2 files changed, 20 insertions, 2 deletions

diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index 37d2dd7ca3e9..34081c168af5 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -14,6 +14,8 @@
 
 #ifdef CONFIG_CPUSETS
 
+extern int number_of_cpusets;   /* How many cpusets are defined in system? */
+
 extern int cpuset_init(void);
 extern void cpuset_init_smp(void);
 extern void cpuset_fork(struct task_struct *p);
@@ -25,7 +27,13 @@ void cpuset_update_task_memory_state(void);
 #define cpuset_nodes_subset_current_mems_allowed(nodes) \
                 nodes_subset((nodes), current->mems_allowed)
 int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl);
-extern int cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask);
+
+extern int __cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask);
+static int inline cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
+{
+        return number_of_cpusets <= 1 || __cpuset_zone_allowed(z, gfp_mask);
+}
+
 extern int cpuset_excl_nodes_overlap(const struct task_struct *p);
 
 #define cpuset_memory_pressure_bump()                           \
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 8f764de3a9e7..6004719f26ee 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -56,6 +56,13 @@
 
 #define CPUSET_SUPER_MAGIC              0x27e0eb
 
+/*
+ * Tracks how many cpusets are currently defined in system.
+ * When there is only one cpuset (the root cpuset) we can
+ * short circuit some hooks.
+ */
+int number_of_cpusets;
+
 /* See "Frequency meter" comments, below. */
 
 struct fmeter {
@@ -1664,6 +1671,7 @@ static long cpuset_create(struct cpuset *parent, const char *name, int mode)
 
         down(&callback_sem);
         list_add(&cs->sibling, &cs->parent->children);
+        number_of_cpusets++;
         up(&callback_sem);
 
         err = cpuset_create_dir(cs, name, mode);
@@ -1726,6 +1734,7 @@ static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry)
         spin_unlock(&d->d_lock);
         cpuset_d_remove_dir(d);
         dput(d);
+        number_of_cpusets--;
         up(&callback_sem);
         if (list_empty(&parent->children))
                 check_for_release(parent, &pathbuf);
@@ -1769,6 +1778,7 @@ int __init cpuset_init(void)
         root->d_inode->i_nlink++;
         top_cpuset.dentry = root;
         root->d_inode->i_op = &cpuset_dir_inode_operations;
+        number_of_cpusets = 1;
         err = cpuset_populate_dir(root);
         /* memory_pressure_enabled is in root cpuset only */
         if (err == 0)
@@ -1982,7 +1992,7 @@ static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs)
  *      GFP_USER     - only nodes in current tasks mems allowed ok.
  **/
 
-int cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
+int __cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
 {
         int node;                       /* node that zone z is on */
         const struct cpuset *cs;        /* current cpuset ancestors */