Re: [PATCH v6 01/24] erofs: add on-disk layout

Gao Xiang
2019-08-29T17:27:08Z

Hi Joe,

On Thu, Aug 29, 2019 at 08:58:17AM -0700, Joe Perches wrote:
> 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:

Thanks for your comment.
I will change those places as you suggested, that is fine.

Thanks,
Gao Xiang

>
> 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 */
>
>