1 files changed, 24 insertions, 12 deletions

diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 648038247a8d..936689d8bcac 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -606,10 +606,32 @@ int walk_page_range(struct mm_struct *mm, unsigned long start,
 int walk_kernel_page_table_range(unsigned long start, unsigned long end,
 		const struct mm_walk_ops *ops, pgd_t *pgd, void *private)
 {
-	struct mm_struct *mm = &init_mm;
+	/*
+	 * Kernel intermediate page tables are usually not freed, so the mmap
+	 * read lock is sufficient. But there are some exceptions.
+	 * E.g. memory hot-remove. In which case, the mmap lock is insufficient
+	 * to prevent the intermediate kernel pages tables belonging to the
+	 * specified address range from being freed. The caller should take
+	 * other actions to prevent this race.
+	 */
+	mmap_assert_locked(&init_mm);
+
+	return walk_kernel_page_table_range_lockless(start, end, ops, pgd,
+						     private);
+}
+
+/*
+ * Use this function to walk the kernel page tables locklessly. It should be
+ * guaranteed that the caller has exclusive access over the range they are
+ * operating on - that there should be no concurrent access, for example,
+ * changing permissions for vmalloc objects.
+ */
+int walk_kernel_page_table_range_lockless(unsigned long start, unsigned long end,
+		const struct mm_walk_ops *ops, pgd_t *pgd, void *private)
+{
 	struct mm_walk walk = {
 		.ops		= ops,
-		.mm		= mm,
+		.mm		= &init_mm,
 		.pgd		= pgd,
 		.private	= private,
 		.no_vma		= true
@@ -620,16 +642,6 @@ int walk_kernel_page_table_range(unsigned long start, unsigned long end,
 	if (!check_ops_valid(ops))
 		return -EINVAL;
 
-	/*
-	 * Kernel intermediate page tables are usually not freed, so the mmap
-	 * read lock is sufficient. But there are some exceptions.
-	 * E.g. memory hot-remove. In which case, the mmap lock is insufficient
-	 * to prevent the intermediate kernel pages tables belonging to the
-	 * specified address range from being freed. The caller should take
-	 * other actions to prevent this race.
-	 */
-	mmap_assert_locked(mm);
-
 	return walk_pgd_range(start, end, &walk);
 }