cgroup/cpuset: Further optimize code if CONFIG_CPUSETS_V1 not set

Currently the cpuset code uses group_subsys_on_dfl() to check if we
are running with cgroup v2. If CONFIG_CPUSETS_V1 isn't set, there is
really no need to do this check and we can optimize out some of the
unneeded v1 specific code paths. Introduce a new cpuset_v2() and use it
to replace the cgroup_subsys_on_dfl() check to further optimize the
code.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 24f2a0c5eba4de0e296d30dae32f5a4968ce0854..142303abb055f4b95d0f6d5863b4fd067afdaff4 100644 (file)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -293,6 +293,12 @@ static inline void dec_attach_in_progress(struct cpuset *cs)
        mutex_unlock(&cpuset_mutex);
 }
 
+static inline bool cpuset_v2(void)
+{
+       return !IS_ENABLED(CONFIG_CPUSETS_V1) ||
+               cgroup_subsys_on_dfl(cpuset_cgrp_subsys);
+}
+
 /*
  * Cgroup v2 behavior is used on the "cpus" and "mems" control files when
  * on default hierarchy or when the cpuset_v2_mode flag is set by mounting
@@ -303,7 +309,7 @@ static inline void dec_attach_in_progress(struct cpuset *cs)
  */
 static inline bool is_in_v2_mode(void)
 {
-       return cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
+       return cpuset_v2() ||
              (cpuset_cgrp_subsys.root->flags & CGRP_ROOT_CPUSET_V2_MODE);
 }
 
@@ -738,7 +744,7 @@ static int generate_sched_domains(cpumask_var_t **domains,
        int nslot;              /* next empty doms[] struct cpumask slot */
        struct cgroup_subsys_state *pos_css;
        bool root_load_balance = is_sched_load_balance(&top_cpuset);
-       bool cgrpv2 = cgroup_subsys_on_dfl(cpuset_cgrp_subsys);
+       bool cgrpv2 = cpuset_v2();
        int nslot_update;
 
        doms = NULL;
@@ -1198,7 +1204,7 @@ static void reset_partition_data(struct cpuset *cs)
 {
        struct cpuset *parent = parent_cs(cs);
 
-       if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
+       if (!cpuset_v2())
                return;
 
        lockdep_assert_held(&callback_lock);
@@ -2017,7 +2023,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct tmpmasks *tmp,
                 */
                if (!cp->partition_root_state && !force &&
                    cpumask_equal(tmp->new_cpus, cp->effective_cpus) &&
-                   (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
+                   (!cpuset_v2() ||
                    (is_sched_load_balance(parent) == is_sched_load_balance(cp)))) {
                        pos_css = css_rightmost_descendant(pos_css);
                        continue;
@@ -2091,8 +2097,7 @@ get_css:
                 * from parent if current cpuset isn't a valid partition root
                 * and their load balance states differ.
                 */
-               if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
-                   !is_partition_valid(cp) &&
+               if (cpuset_v2() && !is_partition_valid(cp) &&
                    (is_sched_load_balance(parent) != is_sched_load_balance(cp))) {
                        if (is_sched_load_balance(parent))
                                set_bit(CS_SCHED_LOAD_BALANCE, &cp->flags);
@@ -2108,8 +2113,7 @@ get_css:
                 */
                if (!cpumask_empty(cp->cpus_allowed) &&
                    is_sched_load_balance(cp) &&
-                  (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
-                   is_partition_valid(cp)))
+                  (!cpuset_v2() || is_partition_valid(cp)))
                        need_rebuild_sched_domains = true;
 
                rcu_read_lock();
@@ -2246,7 +2250,7 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
 
        retval = validate_change(cs, trialcs);
 
-       if ((retval == -EINVAL) && cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) {
+       if ((retval == -EINVAL) && cpuset_v2()) {
                struct cgroup_subsys_state *css;
                struct cpuset *cp;
 
@@ -2738,8 +2742,7 @@ int cpuset_update_flag(cpuset_flagbits_t bit, struct cpuset *cs,
        spin_unlock_irq(&callback_lock);
 
        if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed) {
-               if (!IS_ENABLED(CONFIG_CPUSETS_V1) ||
-                   cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
+               if (cpuset_v2())
                        cpuset_force_rebuild();
                else
                        rebuild_sched_domains_locked();
@@ -2925,8 +2928,7 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
                 * migration permission derives from hierarchy ownership in
                 * cgroup_procs_write_permission()).
                 */
-               if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) ||
-                   (cpus_updated || mems_updated)) {
+               if (!cpuset_v2() || (cpus_updated || mems_updated)) {
                        ret = security_task_setscheduler(task);
                        if (ret)
                                goto out_unlock;
@@ -3040,8 +3042,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
         * in effective cpus and mems. In that case, we can optimize out
         * by skipping the task iteration and update.
         */
-       if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
-           !cpus_updated && !mems_updated) {
+       if (cpuset_v2() && !cpus_updated && !mems_updated) {
                cpuset_attach_nodemask_to = cs->effective_mems;
                goto out;
        }
@@ -3391,7 +3392,7 @@ cpuset_css_alloc(struct cgroup_subsys_state *parent_css)
        INIT_LIST_HEAD(&cs->remote_sibling);
 
        /* Set CS_MEMORY_MIGRATE for default hierarchy */
-       if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
+       if (cpuset_v2())
                __set_bit(CS_MEMORY_MIGRATE, &cs->flags);
 
        return &cs->css;
@@ -3418,8 +3419,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
        /*
         * For v2, clear CS_SCHED_LOAD_BALANCE if parent is isolated
         */
-       if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
-           !is_sched_load_balance(parent))
+       if (cpuset_v2() && !is_sched_load_balance(parent))
                clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
 
        cpuset_inc();
@@ -3489,8 +3489,7 @@ static void cpuset_css_offline(struct cgroup_subsys_state *css)
        if (is_partition_valid(cs))
                update_prstate(cs, 0);
 
-       if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
-           is_sched_load_balance(cs))
+       if (!cpuset_v2() && is_sched_load_balance(cs))
                cpuset_update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
 
        cpuset_dec();