Re: [RFC] Slimming down struct inode

[Avi Kivity <avi@argo.co.il>]

Jan Engelhardt wrote:
> > > > if (inode->i_ops->getblksize)
> > > >     return inode->i_ops->getblksize(inode);
> > > > else
> > > > return inode->i_sb->s_blksize;
> > > >
> > > > Trading some efficiency for space.
> > > >         
> > > Yep, that was what I was planning on doing....
> > >
> > >       
> > Maybe
> >
> > if (inode->i_sb->s_blksize)
> >   return inode->i_sb->s_blksize;
> > else
> > ...
> >
> > is a tiny little bit faster...
> >
> >     
>
> The compiler will anyway pick the one it thinks is better by itself.
> Influence can be taken using likely/unlikely of course.
>   

The compiler cannot infer that (inode->i_ops->getblksize == 0) is 
equivalent to (inode->i_sb->s_blksize != 0).

Maybe someday the language will allow us to specify it, but not today.

--
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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