[PATCH] hwpoison: Fix race with changing page during offlining v2

Andi Kleen
2014-07-01T00:32:25Z

From: Andi Kleen <ak@linux.intel.com>

When a hwpoison page is locked it could change state
due to parallel modifications. Check after the lock
if the page is still the same compound page.

[v2: Removed earlier non LRU check which should be already
covered elsewhere]

Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
mm/memory-failure.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index cd8989c..99e5077 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1168,6 +1168,16 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
lock_page(hpage);

/*
+ * The page could have changed compound pages during the locking.
+ * If this happens just bail out.
+ */
+ if (compound_head(p) != hpage) {
+ action_result(pfn, "different compound page after locking", IGNORED);
+ res = -EBUSY;
+ goto out;
+ }
+
+ /*
* We use page flags to determine what action should be taken, but
* the flags can be modified by the error containment action. One
* example is an mlocked page, where PG_mlocked is cleared by
--
1.9.3