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-rw-r--r--Documentation/cpusets.txt10
-rw-r--r--include/linux/cpuset.h4
-rw-r--r--kernel/cpuset.c28
-rw-r--r--mm/memory_hotplug.c3
4 files changed, 37 insertions, 8 deletions
diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt
index 76b44290c15..842f0d1ab21 100644
--- a/Documentation/cpusets.txt
+++ b/Documentation/cpusets.txt
@@ -217,11 +217,11 @@ exclusive cpuset. Also, the use of a Linux virtual file system (vfs)
to represent the cpuset hierarchy provides for a familiar permission
and name space for cpusets, with a minimum of additional kernel code.
-The cpus file in the root (top_cpuset) cpuset is read-only.
-It automatically tracks the value of cpu_online_map, using a CPU
-hotplug notifier. If and when memory nodes can be hotplugged,
-we expect to make the mems file in the root cpuset read-only
-as well, and have it track the value of node_online_map.
+The cpus and mems files in the root (top_cpuset) cpuset are
+read-only. The cpus file automatically tracks the value of
+cpu_online_map using a CPU hotplug notifier, and the mems file
+automatically tracks the value of node_online_map using the
+cpuset_track_online_nodes() hook.
1.4 What are exclusive cpusets ?
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 9354722a921..4d8adf66368 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -63,6 +63,8 @@ static inline int cpuset_do_slab_mem_spread(void)
return current->flags & PF_SPREAD_SLAB;
}
+extern void cpuset_track_online_nodes(void);
+
#else /* !CONFIG_CPUSETS */
static inline int cpuset_init_early(void) { return 0; }
@@ -126,6 +128,8 @@ static inline int cpuset_do_slab_mem_spread(void)
return 0;
}
+static inline void cpuset_track_online_nodes(void) {}
+
#endif /* !CONFIG_CPUSETS */
#endif /* _LINUX_CPUSET_H */
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 584bb4e6c04..794af5024c2 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -912,6 +912,10 @@ static int update_nodemask(struct cpuset *cs, char *buf)
int fudge;
int retval;
+ /* top_cpuset.mems_allowed tracks node_online_map; it's read-only */
+ if (cs == &top_cpuset)
+ return -EACCES;
+
trialcs = *cs;
retval = nodelist_parse(buf, trialcs.mems_allowed);
if (retval < 0)
@@ -2042,9 +2046,8 @@ out:
* (of no affect) on systems that are actively using CPU hotplug
* but making no active use of cpusets.
*
- * This handles CPU hotplug (cpuhp) events. If someday Memory
- * Nodes can be hotplugged (dynamically changing node_online_map)
- * then we should handle that too, perhaps in a similar way.
+ * This routine ensures that top_cpuset.cpus_allowed tracks
+ * cpu_online_map on each CPU hotplug (cpuhp) event.
*/
#ifdef CONFIG_HOTPLUG_CPU
@@ -2063,6 +2066,25 @@ static int cpuset_handle_cpuhp(struct notifier_block *nb,
}
#endif
+/*
+ * 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);
+}
+#endif
+
/**
* cpuset_init_smp - initialize cpus_allowed
*
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index c37319542b7..9576ed920c0 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -21,6 +21,7 @@
#include <linux/highmem.h>
#include <linux/vmalloc.h>
#include <linux/ioport.h>
+#include <linux/cpuset.h>
#include <asm/tlbflush.h>
@@ -283,6 +284,8 @@ int add_memory(int nid, u64 start, u64 size)
/* we online node here. we can't roll back from here. */
node_set_online(nid);
+ cpuset_track_online_nodes();
+
if (new_pgdat) {
ret = register_one_node(nid);
/*