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Message-Id: <20251020031655.1093-5-laoar.shao@gmail.com>
Date: Mon, 20 Oct 2025 11:16:54 +0800
From: Yafang Shao <laoar.shao@...il.com>
To: akpm@...ux-foundation.org,
ast@...nel.org,
daniel@...earbox.net,
andrii@...nel.org,
martin.lau@...ux.dev,
eddyz87@...il.com,
song@...nel.org,
yonghong.song@...ux.dev,
john.fastabend@...il.com,
kpsingh@...nel.org,
sdf@...ichev.me,
haoluo@...gle.com,
jolsa@...nel.org,
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ziy@...dia.com,
lorenzo.stoakes@...cle.com,
Liam.Howlett@...cle.com,
npache@...hat.com,
ryan.roberts@....com,
dev.jain@....com,
hannes@...xchg.org,
usamaarif642@...il.com,
gutierrez.asier@...wei-partners.com,
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shakeel.butt@...ux.dev,
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rdunlap@...radead.org
Cc: bpf@...r.kernel.org,
linux-mm@...ck.org,
linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org,
Yafang Shao <laoar.shao@...il.com>
Subject: [PATCH v11 mm-new 09/10] selftests/bpf: add test case to update THP policy
This test case exercises the BPF THP update mechanism by modifying an
existing policy. The behavior confirms that:
- EBUSY error occurs when attempting to install a BPF program on a process
that already has an active BPF program
- Updates to currently running programs are successfully processed
- Local prog can't be updated by a global prog
- Global prog can't be updated by a local prog
- Global prog can be attached even if there's a local prog
- Local prog can't be attached if there's a global prog
Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
.../selftests/bpf/prog_tests/thp_adjust.c | 79 +++++++++++++++++++
.../selftests/bpf/progs/test_thp_adjust.c | 29 +++++++
2 files changed, 108 insertions(+)
diff --git a/tools/testing/selftests/bpf/prog_tests/thp_adjust.c b/tools/testing/selftests/bpf/prog_tests/thp_adjust.c
index 2b23e2d08092..0d570cee9006 100644
--- a/tools/testing/selftests/bpf/prog_tests/thp_adjust.c
+++ b/tools/testing/selftests/bpf/prog_tests/thp_adjust.c
@@ -194,6 +194,79 @@ static void subtest_thp_eligible(void)
bpf_link__destroy(ops_link);
}
+static void subtest_thp_policy_update(void)
+{
+ struct bpf_link *old_link, *new_link;
+ int elighble, err, pid;
+ char *ptr;
+
+ pid = getpid();
+ ptr = thp_alloc();
+
+ old_link = bpf_map__attach_struct_ops(skel->maps.thp_eligible_ops);
+ if (!ASSERT_OK_PTR(old_link, "attach_old_link"))
+ goto free;
+
+ elighble = get_thp_eligible(pid, (unsigned long)ptr);
+ ASSERT_EQ(elighble, 0, "THPeligible");
+
+ /* Attach multi BPF-THP to a single process is rejected. */
+ new_link = bpf_map__attach_struct_ops(skel->maps.thp_eligible_ops2);
+ if (!ASSERT_NULL(new_link, "attach_new_link"))
+ goto destory_old;
+ ASSERT_EQ(errno, EBUSY, "attach_new_link");
+
+ elighble = get_thp_eligible(pid, (unsigned long)ptr);
+ ASSERT_EQ(elighble, 0, "THPeligible");
+
+ err = bpf_link__update_map(old_link, skel->maps.thp_eligible_ops2);
+ ASSERT_EQ(err, 0, "update_old_link");
+
+ elighble = get_thp_eligible(pid, (unsigned long)ptr);
