On Mon, Jun 26, 2023 at 08:14:01PM -0700, Vishal Moola (Oracle) wrote:
Currently, page table information is stored within struct page. As part
of simplifying struct page, create struct ptdesc for page table
information.
Signed-off-by: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Acked-by: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
---
include/linux/pgtable.h | 68 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 68 insertions(+)
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 5063b482e34f..d46cb709ce08 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -987,6 +987,74 @@ static inline void ptep_modify_prot_commit(struct vm_area_struct *vma,
#endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
#endif /* CONFIG_MMU */
+
+/**
+ * struct ptdesc - Memory descriptor for page tables.
+ * @__page_flags: Same as page flags. Unused for page tables.
+ * @pt_rcu_head: For freeing page table pages.
+ * @pt_list: List of used page tables. Used for s390 and x86.
+ * @_pt_pad_1: Padding that aliases with page's compound head.
+ * @pmd_huge_pte: Protected by ptdesc->ptl, used for THPs.
+ * @_pt_s390_gaddr: Aliases with page's mapping. Used for s390 gmap only.
Should some arch-specific bits (and a few others) always under some
#ifdefs, so it shouldn't appear on other archs?
+ * @pt_mm: Used for x86 pgds.
+ * @pt_frag_refcount: For fragmented page table tracking. Powerpc and s390 only.
+ * @ptl: Lock for the page table.
+ * @__page_type: Same as page->page_type. Unused for page tables.
+ * @_refcount: Same as page refcount. Used for s390 page tables.
+ * @pt_memcg_data: Memcg data. Tracked for page tables here.
+ *
+ * This struct overlays struct page for now. Do not modify without a good
+ * understanding of the issues.
+ */
+struct ptdesc {
+ unsigned long __page_flags;
+
+ union {
+ struct rcu_head pt_rcu_head;
+ struct list_head pt_list;
+ struct {
+ unsigned long _pt_pad_1;
+ pgtable_t pmd_huge_pte;
+ };
+ };
+ unsigned long _pt_s390_gaddr;
+
+ union {
+ struct mm_struct *pt_mm;
+ atomic_t pt_frag_refcount;
+ };
+
+ union {
+ unsigned long _pt_pad_2;
+#if ALLOC_SPLIT_PTLOCKS
+ spinlock_t *ptl;
+#else
+ spinlock_t ptl;
+#endif
+ };
+ unsigned int __page_type;
+ atomic_t _refcount;
+#ifdef CONFIG_MEMCG
+ unsigned long pt_memcg_data;
+#endif
+};
--
Peter Xu
