[PATCH 1/2] sched/psi: simplify cgroup psi retrieving

[Kairui Song <ryncsn@gmail.com>]

From: Kairui Song <kasong@tencent.com>

Since the only case where cgroup_psi should return psi_system instead of
the cgroup's psi_group is the root cgroup, just set root cgroup's psi to
point to psi_system to remove the if branch.

Signed-off-by: Kairui Song <kasong@tencent.com>
---
 include/linux/psi.h    | 2 +-
 kernel/cgroup/cgroup.c | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/psi.h b/include/linux/psi.h
index b029a847def1..9c3a1638b618 100644
--- a/include/linux/psi.h
+++ b/include/linux/psi.h
@@ -33,7 +33,7 @@ __poll_t psi_trigger_poll(void **trigger_ptr, struct file *file,
 #ifdef CONFIG_CGROUPS
 static inline struct psi_group *cgroup_psi(struct cgroup *cgrp)
 {
-	return cgroup_ino(cgrp) == 1 ? &psi_system : cgrp->psi;
+	return cgrp->psi;
 }
 
 int psi_cgroup_alloc(struct cgroup *cgrp);
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index c099cf3fa02d..1491d63b06b6 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -163,7 +163,12 @@ static struct static_key_true *cgroup_subsys_on_dfl_key[] = {
 static DEFINE_PER_CPU(struct cgroup_rstat_cpu, cgrp_dfl_root_rstat_cpu);
 
 /* the default hierarchy */
-struct cgroup_root cgrp_dfl_root = { .cgrp.rstat_cpu = &cgrp_dfl_root_rstat_cpu };
+struct cgroup_root cgrp_dfl_root = {
+	.cgrp.rstat_cpu = &cgrp_dfl_root_rstat_cpu,
+#ifdef CONFIG_PSI
+	.cgrp.psi = &psi_system
+#endif
+};
 EXPORT_SYMBOL_GPL(cgrp_dfl_root);
 
 /*
-- 
2.39.1