bpf: Remove migrate_{disable|enable} in bpf_obj_free_fields()

The callers of bpf_obj_free_fields() have already guaranteed that the
migration is disabled, therefore, there is no need to invoke
migrate_{disable,enable} pair in bpf_obj_free_fields()'s underly
implementation.

This patch removes unnecessary migrate_{disable|enable} pairs from
bpf_obj_free_fields() and its callees: bpf_list_head_free() and
bpf_rb_root_free().

Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-12-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: Hou Tao

kernel/bpf/helpers.c

@@ -2066,9 +2066,7 @@ void bpf_list_head_free(const struct btf_field *field, void *list_head,
 		/* The contained type can also have resources, including a
 		 * bpf_list_head which needs to be freed.
 		 */
-		migrate_disable();
 		__bpf_obj_drop_impl(obj, field->graph_root.value_rec, false);
-		migrate_enable();
 	}
 }
 
@@ -2105,9 +2103,7 @@ void bpf_rb_root_free(const struct btf_field *field, void *rb_root,
 		obj -= field->graph_root.node_offset;
 
 
-		migrate_disable();
 		__bpf_obj_drop_impl(obj, field->graph_root.value_rec, false);
-		migrate_enable();
 	}
 }
 

kernel/bpf/syscall.c

@@ -796,11 +796,9 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 			if (!btf_is_kernel(field->kptr.btf)) {
 				pointee_struct_meta = btf_find_struct_meta(field->kptr.btf,
 									   field->kptr.btf_id);
-				migrate_disable();
 				__bpf_obj_drop_impl(xchgd_field, pointee_struct_meta ?
 								 pointee_struct_meta->record : NULL,
 								 fields[i].type == BPF_KPTR_PERCPU);
-				migrate_enable();
 			} else {
 				field->kptr.dtor(xchgd_field);
 			}