+ ASSERT_EQ(elighble, 1, "THPeligible");
+
+ /* Per process prog can't be update by a global prog */
+ err = bpf_link__update_map(old_link, skel->maps.swap_ops);
+ ASSERT_EQ(err, -EINVAL, "update_old_link");
+
+destory_old:
+ bpf_link__destroy(old_link);
+free:
+ thp_free(ptr);
+}
+
+static void subtest_thp_global_policy(void)
+{
+ struct bpf_link *local_link, *global_link;
+ int err;
+
+ local_link = bpf_map__attach_struct_ops(skel->maps.thp_eligible_ops);
+ if (!ASSERT_OK_PTR(local_link, "attach_local_link"))
+ return;
+
+ /* global prog can be attached even if there is a local prog */
+ global_link = bpf_map__attach_struct_ops(skel->maps.swap_ops);
+ if (!ASSERT_OK_PTR(global_link, "attach_global_link")) {
+ bpf_link__destroy(local_link);
+ return;
+ }
+
+ bpf_link__destroy(local_link);
+
+ /* local prog can't be attaached if there is a global prog */
+ local_link = bpf_map__attach_struct_ops(skel->maps.thp_eligible_ops);
+ if (!ASSERT_NULL(local_link, "attach_new_link"))
+ goto destory_global;
+ ASSERT_EQ(errno, EBUSY, "attach_new_link");
+
+ /* global prog can't be updated by a local prog */
+ err = bpf_link__update_map(global_link, skel->maps.thp_eligible_ops);
+ ASSERT_EQ(err, -EINVAL, "update_old_link");
+
+destory_global:
+ bpf_link__destroy(global_link);
+}
+
static int thp_adjust_setup(void)
{
int err = -1, pmd_order;
@@ -214,6 +287,8 @@ static int thp_adjust_setup(void)
skel->bss->pmd_order = pmd_order;
skel->struct_ops.thp_eligible_ops->pid = getpid();
+ skel->struct_ops.thp_eligible_ops2->pid = getpid();
+ /* swap_ops is a global prog since its pid is not set. */
err = test_thp_adjust__load(skel);
if (!ASSERT_OK(err, "load"))
@@ -240,6 +315,10 @@ void test_thp_adjust(void)
if (test__start_subtest("thp_eligible"))
subtest_thp_eligible();
+ if (test__start_subtest("policy_update"))
+ subtest_thp_policy_update();
+ if (test__start_subtest("global_policy"))
+ subtest_thp_global_policy();
thp_adjust_destroy();
}
diff --git a/tools/testing/selftests/bpf/progs/test_thp_adjust.c b/tools/testing/selftests/bpf/progs/test_thp_adjust.c
index b180a7f9b923..44648326819a 100644
--- a/tools/testing/selftests/bpf/progs/test_thp_adjust.c
+++ b/tools/testing/selftests/bpf/progs/test_thp_adjust.c
@@ -22,3 +22,32 @@ SEC(".struct_ops.link")
struct bpf_thp_ops thp_eligible_ops = {
.thp_get_order = (void *)thp_not_eligible,
};
+
+SEC("struct_ops/thp_get_order")
+int BPF_PROG(thp_eligible, struct vm_area_struct *vma, enum tva_type type,
+ unsigned long orders)
+{
+ /* THPeligible in /proc/pid/smaps is 1 */
+ if (type == TVA_SMAPS)
+ return pmd_order;
+ return pmd_order;
+}
+
+SEC(".struct_ops.link")
+struct bpf_thp_ops thp_eligible_ops2 = {
+ .thp_get_order = (void *)thp_eligible,
+};
+
+SEC("struct_ops/thp_get_order")
+int BPF_PROG(alloc_not_in_swap, struct vm_area_struct *vma, enum tva_type type,
+ unsigned long orders)
+{
+ if (type == TVA_SWAP_PAGEFAULT)
+ return 0;
+ return -1;
+}
+
+SEC(".struct_ops.link")
+struct bpf_thp_ops swap_ops = {
+ .thp_get_order = (void *)alloc_not_in_swap,
+};
--
2.47.3
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