bpf: refactor special field-type detection

Reduce code duplication in detection of the known special field types in
map values. This refactoring helps to avoid copying a chunk of code in
the next patch of the series.

Signed-off-by: Mykyta Yatsenko <[email protected]>
Acked-by: Eduard Zingerman <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>

Author: mykyta5

kernel/bpf/btf.c

@@ -3488,44 +3488,28 @@ static int btf_get_field_type(const struct btf *btf, const struct btf_type *var_
 			      u32 field_mask, u32 *seen_mask,
 			      int *align, int *sz)
 {
-	int type = 0;
+	const struct {
+		enum btf_field_type type;
+		const char *const name;
+	} field_types[] = { { BPF_SPIN_LOCK, "bpf_spin_lock" },
+			    { BPF_RES_SPIN_LOCK, "bpf_res_spin_lock" },
+			    { BPF_TIMER, "bpf_timer" },
+			    { BPF_WORKQUEUE, "bpf_wq" }};
+	int type = 0, i;
 	const char *name = __btf_name_by_offset(btf, var_type->name_off);
+	const char *field_type_name;
+	enum btf_field_type field_type;
 
-	if (field_mask & BPF_SPIN_LOCK) {
-		if (!strcmp(name, "bpf_spin_lock")) {
-			if (*seen_mask & BPF_SPIN_LOCK)
-				return -E2BIG;
-			*seen_mask |= BPF_SPIN_LOCK;
-			type = BPF_SPIN_LOCK;
-			goto end;
-		}
-	}
-	if (field_mask & BPF_RES_SPIN_LOCK) {
-		if (!strcmp(name, "bpf_res_spin_lock")) {
-			if (*seen_mask & BPF_RES_SPIN_LOCK)
-				return -E2BIG;
-			*seen_mask |= BPF_RES_SPIN_LOCK;
-			type = BPF_RES_SPIN_LOCK;
-			goto end;
-		}
-	}
-	if (field_mask & BPF_TIMER) {
-		if (!strcmp(name, "bpf_timer")) {
-			if (*seen_mask & BPF_TIMER)
-				return -E2BIG;
-			*seen_mask |= BPF_TIMER;
-			type = BPF_TIMER;
-			goto end;
-		}
-	}
-	if (field_mask & BPF_WORKQUEUE) {
-		if (!strcmp(name, "bpf_wq")) {
-			if (*seen_mask & BPF_WORKQUEUE)
-				return -E2BIG;
-			*seen_mask |= BPF_WORKQUEUE;
-			type = BPF_WORKQUEUE;
-			goto end;
-		}
+	for (i = 0; i < ARRAY_SIZE(field_types); ++i) {
+		field_type = field_types[i].type;
+		field_type_name = field_types[i].name;
+		if (!(field_mask & field_type) || strcmp(name, field_type_name))
+			continue;
+		if (*seen_mask & field_type)
+			return -E2BIG;
+		*seen_mask |= field_type;
+		type = field_type;
+		goto end;
 	}
 	field_mask_test_name(BPF_LIST_HEAD, "bpf_list_head");
 	field_mask_test_name(BPF_LIST_NODE, "bpf_list_node");