tools: bpftool: optionally show filenames of pinned objects

Making it optional to show file names of pinned objects because
it scans complete bpf-fs filesystem which is costly.
Added option -f|--bpffs. Documentation updated.

Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 6ad53f1..d6e4762 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -54,6 +54,7 @@ static int (*last_do_help)(int argc, char **argv);
 json_writer_t *json_wtr;
 bool pretty_output;
 bool json_output;
+bool show_pinned;
 struct pinned_obj_table prog_table;
 struct pinned_obj_table map_table;
 
@@ -265,6 +266,7 @@ int main(int argc, char **argv)
 		{ "help",	no_argument,	NULL,	'h' },
 		{ "pretty",	no_argument,	NULL,	'p' },
 		{ "version",	no_argument,	NULL,	'V' },
+		{ "bpffs",	no_argument,	NULL,	'f' },
 		{ 0 }
 	};
 	int opt, ret;
@@ -272,12 +274,13 @@ int main(int argc, char **argv)
 	last_do_help = do_help;
 	pretty_output = false;
 	json_output = false;
+	show_pinned = false;
 	bin_name = argv[0];
 
 	hash_init(prog_table.table);
 	hash_init(map_table.table);
 
-	while ((opt = getopt_long(argc, argv, "Vhpj",
+	while ((opt = getopt_long(argc, argv, "Vhpjf",
 				  options, NULL)) >= 0) {
 		switch (opt) {
 		case 'V':
@@ -290,6 +293,9 @@ int main(int argc, char **argv)
 		case 'j':
 			json_output = true;
 			break;
+		case 'f':
+			show_pinned = true;
+			break;
 		default:
 			usage();
 		}
@@ -316,8 +322,10 @@ int main(int argc, char **argv)
 	if (json_output)
 		jsonw_destroy(&json_wtr);
 
-	delete_pinned_obj_table(&prog_table);
-	delete_pinned_obj_table(&map_table);
+	if (show_pinned) {
+		delete_pinned_obj_table(&prog_table);
+		delete_pinned_obj_table(&map_table);
+	}
 
 	return ret;
 }