[PATCH] mm/hwpoison: In-use hugepage need filter judgement and filter return value should be consistent

[luofei]

After successfully obtaining the reference count of the huge
page, it is still necessary to call hwpoison_filter() to make a
filter judgement, otherwise the filter page will be unmaped and
the related process may be killed.

Also when the huge page meets the filter conditions, it should
not be regarded as successful memory_failure() processing, but
should return an error code to inform the caller, otherwise the
caller regards the error page has been identified and isolated,
which may lead to calling set_mce_nospec() to change page attribute.

Meanwhile, when calling hwpoison_filter() to determine that a page
needs to be filtered, it is better to keep the same EBUSY return
value, so that the caller can recognize that memory_failure() did
not successfully process the error page.

Signed-off-by: luofei <luofei@xxxxxxxxxxxx>
---
 mm/hwpoison-inject.c |  2 +-
 mm/memory-failure.c  | 12 ++++++++++--
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/mm/hwpoison-inject.c b/mm/hwpoison-inject.c
index aff4d27ec235..4ecd77cd1ded 100644
--- a/mm/hwpoison-inject.c
+++ b/mm/hwpoison-inject.c
@@ -44,7 +44,7 @@ static int hwpoison_inject(void *data, u64 val)
 	 */
 	err = hwpoison_filter(hpage);
 	if (err)
-		return 0;
+		return -EBUSY;
 
 inject:
 	pr_info("Injecting memory failure at pfn %#lx\n", pfn);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 97a9ed8f87a9..acf97fb2659a 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1526,7 +1526,7 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
 				if (TestClearPageHWPoison(head))
 					num_poisoned_pages_dec();
 				unlock_page(head);
-				return 0;
+				return -EBUSY;
 			}
 			unlock_page(head);
 			res = MF_FAILED;
@@ -1545,6 +1545,13 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
 	lock_page(head);
 	page_flags = head->flags;
 
+	if (hwpoison_filter(p)) {
+		if (TestClearPageHWPoison(head))
+			num_poisoned_pages_dec();
+		unlock_page(head);
+		res = -EBUSY
+		goto out;
+	}
 	/*
 	 * TODO: hwpoison for pud-sized hugetlb doesn't work right now, so
 	 * simply disable it. In order to make it work properly, we need
@@ -1613,7 +1620,7 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
 		goto out;
 
 	if (hwpoison_filter(page)) {
-		rc = 0;
+		rc = -EBUSY;
 		goto unlock;
 	}
 
@@ -1837,6 +1844,7 @@ int memory_failure(unsigned long pfn, int flags)
 			num_poisoned_pages_dec();
 		unlock_page(p);
 		put_page(p);
+		res = -EBUSY;
 		goto unlock_mutex;
 	}
 
-- 
2.27.0