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SubjectRe: [PATCH 0/4] initramfs: remove sparse warnings
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2010-08-22 (일), 22:33 +0200, Arnd Bergmann:
> On Friday 20 August 2010 17:36:41 Namhyung Kim wrote:
> >
> > 2010-08-20 (금), 13:00 +0100, Al Viro:
> > > No. This code should NOT use the VFS guts, TYVM. The whole fscking point
> > > is that this puppy is a sequence of plain vanilla syscalls, ideally run
> > > simply in userland thread. We used to have a magical mystery shite in there
> > > and it had been a huge PITA.
> >
> > So is it worth to work on removing the warnings like this patchset does?
> > Or else, how can I improve the code even a bit? Can you please give me a
> > direction?
>
> It would be useful to add annotations in those places where they are
> obviously just missing but don't require adding __force.
> Even better would be patches that fix actual bugs found by sparse.
>
> Simply throwing in extra __force arguments will just make people
> nervous, because it is often a sign of papering over a bug instead
> of fixing it, and warnings in the core kernel are there exactly
> because there is no easy correct fix for them.
>
> Try producing patches that clean up the code and result in using
> fewer annotations and especially few __force where possible.
> Also, in places where you need __force, make sure that a person
> reading that code understands why it's needed and that the use is
> correct (or at least permissable).
>
> One possible solution in this particular case would be to add
> helper functions like
>
> /* wrapper for sys_newlstat for use in the init code */
> static inline int kern_newlstat(const char * filename, struct stat * statbuf)
> {
> mm_segment_t fs = get_fs();
> int ret;
>
> set_fs(KERNEL_DS);
> ret = sys_newlstat((const char __user __force*)filename,
> (struct stat __user __force *)statbuf);
> set_fs(fs);
>
> return ret;
> }
>
> Such a function makes it clear that it can only accept a kernel pointer,
> and it documents how the conversion to a __user pointer happens (by
> calling set_fs).
> Then again, it adds some bloat, and it may encourage people to do the
> same thing in device drivers, which could be argued against such helpers.
>
> In general, my recommendation would be to leave code alone if you can't
> come up with a patch that clearly improves it. There is enough
> bad code in the kernel that can use some help along the lines of
> your other patches, so you may want to focus on that.
>
> Arnd

Thank you Arnd for the precious comments and advices. This really helps
me.

--
Regards,
Namhyung Kim


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