cpu/mem hotplug: add try_online_node() for cpu_up()

cpu_up() has #ifdef CONFIG_MEMORY_HOTPLUG code blocks, which call
mem_online_node() to put its node online if offlined and then call
build_all_zonelists() to initialize the zone list.

These steps are specific to memory hotplug, and should be managed in
mm/memory_hotplug.c.  lock_memory_hotplug() should also be held for the
whole steps.

For this reason, this patch replaces mem_online_node() with
try_online_node(), which performs the whole steps with
lock_memory_hotplug() held.  try_online_node() is named after
try_offline_node() as they have similar purpose.

There is no functional change in this patch.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Reviewed-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 26 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 63aa50d7ce1e..973d034acf84 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -437,11 +437,6 @@ int cpu_up(unsigned int cpu)
 {
         int err = 0;
 
-#ifdef  CONFIG_MEMORY_HOTPLUG
-        int nid;
-        pg_data_t       *pgdat;
-#endif
-
         if (!cpu_possible(cpu)) {
                 printk(KERN_ERR "can't online cpu %d because it is not "
                         "configured as may-hotadd at boot time\n", cpu);
@@ -452,27 +447,9 @@ int cpu_up(unsigned int cpu)
                 return -EINVAL;
         }
 
-#ifdef  CONFIG_MEMORY_HOTPLUG
-        nid = cpu_to_node(cpu);
-        if (!node_online(nid)) {
-                err = mem_online_node(nid);
-                if (err)
-                        return err;
-        }
-
-        pgdat = NODE_DATA(nid);
-        if (!pgdat) {
-                printk(KERN_ERR
-                        "Can't online cpu %d due to NULL pgdat\n", cpu);
-                return -ENOMEM;
-        }
-
-        if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
-                mutex_lock(&zonelists_mutex);
-                build_all_zonelists(NULL, NULL);
-                mutex_unlock(&zonelists_mutex);
-        }
-#endif
+        err = try_online_node(cpu_to_node(cpu));
+        if (err)
+                return err;
 
         cpu_maps_update_begin();