Hi Yonghong,
On 29/10/25 07:44, Yonghong Song wrote:
On 10/28/25 5:57 AM, Harshit Mogalapalli wrote:
It is useful to print map ID on successful creation.
JSON case:
$ ./bpftool -j map create /sys/fs/bpf/test_map4 type hash key 4 value
8 entries 128 name map4
{"id":12}
Generic case:
$ ./bpftool map create /sys/fs/bpf/test_map5 type hash key 4 value 8
entries 128 name map5
Map successfully created with ID: 15
Bpftool Issue: https://github.com/libbpf/bpftool/issues/121
Signed-off-by: Harshit Mogalapalli <[email protected]>
---
tools/bpf/bpftool/map.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index c9de44a45778..b6580f25361d 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -1251,6 +1251,8 @@ static int do_create(int argc, char **argv)
LIBBPF_OPTS(bpf_map_create_opts, attr);
enum bpf_map_type map_type = BPF_MAP_TYPE_UNSPEC;
__u32 key_size = 0, value_size = 0, max_entries = 0;
+ struct bpf_map_info map_info = {};
+ __u32 map_info_len = sizeof(map_info);
const char *map_name = NULL;
const char *pinfile;
int err = -1, fd;
@@ -1353,13 +1355,27 @@ static int do_create(int argc, char **argv)
}
err = do_pin_fd(fd, pinfile);
- close(fd);
- if (err)
+ if (err) {
+ close(fd);
I think you can remove close(fd) here,
goto exit;
+ }
- if (json_output)
- jsonw_null(json_wtr);
+ err = bpf_obj_get_info_by_fd(fd, &map_info, &map_info_len);
+ if (err) {
+ p_err("Failed to fetch map info: %s\n", strerror(errno));
+ close(fd);
and here
+ goto exit;
+ }
+ close(fd);
and here,
+
+ if (json_output) {
+ jsonw_start_object(json_wtr);
+ jsonw_int_field(json_wtr, "id", map_info.id);
+ jsonw_end_object(json_wtr);
+ } else {
+ printf("Map successfully created with ID: %u\n", map_info.id);
+ }
exit:
and put close(fd) here.
I think we need one more close_fd: label and then put a close(fd); here.
As there are other gotos to exit earlier in this function when fd is
uninitialized, which can the error like:
map.c: In function ‘do_create’:
map.c:1375:9: warning: ‘fd’ may be used uninitialized
[-Wmaybe-uninitialized]
1375 | close(fd);
| ^~~~~~~~~
map.c:1258:23: note: ‘fd’ was declared here
1258 | int err = -1, fd;
| ^~
So, maybe we could do something like this:
err = do_pin_fd(fd, pinfile);
- close(fd);
if (err)
- goto exit;
+ goto close_fd;
- if (json_output)
- jsonw_null(json_wtr);
+ err = bpf_obj_get_info_by_fd(fd, &map_info, &map_info_len);
+ if (err) {
+ p_err("Failed to fetch map info: %s\n", strerror(errno));
+ goto close_fd;
+ }
+ if (json_output) {
+ jsonw_start_object(json_wtr);
+ jsonw_int_field(json_wtr, "id", map_info.id);
+ jsonw_end_object(json_wtr);
+ } else {
+ printf("Map successfully created with ID: %u\n",
map_info.id);
+ }
+close_fd:
+ close(fd);
exit:
if (attr.inner_map_fd > 0)
close(attr.inner_map_fd);
I can prepare a v2 with this change, but wouldn't it be simpler to add a
direct close(fd); on the few error paths instead of introducing an
additional label for close(fd);?
Thoughts/Suggestions ?
Thanks,
Harshit
if (attr.inner_map_fd > 0)
close(attr.inner_map_fd);
