Re: [PATCH] mm/filemap: add static for function __add_to_page_cache_locked

[Steven Rostedt]

On Wed, 9 Dec 2020 17:12:43 -0800
Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> wrote:

> > > > > FWIW, I intend to do some consolidation/renaming in this area.  I
> > > > > trust that will not be a problem?  
> > > >
> > > > If it does not break anything, it will be not a problem ;-)
> > > >
> > > > It's possible that __add_to_page_cache_locked() can be a global symbol
> > > > with add_to_page_cache_lru() + add_to_page_cache_locked() being just
> > > > static/inline wrappers around it.  
> > >
> > > So what happens to BTF if we change this area entirely?  Your IDs
> > > sound like some kind of ABI to me, which is extremely scary.  
> >
> > Is BTF becoming the new tracepoint? That is, random additions of things like:
> >
> >    BTF_ID(func,__add_to_page_cache_locked)
> >
> > Like was done in commit 1e6c62a882155 ("bpf: Introduce sleepable BPF
> > programs") without any notification to the maintainers of the
> > __add_to_page_cache_locked code, will suddenly become an API?  
> 
> huh? what api/abi you're talking about?

If the function __add_to_page_cache_locked were to be removed due to
the code being rewritten,  would it break any user space? If not, then
there's nothing to worry about. ;-)

-- Steve