820656 for ; Wed, 15 Jul 2020 10:35:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726650AbgGOKfX (ORCPT ); Wed, 15 Jul 2020 06:35:23 -0400 Received: from [195.135.220.15] ([195.135.220.15]:58680 "EHLO mx2.suse.de" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1726437AbgGOKfW (ORCPT ); Wed, 15 Jul 2020 06:35:22 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 7AB14B1F7; Wed, 15 Jul 2020 10:35:22 +0000 (UTC) Subject: Re: [PATCH v2 01/17] bcache: add comments to mark member offset of struct cache_sb_disk To: Johannes Thumshirn , Hannes Reinecke , "linux-bcache@vger.kernel.org" Cc: "linux-block@vger.kernel.org" References: <20200715054612.6349-1-colyli@suse.de> <20200715054612.6349-2-colyli@suse.de> <668b8126-6a34-7029-dea4-2ad0ecc3915e@suse.de> From: Coly Li Autocrypt: addr=colyli@suse.de; keydata= mQINBFYX6S8BEAC9VSamb2aiMTQREFXK4K/W7nGnAinca7MRuFUD4JqWMJ9FakNRd/E0v30F qvZ2YWpidPjaIxHwu3u9tmLKqS+2vnP0k7PRHXBYbtZEMpy3kCzseNfdrNqwJ54A430BHf2S GMVRVENiScsnh4SnaYjFVvB8SrlhTsgVEXEBBma5Ktgq9YSoy5miatWmZvHLFTQgFMabCz/P j5/xzykrF6yHo0rHZtwzQzF8rriOplAFCECp/t05+OeHHxjSqSI0P/G79Ll+AJYLRRm9til/ K6yz/1hX5xMToIkYrshDJDrUc8DjEpISQQPhG19PzaUf3vFpmnSVYprcWfJWsa2wZyyjRFkf J51S82WfclafNC6N7eRXedpRpG6udUAYOA1YdtlyQRZa84EJvMzW96iSL1Gf+ZGtRuM3k49H 1wiWOjlANiJYSIWyzJjxAd/7Xtiy/s3PRKL9u9y25ftMLFa1IljiDG+mdY7LyAGfvdtIkanr iBpX4gWXd7lNQFLDJMfShfu+CTMCdRzCAQ9hIHPmBeZDJxKq721CyBiGAhRxDN+TYiaG/UWT 7IB7LL4zJrIe/xQ8HhRO+2NvT89o0LxEFKBGg39yjTMIrjbl2ZxY488+56UV4FclubrG+t16 r2KrandM7P5RjR+cuHhkKseim50Qsw0B+Eu33Hjry7YCihmGswARAQABtBhDb2x5IExpIDxj b2x5bGlAc3VzZS5kZT6JAlYEEwEIAEACGyMHCwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgBYh BOo+RS/0+Uhgjej60Mc5B5Nrffj8BQJcR84dBQkY++fuAAoJEMc5B5Nrffj8ixcP/3KAKg1X EcoW4u/0z+Ton5rCyb/NpAww8MuRjNW82UBUac7yCi1y3OW7NtLjuBLw5SaVG5AArb7IF3U0 qTOobqfl5XHsT0o5wFHZaKUrnHb6y7V3SplsJWfkP3JmOooJsQB3z3K96ZTkFelsNb0ZaBRu gV+LA4MomhQ+D3BCDR1it1OX/tpvm2uaDF6s/8uFtcDEM9eQeqATN/QAJ49nvU/I8zDSY9rc 0x9mP0x+gH4RccbnoPu/rUG6Fm1ZpLrbb6NpaYBBJ/V1BC4lIOjnd24bsoQrQmnJn9dSr60X 1MY60XDszIyzRw7vbJcUn6ZzPNFDxFFT9diIb+wBp+DD8ZlD/hnVpl4f921ZbvfOSsXAJrKB 1hGY17FPwelp1sPcK2mDT+pfHEMV+OQdZzD2OCKtza/5IYismJJm3oVUYMogb5vDNAw9X2aP XgwUuG+FDEFPamFMUwIfzYHcePfqf0mMsaeSgtA/xTxzx/0MLjUJHl46Bc0uKDhv7QUyGz0j Ywgr2mHTvG+NWQ/mDeHNGkcnsnp3IY7koDHnN2xMFXzY4bn9m8ctqKo2roqjCzoxD/njoAhf KBzdybLHATqJG/yiZSbCxDA1n/J4FzPyZ0rNHUAJ/QndmmVspE9syFpFCKigvvyrzm016+k+ FJ59Q6RG4MSy/+J565Xj+DNY3/dCuQINBFYX6S8BEADZP+2cl4DRFaSaBms08W8/smc5T2CO YhAoygZn71rB7Djml2ZdvrLRjR8Qbn0Q/2L2gGUVc63pJnbrjlXSx2LfAFE0SlfYIJ11aFdF 9w7RvqWByQjDJor3Z0fWvPExplNgMvxpD0U0QrVT5dIGTx9hadejCl/ug09Lr6MPQn+a4+qs aRWwgCSHaIuDkH3zI1MJXiqXXFKUzJ/Fyx6R72rqiMPHH2nfwmMu6wOXAXb7+sXjZz5Po9GJ g2OcEc+rpUtKUJGyeQsnCDxUcqJXZDBi/GnhPCcraQuqiQ7EGWuJfjk51vaI/rW4bZkA9yEP