linux-kernel - Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as EXPORT_SYMBOL

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Date:   Tue, 7 Jul 2020 15:13:02 +0300
From:   Mike Rapoport <rppt@...ux.ibm.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Jia He <justin.he@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Baoquan He <bhe@...hat.com>,
        Chuhong Yuan <hslester96@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-nvdimm@...ts.01.org,
        Kaly Xin <Kaly.Xin@....com>
Subject: Re: [PATCH v2 1/3] arm64/numa: export memory_add_physaddr_to_nid as
 EXPORT_SYMBOL_GPL

On Tue, Jul 07, 2020 at 01:54:54PM +0200, Michal Hocko wrote:
> On Tue 07-07-20 13:59:15, Jia He wrote:
> > This exports memory_add_physaddr_to_nid() for module driver to use.
> > 
> > memory_add_physaddr_to_nid() is a fallback option to get the nid in case
> > NUMA_NO_NID is detected.
> > 
> > Suggested-by: David Hildenbrand <david@...hat.com>
> > Signed-off-by: Jia He <justin.he@....com>
> > ---
> >  arch/arm64/mm/numa.c | 5 +++--
> >  1 file changed, 3 insertions(+), 2 deletions(-)
> > 
> > diff --git a/arch/arm64/mm/numa.c b/arch/arm64/mm/numa.c
> > index aafcee3e3f7e..7eeb31740248 100644
> > --- a/arch/arm64/mm/numa.c
> > +++ b/arch/arm64/mm/numa.c
> > @@ -464,10 +464,11 @@ void __init arm64_numa_init(void)
> >  
> >  /*
> >   * We hope that we will be hotplugging memory on nodes we already know about,
> > - * such that acpi_get_node() succeeds and we never fall back to this...
> > + * such that acpi_get_node() succeeds. But when SRAT is not present, the node
> > + * id may be probed as NUMA_NO_NODE by acpi, Here provide a fallback option.
> >   */
> >  int memory_add_physaddr_to_nid(u64 addr)
> >  {
> > -	pr_warn("Unknown node for memory at 0x%llx, assuming node 0\n", addr);
> >  	return 0;
> >  }
> > +EXPORT_SYMBOL_GPL(memory_add_physaddr_to_nid);
> 
> Does it make sense to export a noop function? Wouldn't make more sense
> to simply make it static inline somewhere in a header? I haven't checked
> whether there is an easy way to do that sanely bu this just hit my eyes.

We'll need to either add a CONFIG_ option or arch specific callback to
make both non-empty (x86, powerpc, ia64) and empty (arm64, sh)
implementations coexist ...

> -- 
> Michal Hocko
> SUSE Labs

-- 
Sincerely yours,
Mike.