This patch introduces a minimal struct_ops for BPF-based THP adjustment.
Currently, only a single BPF program can be attached. Support for multiple
attachments will be added in the future.
Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
---
include/linux/huge_mm.h | 13 +----
mm/Makefile | 3 +
mm/bpf_thp.c | 120 ++++++++++++++++++++++++++++++++++++++++
3 files changed, 124 insertions(+), 12 deletions(-)
create mode 100644 mm/bpf_thp.c
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index fedb5b014d9a..a75f5f902af0 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -193,18 +193,7 @@ static inline bool hugepage_global_always(void)
(1<<TRANSPARENT_HUGEPAGE_FLAG);
}
-static inline bool hugepage_bpf_allowable(void)
-{
- /* Works only for BPF mode */
- if (!(transparent_hugepage_flags & (1<<TRANSPARENT_HUGEPAGE_REQ_BPF_FLAG)))
- return 0;
-
- /* No BPF program is attached */
- if (!(transparent_hugepage_flags & (1<<TRANSPARENT_HUGEPAGE_BPF_ATTACHED)))
- return 0;
- /* We will add struct ops in the future */
- return 1;
-}
+bool hugepage_bpf_allowable(void);
static inline bool hugepaged_bpf_allowable(void)
{
diff --git a/mm/Makefile b/mm/Makefile
index e7f6bbf8ae5f..c355f9426c93 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -99,6 +99,9 @@ obj-$(CONFIG_MIGRATION) += migrate.o
obj-$(CONFIG_NUMA) += memory-tiers.o
obj-$(CONFIG_DEVICE_MIGRATION) += migrate_device.o
obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o khugepaged.o
+ifdef CONFIG_BPF_SYSCALL
+obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += bpf_thp.o
+endif
obj-$(CONFIG_PAGE_COUNTER) += page_counter.o
obj-$(CONFIG_MEMCG_V1) += memcontrol-v1.o
obj-$(CONFIG_MEMCG) += memcontrol.o vmpressure.o
diff --git a/mm/bpf_thp.c b/mm/bpf_thp.c
new file mode 100644
index 000000000000..690980cdb4da
--- /dev/null
+++ b/mm/bpf_thp.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/bpf.h>
+#include <linux/btf.h>
+#include <linux/huge_mm.h>
+
+struct bpf_thp_ops {
+ /**
+ * @thp_bpf_allowable: Determines whether a task is permitted to
+ * allocate a THP when it is allocating anon memory.
+ *
+ * Return: %true if THP allocation is allowed, %false otherwise.
+ */
+ bool (*thp_bpf_allowable)(void);
+};
+
+static struct bpf_thp_ops bpf_thp;
+
+bool hugepage_bpf_allowable(void)
+{
+ /* Works only for "bpf" mode */
+ if (!(transparent_hugepage_flags & (1<<TRANSPARENT_HUGEPAGE_REQ_BPF_FLAG)))
+ return 0;
+
+ /* No BPF program is attached */
+ if (!(transparent_hugepage_flags & (1<<TRANSPARENT_HUGEPAGE_BPF_ATTACHED)))
+ return 0;
+
+ /* BPF adjustment hook */
+ if (bpf_thp.thp_bpf_allowable)
+ return bpf_thp.thp_bpf_allowable();
+ return 0;
+}
+
+static bool bpf_thp_ops_is_valid_access(int off, int size,
+ enum bpf_access_type type,
+ const struct bpf_prog *prog,
+ struct bpf_insn_access_aux *info)
+{
+ return bpf_tracing_btf_ctx_access(off, size, type, prog, info);
+}
+
+static const struct bpf_func_proto *
+bpf_thp_get_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
+{
+ return bpf_base_func_proto(func_id, prog);
+}
+
+static const struct bpf_verifier_ops thp_bpf_verifier_ops = {
+ .get_func_proto = bpf_thp_get_func_proto,
+ .is_valid_access = bpf_thp_ops_is_valid_access,
+};
+
+static int bpf_thp_reg(void *kdata, struct bpf_link *link)
+{
+ struct bpf_thp_ops *ops = kdata;
+
+ /* TODO: add support for multiple attaches */
+ if (test_and_set_bit(TRANSPARENT_HUGEPAGE_BPF_ATTACHED,
+ &transparent_hugepage_flags))
+ return -EOPNOTSUPP;
+ bpf_thp.thp_bpf_allowable = ops->thp_bpf_allowable;
+ return 0;
+}
+
+static void bpf_thp_unreg(void *kdata, struct bpf_link *link)
+{
+ clear_bit(TRANSPARENT_HUGEPAGE_BPF_ATTACHED, &transparent_hugepage_flags);
+ bpf_thp.thp_bpf_allowable = NULL;
+}
+
+static int bpf_thp_check_member(const struct btf_type *t,
+ const struct btf_member *member,
+ const struct bpf_prog *prog)
+{
+ return 0;
+}
+
+static int bpf_thp_init_member(const struct btf_type *t,
+ const struct btf_member *member,
+ void *kdata, const void *udata)
+{
+ return 0;
+}
+
+static int bpf_thp_init(struct btf *btf)
+{
+ return 0;
+}
+
+static bool thp_bpf_allowable(void)
+{
+ return 0;
+}
+
+static struct bpf_thp_ops __bpf_thp_ops = {
+ .thp_bpf_allowable = thp_bpf_allowable,
+};
+
+static struct bpf_struct_ops bpf_bpf_thp_ops = {
+ .verifier_ops = &thp_bpf_verifier_ops,
+ .init = bpf_thp_init,
+ .check_member = bpf_thp_check_member,
+ .init_member = bpf_thp_init_member,
+ .reg = bpf_thp_reg,
+ .unreg = bpf_thp_unreg,
+ .name = "bpf_thp_ops",
+ .cfi_stubs = &__bpf_thp_ops,
+ .owner = THIS_MODULE,
+};
+
+static int __init bpf_thp_ops_init(void)
+{
+ int err = register_bpf_struct_ops(&bpf_bpf_thp_ops, bpf_thp_ops);
+
+ if (err)
+ pr_err("bpf_thp: Failed to register struct_ops (%d)\n", err);
+ return err;
+}
+late_initcall(bpf_thp_ops_init);
--
2.43.5
