thp: compound_trans_order
Read compound_trans_order safe. Noop for CONFIG_TRANSPARENT_HUGEPAGE=n.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 9c2695b..ce97a2b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -450,6 +450,20 @@
return (unsigned long)page[1].lru.prev;
}
+static inline int compound_trans_order(struct page *page)
+{
+ int order;
+ unsigned long flags;
+
+ if (!PageHead(page))
+ return 0;
+
+ flags = compound_lock_irqsave(page);
+ order = compound_order(page);
+ compound_unlock_irqrestore(page, flags);
+ return order;
+}
+
static inline void set_compound_order(struct page *page, unsigned long order)
{
page[1].lru.prev = (void *)order;