netdev - [PATCH bpf-next] selftests/bpf: Fix tests after change in struct file

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Message-ID: <20250327185528.1740787-1-song@kernel.org>
Date: Thu, 27 Mar 2025 11:55:28 -0700
From: Song Liu <song@...nel.org>
To: bpf@...r.kernel.org,
	netdev@...r.kernel.org
Cc: ast@...nel.org,
	daniel@...earbox.net,
	andrii@...nel.org,
	kernel-team@...a.com,
	song@...nel.org,
	Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH bpf-next] selftests/bpf: Fix tests after change in struct file

Change in struct file [1] moves f_ref to the 3rd cache line. This makes
deferencing file pointer as a 8-byte variable invalid, because
btf_struct_walk() will walk into f_lock, which is 4-byte long.

Fix the selftests to deference the file pointer as a 4-byte variable.

[1] commit e249056c91a2 ("fs: place f_ref to 3rd cache line in struct
                          file to resolve false sharing")
Reported-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Song Liu <song@...nel.org>
---
 tools/testing/selftests/bpf/progs/test_module_attach.c    | 2 +-
 tools/testing/selftests/bpf/progs/test_subprogs_extable.c | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/test_module_attach.c b/tools/testing/selftests/bpf/progs/test_module_attach.c
index fb07f5773888..7f3c233943b3 100644
--- a/tools/testing/selftests/bpf/progs/test_module_attach.c
+++ b/tools/testing/selftests/bpf/progs/test_module_attach.c
@@ -117,7 +117,7 @@ int BPF_PROG(handle_fexit_ret, int arg, struct file *ret)
 
 	bpf_probe_read_kernel(&buf, 8, ret);
 	bpf_probe_read_kernel(&buf, 8, (char *)ret + 256);
-	*(volatile long long *)ret;
+	*(volatile int *)ret;
 	*(volatile int *)&ret->f_mode;
 	return 0;
 }
diff --git a/tools/testing/selftests/bpf/progs/test_subprogs_extable.c b/tools/testing/selftests/bpf/progs/test_subprogs_extable.c
index e2a21fbd4e44..dcac69f5928a 100644
--- a/tools/testing/selftests/bpf/progs/test_subprogs_extable.c
+++ b/tools/testing/selftests/bpf/progs/test_subprogs_extable.c
@@ -21,7 +21,7 @@ static __u64 test_cb(struct bpf_map *map, __u32 *key, __u64 *val, void *data)
 SEC("fexit/bpf_testmod_return_ptr")
 int BPF_PROG(handle_fexit_ret_subprogs, int arg, struct file *ret)
 {
-	*(volatile long *)ret;
+	*(volatile int *)ret;
 	*(volatile int *)&ret->f_mode;
 	bpf_for_each_map_elem(&test_array, test_cb, NULL, 0);
 	triggered++;
@@ -31,7 +31,7 @@ int BPF_PROG(handle_fexit_ret_subprogs, int arg, struct file *ret)
 SEC("fexit/bpf_testmod_return_ptr")
 int BPF_PROG(handle_fexit_ret_subprogs2, int arg, struct file *ret)
 {
-	*(volatile long *)ret;
+	*(volatile int *)ret;
 	*(volatile int *)&ret->f_mode;
 	bpf_for_each_map_elem(&test_array, test_cb, NULL, 0);
 	triggered++;
@@ -41,7 +41,7 @@ int BPF_PROG(handle_fexit_ret_subprogs2, int arg, struct file *ret)
 SEC("fexit/bpf_testmod_return_ptr")
 int BPF_PROG(handle_fexit_ret_subprogs3, int arg, struct file *ret)
 {
-	*(volatile long *)ret;
+	*(volatile int *)ret;
 	*(volatile int *)&ret->f_mode;
 	bpf_for_each_map_elem(&test_array, test_cb, NULL, 0);
 	triggered++;
-- 
2.47.1