mm, page_alloc: remove boot pageset initialization from memory hotplug

boot_pageset is a boot time hack which gets superseded by normal
pagesets later in the boot process.  It makes zero sense to reinitialize
it again and again during memory hotplug.

Link: http://lkml.kernel.org/r/20170721143915.14161-3-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 6b23df1..94e6478 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5141,7 +5141,7 @@ DEFINE_MUTEX(zonelists_mutex);
 static int __build_all_zonelists(void *data)
 {
        int nid;
-       int cpu;
+       int __maybe_unused cpu;
        pg_data_t *self = data;
 
 #ifdef CONFIG_NUMA
@@ -5162,23 +5162,8 @@ static int __build_all_zonelists(void *data)
                }
        }
 
-       /*
-        * Initialize the boot_pagesets that are going to be used
-        * for bootstrapping processors. The real pagesets for
-        * each zone will be allocated later when the per cpu
-        * allocator is available.
-        *
-        * boot_pagesets are used also for bootstrapping offline
-        * cpus if the system is already booted because the pagesets
-        * are needed to initialize allocators on a specific cpu too.
-        * F.e. the percpu allocator needs the page allocator which
-        * needs the percpu allocator in order to allocate its pagesets
-        * (a chicken-egg dilemma).
-        */
-       for_each_possible_cpu(cpu) {
-               setup_pageset(&per_cpu(boot_pageset, cpu), 0);
-
 #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.
@@ -5189,8 +5174,8 @@ static int __build_all_zonelists(void *data)
                 */
                if (cpu_online(cpu))
                        set_cpu_numa_mem(cpu, local_memory_node(cpu_to_node(cpu)));
-#endif
        }
+#endif
 
        return 0;
 }
@@ -5198,7 +5183,26 @@ static int __build_all_zonelists(void *data)
 static noinline void __init
 build_all_zonelists_init(void)
 {
+       int cpu;
+
        __build_all_zonelists(NULL);
+
+       /*
+        * Initialize the boot_pagesets that are going to be used
+        * for bootstrapping processors. The real pagesets for
+        * each zone will be allocated later when the per cpu
+        * allocator is available.
+        *
+        * boot_pagesets are used also for bootstrapping offline
+        * cpus if the system is already booted because the pagesets
+        * are needed to initialize allocators on a specific cpu too.
+        * F.e. the percpu allocator needs the page allocator which
+        * needs the percpu allocator in order to allocate its pagesets
+        * (a chicken-egg dilemma).
+        */
+       for_each_possible_cpu(cpu)
+               setup_pageset(&per_cpu(boot_pageset, cpu), 0);
+
        mminit_verify_zonelist();
        cpuset_init_current_mems_allowed();
 }