3 files changed, 27 insertions, 4 deletions

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index a3762d49ba39..d3b3e8fcc717 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -113,6 +113,7 @@ extern unsigned long thp_get_unmapped_area(struct file *filp,
 extern void prep_transhuge_page(struct page *page);
 extern void free_transhuge_page(struct page *page);
 
+bool can_split_huge_page(struct page *page, int *pextra_pins);
 int split_huge_page_to_list(struct page *page, struct list_head *list);
 static inline int split_huge_page(struct page *page)
 {
@@ -231,6 +232,12 @@ static inline void prep_transhuge_page(struct page *page) {}
 
 #define thp_get_unmapped_area   NULL
 
+static inline bool
+can_split_huge_page(struct page *page, int *pextra_pins)
+{
+        BUILD_BUG();
+        return false;
+}
 static inline int
 split_huge_page_to_list(struct page *page, struct list_head *list)
 {
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1a168e4bac4b..86975dec0ba1 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2390,6 +2390,21 @@ int page_trans_huge_mapcount(struct page *page, int *total_mapcount)
         return ret;
 }
 
+/* Racy check whether the huge page can be split */
+bool can_split_huge_page(struct page *page, int *pextra_pins)
+{
+        int extra_pins;
+
+        /* Additional pins from radix tree */
+        if (PageAnon(page))
+                extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
+        else
+                extra_pins = HPAGE_PMD_NR;
+        if (pextra_pins)
+                *pextra_pins = extra_pins;
+        return total_mapcount(page) == page_count(page) - extra_pins - 1;
+}
+
 /*
  * This function splits huge page into normal pages. @page can point to any
  * subpage of huge page to split. Split doesn't change the position of @page.
@@ -2437,7 +2452,6 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
                         ret = -EBUSY;
                         goto out;
                 }
-                extra_pins = PageSwapCache(page) ? HPAGE_PMD_NR : 0;
                 mapping = NULL;
                 anon_vma_lock_write(anon_vma);
         } else {
@@ -2449,8 +2463,6 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
                         goto out;
                 }
 
-                /* Addidional pins from radix tree */
-                extra_pins = HPAGE_PMD_NR;
                 anon_vma = NULL;
                 i_mmap_lock_read(mapping);
         }
@@ -2459,7 +2471,7 @@ int split_huge_page_to_list(struct page *page, struct list_head *list)
          * Racy check if we can split the page, before freeze_page() will
          * split PMDs
          */
-        if (total_mapcount(head) != page_count(head) - extra_pins - 1) {
+        if (!can_split_huge_page(head, &extra_pins)) {
                 ret = -EBUSY;
                 goto out_unlock;
         }
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 729e37f02de6..abaf0215a352 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1125,6 +1125,10 @@ static unsigned long shrink_page_list(struct list_head *page_list,
                     !PageSwapCache(page)) {
                         if (!(sc->gfp_mask & __GFP_IO))
                                 goto keep_locked;
+                        /* cannot split THP, skip it */
+                        if (PageTransHuge(page) &&
+                            !can_split_huge_page(page, NULL))
+                                goto activate_locked;
                         if (!add_to_swap(page)) {
                                 if (!PageTransHuge(page))
                                         goto activate_locked;