Messages in this thread | | | Date | Wed, 18 Dec 2013 20:28:55 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH -mm 7/7] mm: thp: introduce compound_head_put_tail(), change get_futex_key() to use it |
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On Wed, Dec 18, 2013 at 08:20:08PM +0100, Oleg Nesterov wrote: > +struct page *compound_head_put_tail(struct page *page) > +{ > + struct page *page_head; > + unsigned long flags; > + > + if (!PageTail(page)) > + return page; > + > + page_head = compound_trans_head(page); > + > + if (!__compound_tail_refcounted(page_head)) {
This barrier is missing a comment describing the ordering and the pairing.
> + smp_rmb(); > + if (likely(PageTail(page))) > + return page_head; > + else > + return page; > + } > + > + if (likely(get_lock_thp_head(page_head, page, &flags))) { > + if (put_page_testzero(page_head)) > + VM_BUG_ON(1); > + atomic_dec(&page->_mapcount); > + compound_unlock_irqrestore(page_head, flags); > + > + return page_head; > + } > + > + return page; > +}
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