libbpf: bpf_program__pin: add special case for instances.nr == 1

When bpf_program has only one instance, don't create a subdirectory with
per-instance pin files (<prog>/0). Instead, just create a single pin file
for that single instance. This simplifies object pinning by not creating
unnecessary subdirectories.

This can potentially break existing users that depend on the case
where '/0' is always created. However, I couldn't find any serious
usage of bpf_program__pin inside the kernel tree and I suppose there
should be none outside.

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 341008f..97ce9f2 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1761,6 +1761,11 @@ int bpf_program__pin(struct bpf_program *prog, const char *path)
                return -EINVAL;
        }
 
+       if (prog->instances.nr == 1) {
+               /* don't create subdirs when pinning single instance */
+               return bpf_program__pin_instance(prog, path, 0);
+       }
+
        err = make_dir(path);
        if (err)
                return err;
@@ -1823,6 +1828,11 @@ int bpf_program__unpin(struct bpf_program *prog, const char *path)
                return -EINVAL;
        }
 
+       if (prog->instances.nr == 1) {
+               /* don't create subdirs when pinning single instance */
+               return bpf_program__unpin_instance(prog, path, 0);
+       }
+
        for (i = 0; i < prog->instances.nr; i++) {
                char buf[PATH_MAX];
                int len;