linux-kernel - [PATCH 4/3] mm, hugetlb, hwpoison: separate branch for free and in-use hugepage

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Date:   Fri, 15 Apr 2022 13:18:48 +0900
From:   Naoya Horiguchi <naoya.horiguchi@...ux.dev>
To:     Miaohe Lin <linmiaohe@...wei.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Yang Shi <shy828301@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        naoya.horiguchi@....com,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH 4/3] mm, hugetlb, hwpoison: separate branch for free and
 in-use hugepage

From: Naoya Horiguchi <naoya.horiguchi@....com>

We know that HPageFreed pages should have page refcount 0, so
get_page_unless_zero() always fails and returns 0.  So explicitly separate
the branch based on page state for minor optimization and better readability.

Suggested-by: Mike Kravetz <mike.kravetz@...cle.com>
Suggested-by: Miaohe Lin <linmiaohe@...wei.com>
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>
---
 mm/hugetlb.c        | 4 +++-
 mm/memory-failure.c | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index e38cbfdf3e61..3638f166e554 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6786,7 +6786,9 @@ int get_hwpoison_huge_page(struct page *page, bool *hugetlb)
 	spin_lock_irq(&hugetlb_lock);
 	if (PageHeadHuge(page)) {
 		*hugetlb = true;
-		if (HPageFreed(page) || HPageMigratable(page))
+		if (HPageFreed(page))
+			ret = 0;
+		else if (HPageMigratable(page))
 			ret = get_page_unless_zero(page);
 		else
 			ret = -EBUSY;
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 5e3ad640f5bb..661079a37f29 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1517,7 +1517,9 @@ int __get_huge_page_for_hwpoison(unsigned long pfn, int flags)
 	if (flags & MF_COUNT_INCREASED) {
 		ret = 1;
 		count_increased = true;
-	} else if (HPageFreed(head) || HPageMigratable(head)) {
+	} else if (HPageFreed(head)) {
+		ret = 0;
+	} else if (HPageMigratable(head)) {
 		ret = get_page_unless_zero(head);
 		if (ret)
 			count_increased = true;
-- 
2.23.0