cpu-hotplug: return better errno on cpu hotplug failure

Currently, onlining or offlining a CPU failure by one of the cpu notifiers
error always cause -EINVAL error.  (i.e.  writing 0 or 1 to
/sys/devices/system/cpu/cpuX/online gets EINVAL)

To get better error reporting rather than always getting -EINVAL, This
changes cpu_notify() to return -errno value with notifier_to_errno() and
fix the callers.  Now that cpu notifiers can return encapsulate errno
value.

Currently, all cpu hotplug notifiers return NOTIFY_OK, NOTIFY_BAD, or
NOTIFY_DONE.  So cpu_notify() can returns 0 or -EPERM with this change for
now.

(notifier_to_errno(NOTIFY_OK) == 0, notifier_to_errno(NOTIFY_DONE) == 0,
notifier_to_errno(NOTIFY_BAD) == -EPERM)

Forthcoming patches convert several cpu notifiers to return encapsulate
errno value with notifier_from_errno().

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 6 deletions

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 09207c772c25..0690ac27a253 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -137,8 +137,12 @@ int __ref register_cpu_notifier(struct notifier_block *nb)
 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
                         int *nr_calls)
 {
-        return __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
+        int ret;
+
+        ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
                                         nr_calls);
+
+        return notifier_to_errno(ret);
 }
 
 static int cpu_notify(unsigned long val, void *v)
@@ -151,7 +155,7 @@ static void cpu_notify_nofail(unsigned long val, void *v)
         int err;
 
         err = cpu_notify(val, v);
-        BUG_ON(err == NOTIFY_BAD);
+        BUG_ON(err);
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
@@ -232,14 +236,13 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
         cpu_hotplug_begin();
         set_cpu_active(cpu, false);
         err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
-        if (err == NOTIFY_BAD) {
+        if (err) {
                 set_cpu_active(cpu, true);
 
                 nr_calls--;
                 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
                 printk("%s: attempt to take down CPU %u failed\n",
                                 __func__, cpu);
-                err = -EINVAL;
                 goto out_release;
         }
 
@@ -304,11 +307,10 @@ static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
 
         cpu_hotplug_begin();
         ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
-        if (ret == NOTIFY_BAD) {
+        if (ret) {
                 nr_calls--;
                 printk("%s: attempt to bring up CPU %u failed\n",
                                 __func__, cpu);
-                ret = -EINVAL;
                 goto out_notify;
         }