Re: [Ext2-devel] [RFC] [PATCH] Clean up fs.h union for ext2

Oliver Xymoron
2001-12-29T16:05:17Z

On Thu, 27 Dec 2001, Andreas Dilger wrote:

> On Dec 27, 2001 04:21 +0100, Daniel Phillips wrote:
> > The strategy is to abstract all references to the struct inode union through
> > an inline function:
> >
> > static inline struct ext2_inode_info *ext2_i (struct inode *inode)
> > {
> > return &(inode->u.ext2_inode_info);
> > }
> >
> > There is some grist here for the mills of language lawyers here. Note the
> > compilation warning:
> >
> > ialloc.c:336: warning: passing arg 1 of `ext2_i' discards qualifiers from
> > pointer target type
>
> Why not just declare ext2_i like the following? It _should_ work:
>
> static inline struct ext2_inode_info *ext2_i(const struct inode *inode)
> {
> return &(inode->u.ext2_inode_info);
> }

This will get rid of the warning but it doesn't solve the underlying
problem of discarding the potentially useful const information. In C++,
you'd define a pair of functions to deal with this, one with and one
without const.

> Minor nit: this is already done for the ext3 code, but it looks like:
>
> #define EXT3_I (&((inode)->u.ext3_i))
>
> We already have the EXT3_SB, so I thought I would be consistent with it:
>
> #define EXT3_SB (&((sb)->u.ext3_sb))
>
> Do people like the inline version better? Either way, I would like to make
> the ext2 and ext3 codes more similar, rather than less.

The ext3 macros are rather revolting, simply because they assume the
variable name. A parameterized macro might be the best compromise:

#define EXT2_I(i) (&(i->u.ext2_inode_info))

--
"Love the dolphins," she advised him. "Write by W.A.S.T.E.."