[PATCH v2] smpboot: Check for successfull allocation of cpumask vars

[Pranith Kumar <bobby.prani@gmail.com>]

zalloc_cpumask_var() can return 0 on allocation failure when
CONFIG_CPUMASK_OFFSTACK is set. Check for the return value and warn on failure
of an allocation in such cases. Also remove the cpus from cpu masks so
that they are not accessed later on.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
---
 arch/x86/kernel/smpboot.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 7a8f584..35bc3f1 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1083,6 +1083,7 @@ static void __init smp_cpu_index_default(void)
 void __init native_smp_prepare_cpus(unsigned int max_cpus)
 {
 	unsigned int i;
+	bool ret = true;
 
 	preempt_disable();
 	smp_cpu_index_default();
@@ -1096,9 +1097,23 @@ void __init native_smp_prepare_cpus(unsigned int max_cpus)
 
 	current_thread_info()->cpu = 0;  /* needed? */
 	for_each_possible_cpu(i) {
-		zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
-		zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
-		zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
+		ret &= zalloc_cpumask_var(&per_cpu(cpu_sibling_map, i), GFP_KERNEL);
+		ret &= zalloc_cpumask_var(&per_cpu(cpu_core_map, i), GFP_KERNEL);
+		ret &= zalloc_cpumask_var(&per_cpu(cpu_llc_shared_map, i), GFP_KERNEL);
+
+		if (!ret) {
+			/* cpumask allocation failed, remove this and next cpus from
+			 * possible/present/online/active masks
+			 */
+			pr_warn("cpumask allocation failed!\n");
+			for (; i < nr_cpu_ids; i = cpumask_next(i, &cpu_possible_mask)) {
+				set_cpu_possible(i, false);
+				set_cpu_active(i, false);
+				set_cpu_online(i, false);
+				set_cpu_present(i, false);
+			}
+			break;
+		}
 	}
 	set_cpu_sibling_map(0);
 
-- 
1.9.1