mm,ksm: FOLL_MIGRATION do migration_entry_wait

[deliverable/linux.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index 5d2ef1217d0c6f8747f3efc448a8cc65b27c2867..ec8ba011fa7dd3397a3ba629b40082eabf6c45d3 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1548,8 +1548,24 @@ split_fallthrough:
        ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
 
        pte = *ptep;
-       if (!pte_present(pte))
-               goto no_page;
+       if (!pte_present(pte)) {
+               swp_entry_t entry;
+               /*
+                * KSM's break_ksm() relies upon recognizing a ksm page
+                * even while it is being migrated, so for that case we
+                * need migration_entry_wait().
+                */
+               if (likely(!(flags & FOLL_MIGRATION)))
+                       goto no_page;
+               if (pte_none(pte) || pte_file(pte))
+                       goto no_page;
+               entry = pte_to_swp_entry(pte);
+               if (!is_migration_entry(entry))
+                       goto no_page;
+               pte_unmap_unlock(ptep, ptl);
+               migration_entry_wait(mm, pmd, address);
+               goto split_fallthrough;
+       }
        if ((flags & FOLL_NUMA) && pte_numa(pte))
                goto no_page;
        if ((flags & FOLL_WRITE) && !pte_write(pte))