netdev - [PATCH bpf-next 13/19] bpf: Remove migrate_{disable|enable} in bpf_obj_free

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Message-Id: <20250106081900.1665573-14-houtao@huaweicloud.com>
Date: Mon,  6 Jan 2025 16:18:54 +0800
From: Hou Tao <houtao@...weicloud.com>
To: bpf@...r.kernel.org,
	netdev@...r.kernel.org
Cc: Martin KaFai Lau <martin.lau@...ux.dev>,
	Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Hao Luo <haoluo@...gle.com>,
	Yonghong Song <yonghong.song@...ux.dev>,
	Daniel Borkmann <daniel@...earbox.net>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...ichev.me>,
	Jiri Olsa <jolsa@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	houtao1@...wei.com,
	xukuohai@...wei.com
Subject: [PATCH bpf-next 13/19] bpf: Remove migrate_{disable|enable} in bpf_obj_free_fields()

From: Hou Tao <houtao1@...wei.com>

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 adds a cant_migrate() check in bpf_obj_free_fields() to
ensure the guarantee isn't broken, and 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@...wei.com>
---
 kernel/bpf/helpers.c | 4 ----
 kernel/bpf/syscall.c | 4 ++--
 2 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index cd5f9884d85b..bcda671feafd 100644
--- a/kernel/bpf/helpers.c
+++ b/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();
 	}
 }
 
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4e88797fdbeb..0503ce1916b6 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -766,6 +766,8 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
 	const struct btf_field *fields;
 	int i;
 
+	cant_migrate();
+
 	if (IS_ERR_OR_NULL(rec))
 		return;
 	fields = rec->fields;
@@ -796,11 +798,9 @@ 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);
 			}
-- 
2.29.2