[PATCH v2 3/3] mm/memory-failure.c: make non-LRU movable pages unhandlable

Miaohe Lin
2022-03-12T07:47:23Z

We can not really handle non-LRU movable pages in memory failure. Typically
they are balloon, zsmalloc, etc. Assuming we run into a base (4K) non-LRU
movable page, we could reach as far as identify_page_state(), it should not
fall into any category except me_unknown. For the non-LRU compound movable
pages, they could be taken for transhuge pages but it's unexpected to split
non-LRU movable pages using split_huge_page_to_list in memory_failure. So
we could just simply make non-LRU movable pages unhandlable to avoid these
possible nasty cases.

Suggested-by: Yang Shi <shy828301@gmail.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/memory-failure.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 2ff7dd2078c4..ba621c6823ed 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1177,12 +1177,18 @@ void ClearPageHWPoisonTakenOff(struct page *page)
* does not return true for hugetlb or device memory pages, so it's assumed
* to be called only in the context where we never have such pages.
*/
-static inline bool HWPoisonHandlable(struct page *page)
+static inline bool HWPoisonHandlable(struct page *page, unsigned long flags)
{
- return PageLRU(page) || __PageMovable(page) || is_free_buddy_page(page);
+ bool movable = false;
+
+ /* Soft offline could mirgate non-LRU movable pages */
+ if ((flags & MF_SOFT_OFFLINE) && __PageMovable(page))
+ movable = true;
+
+ return movable || PageLRU(page) || is_free_buddy_page(page);
}

-static int __get_hwpoison_page(struct page *page)
+static int __get_hwpoison_page(struct page *page, unsigned long flags)
{
struct page *head = compound_head(page);
int ret = 0;
@@ -1197,7 +1203,7 @@ static int __get_hwpoison_page(struct page *page)
* for any unsupported type of page in order to reduce the risk of
* unexpected races caused by taking a page refcount.
*/
- if (!HWPoisonHandlable(head))
+ if (!HWPoisonHandlable(head, flags))
return -EBUSY;

if (get_page_unless_zero(head)) {
@@ -1222,7 +1228,7 @@ static int get_any_page(struct page *p, unsigned long flags)

try_again:
if (!count_increased) {
- ret = __get_hwpoison_page(p);
+ ret = __get_hwpoison_page(p, flags);
if (!ret) {
if (page_count(p)) {
/* We raced with an allocation, retry. */
@@ -1250,7 +1256,7 @@ static int get_any_page(struct page *p, unsigned long flags)
}
}

- if (PageHuge(p) || HWPoisonHandlable(p)) {
+ if (PageHuge(p) || HWPoisonHandlable(p, flags)) {
ret = 1;
} else {
/*
@@ -2308,7 +2314,7 @@ int soft_offline_page(unsigned long pfn, int flags)

retry:
get_online_mems();
- ret = get_hwpoison_page(page, flags);
+ ret = get_hwpoison_page(page, flags | MF_SOFT_OFFLINE);
put_online_mems();

if (ret > 0) {
--
2.23.0