mm/page_ref: use atomic_set_release in page_ref_unfreeze

page_ref_unfreeze() has exactly that semantic.  No functional changes:
just minus one barrier and proper handling of PPro errata.

Link: http://lkml.kernel.org/r/151844393004.210639.4672319312617954272.stgit@buzz
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/page_ref.h b/include/linux/page_ref.h
index 760d74a..14d14be 100644 (file)
--- a/include/linux/page_ref.h
+++ b/include/linux/page_ref.h
@@ -175,8 +175,7 @@ static inline void page_ref_unfreeze(struct page *page, int count)
        VM_BUG_ON_PAGE(page_count(page) != 0, page);
        VM_BUG_ON(count == 0);
 
-       smp_mb();
-       atomic_set(&page->_refcount, count);
+       atomic_set_release(&page->_refcount, count);
        if (page_ref_tracepoint_active(__tracepoint_page_ref_unfreeze))
                __page_ref_unfreeze(page, count);
 }