libbpf: Store map pin path and status in struct bpf_map

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 <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/157269297876.394725.14782206533681896279.stgit@toke.dk

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 36152c8..22f6dd1 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -227,6 +227,8 @@ 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 {
@@ -4036,47 +4038,119 @@ 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;
+               }
+       } else {
+               if (!path) {
+                       pr_warn("missing a path to pin map '%s' at\n",
+                               bpf_map__name(map));
+                       return -EINVAL;
+               } else if (map->pinned) {
+                       pr_warn("map '%s' already pinned\n", bpf_map__name(map));
+                       return -EEXIST;
+               }
+
+               map->pin_path = strdup(path);
+               if (!map->pin_path) {
+                       err = -errno;
+                       goto out_err;
+               }
        }
 
-       pr_debug("pinned map '%s'\n", path);
+       err = check_path(map->pin_path);
+       if (err)
+               return err;
+
+       if (bpf_obj_pin(map->fd, map->pin_path)) {
+               err = -errno;
+               goto out_err;
+       }
+
+       map->pinned = true;
+       pr_debug("pinned map '%s'\n", map->pin_path);
 
        return 0;
+
+out_err:
+       cp = libbpf_strerror_r(-err, errmsg, sizeof(errmsg));
+       pr_warn("failed to pin map: %s\n", cp);
+       return err;
 }
 
 int bpf_map__unpin(struct bpf_map *map, const char *path)
 {
        int err;
 
-       err = check_path(path);
-       if (err)
-               return err;
-
        if (map == NULL) {
                pr_warn("invalid map pointer\n");
                return -EINVAL;
        }
 
+       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;
+               }
+               path = map->pin_path;
+       } else if (!path) {
+               pr_warn("no path to unpin map '%s' from\n",
+                       bpf_map__name(map));
+               return -EINVAL;
+       }
+
+       err = check_path(path);
+       if (err)
+               return err;
+
        err = unlink(path);
        if (err != 0)
                return -errno;
-       pr_debug("unpinned map '%s'\n", path);
+
+       map->pinned = false;
+       pr_debug("unpinned map '%s' from '%s'\n", bpf_map__name(map), path);
 
        return 0;
 }
 
+int bpf_map__set_pin_path(struct bpf_map *map, const char *path)
+{
+       char *new = NULL;
+
+       if (path) {
+               new = strdup(path);
+               if (!new)
+                       return -errno;
+       }
+
+       free(map->pin_path);
+       map->pin_path = new;
+       return 0;
+}
+
+const char *bpf_map__get_pin_path(const struct bpf_map *map)
+{
+       return map->pin_path;
+}
+
+bool bpf_map__is_pinned(const struct bpf_map *map)
+{
+       return map->pinned;
+}
+
 int bpf_object__pin_maps(struct bpf_object *obj, const char *path)
 {
        struct bpf_map *map;
@@ -4095,20 +4169,27 @@ int bpf_object__pin_maps(struct bpf_object *obj, const char *path)
                return err;
 
        bpf_object__for_each_map(map, obj) {
+               char *pin_path = NULL;
                char buf[PATH_MAX];
-               int len;
 
-               len = snprintf(buf, PATH_MAX, "%s/%s", path,
-                              bpf_map__name(map));
-               if (len < 0) {
-                       err = -EINVAL;
-                       goto err_unpin_maps;
-               } else if (len >= PATH_MAX) {
-                       err = -ENAMETOOLONG;
-                       goto err_unpin_maps;
+               if (path) {
+                       int len;
+
+                       len = snprintf(buf, PATH_MAX, "%s/%s", path,
+                                      bpf_map__name(map));
+                       if (len < 0) {
+                               err = -EINVAL;
+                               goto err_unpin_maps;
+                       } else if (len >= PATH_MAX) {
+                               err = -ENAMETOOLONG;
+                               goto err_unpin_maps;
+                       }
+                       pin_path = buf;
+               } else if (!map->pin_path) {
+                       continue;
                }
 
