[PATCH bpf-next] bpf: print a little more info about maps via cat /sys/fs/bpf/pinned_name

["Maciej Żenczykowski" <zenczykowski@gmail.com>]

From: Maciej Żenczykowski <maze@google.com>

While this information can be fetched via bpftool,
the cli tool itself isn't always available on more limited systems.

From the information printed particularly the 'id' is useful since
when combined with /proc/pid/fd/X and /proc/pid/fdinfo/X it allows
tracking down which bpf maps a process has open (which can be
useful for tracking down fd leaks).

Signed-off-by: Maciej Żenczykowski <maze@google.com>
---
 kernel/bpf/inode.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/bpf/inode.c b/kernel/bpf/inode.c
index 4f841e16779e..784266e258fe 100644
--- a/kernel/bpf/inode.c
+++ b/kernel/bpf/inode.c
@@ -257,6 +257,9 @@ static int map_seq_show(struct seq_file *m, void *v)
 	if (unlikely(v == SEQ_START_TOKEN)) {
 		seq_puts(m, "# WARNING!! The output is for debug purpose only\n");
 		seq_puts(m, "# WARNING!! The output format will change\n");
+		seq_printf(m, "# type: %d, key_size: %d, value_size: %d, max_entries: %d, id: %d\n",
+			   map->map_type, map->key_size, map->value_size, map->max_entries,
+			   map->id);
 	} else {
 		map->ops->map_seq_show_elem(map, key, m);
 	}
-- 
2.36.1.124.g0e6072fb45-goog