1 files changed, 46 insertions, 7 deletions

diff --git a/mm/mapping_dirty_helpers.c b/mm/mapping_dirty_helpers.c
index 71070dda9643..1b0ab8fcfd8b 100644
--- a/mm/mapping_dirty_helpers.c
+++ b/mm/mapping_dirty_helpers.c
@@ -3,6 +3,7 @@
 #include <linux/hugetlb.h>
 #include <linux/bitops.h>
 #include <linux/mmu_notifier.h>
+#include <linux/mm_inline.h>
 #include <asm/cacheflush.h>
 #include <asm/tlbflush.h>
 
@@ -23,7 +24,8 @@ struct wp_walk {
 /**
  * wp_pte - Write-protect a pte
  * @pte: Pointer to the pte
- * @addr: The virtual page address
+ * @addr: The start of protecting virtual address
+ * @end: The end of protecting virtual address
  * @walk: pagetable walk callback argument
  *
  * The function write-protects a pte and records the range in
@@ -74,7 +76,8 @@ struct clean_walk {
  * clean_record_pte - Clean a pte and record its address space offset in a
  * bitmap
  * @pte: Pointer to the pte
- * @addr: The virtual page address
+ * @addr: The start of virtual address to be clean
+ * @end: The end of virtual address to be clean
  * @walk: pagetable walk callback argument
  *
  * The function cleans a pte and records the range in
@@ -111,28 +114,64 @@ static int clean_record_pte(pte_t *pte, unsigned long addr,
 	return 0;
 }
 
-/* wp_clean_pmd_entry - The pagewalk pmd callback. */
+/*
+ * wp_clean_pmd_entry - The pagewalk pmd callback.
+ *
+ * Dirty-tracking should take place on the PTE level, so
+ * WARN() if encountering a dirty huge pmd.
+ * Furthermore, never split huge pmds, since that currently
+ * causes dirty info loss. The pagefault handler should do
+ * that if needed.
+ */
 static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end,
 			      struct mm_walk *walk)
 {
-	/* Dirty-tracking should be handled on the pte level */
 	pmd_t pmdval = pmd_read_atomic(pmd);
 
+	if (!pmd_trans_unstable(&pmdval))
+		return 0;
+
+	if (pmd_none(pmdval)) {
+		walk->action = ACTION_AGAIN;
+		return 0;
+	}
+
+	/* Huge pmd, present or migrated */
+	walk->action = ACTION_CONTINUE;
 	if (pmd_trans_huge(pmdval) || pmd_devmap(pmdval))
 		WARN_ON(pmd_write(pmdval) || pmd_dirty(pmdval));
 
 	return 0;
 }
 
-/* wp_clean_pud_entry - The pagewalk pud callback. */
+/*
+ * wp_clean_pud_entry - The pagewalk pud callback.
+ *
+ * Dirty-tracking should take place on the PTE level, so
+ * WARN() if encountering a dirty huge puds.
+ * Furthermore, never split huge puds, since that currently
+ * causes dirty info loss. The pagefault handler should do
+ * that if needed.
+ */
 static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,
 			      struct mm_walk *walk)
 {
-	/* Dirty-tracking should be handled on the pte level */
 	pud_t pudval = READ_ONCE(*pud);
 
+	if (!pud_trans_unstable(&pudval))
+		return 0;
+
+	if (pud_none(pudval)) {
+		walk->action = ACTION_AGAIN;
+		return 0;
+	}
+
+#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+	/* Huge pud */
+	walk->action = ACTION_CONTINUE;
 	if (pud_trans_huge(pudval) || pud_devmap(pudval))
 		WARN_ON(pud_write(pudval) || pud_dirty(pudval));
+#endif
 
 	return 0;
 }
@@ -279,7 +318,7 @@ EXPORT_SYMBOL_GPL(wp_shared_mapping_range);
  * pfn_mkwrite(). And then after a TLB flush following the write-protection
  * pick up all dirty bits.
  *
- * Note: This function currently skips transhuge page-table entries, since
+ * This function currently skips transhuge page-table entries, since
  * it's intended for dirty-tracking on the PTE level. It will warn on
  * encountering transhuge dirty entries, though, and can easily be extended
  * to handle them as well.