linux-kernel - [PATCH] mm/memory-failure: fix race with compound page split/merge

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Date:	Mon, 18 Apr 2016 14:43:45 +0300
From:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:	linux-mm@...ck.org, Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	linux-kernel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH] mm/memory-failure: fix race with compound page split/merge

Get_hwpoison_page() must recheck relation between head and tail pages.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
 mm/memory-failure.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 78f5f2641b91..ca5acee53b7a 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -888,7 +888,15 @@ int get_hwpoison_page(struct page *page)
 		}
 	}
 
-	return get_page_unless_zero(head);
+	if (get_page_unless_zero(head)) {
+		if (head == compound_head(page))
+			return 1;
+
+		pr_info("MCE: %#lx cannot catch tail\n", page_to_pfn(page));
+		put_page(head);
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(get_hwpoison_page);