1 files changed, 70 insertions, 17 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 794af5024c2f..cc0395d7eba1 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -2040,6 +2040,73 @@ out:
         return err;
 }
 
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
+/*
+ * If common_cpu_mem_hotplug_unplug(), below, unplugs any CPUs
+ * or memory nodes, we need to walk over the cpuset hierarchy,
+ * removing that CPU or node from all cpusets.  If this removes the
+ * last CPU or node from a cpuset, then the guarantee_online_cpus()
+ * or guarantee_online_mems() code will use that emptied cpusets
+ * parent online CPUs or nodes.  Cpusets that were already empty of
+ * CPUs or nodes are left empty.
+ *
+ * This routine is intentionally inefficient in a couple of regards.
+ * It will check all cpusets in a subtree even if the top cpuset of
+ * the subtree has no offline CPUs or nodes.  It checks both CPUs and
+ * nodes, even though the caller could have been coded to know that
+ * only one of CPUs or nodes needed to be checked on a given call.
+ * This was done to minimize text size rather than cpu cycles.
+ *
+ * Call with both manage_mutex and callback_mutex held.
+ *
+ * Recursive, on depth of cpuset subtree.
+ */
+
+static void guarantee_online_cpus_mems_in_subtree(const struct cpuset *cur)
+{
+        struct cpuset *c;
+
+        /* Each of our child cpusets mems must be online */
+        list_for_each_entry(c, &cur->children, sibling) {
+                guarantee_online_cpus_mems_in_subtree(c);
+                if (!cpus_empty(c->cpus_allowed))
+                        guarantee_online_cpus(c, &c->cpus_allowed);
+                if (!nodes_empty(c->mems_allowed))
+                        guarantee_online_mems(c, &c->mems_allowed);
+        }
+}
+
+/*
+ * The cpus_allowed and mems_allowed nodemasks in the top_cpuset track
+ * cpu_online_map and node_online_map.  Force the top cpuset to track
+ * whats online after any CPU or memory node hotplug or unplug event.
+ *
+ * To ensure that we don't remove a CPU or node from the top cpuset
+ * that is currently in use by a child cpuset (which would violate
+ * the rule that cpusets must be subsets of their parent), we first
+ * call the recursive routine guarantee_online_cpus_mems_in_subtree().
+ *
+ * Since there are two callers of this routine, one for CPU hotplug
+ * events and one for memory node hotplug events, we could have coded
+ * two separate routines here.  We code it as a single common routine
+ * in order to minimize text size.
+ */
+
+static void common_cpu_mem_hotplug_unplug(void)
+{
+        mutex_lock(&manage_mutex);
+        mutex_lock(&callback_mutex);
+
+        guarantee_online_cpus_mems_in_subtree(&top_cpuset);
+        top_cpuset.cpus_allowed = cpu_online_map;
+        top_cpuset.mems_allowed = node_online_map;
+
+        mutex_unlock(&callback_mutex);
+        mutex_unlock(&manage_mutex);
+}
+#endif
+
+#ifdef CONFIG_HOTPLUG_CPU
 /*
  * The top_cpuset tracks what CPUs and Memory Nodes are online,
  * period.  This is necessary in order to make cpusets transparent
@@ -2050,38 +2117,24 @@ out:
  * cpu_online_map on each CPU hotplug (cpuhp) event.
  */
 
-#ifdef CONFIG_HOTPLUG_CPU
 static int cpuset_handle_cpuhp(struct notifier_block *nb,
                                 unsigned long phase, void *cpu)
 {
-        mutex_lock(&manage_mutex);
-        mutex_lock(&callback_mutex);
-
-        top_cpuset.cpus_allowed = cpu_online_map;
-
-        mutex_unlock(&callback_mutex);
-        mutex_unlock(&manage_mutex);
-
+        common_cpu_mem_hotplug_unplug();
         return 0;
 }
 #endif
 
+#ifdef CONFIG_MEMORY_HOTPLUG
 /*
  * Keep top_cpuset.mems_allowed tracking node_online_map.
  * Call this routine anytime after you change node_online_map.
  * See also the previous routine cpuset_handle_cpuhp().
  */
 
-#ifdef CONFIG_MEMORY_HOTPLUG
 void cpuset_track_online_nodes()
 {
-        mutex_lock(&manage_mutex);
-        mutex_lock(&callback_mutex);
-
-        top_cpuset.mems_allowed = node_online_map;
-
-        mutex_unlock(&callback_mutex);
-        mutex_unlock(&manage_mutex);
+        common_cpu_mem_hotplug_unplug();
 }
 #endif