2 files changed, 28 insertions, 6 deletions

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 70e7429fd8ea..7de1bf85f683 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -882,6 +882,10 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
                 ret = 0;
                 goto out_unlock;
         }
+
+        /* mmap_sem prevents this happening but warn if that changes */
+        WARN_ON(pmd_trans_migrating(pmd));
+
         if (unlikely(pmd_trans_splitting(pmd))) {
                 /* split huge page running from under us */
                 spin_unlock(src_ptl);
@@ -1299,6 +1303,17 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
         if (unlikely(!pmd_same(pmd, *pmdp)))
                 goto out_unlock;
 
+        /*
+         * If there are potential migrations, wait for completion and retry
+         * without disrupting NUMA hinting information. Do not relock and
+         * check_same as the page may no longer be mapped.
+         */
+        if (unlikely(pmd_trans_migrating(*pmdp))) {
+                spin_unlock(ptl);
+                wait_migrate_huge_page(vma->anon_vma, pmdp);
+                goto out;
+        }
+
         page = pmd_page(pmd);
         BUG_ON(is_huge_zero_page(page));
         page_nid = page_to_nid(page);
@@ -1329,12 +1344,7 @@ int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
                         goto clear_pmdnuma;
         }
 
-        /*
-         * If there are potential migrations, wait for completion and retry. We
-         * do not relock and check_same as the page may no longer be mapped.
-         * Furtermore, even if the page is currently misplaced, there is no
-         * guarantee it is still misplaced after the migration completes.
-         */
+        /* Migration could have started since the pmd_trans_migrating check */
         if (!page_locked) {
                 spin_unlock(ptl);
                 wait_on_page_locked(page);
diff --git a/mm/migrate.c b/mm/migrate.c
index a987525810ae..cfb419085261 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1655,6 +1655,18 @@ int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
         return 1;
 }
 
+bool pmd_trans_migrating(pmd_t pmd)
+{
+        struct page *page = pmd_page(pmd);
+        return PageLocked(page);
+}
+
+void wait_migrate_huge_page(struct anon_vma *anon_vma, pmd_t *pmd)
+{
+        struct page *page = pmd_page(*pmd);
+        wait_on_page_locked(page);
+}
+
 /*
  * Attempt to migrate a misplaced page to the specified destination
  * node. Caller is expected to have an elevated reference count on