netdev - [PATCH bpf-next 1/6] libbpf: Unpin auto-pinned maps if loading fails

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Date:   Thu, 07 Nov 2019 17:52:19 +0100
From:   Toke Høiland-Jørgensen <toke@...hat.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH bpf-next 1/6] libbpf: Unpin auto-pinned maps if loading fails

From: Toke Høiland-Jørgensen <toke@...hat.com>

Since the automatic map-pinning happens during load, it will leave pinned
maps around if the load fails at a later stage. Fix this by unpinning any
pinned maps on cleanup. To avoid unpinning pinned maps that were reused
rather than newly pinned, add a new boolean property on struct bpf_map to
keep track of whether that map was reused or not; and only unpin those maps
that were not reused.

Fixes: 57a00f41644f ("libbpf: Add auto-pinning of maps when loading BPF objects")
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
---
 tools/lib/bpf/libbpf.c |   16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index be4af95d5a2c..cea61b2ec9d3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -229,6 +229,7 @@ struct bpf_map {
 	enum libbpf_map_type libbpf_type;
 	char *pin_path;
 	bool pinned;
+	bool was_reused;
 };
 
 struct bpf_secdata {
@@ -1995,6 +1996,7 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd)
 	map->def.map_flags = info.map_flags;
 	map->btf_key_type_id = info.btf_key_type_id;
 	map->btf_value_type_id = info.btf_value_type_id;
+	map->was_reused = true;
 
 	return 0;
 
@@ -4007,15 +4009,18 @@ bpf_object__open_buffer(const void *obj_buf, size_t obj_buf_sz,
 	return bpf_object__open_mem(obj_buf, obj_buf_sz, &opts);
 }
 
-int bpf_object__unload(struct bpf_object *obj)
+static int __bpf_object__unload(struct bpf_object *obj, bool unpin)
 {
 	size_t i;
 
 	if (!obj)
 		return -EINVAL;
 
-	for (i = 0; i < obj->nr_maps; i++)
+	for (i = 0; i < obj->nr_maps; i++) {
 		zclose(obj->maps[i].fd);
+		if (unpin && obj->maps[i].pinned && !obj->maps[i].was_reused)
+			bpf_map__unpin(&obj->maps[i], NULL);
+	}
 
 	for (i = 0; i < obj->nr_programs; i++)
 		bpf_program__unload(&obj->programs[i]);
@@ -4023,6 +4028,11 @@ int bpf_object__unload(struct bpf_object *obj)
 	return 0;
 }
 
+int bpf_object__unload(struct bpf_object *obj)
+{
+	return __bpf_object__unload(obj, false);
+}
+
 int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
 {
 	struct bpf_object *obj;
@@ -4047,7 +4057,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
 
 	return 0;
 out:
-	bpf_object__unload(obj);
+	__bpf_object__unload(obj, true);
 	pr_warn("failed to load object '%s'\n", obj->path);
 	return err;
 }