On 07/04/2017 09:58 AM, Michal Hocko wrote: > From: Michal Hocko <mho...@suse.com> > > early_pfn_to_nid will return node 0 if both HAVE_ARCH_EARLY_PFN_TO_NID > and HAVE_MEMBLOCK_NODE_MAP are disabled. It seems we are safe now > because all architectures which support NUMA define one of them (with an > exception of alpha which however has CONFIG_NUMA marked as broken) so > this works as expected. It can get silently and subtly broken too > easily, though. Make sure we fail the compilation if NUMA is enabled and > there is no proper implementation for this function. If that ever > happens we know that either the specific configuration is invalid > and the fix should either disable NUMA or enable one of the above > configs. > > Signed-off-by: Michal Hocko <mho...@suse.com>
Acked-by: Vlastimil Babka <vba...@suse.cz> > --- > Hi, > I have brought this up earlier [1] because I thought the deferred > initialization might be broken but then found out that this is not the > case right now. This is an attempt to prevent any subtly broken users in > future. > > [1] http://lkml.kernel.org/r/20170630141847.gn22...@dhcp22.suse.cz > > include/linux/mmzone.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 16532fa0bb64..fc14b8b3f6ce 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -1055,6 +1055,7 @@ static inline struct zoneref > *first_zones_zonelist(struct zonelist *zonelist, > !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) > static inline unsigned long early_pfn_to_nid(unsigned long pfn) > { > + BUILD_BUG_ON(IS_ENABLED(CONFIG_NUMA)); > return 0; > } > #endif >
