Re: [PATCH net-next v4 04/13] devlink: allow to use devlink index as a command handle

From: Geert Uytterhoeven

Date: Wed Apr 15 2026 - 15:08:54 EST

On Thu, 12 Mar 2026, Jiri Pirko wrote:
> Currently devlink instances are addressed bus_name/dev_name tuple.
> Allow the newly introduced DEVLINK_ATTR_INDEX to be used as
> an alternative handle for all devlink commands.
>
> When DEVLINK_ATTR_INDEX is present in the request, use it for a direct
> xarray lookup instead of iterating over all instances comparing
> bus_name/dev_name strings.
>
> Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxx>

Thanks for your patch, which is now commit d85a8af57da87196 ("devlink:
allow to use devlink index as a command handle").

This has a rather large impact on kernel size.
For e.g. m68k/atari_defconfig, bloat-o-meter reports:

add/remove: 4/1 grow/shrink: 72/1 up/down: 65804/-76 (65728)
Function old new delta
devlink_trap_policer_get_dump_nl_policy 24 1480 +1456
devlink_trap_group_get_dump_nl_policy 24 1480 +1456
devlink_trap_get_dump_nl_policy 24 1480 +1456
devlink_selftests_get_nl_policy 24 1480 +1456
devlink_sb_tc_pool_bind_get_dump_nl_policy 24 1480 +1456
devlink_sb_port_pool_get_dump_nl_policy 24 1480 +1456
devlink_sb_pool_get_dump_nl_policy 24 1480 +1456
devlink_sb_get_dump_nl_policy 24 1480 +1456
devlink_resource_dump_nl_policy 24 1480 +1456
devlink_region_get_dump_nl_policy 24 1480 +1456
devlink_rate_get_dump_nl_policy 24 1480 +1456
devlink_port_get_dump_nl_policy 24 1480 +1456
devlink_param_get_dump_nl_policy 24 1480 +1456
devlink_linecard_get_dump_nl_policy 24 1480 +1456
devlink_info_get_nl_policy 24 1480 +1456
devlink_get_nl_policy 24 1480 +1456
devlink_eswitch_get_nl_policy 24 1480 +1456
devlink_dpipe_headers_get_nl_policy 24 1480 +1456
devlink_port_unsplit_nl_policy 32 1480 +1448
devlink_port_param_set_nl_policy 32 1480 +1448
devlink_port_param_get_nl_policy 32 1480 +1448
devlink_port_get_do_nl_policy 32 1480 +1448
devlink_port_del_nl_policy 32 1480 +1448
devlink_notify_filter_set_nl_policy 32 1480 +1448
devlink_health_reporter_get_dump_nl_policy 32 1480 +1448
devlink_port_split_nl_policy 80 1480 +1400
devlink_sb_occ_snapshot_nl_policy 96 1480 +1384
devlink_sb_occ_max_clear_nl_policy 96 1480 +1384
devlink_sb_get_do_nl_policy 96 1480 +1384
devlink_sb_port_pool_get_do_nl_policy 144 1480 +1336
devlink_sb_pool_get_do_nl_policy 144 1480 +1336
devlink_sb_pool_set_nl_policy 168 1480 +1312
devlink_sb_port_pool_set_nl_policy 176 1480 +1304
devlink_sb_tc_pool_bind_set_nl_policy 184 1480 +1296
devlink_sb_tc_pool_bind_get_do_nl_policy 184 1480 +1296
devlink_dpipe_table_get_nl_policy 240 1480 +1240
devlink_dpipe_entries_get_nl_policy 240 1480 +1240
devlink_dpipe_table_counters_set_nl_policy 272 1480 +1208
devlink_eswitch_set_nl_policy 504 1480 +976
devlink_resource_set_nl_policy 544 1480 +936
devlink_param_get_do_nl_policy 656 1480 +824
devlink_region_get_do_nl_policy 712 1480 +768
devlink_region_new_nl_policy 744 1480 +736
devlink_region_del_nl_policy 744 1480 +736
devlink_health_reporter_test_nl_policy 928 1480 +552
devlink_health_reporter_recover_nl_policy 928 1480 +552
devlink_health_reporter_get_do_nl_policy 928 1480 +552
devlink_health_reporter_dump_get_nl_policy 928 1480 +552
devlink_health_reporter_dump_clear_nl_policy 928 1480 +552
devlink_health_reporter_diagnose_nl_policy 928 1480 +552
devlink_trap_get_do_nl_policy 1048 1480 +432
devlink_trap_set_nl_policy 1056 1480 +424
devlink_trap_group_get_do_nl_policy 1088 1480 +392
devlink_trap_policer_get_do_nl_policy 1144 1480 +336
devlink_trap_group_set_nl_policy 1144 1480 +336
devlink_trap_policer_set_nl_policy 1160 1480 +320
devlink_port_set_nl_policy 1168 1480 +312
devlink_flash_update_nl_policy 1224 1480 +256
devlink_reload_nl_policy 1248 1480 +232
devlink_port_new_nl_policy 1320 1480 +160
devlink_rate_get_do_nl_policy 1352 1480 +128
devlink_rate_del_nl_policy 1352 1480 +128
devlink_linecard_get_do_nl_policy 1376 1480 +104
__devlinks_xa_find_get - 96 +96
devlink_linecard_set_nl_policy 1392 1480 +88
devlink_selftests_run_nl_policy 1416 1480 +64
devlink_get_from_attrs_lock 262 314 +52
devlink_region_read_nl_policy 1440 1480 +40
devlink_rate_set_nl_policy 1448 1480 +32
devlink_rate_new_nl_policy 1448 1480 +32
devlinks_xa_lookup_get - 30 +30
devlink_health_reporter_set_nl_policy 1456 1480 +24
devlink_attr_index_range - 16 +16
devlink_param_set_nl_policy 1472 1480 +8
devlink_nl_dumpit 276 282 +6
__initcall__kmod_core__670_573_devlink_init4 - 4 +4
__initcall__kmod_core__670_561_devlink_init4 4 - -4
devlinks_xa_find_get 96 24 -72
Total: Before=5203976, After=5269704, chg +1.26%