B9rBYngbz7cQymUsfxuTT8OSlhxjP3l4ZIZFKIhDaQeZMj8pumBfEVUyiF6KVSfgfNQ/5PpM R4/pmGbRqrAAElhrRPbKQnCkGWDr8zG+AjN1KF6rHaFgAIO7TtZ+F28jq4reLkur0N5tQFww wFwxzROdeLHuZjL7eEtcnNnzSkXHczLkV4kQ3+vr/7Gm65mQfnVpg6JpwpVrbDYQeOFlxZ8+ GERY5Dag4KgKa/4cSZX2x/5+KkQx9wHwackw5gDCvAdZ+Q81nm6tRxEYBBiVDQZYqO73stgT ZyrkxykUbQIy8PI+g7XMDCMnPiDncQqgf96KR3cvw4wN8QrgA6xRo8xOc2C3X7jTMQUytCz9 0MyV1QARAQABiQI8BBgBCAAmAhsMFiEE6j5FL/T5SGCN6PrQxzkHk2t9+PwFAlxHziAFCRj7 5/EACgkQxzkHk2t9+PxgfA//cH5R1DvpJPwraTAl24SUcG9EWe+NXyqveApe05nk15zEuxxd e4zFEjo+xYZilSveLqYHrm/amvQhsQ6JLU+8N60DZHVcXbw1Eb8CEjM5oXdbcJpXh1/1BEwl 4phsQMkxOTns51bGDhTQkv4lsZKvNByB9NiiMkT43EOx14rjkhHw3rnqoI7ogu8OO7XWfKcL CbchjJ8t3c2XK1MUe056yPpNAT2XPNF2EEBPG2Y2F4vLgEbPv1EtpGUS1+JvmK3APxjXUl5z 6xrxCQDWM5AAtGfM/IswVjbZYSJYyH4BQKrShzMb0rWUjkpXvvjsjt8rEXpZEYJgX9jvCoxt oqjCKiVLpwje9WkEe9O9VxljmPvxAhVqJjX62S+TGp93iD+mvpCoHo3+CcvyRcilz+Ko8lfO hS9tYT0HDUiDLvpUyH1AR2xW9RGDevGfwGTpF0K6cLouqyZNdhlmNciX48tFUGjakRFsxRmX K0Jx4CEZubakJe+894sX6pvNFiI7qUUdB882i5GR3v9ijVPhaMr8oGuJ3kvwBIA8lvRBGVGn 9xvzkQ8Prpbqh30I4NMp8MjFdkwCN6znBKPHdjNTwE5PRZH0S9J0o67IEIvHfH0eAWAsgpTz +jwc7VKH7vkvgscUhq/v1/PEWCAqh9UHy7R/jiUxwzw/288OpgO+i+2l11Y= Message-ID: <8ba5d50d-5fa3-9aa3-3f82-b790a51bef9a@suse.de> Date: Wed, 15 Jul 2020 18:35:15 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-bcache-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org On 2020/7/15 17:08, Johannes Thumshirn wrote: > On 15/07/2020 11:03, Coly Li wrote: >> On 2020/7/15 14:02, Hannes Reinecke wrote: >>> On 7/15/20 7:45 AM, Coly Li wrote: >>>> This patch adds comments to mark each member of struct cache_sb_disk, >>>> it is helpful to understand the bcache superblock on-disk layout. >>>> >>>> Signed-off-by: Coly Li >>>> --- >>>>   include/uapi/linux/bcache.h | 39 +++++++++++++++++++------------------ >>>>   1 file changed, 20 insertions(+), 19 deletions(-) >>>> >>>> diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h >>>> index 9a1965c6c3d0..afbd1b56a661 100644 >>>> --- a/include/uapi/linux/bcache.h >>>> +++ b/include/uapi/linux/bcache.h >>>> @@ -158,33 +158,33 @@ static inline struct bkey *bkey_idx(const struct >>>> bkey *k, unsigned int nr_keys) >>>>   #define BDEV_DATA_START_DEFAULT        16    /* sectors */ >>>>     struct cache_sb_disk { >>>> -    __le64            csum; >>>> -    __le64            offset;    /* sector where this sb was written */ >>>> -    __le64            version; >>>> +/*000*/    __le64            csum; >>>> +/*008*/    __le64            offset;    /* sector where this sb was >>>> written */ >>>> +/*010*/    __le64            version; >>>>   -    __u8            magic[16]; >>>> +/*018*/    __u8            magic[16]; >>>>   -    __u8            uuid[16]; >>>> +/*028*/    __u8            uuid[16]; >>>>       union { >>>> -        __u8        set_uuid[16]; >>>> +/*038*/        __u8        set_uuid[16]; >>>>           __le64        set_magic; >>>>       }; >>>> -    __u8            label[SB_LABEL_SIZE]; >>>> +/*048*/    __u8            label[SB_LABEL_SIZE]; >>>>   -    __le64            flags; >>>> -    __le64            seq; >>>> -    __le64            pad[8]; >>>> +/*068*/    __le64            flags; >>>> +/*070*/    __le64            seq; >>>> +/*078*/    __le64            pad[8]; >>>>         union { >>>>       struct { >>>>           /* Cache devices */ >>>> -        __le64        nbuckets;    /* device size */ >>>> +/*0b8*/        __le64        nbuckets;    /* device size */ >>>>   -        __le16        block_size;    /* sectors */ >>>> -        __le16        bucket_size;    /* sectors */ >>>> +/*0c0*/        __le16        block_size;    /* sectors */ >>>> +/*0c2*/        __le16        bucket_size;    /* sectors */ >>>>   -        __le16        nr_in_set; >>>> -        __le16        nr_this_dev; >>>> +/*0c4*/        __le16        nr_in_set; >>>> +/*0c6*/        __le16        nr_this_dev; >>>>       }; >>>>       struct { >>>>           /* Backing devices */ >>>> @@ -198,14 +198,15 @@ struct cache_sb_disk { >>>>       }; >>>>       }; >>>>   -    __le32            last_mount;    /* time overflow in y2106 */ >>>> +/*0c8*/    __le32            last_mount;    /* time overflow in y2106 */ >>>>   -    __le16            first_bucket; >>>> +/*0cc*/    __le16            first_bucket; >>>>       union { >>>> -        __le16        njournal_buckets; >>>> +/*0ce*/        __le16        njournal_buckets; >>>>           __le16        keys; >>>>       }; >>>> -    __le64            d[SB_JOURNAL_BUCKETS];    /* journal buckets */ >>>> +/*0d0*/    __le64            d[SB_JOURNAL_BUCKETS];    /* journal >>>> buckets */ >>>> +/*8d0*/ >>>>   }; >>>>     struct cache_sb { >>>> >>> Common practice is to place comments at the end; please don't use the >>> start of the line here. >> >> Hi Hannes, >> >> When I try to move the offset comment to the line end, I find it >> conflicts with normal code comment, e.g. >> __le64 d[SB_JOURNAL_BUCKETS]; /* journal buckets */ >> >> I have to add the offset comment to the line start. I guess this is why >> ocfs2 code adds the offset comment at the line start. >> >> So finally I have to keep the offset comment on line start still... > > Why at them at all? pahole -C or crash/gdb will show them for you if you're > interested and if you need it in the code you can use offsetof(). > > I don't really see a good reason to add these comments. > You are right :-) With pahole there is no reason for having this patch. Thanks for the informative hint, this patch will disappear in next version series. Coly Li