Andrii Nakryiko [off-list ref] writes:

On Tue, Oct 29, 2019 at 12:39 PM Toke Høiland-Jørgensen [off-list ref] wrote:

quoted

From: Toke Høiland-Jørgensen <redacted>

Support storing and setting a pin path in struct bpf_map, which can be used
for automatic pinning. Also store the pin status so we can avoid attempts
to re-pin a map that has already been pinned (or reused from a previous
pinning).

The behaviour of bpf_object__{un,}pin_maps() is changed so that if it is
called with a NULL path argument (which was previously illegal), it will
(un)pin only those maps that have a pin_path set.

Signed-off-by: Toke Høiland-Jørgensen <redacted>
---

Looks good, thanks! Just some minor things to fix up below.

Acked-by: Andrii Nakryiko <redacted>

quoted

 tools/lib/bpf/libbpf.c   |  164 +++++++++++++++++++++++++++++++++++-----------
 tools/lib/bpf/libbpf.h   |    8 ++
 tools/lib/bpf/libbpf.map |    3 +
 3 files changed, 134 insertions(+), 41 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index ce5ef3ddd263..fd11f6aeb32c 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c

@@ -226,6 +226,8 @@ struct bpf_map {
        void *priv;
        bpf_map_clear_priv_t clear_priv;
        enum libbpf_map_type libbpf_type;
+       char *pin_path;
+       bool pinned;
 };

 struct bpf_secdata {

@@ -4025,47 +4027,119 @@ int bpf_map__pin(struct bpf_map *map, const char *path)
        char *cp, errmsg[STRERR_BUFSIZE];
        int err;

-       err = check_path(path);
-       if (err)
-               return err;
-
        if (map == NULL) {
                pr_warn("invalid map pointer\n");
                return -EINVAL;
        }

-       if (bpf_obj_pin(map->fd, path)) {
-               cp = libbpf_strerror_r(errno, errmsg, sizeof(errmsg));
-               pr_warn("failed to pin map: %s\n", cp);
-               return -errno;
+       if (map->pin_path) {
+               if (path && strcmp(path, map->pin_path)) {
+                       pr_warn("map '%s' already has pin path '%s' different from '%s'\n",
+                               bpf_map__name(map), map->pin_path, path);
+                       return -EINVAL;
+               } else if (map->pinned) {
+                       pr_debug("map '%s' already pinned at '%s'; not re-pinning\n",
+                                bpf_map__name(map), map->pin_path);
+                       return 0;
+               }

`if (map->pinned)` check is the same in both branches, so I'd do it
first, before this map->pin_path if/else.

But it's not. It's debug & return if pin_path is set, and an error
otherwise.

Will fix the rest of your nits :)

-Toke