mm, page_alloc: do not set_cpu_numa_mem on empty nodes initialization

__build_all_zonelists reinitializes each online cpu local node for
CONFIG_HAVE_MEMORYLESS_NODES.  This makes sense because previously
memory less nodes could gain some memory during memory hotplug and so
the local node should be changed for CPUs close to such a node.  It
makes less sense to do that unconditionally for a newly creaded NUMA
node which is still offline and without any memory.

Let's also simplify the cpu loop and use for_each_online_cpu instead of
an explicit cpu_online check for all possible cpus.

Link: http://lkml.kernel.org/r/20170721143915.14161-4-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <js1304@gmail.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: Toshi Kani <toshi.kani@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 94e6478..94fb437 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5160,10 +5160,8 @@ static int __build_all_zonelists(void *data)
 
                        build_zonelists(pgdat);
                }
-       }
 
 #ifdef CONFIG_HAVE_MEMORYLESS_NODES
-       for_each_possible_cpu(cpu) {
                /*
                 * We now know the "local memory node" for each node--
                 * i.e., the node of the first zone in the generic zonelist.
@@ -5172,10 +5170,10 @@ static int __build_all_zonelists(void *data)
                 * secondary cpus' numa_mem as they come on-line.  During
                 * node/memory hotplug, we'll fixup all on-line cpus.
                 */
-               if (cpu_online(cpu))
+               for_each_online_cpu(cpu)
                        set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
-       }
 #endif
+       }
 
        return 0;
 }