bpf: Use rcu_trace_implies_rcu_gp() in local storage map

Local storage map is accessible for both sleepable and non-sleepable bpf
program, and its memory is freed by using both call_rcu_tasks_trace() and
kfree_rcu() to wait for both RCU-tasks-trace grace period and RCU grace
period to pass.

With the introduction of rcu_trace_implies_rcu_gp(), both
bpf_selem_free_rcu() and bpf_local_storage_free_rcu() can check whether
or not a normal RCU grace period has also passed after a RCU-tasks-trace
grace period has passed. If it is true, it is safe to call kfree()
directly.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20221014113946.965131-4-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index 802fc15..9dc6de1 100644 (file)
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -88,8 +88,14 @@ void bpf_local_storage_free_rcu(struct rcu_head *rcu)
 {
        struct bpf_local_storage *local_storage;
 
+       /* If RCU Tasks Trace grace period implies RCU grace period, do
+        * kfree(), else do kfree_rcu().
+        */
        local_storage = container_of(rcu, struct bpf_local_storage, rcu);
-       kfree_rcu(local_storage, rcu);
+       if (rcu_trace_implies_rcu_gp())
+               kfree(local_storage);
+       else
+               kfree_rcu(local_storage, rcu);
 }
 
 static void bpf_selem_free_rcu(struct rcu_head *rcu)
@@ -97,7 +103,10 @@ static void bpf_selem_free_rcu(struct rcu_head *rcu)
        struct bpf_local_storage_elem *selem;
 
        selem = container_of(rcu, struct bpf_local_storage_elem, rcu);
-       kfree_rcu(selem, rcu);
+       if (rcu_trace_implies_rcu_gp())
+               kfree(selem);
+       else
+               kfree_rcu(selem, rcu);
 }
 
 /* local_storage->lock must be held and selem->local_storage == local_storage.