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From: Joe Perches <joe@perches.com>
To: Gao Xiang <gaoxiang25@huawei.com>, Christoph Hellwig <hch@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Theodore Ts'o <tytso@mit.edu>, Pavel Machek <pavel@denx.de>,
	David Sterba <dsterba@suse.cz>,
	Amir Goldstein <amir73il@gmail.com>,
	"Darrick J . Wong" <darrick.wong@oracle.com>,
	Dave Chinner <david@fromorbit.com>,
	Jaegeuk Kim <jaegeuk@kernel.org>, Jan Kara <jack@suse.cz>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	linux-fsdevel@vger.kernel.org, devel@driverdev.osuosl.org,
	LKML <linux-kernel@vger.kernel.org>,
	linux-erofs@lists.ozlabs.org, Chao Yu <yuchao0@huawei.com>,
	Miao Xie <miaoxie@huawei.com>,
	Li Guifu <bluce.liguifu@huawei.com>,
	Fang Wei <fangwei1@huawei.com>
Subject: Re: [PATCH v6 01/24] erofs: add on-disk layout
Date: Thu, 29 Aug 2019 08:58:17 -0700
Message-ID: <67d6efbbc9ac6db23215660cb970b7ef29dc0c1d.camel@perches.com> (raw)
In-Reply-To: <20190829103252.GA64893@architecture4>

On Thu, 2019-08-29 at 18:32 +0800, Gao Xiang wrote:
> Hi Christoph,
> 
> On Thu, Aug 29, 2019 at 02:59:54AM -0700, Christoph Hellwig wrote:
> > > --- /dev/null
> > > +++ b/fs/erofs/erofs_fs.h
> > > @@ -0,0 +1,316 @@
> > > +/* SPDX-License-Identifier: GPL-2.0-only OR Apache-2.0 */
> > > +/*
> > > + * linux/fs/erofs/erofs_fs.h
> > 
> > Please remove the pointless file names in the comment headers.
> 
> Already removed in the latest version.
> 
> > > +struct erofs_super_block {
> > > +/*  0 */__le32 magic;           /* in the little endian */
> > > +/*  4 */__le32 checksum;        /* crc32c(super_block) */
> > > +/*  8 */__le32 features;        /* (aka. feature_compat) */
> > > +/* 12 */__u8 blkszbits;         /* support block_size == PAGE_SIZE only */
> > 
> > Please remove all the byte offset comments.  That is something that can
> > easily be checked with gdb or pahole.
> 
> I have no idea the actual issue here.
> It will help all developpers better add fields or calculate
> these offsets in their mind, and with care.
> 
> Rather than they didn't run "gdb" or "pahole" and change it by mistake.

I think Christoph is not right here.

Using external tools for validation is extra work
when necessary for understanding the code.

The expected offset is somewhat valuable, but
perhaps the form is a bit off given the visual
run-in to the field types.

The extra work with this form is manipulating all
the offsets whenever a structure change occurs.

The comments might be better with a form more like:

struct erofs_super_block {	/* offset description */
	__le32 magic;		/*   0  */
	__le32 checksum;	/*   4  crc32c(super_block) */
	__le32 features;	/*   8  (aka. feature_compat) */
	__u8 blkszbits;		/*  12  support block_size == PAGE_SIZE only */



