[PATCH bpf-next v2 2/3] bpf: implement link_query callbacks in map element iterators

[Yonghong Song]

For bpf_map_elem and bpf_sk_local_storage bpf iterators,
additional map_id should be shown for fdinfo and
userspace query. For example, the following is for
a bpf_map_elem iterator.
  $ cat /proc/1753/fdinfo/9
  pos:    0
  flags:  02000000
  mnt_id: 14
  link_type:      iter
  link_id:        34
  prog_tag:       104be6d3fe45e6aa
  prog_id:        173
  target_name:    bpf_map_elem
  map_id:         127

Signed-off-by: Yonghong Song <y...@fb.com>
---
 include/linux/bpf.h       |  4 ++++
 kernel/bpf/map_iter.c     | 15 +++++++++++++++
 net/core/bpf_sk_storage.c |  2 ++
 3 files changed, 21 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 529e9b183eeb..30c144af894a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1256,6 +1256,10 @@ int bpf_iter_new_fd(struct bpf_link *link);
 bool bpf_link_is_iter(struct bpf_link *link);
 struct bpf_prog *bpf_iter_get_info(struct bpf_iter_meta *meta, bool in_stop);
 int bpf_iter_run_prog(struct bpf_prog *prog, void *ctx);
+void bpf_iter_map_show_fdinfo(const struct bpf_iter_aux_info *aux,
+                             struct seq_file *seq);
+int bpf_iter_map_fill_link_info(const struct bpf_iter_aux_info *aux,
+                               struct bpf_link_info *info);
 
 int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
 int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value);
diff --git a/kernel/bpf/map_iter.c b/kernel/bpf/map_iter.c
index af86048e5afd..714e74556aa2 100644
--- a/kernel/bpf/map_iter.c
+++ b/kernel/bpf/map_iter.c
@@ -149,6 +149,19 @@ static void bpf_iter_detach_map(struct bpf_iter_aux_info 
*aux)
        bpf_map_put_with_uref(aux->map);
 }
 
+void bpf_iter_map_show_fdinfo(const struct bpf_iter_aux_info *aux,
+                             struct seq_file *seq)
+{
+       seq_printf(seq, "map_id:\t\t%u\n", aux->map->id);
+}
+
+int bpf_iter_map_fill_link_info(const struct bpf_iter_aux_info *aux,
+                               struct bpf_link_info *info)
+{
+       info->iter.map.map_id = aux->map->id;
+       return 0;
+}
+
 DEFINE_BPF_ITER_FUNC(bpf_map_elem, struct bpf_iter_meta *meta,
                     struct bpf_map *map, void *key, void *value)
 
@@ -156,6 +169,8 @@ static const struct bpf_iter_reg bpf_map_elem_reg_info = {
        .target                 = "bpf_map_elem",
        .attach_target          = bpf_iter_attach_map,
        .detach_target          = bpf_iter_detach_map,
+       .show_fdinfo            = bpf_iter_map_show_fdinfo,
+       .fill_link_info         = bpf_iter_map_fill_link_info,
        .ctx_arg_info_size      = 2,
        .ctx_arg_info           = {
                { offsetof(struct bpf_iter__bpf_map_elem, key),
diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c
index b988f48153a4..281200dc0a01 100644
--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -1437,6 +1437,8 @@ static struct bpf_iter_reg bpf_sk_storage_map_reg_info = {
        .target                 = "bpf_sk_storage_map",
        .attach_target          = bpf_iter_attach_map,
        .detach_target          = bpf_iter_detach_map,
+       .show_fdinfo            = bpf_iter_map_show_fdinfo,
+       .fill_link_info         = bpf_iter_map_fill_link_info,
        .ctx_arg_info_size      = 2,
        .ctx_arg_info           = {
                { offsetof(struct bpf_iter__bpf_sk_storage_map, sk),
-- 
2.24.1