[PATCH rfc bpf-next 2/8] bpf: add bpf_prog_under_eviction helper

[Daniel Borkmann <daniel@iogearbox.net>]

Add a small helper which can be used to check whether we're
currently tearing down a BPF program.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 include/linux/bpf.h  | 1 +
 kernel/bpf/syscall.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 562d9ade2926..0a20618fd8e2 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -774,6 +774,7 @@ struct bpf_prog * __must_check bpf_prog_add(struct bpf_prog *prog, int i);
 void bpf_prog_sub(struct bpf_prog *prog, int i);
 struct bpf_prog * __must_check bpf_prog_inc(struct bpf_prog *prog);
 struct bpf_prog * __must_check bpf_prog_inc_not_zero(struct bpf_prog *prog);
+bool bpf_prog_under_eviction(struct bpf_prog *prog);
 void bpf_prog_put(struct bpf_prog *prog);
 int __bpf_prog_charge(struct user_struct *user, u32 pages);
 void __bpf_prog_uncharge(struct user_struct *user, u32 pages);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index c88c815c2154..2a687cb9b0d2 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1482,6 +1482,11 @@ struct bpf_prog *bpf_prog_inc(struct bpf_prog *prog)
 }
 EXPORT_SYMBOL_GPL(bpf_prog_inc);
 
+bool bpf_prog_under_eviction(struct bpf_prog *prog)
+{
+	return atomic_read(&prog->aux->refcnt) == 0;
+}
+
 /* prog_idr_lock should have been held */
 struct bpf_prog *bpf_prog_inc_not_zero(struct bpf_prog *prog)
 {
-- 
2.21.0