-               err = bpf_map__pin(map, buf);
+               err = bpf_map__pin(map, pin_path);
                if (err)
                        goto err_unpin_maps;
        }
@@ -4117,17 +4198,10 @@ int bpf_object__pin_maps(struct bpf_object *obj, const char *path)
 
 err_unpin_maps:
        while ((map = bpf_map__prev(map, obj))) {
-               char buf[PATH_MAX];
-               int len;
-
-               len = snprintf(buf, PATH_MAX, "%s/%s", path,
-                              bpf_map__name(map));
-               if (len < 0)
-                       continue;
-               else if (len >= PATH_MAX)
+               if (!map->pin_path)
                        continue;
 
-               bpf_map__unpin(map, buf);
+               bpf_map__unpin(map, NULL);
        }
 
        return err;
@@ -4142,17 +4216,24 @@ int bpf_object__unpin_maps(struct bpf_object *obj, const char *path)
                return -ENOENT;
 
        bpf_object__for_each_map(map, obj) {
+               char *pin_path = NULL;
                char buf[PATH_MAX];
-               int len;
 
-               len = snprintf(buf, PATH_MAX, "%s/%s", path,
-                              bpf_map__name(map));
-               if (len < 0)
-                       return -EINVAL;
-               else if (len >= PATH_MAX)
-                       return -ENAMETOOLONG;
+               if (path) {
+                       int len;
+
+                       len = snprintf(buf, PATH_MAX, "%s/%s", path,
+                                      bpf_map__name(map));
+                       if (len < 0)
+                               return -EINVAL;
+                       else if (len >= PATH_MAX)
+                               return -ENAMETOOLONG;
+                       pin_path = buf;
+               } else if (!map->pin_path) {
+                       continue;
+               }
 
-               err = bpf_map__unpin(map, buf);
+               err = bpf_map__unpin(map, pin_path);
                if (err)
                        return err;
        }
@@ -4277,6 +4358,7 @@ void bpf_object__close(struct bpf_object *obj)
 
        for (i = 0; i < obj->nr_maps; i++) {
                zfree(&obj->maps[i].name);
+               zfree(&obj->maps[i].pin_path);
                if (obj->maps[i].clear_priv)
                        obj->maps[i].clear_priv(&obj->maps[i],
                                                obj->maps[i].priv);

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 2b126ee..e71773a 100644 (file)
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -124,6 +124,11 @@ int bpf_object__section_size(const struct bpf_object *obj, const char *name,
                             __u32 *size);
 int bpf_object__variable_offset(const struct bpf_object *obj, const char *name,
                                __u32 *off);
+
+/* pin_maps and unpin_maps can both be called with a NULL path, in which case
+ * they will use the pin_path attribute of each map (and ignore all maps that
+ * don't have a pin_path set).
+ */
 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);
@@ -387,6 +392,9 @@ LIBBPF_API int bpf_map__resize(struct bpf_map *map, __u32 max_entries);
 LIBBPF_API bool bpf_map__is_offload_neutral(const struct bpf_map *map);
 LIBBPF_API bool bpf_map__is_internal(const struct bpf_map *map);
 LIBBPF_API void bpf_map__set_ifindex(struct bpf_map *map, __u32 ifindex);
+LIBBPF_API int bpf_map__set_pin_path(struct bpf_map *map, const char *path);
+LIBBPF_API const char *bpf_map__get_pin_path(const struct bpf_map *map);
+LIBBPF_API bool bpf_map__is_pinned(const struct bpf_map *map);
 LIBBPF_API int bpf_map__pin(struct bpf_map *map, const char *path);
 LIBBPF_API int bpf_map__unpin(struct bpf_map *map, const char *path);
 

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 69dded5..86173cb 100644 (file)
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -193,6 +193,9 @@ LIBBPF_0.0.5 {
 
 LIBBPF_0.0.6 {
        global:
+               bpf_map__get_pin_path;
+               bpf_map__is_pinned;
+               bpf_map__set_pin_path;
                bpf_object__open_file;
                bpf_object__open_mem;
                bpf_program__get_expected_attach_type;