[v5,bpf-next,3/7] libbpf: bpf_program__pin: add special case for instances.nr == 1

Commit Message

Stanislav Fomichev Nov. 9, 2018, 4:21 p.m. UTC

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 <[e-mail]>
---
 tools/lib/bpf/libbpf.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

Patch

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 341008f47c8a..97ce9f214002 100644
--- 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;