Commit d39d1445 authored Oct 14, 2022 by Hou Tao Committed by Alexei Starovoitov Oct 18, 2022

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>

parent 59be91e5

kernel/bpf/bpf_local_storage.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -88,7 +88,13 @@ 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);
		if (rcu_trace_implies_rcu_gp())
		kfree(local_storage);
		else
		kfree_rcu(local_storage, rcu);
		}

		@@ -97,6 +103,9 @@ 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);
		if (rcu_trace_implies_rcu_gp())
		kfree(selem);
		else
		kfree_rcu(selem, rcu);
		}