bpf: use rcu_read_lock_dont_migrate() for bpf_cgrp_storage_free()

Use rcu_read_lock_dont_migrate() and rcu_read_unlock_migrate() in
bpf_cgrp_storage_free to obtain better performance when PREEMPT_RCU is
not enabled.

Signed-off-by: Menglong Dong <[email protected]>

Author: image-dragon

kernel/bpf/bpf_cgrp_storage.c

@@ -45,8 +45,7 @@ void bpf_cgrp_storage_free(struct cgroup *cgroup)
 {
 	struct bpf_local_storage *local_storage;
 
-	migrate_disable();
-	rcu_read_lock();
+	rcu_read_lock_dont_migrate();
 	local_storage = rcu_dereference(cgroup->bpf_cgrp_storage);
 	if (!local_storage)
 		goto out;
@@ -55,8 +54,7 @@ void bpf_cgrp_storage_free(struct cgroup *cgroup)
 	bpf_local_storage_destroy(local_storage);
 	bpf_cgrp_storage_unlock();
 out:
-	rcu_read_unlock();
-	migrate_enable();
+	rcu_read_unlock_migrate();
 }
 
 static struct bpf_local_storage_data *