[PATCH v2] sched_ext: Use btf_ids to resolve task_struct

[Tianchen Ding <dtcccc@linux.alibaba.com>]

Save the searching time during bpf_scx_init.

Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
---
v2:
Use the existing btf_tracing_ids[BTF_TRACING_TYPE_TASK].

v1: https://lore.kernel.org/all/20241016024100.7409-1-dtcccc@linux.alibaba.com/
---
 kernel/sched/ext.c | 11 ++---------
 1 file changed, 2 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 609b9fb00d6f..09fe4e1552bb 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -5343,7 +5343,6 @@ static int scx_ops_enable(struct sched_ext_ops *ops, struct bpf_link *link)
 
 extern struct btf *btf_vmlinux;
 static const struct btf_type *task_struct_type;
-static u32 task_struct_type_id;
 
 static bool set_arg_maybe_null(const char *op, int arg_n, int off, int size,
 			       enum bpf_access_type type,
@@ -5395,7 +5394,7 @@ static bool set_arg_maybe_null(const char *op, int arg_n, int off, int size,
 		 */
 		info->reg_type = PTR_MAYBE_NULL | PTR_TO_BTF_ID | PTR_TRUSTED;
 		info->btf = btf_vmlinux;
-		info->btf_id = task_struct_type_id;
+		info->btf_id = btf_tracing_ids[BTF_TRACING_TYPE_TASK];
 
 		return true;
 	}
@@ -5547,13 +5546,7 @@ static void bpf_scx_unreg(void *kdata, struct bpf_link *link)
 
 static int bpf_scx_init(struct btf *btf)
 {
-	s32 type_id;
-
-	type_id = btf_find_by_name_kind(btf, "task_struct", BTF_KIND_STRUCT);
-	if (type_id < 0)
-		return -EINVAL;
-	task_struct_type = btf_type_by_id(btf, type_id);
-	task_struct_type_id = type_id;
+	task_struct_type = btf_type_by_id(btf, btf_tracing_ids[BTF_TRACING_TYPE_TASK]);
 
 	return 0;
 }
-- 
2.39.3