[PATCH] sched_domain: handle kmalloc failure

Try to handle mem allocation failures in build_sched_domains by bailing out
and cleaning up thus-far allocated memory.  The patch has a direct consequence
that we disable load balancing completely (even at sibling level) upon *any*
memory allocation failure.

[Lee.Schermerhorn@hp.com: bugfix]
Signed-off-by: Srivatsa Vaddagir <vatsa@in.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Signed-off-by: Lee Schermerhorn <lee.schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 79 insertions, 62 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 74a1e39e0d3d..ab8ffc54423a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -639,7 +639,7 @@ struct sched_domain {
 #endif
 };
 
-extern void partition_sched_domains(cpumask_t *partition1,
+extern int partition_sched_domains(cpumask_t *partition1,
                                     cpumask_t *partition2);
 
 /*
diff --git a/kernel/sched.c b/kernel/sched.c
index 0ec84f57695d..77a2ec55ef7d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5820,11 +5820,56 @@ next_sg:
 }
 #endif
 
+/* Free memory allocated for various sched_group structures */
+static void free_sched_groups(const cpumask_t *cpu_map)
+{
+#ifdef CONFIG_NUMA
+        int i;
+        int cpu;
+
+        for_each_cpu_mask(cpu, *cpu_map) {
+                struct sched_group *sched_group_allnodes
+                        = sched_group_allnodes_bycpu[cpu];
+                struct sched_group **sched_group_nodes
+                        = sched_group_nodes_bycpu[cpu];
+
+                if (sched_group_allnodes) {
+                        kfree(sched_group_allnodes);
+                        sched_group_allnodes_bycpu[cpu] = NULL;
+                }
+
+                if (!sched_group_nodes)
+                        continue;
+
+                for (i = 0; i < MAX_NUMNODES; i++) {
+                        cpumask_t nodemask = node_to_cpumask(i);
+                        struct sched_group *oldsg, *sg = sched_group_nodes[i];
+
+                        cpus_and(nodemask, nodemask, *cpu_map);
+                        if (cpus_empty(nodemask))
+                                continue;
+
+                        if (sg == NULL)
+                                continue;
+                        sg = sg->next;
+next_sg:
+                        oldsg = sg;
+                        sg = sg->next;
+                        kfree(oldsg);
+                        if (oldsg != sched_group_nodes[i])
+                                goto next_sg;
+                }
+                kfree(sched_group_nodes);
+                sched_group_nodes_bycpu[cpu] = NULL;
+        }
+#endif
+}
+
 /*
  * Build sched domains for a given set of cpus and attach the sched domains
  * to the individual cpus
  */
-void build_sched_domains(const cpumask_t *cpu_map)
+static int build_sched_domains(const cpumask_t *cpu_map)
 {
         int i;
 #ifdef CONFIG_NUMA
@@ -5834,11 +5879,11 @@ void build_sched_domains(const cpumask_t *cpu_map)
         /*
          * Allocate the per-node list of sched groups
          */
-        sched_group_nodes = kmalloc(sizeof(struct sched_group*)*MAX_NUMNODES,
+        sched_group_nodes = kzalloc(sizeof(struct sched_group*)*MAX_NUMNODES,
                                            GFP_ATOMIC);
         if (!sched_group_nodes) {
                 printk(KERN_WARNING "Can not alloc sched group node list\n");
-                return;
+                return -ENOMEM;
         }
         sched_group_nodes_bycpu[first_cpu(*cpu_map)] = sched_group_nodes;
 #endif
@@ -5864,7 +5909,7 @@ void build_sched_domains(const cpumask_t *cpu_map)
                                 if (!sched_group_allnodes) {
                                         printk(KERN_WARNING
                                         "Can not alloc allnodes sched group\n");
-                                        break;
+                                        goto error;
                                 }
                                 sched_group_allnodes_bycpu[i]
                                                 = sched_group_allnodes;
@@ -5978,23 +6023,20 @@ void build_sched_domains(const cpumask_t *cpu_map)
                 cpus_and(domainspan, domainspan, *cpu_map);
 
                 sg = kmalloc(sizeof(struct sched_group), GFP_KERNEL);
+                if (!sg) {
+                        printk(KERN_WARNING "Can not alloc domain group for "
+                                "node %d\n", i);
+                        goto error;
+                }
                 sched_group_nodes[i] = sg;
                 for_each_cpu_mask(j, nodemask) {
                         struct sched_domain *sd;
                         sd = &per_cpu(node_domains, j);
                         sd->groups = sg;
-                        if (sd->groups == NULL) {
-                                /* Turn off balancing if we have no groups */
-                                sd->flags = 0;
-                        }
-                }
-                if (!sg) {
-                        printk(KERN_WARNING
-                        "Can not alloc domain group for node %d\n", i);
-                        continue;
                 }
                 sg->cpu_power = 0;
                 sg->cpumask = nodemask;
+                sg->next = sg;
                 cpus_or(covered, covered, nodemask);
                 prev = sg;
 
