[PATCH bpf-next 1/2] bpf, libbpf: add a new API bpf_object__reuse_maps()

[Anton Protopopov]

Add a new API bpf_object__reuse_maps() which can be used to replace all maps in
an object by maps pinned to a directory provided in the path argument.  Namely,
each map M in the object will be replaced by a map pinned to path/M.name.

Signed-off-by: Anton Protopopov <a.s.protopo...@gmail.com>
---
 tools/lib/bpf/libbpf.c   | 34 ++++++++++++++++++++++++++++++++++
 tools/lib/bpf/libbpf.h   |  2 ++
 tools/lib/bpf/libbpf.map |  1 +
 3 files changed, 37 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 4907997289e9..84c9e8f7bfd3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -3144,6 +3144,40 @@ int bpf_object__unpin_maps(struct bpf_object *obj, const 
char *path)
        return 0;
 }
 
+int bpf_object__reuse_maps(struct bpf_object *obj, const char *path)
+{
+       struct bpf_map *map;
+
+       if (!obj)
+               return -ENOENT;
+
+       if (!path)
+               return -EINVAL;
+
+       bpf_object__for_each_map(map, obj) {
+               int len, err;
+               int pinned_map_fd;
+               char buf[PATH_MAX];
+
+               len = snprintf(buf, PATH_MAX, "%s/%s", path, 
bpf_map__name(map));
+               if (len < 0) {
+                       return -EINVAL;
+               } else if (len >= PATH_MAX) {
+                       return -ENAMETOOLONG;
+               }
+
+               pinned_map_fd = bpf_obj_get(buf);
+               if (pinned_map_fd < 0)
+                       return pinned_map_fd;
+
+               err = bpf_map__reuse_fd(map, pinned_map_fd);
+               if (err)
+                       return err;
+       }
+
+       return 0;
+}
+
 int bpf_object__pin_programs(struct bpf_object *obj, const char *path)
 {
        struct bpf_program *prog;
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index d639f47e3110..7fe465a1be76 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -82,6 +82,8 @@ int bpf_object__variable_offset(const struct bpf_object *obj, 
const char *name,
 LIBBPF_API int bpf_object__pin_maps(struct bpf_object *obj, const char *path);
 LIBBPF_API int bpf_object__unpin_maps(struct bpf_object *obj,
                                      const char *path);
+LIBBPF_API int bpf_object__reuse_maps(struct bpf_object *obj,
+                                     const char *path);
 LIBBPF_API int bpf_object__pin_programs(struct bpf_object *obj,
                                        const char *path);
 LIBBPF_API int bpf_object__unpin_programs(struct bpf_object *obj,
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 2c6d835620d2..66a30be6696c 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -172,5 +172,6 @@ LIBBPF_0.0.4 {
                btf_dump__new;
                btf__parse_elf;
                bpf_object__load_xattr;
+               bpf_object__reuse_maps;
                libbpf_num_possible_cpus;
 } LIBBPF_0.0.3;
-- 
2.19.1