[mm-unstable PATCH v6 5/8] mm, hwpoison: set PG_hwpoison for busy hugetlb pages

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>

If memory_failure() fails to grab page refcount on a hugetlb page
because it's busy, it returns without setting PG_hwpoison on it.
This not only loses a chance of error containment, but breaks the rule
that action_result() should be called only when memory_failure() do
any of handling work (even if that's just setting PG_hwpoison).
This inconsistency could harm code maintainability.

So set PG_hwpoison and call hugetlb_set_page_hwpoison() for such a case.

Fixes: 405ce051236c ("mm/hwpoison: fix race between hugetlb free/demotion and memory_failure_hugetlb()")
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Reviewed-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
---
 include/linux/mm.h  | 1 +
 mm/memory-failure.c | 8 ++++----
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4287bec50c28..7668831c919f 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3188,6 +3188,7 @@ enum mf_flags {
 	MF_SOFT_OFFLINE = 1 << 3,
 	MF_UNPOISON = 1 << 4,
 	MF_SW_SIMULATED = 1 << 5,
+	MF_NO_RETRY = 1 << 6,
 };
 int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
 		      unsigned long count, int mf_flags);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 56fd9d809013..e90a685e326b 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1785,7 +1785,8 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
 			count_increased = true;
 	} else {
 		ret = -EBUSY;
-		goto out;
+		if (!(flags & MF_NO_RETRY))
+			goto out;
 	}
 
 	if (hugetlb_set_page_hwpoison(head, page)) {
@@ -1812,7 +1813,6 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 	struct page *p = pfn_to_page(pfn);
 	struct page *head;
 	unsigned long page_flags;
-	bool retry = true;
 
 	*hugetlb = 1;
 retry:
@@ -1828,8 +1828,8 @@ static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb
 		}
 		return res;
 	} else if (res == -EBUSY) {
-		if (retry) {
-			retry = false;
+		if (!(flags & MF_NO_RETRY)) {
+			flags |= MF_NO_RETRY;
 			goto retry;
 		}
 		action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED);
-- 
2.25.1