mem-hotplug: fix potential race while building zonelist for new populated zone

[linux-2.6-block.git] / mm / page_alloc.c

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 21c52d2d8624a368c388e15e6df338441f6ba5ca..08b349931ebc6bffef8be14c1d5d890750a88038 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2571,8 +2571,11 @@ int numa_zonelist_order_handler(ctl_table *table, int write,
                        strncpy((char*)table->data, saved_string,
                                NUMA_ZONELIST_ORDER_LEN);
                        user_zonelist_order = oldval;
-               } else if (oldval != user_zonelist_order)
+               } else if (oldval != user_zonelist_order) {
+                       mutex_lock(&zonelists_mutex);
                        build_all_zonelists(NULL);
+                       mutex_unlock(&zonelists_mutex);
+               }
        }
 out:
        mutex_unlock(&zl_order_mutex);
@@ -2924,6 +2927,12 @@ static void setup_pageset(struct per_cpu_pageset *p, unsigned long batch);
 static DEFINE_PER_CPU(struct per_cpu_pageset, boot_pageset);
 static void setup_zone_pageset(struct zone *zone);
 
+/*
+ * Global mutex to protect against size modification of zonelists
+ * as well as to serialize pageset setup for the new populated zone.
+ */
+DEFINE_MUTEX(zonelists_mutex);
+
 /* return values int ....just for stop_machine() */
 static __init_refok int __build_all_zonelists(void *data)
 {
@@ -2967,6 +2976,10 @@ static __init_refok int __build_all_zonelists(void *data)
        return 0;
 }
 
+/*
+ * Called with zonelists_mutex held always
+ * unless system_state == SYSTEM_BOOTING.
+ */
 void build_all_zonelists(void *data)
 {
        set_zonelist_order();