From e37e7b0b3bd52ec4f8ab71b027bcec08f57f1b3b Mon Sep 17 00:00:00 2001 From: Naoya Horiguchi Date: Fri, 24 Dec 2021 21:12:45 -0800 Subject: [PATCH] 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__page_handle_poison() is expected to be called to isolate the error in 4kB unit, but it's not called due to the outdated if-condition in memory_failure_hugetlb().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") [naoya.horiguchi@linux.dev: fix "HardwareCorrupted" counter] Link: https://lkml.kernel.org/r/20211220084851.GA1460264@u2004 Link: https://lkml.kernel.org/r/20211210110208.879740-1-naoya.horiguchi@linux.dev Signed-off-by: Naoya Horiguchi Reported-by: Fei Luo Reviewed-by: Mike Kravetz Cc: [5.14+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory-failure.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-) diff --git a/mm/memory-failure.c b/mm/memory-failure.c index 07c875fdeaf0..682828b94ab6 100644 --- a/mm/memory-failure.c +++ b/mm/memory-failure.c @@ -1470,17 +1470,12 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags) 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;