  parent reply index

Thread overview: 70+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-02 12:53 [PATCH v6 00/24] erofs: promote erofs from staging Gao Xiang
2019-08-02 12:53 ` [PATCH v6 01/24] erofs: add on-disk layout Gao Xiang
2019-08-29  9:59   ` Christoph Hellwig
2019-08-29 10:32     ` Gao Xiang
2019-08-29 10:36       ` Christoph Hellwig
2019-08-29 10:58         ` Gao Xiang
2019-08-29 15:58       ` Joe Perches [this message]
2019-08-29 17:26         ` Gao Xiang
2019-08-30 12:07         ` David Sterba
2019-08-30 12:18           ` Gao Xiang
2019-09-02  8:43           ` Pavel Machek
2019-09-02 14:07             ` David Sterba
2019-09-03 11:27               ` Pavel Machek
2019-08-29 15:41     ` Gao Xiang
2019-09-01  7:54     ` Gao Xiang
2019-09-02 12:45       ` Christoph Hellwig
2019-09-02 13:02         ` Gao Xiang
2019-09-02  8:40     ` Pavel Machek
2019-09-02 10:35       ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 02/24] erofs: add erofs in-memory stuffs Gao Xiang
2019-08-02 12:53 ` [PATCH v6 03/24] erofs: add super block operations Gao Xiang
2019-08-29 10:15   ` Christoph Hellwig
2019-08-29 10:50     ` Gao Xiang
2019-08-30 16:39       ` Christoph Hellwig
2019-08-30 17:15         ` Gao Xiang
2019-08-31  0:54           ` Gao Xiang
2019-08-31  6:34           ` Amir Goldstein
2019-08-31  6:48             ` Gao Xiang
2019-09-01  8:54     ` Gao Xiang
2019-09-02 12:51       ` Christoph Hellwig
2019-09-02 14:43         ` Gao Xiang
2019-09-02 15:19           ` Christoph Hellwig
2019-09-02 15:24             ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 04/24] erofs: add raw address_space operations Gao Xiang
2019-08-29 10:17   ` Christoph Hellwig
2019-08-29 11:46     ` Gao Xiang
2019-08-30 16:40       ` Christoph Hellwig
2019-08-30 17:23         ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 05/24] erofs: add inode operations Gao Xiang
2019-08-29 10:24   ` Christoph Hellwig
2019-08-29 11:59     ` Gao Xiang
2019-08-30 16:42       ` Christoph Hellwig
2019-08-30 18:46         ` Gao Xiang
2019-09-01  9:34     ` Gao Xiang
2019-09-02 12:53       ` Christoph Hellwig
2019-09-02 13:43       ` David Sterba
2019-09-02 13:55         ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 06/24] erofs: support special inode Gao Xiang
2019-08-29 10:25   ` Christoph Hellwig
2019-09-01  9:39     ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 07/24] erofs: add directory operations Gao Xiang
2019-08-02 12:53 ` [PATCH v6 08/24] erofs: add namei functions Gao Xiang
2019-08-29 10:28   ` Christoph Hellwig
2019-08-29 11:28     ` Gao Xiang
2019-08-02 12:53 ` [PATCH v6 09/24] erofs: support tracepoint Gao Xiang
2019-08-02 12:53 ` [PATCH v6 10/24] erofs: update Kconfig and Makefile Gao Xiang
2019-08-02 12:53 ` [PATCH v6 11/24] erofs: introduce xattr & posixacl support Gao Xiang
2019-08-02 12:53 ` [PATCH v6 12/24] erofs: introduce tagged pointer Gao Xiang
2019-08-02 12:53 ` [PATCH v6 13/24] erofs: add compression indexes support Gao Xiang
2019-08-02 12:53 ` [PATCH v6 14/24] erofs: introduce superblock registration Gao Xiang
2019-08-02 12:53 ` [PATCH v6 15/24] erofs: introduce erofs shrinker Gao Xiang
2019-08-02 12:53 ` [PATCH v6 16/24] erofs: introduce workstation for decompression Gao Xiang
2019-08-02 12:53 ` [PATCH v6 17/24] erofs: introduce per-CPU buffers implementation Gao Xiang
2019-08-02 12:53 ` [PATCH v6 18/24] erofs: introduce pagevec for decompression subsystem Gao Xiang
2019-08-02 12:53 ` [PATCH v6 19/24] erofs: add erofs_allocpage() Gao Xiang
2019-08-02 12:53 ` [PATCH v6 20/24] erofs: introduce generic decompression backend Gao Xiang
2019-08-02 12:53 ` [PATCH v6 21/24] erofs: introduce LZ4 decompression inplace Gao Xiang
2019-08-02 12:53 ` [PATCH v6 22/24] erofs: introduce the decompression frontend Gao Xiang
2019-08-02 12:53 ` [PATCH v6 23/24] erofs: introduce cached decompression Gao Xiang
2019-08-02 12:53 ` [PATCH v6 24/24] erofs: add document Gao Xiang

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