cpuset: export effective masks to userspace

cpuset.cpus and cpuset.mems are the configured masks, and we need
to export effective masks to userspace, so users know the real
cpus_allowed and mems_allowed that apply to the tasks in a cpuset.

v2:
- export those masks unconditionally, suggested by Tejun.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/cpuset.c

@@ -1535,6 +1535,8 @@ typedef enum {
 	FILE_MEMORY_MIGRATE,
 	FILE_CPULIST,
 	FILE_MEMLIST,
+	FILE_EFFECTIVE_CPULIST,
+	FILE_EFFECTIVE_MEMLIST,
 	FILE_CPU_EXCLUSIVE,
 	FILE_MEM_EXCLUSIVE,
 	FILE_MEM_HARDWALL,
@@ -1701,6 +1703,12 @@ static int cpuset_common_seq_show(struct seq_file *sf, void *v)
 	case FILE_MEMLIST:
 		s += nodelist_scnprintf(s, count, cs->mems_allowed);
 		break;
+	case FILE_EFFECTIVE_CPULIST:
+		s += cpulist_scnprintf(s, count, cs->effective_cpus);
+		break;
+	case FILE_EFFECTIVE_MEMLIST:
+		s += nodelist_scnprintf(s, count, cs->effective_mems);
+		break;
 	default:
 		ret = -EINVAL;
 		goto out_unlock;
@@ -1785,6 +1793,18 @@ static struct cftype files[] = {
 		.private = FILE_MEMLIST,
 	},
 
+	{
+		.name = "effective_cpus",
+		.seq_show = cpuset_common_seq_show,
+		.private = FILE_EFFECTIVE_CPULIST,
+	},
+
+	{
+		.name = "effective_mems",
+		.seq_show = cpuset_common_seq_show,
+		.private = FILE_EFFECTIVE_MEMLIST,
+	},
+
 	{
 		.name = "cpu_exclusive",
 		.read_u64 = cpuset_read_u64,