Commit 8e5290e7 authored Mar 04, 2020 by Martin KaFai Lau Committed by Alexei Starovoitov Mar 05, 2020

bpf: Return better error value in delete_elem for struct_ops map



The current always succeed behavior in bpf_struct_ops_map_delete_elem()
is not ideal for userspace tool.  It can be improved to return proper
error value.

If it is in TOBEFREE, it means unregistration has been already done
before but it is in progress and waiting for the subsystem to clear
the refcnt to zero, so -EINPROGRESS.

If it is INIT, it means the struct_ops has not been registered yet,
so -ENOENT.

Fixes: 85d33df3 ("bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS")
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200305013447.535326-1-kafai@fb.com

parent a35a76fa

kernel/bpf/bpf_struct_ops.c

+11 −3

Original line number	Diff line number	Diff line
		@@ -482,13 +482,21 @@ static int bpf_struct_ops_map_delete_elem(struct bpf_map map, void key)
		prev_state = cmpxchg(&st_map->kvalue.state,
		BPF_STRUCT_OPS_STATE_INUSE,
		BPF_STRUCT_OPS_STATE_TOBEFREE);
		if (prev_state == BPF_STRUCT_OPS_STATE_INUSE) {
		switch (prev_state) {
		case BPF_STRUCT_OPS_STATE_INUSE:
		st_map->st_ops->unreg(&st_map->kvalue.data);
		if (refcount_dec_and_test(&st_map->kvalue.refcnt))
		bpf_map_put(map);
		}

		return 0;
		case BPF_STRUCT_OPS_STATE_TOBEFREE:
		return -EINPROGRESS;
		case BPF_STRUCT_OPS_STATE_INIT:
		return -ENOENT;
		default:
		WARN_ON_ONCE(1);
		/* Should never happen. Treat it as not found. */
		return -ENOENT;
		}
		}

		static void bpf_struct_ops_map_seq_show_elem(struct bpf_map map, void key,

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