mm: dirty page accounting vs VM_MIXEDMAP

[linux-2.6-omap-h63xx.git] / mm / memory.c

diff --git a/mm/memory.c b/mm/memory.c
index d14b251a25a638dec1b5327a6261a67660ba67d5..350e646032f52ddaefa5c5ee44efa2376261f382 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1697,8 +1697,19 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
        struct page *dirty_page = NULL;
 
        old_page = vm_normal_page(vma, address, orig_pte);
-       if (!old_page)
+       if (!old_page) {
+               /*
+                * VM_MIXEDMAP !pfn_valid() case
+                *
+                * We should not cow pages in a shared writeable mapping.
+                * Just mark the pages writable as we can't do any dirty
+                * accounting on raw pfn maps.
+                */
+               if ((vma->vm_flags & (VM_WRITE|VM_SHARED)) ==
+                                    (VM_WRITE|VM_SHARED))
+                       goto reuse;
                goto gotten;
+       }
 
        /*
         * Take out anonymous pages first, anonymous shared vmas are
@@ -1751,6 +1762,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
        }
 
        if (reuse) {
+reuse:
                flush_cache_page(vma, address, pte_pfn(orig_pte));
                entry = pte_mkyoung(orig_pte);
                entry = maybe_mkwrite(pte_mkdirty(entry), vma);