Cpuset hardwall flag: switch cpusets to use the bulk cgroup_add_files() API

Currently the cpusets mem_exclusive flag is overloaded to mean both
"no-overlapping" and "no GFP_KERNEL allocations outside this cpuset".

These patches add a new mem_hardwall flag with just the allocation restriction
part of the mem_exclusive semantics, without breaking backwards-compatibility
for those who continue to use just mem_exclusive.  Additionally, the cgroup
control file registration for cpusets is cleaned up to reduce boilerplate.

This patch:

This change tidies up the cpusets control file definitions, and reduces the
amount of boilerplate required to add/change control files in the future.
Signed-off-by: Paul Menage <menage@google.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/cpuset.c

@@ -1445,113 +1445,97 @@ static u64 cpuset_read_u64(struct cgroup *cont, struct cftype *cft)
  * for the common functions, 'private' gives the type of file
  */
 
-static struct cftype cft_cpus = {
+static struct cftype files[] = {
+	{
 		.name = "cpus",
 		.read = cpuset_common_file_read,
 		.write = cpuset_common_file_write,
 		.private = FILE_CPULIST,
-};
+	},
 
-static struct cftype cft_mems = {
+	{
 		.name = "mems",
 		.read = cpuset_common_file_read,
 		.write = cpuset_common_file_write,
 		.private = FILE_MEMLIST,
-};
+	},
 
-static struct cftype cft_cpu_exclusive = {
+	{
 		.name = "cpu_exclusive",
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
 		.private = FILE_CPU_EXCLUSIVE,
-};
+	},
 
-static struct cftype cft_mem_exclusive = {
+	{
 		.name = "mem_exclusive",
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
 		.private = FILE_MEM_EXCLUSIVE,
-};
+	},
 
-static struct cftype cft_sched_load_balance = {
+	{
 		.name = "sched_load_balance",
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
 		.private = FILE_SCHED_LOAD_BALANCE,
-};
+	},
 
-static struct cftype cft_sched_relax_domain_level = {
+	{
 		.name = "sched_relax_domain_level",
-	.read = cpuset_common_file_read,
-	.write = cpuset_common_file_write,
+		.read_u64 = cpuset_read_u64,
+		.write_u64 = cpuset_write_u64,
 		.private = FILE_SCHED_RELAX_DOMAIN_LEVEL,
-};
+	},
 
-static struct cftype cft_memory_migrate = {
+	{
 		.name = "memory_migrate",
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
 		.private = FILE_MEMORY_MIGRATE,
-};
+	},
 
-static struct cftype cft_memory_pressure_enabled = {
-	.name = "memory_pressure_enabled",
-	.read_u64 = cpuset_read_u64,
-	.write_u64 = cpuset_write_u64,
-	.private = FILE_MEMORY_PRESSURE_ENABLED,
-};
-
-static struct cftype cft_memory_pressure = {
+	{
 		.name = "memory_pressure",
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
 		.private = FILE_MEMORY_PRESSURE,
-};
+	},
 
-static struct cftype cft_spread_page = {
+	{
 		.name = "memory_spread_page",
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
 		.private = FILE_SPREAD_PAGE,
-};
+	},
 
-static struct cftype cft_spread_slab = {
+	{
 		.name = "memory_spread_slab",
 		.read_u64 = cpuset_read_u64,
 		.write_u64 = cpuset_write_u64,
 		.private = FILE_SPREAD_SLAB,
+	},
+};
+
+static struct cftype cft_memory_pressure_enabled = {
+	.name = "memory_pressure_enabled",
+	.read_u64 = cpuset_read_u64,
+	.write_u64 = cpuset_write_u64,
+	.private = FILE_MEMORY_PRESSURE_ENABLED,
 };
 
 static int cpuset_populate(struct cgroup_subsys *ss, struct cgroup *cont)
 {
 	int err;
 
-	if ((err = cgroup_add_file(cont, ss, &cft_cpus)) < 0)
-		return err;
-	if ((err = cgroup_add_file(cont, ss, &cft_mems)) < 0)
-		return err;
-	if ((err = cgroup_add_file(cont, ss, &cft_cpu_exclusive)) < 0)
-		return err;
-	if ((err = cgroup_add_file(cont, ss, &cft_mem_exclusive)) < 0)
-		return err;
-	if ((err = cgroup_add_file(cont, ss, &cft_memory_migrate)) < 0)
-		return err;
-	if ((err = cgroup_add_file(cont, ss, &cft_sched_load_balance)) < 0)
-		return err;
-	if ((err = cgroup_add_file(cont, ss,
-					&cft_sched_relax_domain_level)) < 0)
-		return err;
-	if ((err = cgroup_add_file(cont, ss, &cft_memory_pressure)) < 0)
-		return err;
-	if ((err = cgroup_add_file(cont, ss, &cft_spread_page)) < 0)
-		return err;
-	if ((err = cgroup_add_file(cont, ss, &cft_spread_slab)) < 0)
+	err = cgroup_add_files(cont, ss, files, ARRAY_SIZE(files));
+	if (err)
 		return err;
 	/* memory_pressure_enabled is in root cpuset only */
-	if (err == 0 && !cont->parent)
+	if (!cont->parent)
 		err = cgroup_add_file(cont, ss,
 				      &cft_memory_pressure_enabled);
-	return 0;
+	return err;
 }
 
 /*