[PATCH mmotm v1] mm/hwpoison: disable pcp for page_handle_poison()

[Naoya Horiguchi]

From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>

Recent changes by patch "mm/page_alloc: allow high-order pages to be
stored on the per-cpu lists" makes kernels determine whether to use pcp
by pcp_allowed_order(), which breaks soft-offline for hugetlb pages.

Soft-offline dissolves a migration source page, then removes it from
buddy free list, so it's assumed that any subpage of the soft-offlined
hugepage are recognized as a buddy page just after returning from
dissolve_free_huge_page().  pcp_allowed_order() returns true for
hugetlb, so this assumption is no longer true.

So disable pcp during dissolve_free_huge_page() and
take_page_off_buddy() to prevent soft-offlined hugepages from linking to
pcp lists.  Soft-offline should not be common events so the impact on
performance should be minimal.  And I think that the optimization of
Mel's patch could benefit to hugetlb so zone_pcp_disable() is called
only in hwpoison context.

Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
---
 mm/memory-failure.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git v5.13-rc6-mmotm-2021-06-15-20-24/mm/memory-failure.c v5.13-rc6-mmotm-2021-06-15-20-24_patched/mm/memory-failure.c
index 1842822a10da..593079766655 100644
--- v5.13-rc6-mmotm-2021-06-15-20-24/mm/memory-failure.c
+++ v5.13-rc6-mmotm-2021-06-15-20-24_patched/mm/memory-failure.c
@@ -66,6 +66,19 @@ int sysctl_memory_failure_recovery __read_mostly = 1;
 
 atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0);
 
+static bool __page_handle_poison(struct page *page)
+{
+	bool ret;
+
+	zone_pcp_disable(page_zone(page));
+	ret = dissolve_free_huge_page(page);
+	if (!ret)
+		ret = take_page_off_buddy(page);
+	zone_pcp_enable(page_zone(page));
+
+	return ret;
+}
+
 static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release)
 {
 	if (hugepage_or_freepage) {
@@ -73,7 +86,7 @@ static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, boo
 		 * Doing this check for free pages is also fine since dissolve_free_huge_page
 		 * returns 0 for non-hugetlb pages as well.
 		 */
-		if (dissolve_free_huge_page(page) || !take_page_off_buddy(page))
+		if (!__page_handle_poison(page))
 			/*
 			 * We could fail to take off the target page from buddy
 			 * for example due to racy page allocation, but that's
@@ -986,7 +999,7 @@ static int me_huge_page(struct page *p, unsigned long pfn)
 		 */
 		if (PageAnon(hpage))
 			put_page(hpage);
-		if (!dissolve_free_huge_page(p) && take_page_off_buddy(p)) {
+		if (__page_handle_poison(p)) {
 			page_ref_inc(p);
 			res = MF_RECOVERED;
 		}
@@ -1441,7 +1454,7 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
 		res = get_hwpoison_page(p, flags);
 		if (!res) {
 			res = MF_FAILED;
-			if (!dissolve_free_huge_page(p) && take_page_off_buddy(p)) {
+			if (__page_handle_poison(p)) {
 				page_ref_inc(p);
 				res = MF_RECOVERED;
 			}
-- 
2.25.1