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Subject[PATCH 4/8] HWPOISON, hugetlb: set/clear PG_hwpoison bits on hugepage
Date
To avoid race condition between concurrent memory errors on identified
hugepage, we atomically test and set PG_hwpoison bit on the head page.
All pages in the error hugepage are considered as hwpoisoned
for now, so set and clear all PG_hwpoison bits in the hugepage
with page lock of the head page held.

Dependency:
"HWPOISON, hugetlb: enable error handling path for hugepage"

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
---
mm/memory-failure.c | 38 ++++++++++++++++++++++++++++++++++++++
1 files changed, 38 insertions(+), 0 deletions(-)
diff --git v2.6.34/mm/memory-failure.c v2.6.34/mm/memory-failure.c
index 1ec68c8..fee648b 100644
--- v2.6.34/mm/memory-failure.c
+++ v2.6.34/mm/memory-failure.c
@@ -920,6 +920,22 @@ static int hwpoison_user_mappings(struct page *p, unsigned long pfn,
return ret;
}

+static void set_page_hwpoison_huge_page(struct page *hpage)
+{
+ int i;
+ int nr_pages = 1 << compound_order(hpage);
+ for (i = 0; i < nr_pages; i++)
+ SetPageHWPoison(hpage + i);
+}
+
+static void clear_page_hwpoison_huge_page(struct page *hpage)
+{
+ int i;
+ int nr_pages = 1 << compound_order(hpage);
+ for (i = 0; i < nr_pages; i++)
+ ClearPageHWPoison(hpage + i);
+}
+
int __memory_failure(unsigned long pfn, int trapno, int flags)
{
struct page_state *ps;
@@ -1014,6 +1030,26 @@ int __memory_failure(unsigned long pfn, int trapno, int flags)
return 0;
}

+ /*
+ * For error on the tail page, we should set PG_hwpoison
+ * on the head page to show that the hugepage is hwpoisoned
+ */
+ if (PageTail(p) && TestSetPageHWPoison(hpage)) {
+ action_result(pfn, "hugepage already hardware poisoned",
+ IGNORED);
+ unlock_page(hpage);
+ put_page(hpage);
+ return 0;
+ }
+ /*
+ * Set PG_hwpoison on all pages in an error hugepage,
+ * because containment is done in hugepage unit for now.
+ * Since we have done TestSetPageHWPoison() for the head page with
+ * page lock held, we can safely set PG_hwpoison bits on tail pages.
+ */
+ if (PageHuge(p))
+ set_page_hwpoison_huge_page(hpage);
+
wait_on_page_writeback(p);

/*
@@ -1118,6 +1154,8 @@ int unpoison_memory(unsigned long pfn)
atomic_long_dec(&mce_bad_pages);
freeit = 1;
}
+ if (PageHuge(p))
+ clear_page_hwpoison_huge_page(page);
unlock_page(page);

put_page(page);
--
1.7.0


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