-static inline struct page *compound_head_by_tail(struct page *tail)
-{
- struct page *head = tail->first_page;
-
- /*
- * page->first_page may be a dangling pointer to an old
- * compound page, so recheck that it is still a tail
- * page before returning.
- */
- smp_rmb();
- if (likely(PageTail(tail)))
- return head;
- return tail;
-}
-
-/*
- * Since either compound page could be dismantled asynchronously in THP
- * or we access asynchronously arbitrary positioned struct page, there
- * would be tail flag race. To handle this race, we should call
- * smp_rmb() before checking tail flag. compound_head_by_tail() did it.
- */
-static inline struct page *compound_head(struct page *page)
-{
- if (unlikely(PageTail(page)))
- return compound_head_by_tail(page);
- return page;
-}
-
-/*
- * If we access compound page synchronously such as access to
- * allocated page, there is no need to handle tail flag race, so we can
- * check tail flag directly without any synchronization primitive.
- */
-static inline struct page *compound_head_fast(struct page *page)
-{
- if (unlikely(PageTail(page)))
- return page->first_page;
- return page;
-}
-