The track_pte_set() is used to track the setting of the PTE page table
entry, and the track_pte_clear() is used to track the clearing of the
PTE page table entry, we update the pte_refcount of the PTE page in
these two functions.
In this way, the usage of the PTE page table page can be tracked by
its pte_refcount.
Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
include/linux/pte_ref.h | 13 +++++++++++++
mm/pte_ref.c | 36 ++++++++++++++++++++++++++++++++++++
2 files changed, 49 insertions(+)
diff --git a/include/linux/pte_ref.h b/include/linux/pte_ref.h
index db14e03e1dff..ab49c7fac120 100644
--- a/include/linux/pte_ref.h
+++ b/include/linux/pte_ref.h
@@ -12,12 +12,25 @@
void pte_ref_init(pgtable_t pte);
+void track_pte_set(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
+ pte_t pte);
+void track_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
+ pte_t pte);
#else /* !CONFIG_FREE_USER_PTE */
static inline void pte_ref_init(pgtable_t pte)
{
}
+static inline void track_pte_set(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep, pte_t pte)
+{
+}
+
+static inline void track_pte_clear(struct mm_struct *mm, unsigned long addr,
+ pte_t *ptep, pte_t pte)
+{
+}
#endif /* CONFIG_FREE_USER_PTE */
#endif /* _LINUX_PTE_REF_H */
diff --git a/mm/pte_ref.c b/mm/pte_ref.c
index 12b27646e88c..818821d068af 100644
--- a/mm/pte_ref.c
+++ b/mm/pte_ref.c
@@ -69,4 +69,40 @@ void pte_ref_init(pgtable_t pte)
pte->pte_refcount = 0;
}
+void track_pte_set(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
+ pte_t pte)
+{
+ pgtable_t page;
+
+ if (&init_mm == mm || pte_huge(pte))
+ return;
+
+ page = pte_to_page(ptep);
+ if (pte_none(*ptep) && !pte_none(pte)) {
+ pte_refcount_add(mm, page, PTE_MAPPED_OFFSET);
+ if (is_zero_pfn(pte_pfn(pte)))
+ pte_refcount_add(mm, page, PTE_ZERO_OFFSET);
+ } else if (is_zero_pfn(pte_pfn(*ptep)) && !is_zero_pfn(pte_pfn(pte))) {
+ pte_refcount_sub(mm, page, PTE_ZERO_OFFSET);
+ }
+}
+EXPORT_SYMBOL(track_pte_set);
+
+void track_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
+ pte_t pte)
+{
+ pgtable_t page;
+
+ if (&init_mm == mm || pte_huge(pte))
+ return;
+
+ page = pte_to_page(ptep);
+ if (!pte_none(pte)) {
+ pte_refcount_sub(mm, page, PTE_MAPPED_OFFSET);
+ if (is_zero_pfn(pte_pfn(pte)))
+ pte_refcount_sub(mm, page, PTE_ZERO_OFFSET);
+ }
+}
+EXPORT_SYMBOL(track_pte_clear);
+
#endif /* CONFIG_FREE_USER_PTE */
--
2.20.1
