Commit 9d1f4b3f authored Jul 10, 2017 by Michal Hocko Committed by Linus Torvalds Jul 10, 2017

mm: disallow early_pfn_to_nid on configurations which do not implement it

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.

Link: http://lkml.kernel.org/r/20170704075803.15979-1-mhocko@kernel.org


Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Yang Shi <yang.shi@linaro.org>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 3f906ba2

include/linux/mmzone.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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

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