Commit a95a82e9 authored Jan 13, 2011 by Andrea Arcangeli Committed by Linus Torvalds Jan 13, 2011

thp: put_page: recheck PageHead after releasing the compound_lock



After releasing the compound_lock split_huge_page can still run and release the
page before put_page_testzero runs.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 91807063

mm/swap.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -131,8 +131,12 @@ static void put_compound_page(struct page *page)
		atomic_dec(&page->_count);
		VM_BUG_ON(atomic_read(&page_head->_count) <= 0);
		compound_unlock_irqrestore(page_head, flags);
		if (put_page_testzero(page_head))
		if (put_page_testzero(page_head)) {
		if (PageHead(page_head))
		__put_compound_page(page_head);
		else
		__put_single_page(page_head);
		}
		} else {
		/* page_head is a dangling pointer */
		VM_BUG_ON(PageTail(page));