mm: do not allow MADV_PAGEOUT for CoW pages

[linux.git] / mm / madvise.c

diff --git a/mm/madvise.c b/mm/madvise.c
index 43b47d3fae02e1cf86c0b9a98c5ce16471874841..4bb30ed6c8d216cdc6bff02ef2b89d0331479f09 100644 (file)
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -335,12 +335,14 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
                }
 
                page = pmd_page(orig_pmd);
+
+               /* Do not interfere with other mappings of this page */
+               if (page_mapcount(page) != 1)
+                       goto huge_unlock;
+
                if (next - addr != HPAGE_PMD_SIZE) {
                        int err;
 
-                       if (page_mapcount(page) != 1)
-                               goto huge_unlock;
-
                        get_page(page);
                        spin_unlock(ptl);
                        lock_page(page);
@@ -426,6 +428,10 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
                        continue;
                }
 
+               /* Do not interfere with other mappings of this page */
+               if (page_mapcount(page) != 1)
+                       continue;
+
                VM_BUG_ON_PAGE(PageTransCompound(page), page);
 
                if (pte_young(ptent)) {