linux-kernel - [PATCH v2 6/6] mm, hwpoison: avoid trying to unpoison reserved page

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Date:   Tue, 23 Aug 2022 11:23:46 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <naoya.horiguchi@....com>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <linmiaohe@...wei.com>
Subject: [PATCH v2 6/6] mm, hwpoison: avoid trying to unpoison reserved page

For reserved pages, HWPoison flag will be set without increasing the page
refcnt. So we shouldn't even try to unpoison these pages and thus decrease
the page refcnt unexpectly. Add a PageReserved() check to filter this case
out and remove the below unneeded zero page (zero page is reserved) check.

Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>
---
 mm/memory-failure.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index c2910f9af1d4..f3ff2515ccc6 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2351,7 +2351,7 @@ int unpoison_memory(unsigned long pfn)
 		goto unlock_mutex;
 	}
 
-	if (PageSlab(page) || PageTable(page))
+	if (PageSlab(page) || PageTable(page) || PageReserved(page))
 		goto unlock_mutex;
 
 	ret = get_hwpoison_page(p, MF_UNPOISON);
@@ -2382,7 +2382,7 @@ int unpoison_memory(unsigned long pfn)
 		freeit = !!TestClearPageHWPoison(p);
 
 		put_page(page);
-		if (freeit && !(pfn == my_zero_pfn(0) && page_count(p) == 1)) {
+		if (freeit) {
 			put_page(page);
 			ret = 0;
 		}
-- 
2.23.0