From: Naoya Horiguchi <naoya.horiguchi@nec.com>
Subject: mm/hwpoison: put page in already hwpoisoned case with MF_COUNT_INCREASED

In already hwpoisoned case, memory_failure() is supposed to return with
releasing the page refcount taken for error handling.  But currently the
refcount is not released when called with MF_COUNT_INCREASED, which makes
page refcount inconsistent.  This should be rare and non-critical, but it
might be inconvenient in testing (unpoison doesn't work).

Link: https://lkml.kernel.org/r/20220408135323.1559401-3-naoya.horiguchi@linux.dev
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Suggested-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory-failure.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/memory-failure.c~mm-hwpoison-put-page-in-already-hwpoisoned-case-with-mf_count_increased
+++ a/mm/memory-failure.c
@@ -1812,6 +1812,8 @@ try_again:
 		res = -EHWPOISON;
 		if (flags & MF_ACTION_REQUIRED)
 			res = kill_accessing_process(current, pfn, flags);
+		if (flags & MF_COUNT_INCREASED)
+			put_page(p);
 		goto unlock_mutex;
 	}
 
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