The patch titled
Subject: mm, hwpoison: fix condition in free hugetlb page path
has been added to the -mm tree. Its filename is
mm-hwpoison-fix-condition-in-free-hugetlb-page-path.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-hwpoison-fix-condition-in-free-hugetlb-page-path.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-hwpoison-fix-condition-in-free-hugetlb-page-path.patch
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------------------------------------------------------
From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Subject: mm, hwpoison: fix condition in free hugetlb page path
When a memory error hits a tail page of a free hugepage,
__page_handle_poison() is expected to be called to isolate the error in
4kB unit, but it's not called due to the outdated if-condition in
memory_failure_hugetlb(). This loses the chance to isolate the error in
the finer unit, so it's not optimal. Drop the condition.
This "(p != head && TestSetPageHWPoison(head)" condition is based on the
old semantics of PageHWPoison on hugepage (where PG_hwpoison flag was set
on the subpage), so it's not necessray any more. By getting to set
PG_hwpoison on head page for hugepages, concurrent error events on
different subpages in a single hugepage can be prevented by
TestSetPageHWPoison(head) at the beginning of memory_failure_hugetlb().
So dropping the condition should not reopen the race window originally
mentioned in commit b985194c8c0a ("hwpoison, hugetlb:
lock_page/unlock_page does not match for handling a free hugepage")
Link: https://lkml.kernel.org/r/20211210110208.879740-1-naoya.horiguchi@xxxxxxxxx
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Reported-by: Fei Luo <luofei@xxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [5.14+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memory-failure.c | 21 +++++++--------------
1 file changed, 7 insertions(+), 14 deletions(-)
--- a/mm/memory-failure.c~mm-hwpoison-fix-condition-in-free-hugetlb-page-path
+++ a/mm/memory-failure.c
@@ -1470,24 +1470,17 @@ static int memory_failure_hugetlb(unsign
if (!(flags & MF_COUNT_INCREASED)) {
res = get_hwpoison_page(p, flags);
if (!res) {
- /*
- * Check "filter hit" and "race with other subpage."
- */
lock_page(head);
- if (PageHWPoison(head)) {
- if ((hwpoison_filter(p) && TestClearPageHWPoison(p))
- || (p != head && TestSetPageHWPoison(head))) {
+ if (hwpoison_filter(p)) {
+ if (TestClearPageHWPoison(head))
num_poisoned_pages_dec();
- unlock_page(head);
- return 0;
- }
+ unlock_page(head);
+ return 0;
}
unlock_page(head);
- res = MF_FAILED;
- if (__page_handle_poison(p)) {
- page_ref_inc(p);
- res = MF_RECOVERED;
- }
+ res = MF_RECOVERED;
+ if (!page_handle_poison(p, true, false))
+ res = MF_FAILED;
action_result(pfn, MF_MSG_FREE_HUGE, res);
return res == MF_RECOVERED ? 0 : -EBUSY;
} else if (res < 0) {
_
Patches currently in -mm which might be from naoya.horiguchi@xxxxxxx are
mm-hwpoison-fix-condition-in-free-hugetlb-page-path.patch
mm-hwpoison-mf_mutex-for-soft-offline-and-unpoison.patch
mm-hwpoison-remove-mf_msg_buddy_2nd-and-mf_msg_poisoned_huge.patch
mm-hwpoison-fix-unpoison_memory.patch
