Hi Naoya or Greg,
We found a bug in 3.10.x.
1) use sysfs interface soft_offline_page() to migrate a huge page.
2) the hpage become free after migrate_huge_page().
3) the free hpage is alloced and used by process A.
4) hwpoison flag is set by set_page_hwpoison_huge_page()
5) mce find this poisoned page.
6) process A was killed.
7) other processes which use this page will be killed too.
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 latter is not a bug fix and it's too big, the following patch
can fix this bug.
What do you think? Use the simple fix or backport the big patch?
Thanks,
Xishi Qiu
Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx>
---
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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