mm: close PageTail race

[GitHub/mt8127/android_kernel_alcatel_ttab.git] / mm / page_alloc.c

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 2ee0fd313f036e8bab7af2b4d6e0ae6a8ce93378..0ab02fb8e9b1d6093ab12ee521e7dfb2f37576dc 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -360,9 +360,11 @@ void prep_compound_page(struct page *page, unsigned long order)
        __SetPageHead(page);
        for (i = 1; i < nr_pages; i++) {
                struct page *p = page + i;
-               __SetPageTail(p);
                set_page_count(p, 0);
                p->first_page = page;
+               /* Make sure p->first_page is always valid for PageTail() */
+               smp_wmb();
+               __SetPageTail(p);
        }
 }