bpf: add missing map_flags to bpf_map_show_fdinfo

Add map_flags attribute to bpf_map_show_fdinfo(), so that tools like
tc can check for them when loading objects from a pinned entry, e.g.
if user intent wrt allocation (BPF_F_NO_PREALLOC) is different to the
pinned object, it can bail out. Follow-up to 6c90598174 ("bpf:
pre-allocate hash map elements"), so that tc can still support this
with v4.6.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

kernel/bpf/syscall.c

@@ -137,11 +137,13 @@ static void bpf_map_show_fdinfo(struct seq_file *m, struct file *filp)
 		   "map_type:\t%u\n"
 		   "key_size:\t%u\n"
 		   "value_size:\t%u\n"
-		   "max_entries:\t%u\n",
+		   "max_entries:\t%u\n"
+		   "map_flags:\t%#x\n",
 		   map->map_type,
 		   map->key_size,
 		   map->value_size,
-		   map->max_entries);
+		   map->max_entries,
+		   map->map_flags);
 }
 #endif