[PATCH] swap: swap_lock replace list+device

[linux-2.6] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index e046b7e4b53092bb879f8d183d24de36b3389d83..a596c1172248e56b8fb220408548330ebd1de538 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -498,6 +498,17 @@ int copy_page_range(struct mm_struct *dst_mm, struct mm_struct *src_mm,
        unsigned long addr = vma->vm_start;
        unsigned long end = vma->vm_end;
 
+       /*
+        * Don't copy ptes where a page fault will fill them correctly.
+        * Fork becomes much lighter when there are big shared or private
+        * readonly mappings. The tradeoff is that copy_page_range is more
+        * efficient than faulting.
+        */
+       if (!(vma->vm_flags & (VM_HUGETLB|VM_NONLINEAR|VM_RESERVED))) {
+               if (!vma->anon_vma)
+                       return 0;
+       }
+
        if (is_vm_hugetlb_page(vma))
                return copy_hugetlb_page_range(dst_mm, src_mm, vma);