"non anonymous thp" case is still racy with freeing thp, which causes panic
due to put_page() for refcount-0 page. It seems that closing up this race
might be hard (and/or not worth doing,) so let's give up the error handling
for this case.
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
v1 -> v2:
- keep pr_err() message
---
mm/memory-failure.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git v4.2-rc4.orig/mm/memory-failure.c v4.2-rc4/mm/memory-failure.c
index f72d2fad0b90..cd985530f102 100644
--- v4.2-rc4.orig/mm/memory-failure.c
+++ v4.2-rc4/mm/memory-failure.c
@@ -909,6 +909,18 @@ int get_hwpoison_page(struct page *page)
* directly for tail pages.
*/
if (PageTransHuge(head)) {
+ /*
+ * Non anonymous thp exists only in allocation/free time. We
+ * can't handle such a case correctly, so let's give it up.
+ * This should be better than triggering BUG_ON when kernel
+ * tries to touch the "partially handled" page.
+ */
+ if (!PageAnon(head)) {
+ pr_err("MCE: %#lx: non anonymous thp\n",
+ page_to_pfn(page));
+ return 0;
+ }
+
if (get_page_unless_zero(head)) {
if (PageTail(page))
get_page(page);
@@ -1134,15 +1146,6 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
}
if (!PageHuge(p) && PageTransHuge(hpage)) {
- if (!PageAnon(hpage)) {
- pr_err("MCE: %#lx: non anonymous thp\n", pfn);
- if (TestClearPageHWPoison(p))
- atomic_long_sub(nr_pages, &num_poisoned_pages);
- put_page(p);
- if (p != hpage)
- put_page(hpage);
- return -EBUSY;
- }
if (unlikely(split_huge_page(hpage))) {
pr_err("MCE: %#lx: thp split failed\n", pfn);
if (TestClearPageHWPoison(p))
--
2.4.3
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