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-rw-r--r--mm/rmap.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/mm/rmap.c b/mm/rmap.c
index 24dd3f9fee27..7af1ecb21ccb 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -625,7 +625,7 @@ pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address)
pmd = pmd_offset(pud, address);
/*
- * Some THP functions use the sequence pmdp_clear_flush(), set_pmd_at()
+ * Some THP functions use the sequence pmdp_huge_clear_flush(), set_pmd_at()
* without holding anon_vma lock for write. So when looking for a
* genuine pmde (in which to find pte), test present and !THP together.
*/
@@ -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);
}
/**