Hi Naoya or Greg,
We found a bug in 3.10.x.
The problem is that we accidentally have a hwpoisoned hugepage in free
hugepage list. It could happend in the the following scenario:
process A process B
migrate_huge_page
put_page (old hugepage)
linked to free hugepage list
hugetlb_fault
hugetlb_no_page
alloc_huge_page
dequeue_huge_page_vma
dequeue_huge_page_node
(steal hwpoisoned hugepage)
set_page_hwpoison_huge_page
dequeue_hwpoisoned_huge_page
(fail to dequeue)
I tested this bug, one process keeps allocating huge page, and I
use sysfs interface to soft offline a huge page, then received:
"MCE: Killing UCP:2717 due to hardware memory corruption fault at 8200034"
Upstream kernel is free from this bug because of these two commits:
f15bdfa802bfa5eb6b4b5a241b97ec9fa1204a35
mm/memory-failure.c: fix memory leak in successful soft offlining
c8721bbbdd36382de51cd6b7a56322e0acca2414
mm: memory-hotplug: enable memory hotplug to handle hugepage
The first one, although the problem is about memory leak, this patch
moves unset_migratetype_isolate(), which is important to avoid the race.
The latter is not a bug fix and it's too big, so I rewrite a small one.
The following patch can fix this bug.(please apply f15bdfa802bf first)
Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
mm/hugetlb.c | 11 +++++++++--
1 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7c5eb85..6cb5b3b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -21,6 +21,7 @@
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/swapops.h>
+#include <linux/page-isolation.h>
#include <asm/page.h>
#include <asm/pgtable.h>
@@ -517,9 +518,15 @@ static struct page *dequeue_huge_page_node(struct hstate *h, int nid)
{
struct page *page;
- if (list_empty(&h->hugepage_freelists[nid]))
+ list_for_each_entry(page, &h->hugepage_freelists[nid], lru)
+ if (!is_migrate_isolate_page(page))
+ break;
+ /*
+ * if 'non-isolated free hugepage' not found on the list,
+ * the allocation fails.
+ */
+ if (&h->hugepage_freelists[nid] == &page->lru)
return NULL;
- page = list_entry(h->hugepage_freelists[nid].next, struct page, lru);
list_move(&page->lru, &h->hugepage_activelist);
set_page_refcounted(page);
h->free_huge_pages--;
--
1.7.1
--
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