powerpc/pseries: avoid blocking in irq when queuing hotplug events

A couple of bugs in queue_hotplug_event():

1. Unchecked kmalloc result which could lead to an oops.
2. Use of GFP_KERNEL allocations in interrupt context (this code's
   only caller is ras_hotplug_interrupt()).

Use kmemdup to avoid open-coding the allocation+copy and check for
failure; use GFP_ATOMIC for both allocations.

Ultimately it probably would be better to avoid or reduce allocations
in this path if possible.
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/pseries/dlpar.c

@@ -390,11 +390,11 @@ void queue_hotplug_event(struct pseries_hp_errorlog *hp_errlog)
 	struct pseries_hp_work *work;
 	struct pseries_hp_errorlog *hp_errlog_copy;
 
-	hp_errlog_copy = kmalloc(sizeof(struct pseries_hp_errorlog),
-				 GFP_KERNEL);
-	memcpy(hp_errlog_copy, hp_errlog, sizeof(struct pseries_hp_errorlog));
+	hp_errlog_copy = kmemdup(hp_errlog, sizeof(*hp_errlog), GFP_ATOMIC);
+	if (!hp_errlog_copy)
+		return;
 
-	work = kmalloc(sizeof(struct pseries_hp_work), GFP_KERNEL);
+	work = kmalloc(sizeof(struct pseries_hp_work), GFP_ATOMIC);
 	if (work) {
 		INIT_WORK((struct work_struct *)work, pseries_hp_work_fn);
 		work->errlog = hp_errlog_copy;