Subject: [merged] mm-hwpoison-fix-race-against-poison-thp.patch removed from -mm tree
To: liwanp@xxxxxxxxxxxxxxxxxx,andi@xxxxxxxxxxxxxx,n-horiguchi@xxxxxxxxxxxxx,tony.luck@xxxxxxxxx,mm-commits@xxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Thu, 12 Sep 2013 12:45:25 -0700
The patch titled
Subject: mm/hwpoison: fix race against poison thp
has been removed from the -mm tree. Its filename was
mm-hwpoison-fix-race-against-poison-thp.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
Subject: mm/hwpoison: fix race against poison thp
There is a race between hwpoison page and unpoison page, memory_failure
set the page hwpoison and increase num_poisoned_pages without hold page
lock, and one page count will be accounted against thp for
num_poisoned_pages. However, unpoison can occur before memory_failure
hold page lock and split transparent hugepage, unpoison will decrease
num_poisoned_pages by 1 << compound_order since memory_failure has not yet
split transparent hugepage with page lock held. That means we account one
page for hwpoison and 1 << compound_order for unpoison. This patch fix it
by inserting a PageTransHuge check before doing TestClearPageHWPoison,
unpoison failed without clearing PageHWPoison and decreasing
num_poisoned_pages.
A B
memory_failue
TestSetPageHWPoison(p);
if (PageHuge(p))
nr_pages = 1 << compound_order(hpage);
else
nr_pages = 1;
atomic_long_add(nr_pages, &num_poisoned_pages);
unpoison_memory
nr_pages = 1<< compound_trans_order(page);
if(TestClearPageHWPoison(p))
atomic_long_sub(nr_pages, &num_poisoned_pages);
lock page
if (!PageHWPoison(p))
unlock page and return
hwpoison_user_mappings
if (PageTransHuge(hpage))
split_huge_page(hpage);
Signed-off-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
Suggested-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory-failure.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff -puN mm/memory-failure.c~mm-hwpoison-fix-race-against-poison-thp mm/memory-failure.c
--- a/mm/memory-failure.c~mm-hwpoison-fix-race-against-poison-thp
+++ a/mm/memory-failure.c
@@ -1342,6 +1342,16 @@ int unpoison_memory(unsigned long pfn)
return 0;
}
+ /*
+ * unpoison_memory() can encounter thp only when the thp is being
+ * worked by memory_failure() and the page lock is not held yet.
+ * In such case, we yield to memory_failure() and make unpoison fail.
+ */
+ if (PageTransHuge(page)) {
+ pr_info("MCE: Memory failure is now running on %#lx\n", pfn);
+ return 0;
+ }
+
nr_pages = 1 << compound_order(page);
if (!get_page_unless_zero(page)) {
_
Patches currently in -mm which might be from liwanp@xxxxxxxxxxxxxxxxxx are
origin.patch
mm-drop-actor-argument-of-do_generic_file_read.patch
mm-drop-actor-argument-of-do_generic_file_read-fix.patch
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