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-rw-r--r--mm/rmap.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 24dd3f9..9f47f15 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -950,7 +950,12 @@ void page_move_anon_rmap(struct page *page,
VM_BUG_ON_PAGE(page->index != linear_page_index(vma, address), page);
anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
- page->mapping = (struct address_space *) anon_vma;
+ /*
+ * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
+ * simultaneously, so a concurrent reader (eg page_referenced()'s
+ * PageAnon()) will not see one without the other.
+ */
+ WRITE_ONCE(page->mapping, (struct address_space *) anon_vma);
}
/**
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