+ mm-hwpoison-disable-pcp-for-page_handle_poison.patch added to -mm tree

+ mm-hwpoison-disable-pcp-for-page_handle_poison.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/hwpoison: disable pcp for page_handle_poison()
has been added to the -mm tree.  Its filename is
     mm-hwpoison-disable-pcp-for-page_handle_poison.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-hwpoison-disable-pcp-for-page_handle_poison.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-hwpoison-disable-pcp-for-page_handle_poison.patch

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------------------------------------------------------
From: Naoya Horiguchi <naoya.horiguchi@nec.com>
Subject: mm/hwpoison: disable pcp for page_handle_poison()

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.

Link: https://lkml.kernel.org/r/20210617092626.291006-1-nao.horiguchi@gmail.com
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Acked-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memory-failure.c |   19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

--- a/mm/memory-failure.c~mm-hwpoison-disable-pcp-for-page_handle_poison
+++ a/mm/memory-failure.c
@@ -65,6 +65,19 @@ int sysctl_memory_failure_recovery __rea
 
 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) {
@@ -72,7 +85,7 @@ static bool page_handle_poison(struct pa
 		 * 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
@@ -842,7 +855,7 @@ static int me_huge_page(struct page *p,
 		 */
 		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;
 		}
@@ -1287,7 +1300,7 @@ static int memory_failure_hugetlb(unsign
 		}
 		unlock_page(head);
 		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;
 		}
_

Patches currently in -mm which might be from naoya.horiguchi@nec.com are

mm-hwpoison-do-not-lock-page-again-when-me_huge_page-successfully-recovers.patch
mm-hwpoison-disable-pcp-for-page_handle_poison.patch
mmhwpoison-send-sigbus-with-error-virutal-address.patch
mmhwpoison-send-sigbus-with-error-virutal-address-fix.patch
mmhwpoison-make-get_hwpoison_page-call-get_any_page.patch