From: Michal Hocko <mhocko@xxxxxxxx> 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 <mhocko@xxxxxxxx> --- 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.GN22917@xxxxxxxxxxxxxx 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 -- 2.11.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