> --- a/net/devlink/netlink_gen.c
> +++ b/net/devlink/netlink_gen.c
> @@ -11,6 +11,11 @@
>
> #include <uapi/linux/devlink.h>
>
> +/* Integer value ranges */
> +static const struct netlink_range_validation devlink_attr_index_range = {
> + .max = U32_MAX,
> +};
> +
> /* Sparse enums validation callbacks */
> static int
> devlink_attr_param_type_validate(const struct nlattr *attr,
> @@ -56,37 +61,42 @@ const struct nla_policy devlink_dl_selftest_id_nl_policy[DEVLINK_ATTR_SELFTEST_I
> };
>
> /* DEVLINK_CMD_GET - do */
> -static const struct nla_policy devlink_get_nl_policy[DEVLINK_ATTR_DEV_NAME + 1] = {
> +static const struct nla_policy devlink_get_nl_policy[DEVLINK_ATTR_INDEX + 1] = {

Unrelated to this change, but the explicit sizing of these arrays is not
needed, as the compiler will take care of that.

> [DEVLINK_ATTR_BUS_NAME] = { .type = NLA_NUL_STRING, },
> [DEVLINK_ATTR_DEV_NAME] = { .type = NLA_NUL_STRING, },
> + [DEVLINK_ATTR_INDEX] = NLA_POLICY_FULL_RANGE(NLA_UINT, &devlink_attr_index_range),

This array, and many others below, are sparse, with large gaps (up to
1456 or 2912 bytes on 32-bit resp. 64-bit systems) before the last
entries.

> };
>
> /* DEVLINK_CMD_PORT_GET - do */
> -static const struct nla_policy devlink_port_get_do_nl_policy[DEVLINK_ATTR_PORT_INDEX + 1] = {
> +static const struct nla_policy devlink_port_get_do_nl_policy[DEVLINK_ATTR_INDEX + 1] = {
> [DEVLINK_ATTR_BUS_NAME] = { .type = NLA_NUL_STRING, },
> [DEVLINK_ATTR_DEV_NAME] = { .type = NLA_NUL_STRING, },
> + [DEVLINK_ATTR_INDEX] = NLA_POLICY_FULL_RANGE(NLA_UINT, &devlink_attr_index_range),

Shouldn't this be inserted at the end, as DEVLINK_ATTR_INDEX >
DEVLINK_ATTR_PORT_INDEX, for readability?

> [DEVLINK_ATTR_PORT_INDEX] = { .type = NLA_U32, },
> };

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds