Re: [PATCH] [RFC] maple_tree: reduce stack usage with gcc-9 and earlier

[Andrey Konovalov]

On Tue, Feb 14, 2023 at 8:40 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Tue, 14 Feb 2023 11:30:24 +0100 Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
>
> > From: Arnd Bergmann <arnd@xxxxxxxx>
> >
> > gcc-10 changed the way inlining works to be less aggressive, but
> > older versions run into an oversized stack frame warning whenever
> > CONFIG_KASAN_STACK is enabled, as that forces variables from
> > inlined callees to be non-overlapping:
> >
> > lib/maple_tree.c: In function 'mas_wr_bnode':
> > lib/maple_tree.c:4320:1: error: the frame size of 1424 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]
> >
> > Change the annotations on mas_store_b_node() and mas_commit_b_node()
> > to explicitly forbid inlining in this configuration, which is
> > the same behavior that newer versions already have.
> >
> > ...
> >
> > --- a/lib/maple_tree.c
> > +++ b/lib/maple_tree.c
> > @@ -146,6 +146,13 @@ struct maple_subtree_state {
> >       struct maple_big_node *bn;
> >  };
> >
> > +#ifdef CONFIG_KASAN_STACK
> > +/* Prevent mas_wr_bnode() from exceeding the stack frame limit */
> > +#define noinline_for_kasan noinline_for_stack
> > +#else
> > +#define noinline_for_kasan inline
> > +#endif
>
> Should noinline_for_kasan be defined in kasan.h?  maple_tree.c is
> unlikely to be the only place in the kernel which could use this
> treatment?

We could also define it in include/linux/compiler_types.h along with
other KASAN attributes.