@@ -6017,15 +6059,15 @@ void build_sched_domains(const cpumask_t *cpu_map)
                         if (!sg) {
                                 printk(KERN_WARNING
                                 "Can not alloc domain group for node %d\n", j);
-                                break;
+                                goto error;
                         }
                         sg->cpu_power = 0;
                         sg->cpumask = tmp;
+                        sg->next = prev->next;
                         cpus_or(covered, covered, tmp);
                         prev->next = sg;
                         prev = sg;
                 }
-                prev->next = sched_group_nodes[i];
         }
 #endif
 
@@ -6088,13 +6130,22 @@ void build_sched_domains(const cpumask_t *cpu_map)
          * Tune cache-hot values:
          */
         calibrate_migration_costs(cpu_map);
+
+        return 0;
+
+#ifdef CONFIG_NUMA
+error:
+        free_sched_groups(cpu_map);
+        return -ENOMEM;
+#endif
 }
 /*
  * Set up scheduler domains and groups.  Callers must hold the hotplug lock.
  */
-static void arch_init_sched_domains(const cpumask_t *cpu_map)
+static int arch_init_sched_domains(const cpumask_t *cpu_map)
 {
         cpumask_t cpu_default_map;
+        int err;
 
         /*
          * Setup mask for cpus without special case scheduling requirements.
@@ -6103,51 +6154,14 @@ static void arch_init_sched_domains(const cpumask_t *cpu_map)
          */
         cpus_andnot(cpu_default_map, *cpu_map, cpu_isolated_map);
 
-        build_sched_domains(&cpu_default_map);
+        err = build_sched_domains(&cpu_default_map);
+
+        return err;
 }
 
 static void arch_destroy_sched_domains(const cpumask_t *cpu_map)
 {
-#ifdef CONFIG_NUMA
-        int i;
-        int cpu;
-
-        for_each_cpu_mask(cpu, *cpu_map) {
-                struct sched_group *sched_group_allnodes
-                        = sched_group_allnodes_bycpu[cpu];
-                struct sched_group **sched_group_nodes
-                        = sched_group_nodes_bycpu[cpu];
-
-                if (sched_group_allnodes) {
-                        kfree(sched_group_allnodes);
-                        sched_group_allnodes_bycpu[cpu] = NULL;
-                }
-
-                if (!sched_group_nodes)
-                        continue;
-
-                for (i = 0; i < MAX_NUMNODES; i++) {
-                        cpumask_t nodemask = node_to_cpumask(i);
-                        struct sched_group *oldsg, *sg = sched_group_nodes[i];
-
-                        cpus_and(nodemask, nodemask, *cpu_map);
-                        if (cpus_empty(nodemask))
-                                continue;
-
-                        if (sg == NULL)
-                                continue;
-                        sg = sg->next;
-next_sg:
-                        oldsg = sg;
-                        sg = sg->next;
-                        kfree(oldsg);
-                        if (oldsg != sched_group_nodes[i])
-                                goto next_sg;
-                }
-                kfree(sched_group_nodes);
-                sched_group_nodes_bycpu[cpu] = NULL;
-        }
-#endif
+        free_sched_groups(cpu_map);
 }
 
 /*
@@ -6172,9 +6186,10 @@ static void detach_destroy_domains(const cpumask_t *cpu_map)
  * correct sched domains
  * Call with hotplug lock held
  */
-void partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2)
+int partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2)
 {
         cpumask_t change_map;
+        int err = 0;
 
         cpus_and(*partition1, *partition1, cpu_online_map);
         cpus_and(*partition2, *partition2, cpu_online_map);
@@ -6183,9 +6198,11 @@ void partition_sched_domains(cpumask_t *partition1, cpumask_t *partition2)
         /* Detach sched domains from all of the affected cpus */
         detach_destroy_domains(&change_map);
         if (!cpus_empty(*partition1))
-                build_sched_domains(partition1);
-        if (!cpus_empty(*partition2))
-                build_sched_domains(partition2);
+                err = build_sched_domains(partition1);
+        if (!err && !cpus_empty(*partition2))
+                err = build_sched_domains(partition2);
+
+        return err;
 }
 
 #ifdef CONFIG_HOTPLUG_CPU