X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=mm%2Fmemory.c;h=b25f5e58a14c33a256c73dd7d9c5e4f9b134ade7;hb=4944e76d81801b8e60ed3e7789443f210c16ed65;hp=e046b7e4b53092bb879f8d183d24de36b3389d83;hpb=d95a1b4818f2fe38a3cfc9a7d5817dc9a1a69329;p=linux-2.6

diff --git a/mm/memory.c b/mm/memory.c
index e046b7e4b5..b25f5e58a1 100644
--- 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);
 
@@ -1944,7 +1955,7 @@ static int do_file_page(struct mm_struct * mm, struct vm_area_struct * vma,
 	 * Fall back to the linear mapping if the fs does not support
 	 * ->populate:
 	 */
-	if (!vma->vm_ops || !vma->vm_ops->populate || 
+	if (!vma->vm_ops->populate ||
 			(write_access && !(vma->vm_flags & VM_SHARED))) {
 		pte_clear(mm, address, pte);
 		return do_no_page(mm, vma, address, write_access, pte, pmd);