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-rw-r--r--mm/memory.c14
1 files changed, 13 insertions, 1 deletions
diff --git a/mm/memory.c b/mm/memory.c
index d14b251a25a..350e646032f 100644
--- 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);