From: Andrea Arcangeli <aarcange@redhat.com>
Date: Thu, 13 Jan 2011 23:46:33 +0000 (-0800)
Subject: thp: put_page: recheck PageHead after releasing the compound_lock
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=a95a82e96c48270980dd248ccd5546f1b49e6f8a;p=linux-beck.git

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>
---

diff --git a/mm/swap.c b/mm/swap.c
index 33f5292fe132..e0eeef940886 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -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))
-				__put_compound_page(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));