linux-kernel - [PATCH v2 3/4] mm: memory-failure: avoid false hwpoison page mapped error info

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Message-ID: <20230727115643.639741-4-linmiaohe@huawei.com>
Date:   Thu, 27 Jul 2023 19:56:42 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     <akpm@...ux-foundation.org>, <naoya.horiguchi@....com>
CC:     <willy@...radead.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>, <linmiaohe@...wei.com>
Subject: [PATCH v2 3/4] mm: memory-failure: avoid false hwpoison page mapped error info

folio->_mapcount is overloaded in SLAB, so folio_mapped() has to be done
after folio_test_slab() is checked. Otherwise slab folio might be treated
as a mapped folio leading to false 'Someone maps the hwpoison page' error
info.

Fixes: 230ac719c500 ("mm/hwpoison: don't try to unpoison containment-failed pages")
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>
Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>
---
 mm/memory-failure.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 4a3e88c15631..d975a6b224f7 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2535,6 +2535,13 @@ int unpoison_memory(unsigned long pfn)
 		goto unlock_mutex;
 	}
 
+	if (folio_test_slab(folio) || PageTable(&folio->page) || folio_test_reserved(folio))
+		goto unlock_mutex;
+
+	/*
+	 * Note that folio->_mapcount is overloaded in SLAB, so the simple test
+	 * in folio_mapped() has to be done after folio_test_slab() is checked.
+	 */
 	if (folio_mapped(folio)) {
 		unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n",
 				 pfn, &unpoison_rs);
@@ -2547,9 +2554,6 @@ int unpoison_memory(unsigned long pfn)
 		goto unlock_mutex;
 	}
 
-	if (folio_test_slab(folio) || PageTable(&folio->page) || folio_test_reserved(folio))
-		goto unlock_mutex;
-
 	ghp = get_hwpoison_page(p, MF_UNPOISON);
 	if (!ghp) {
 		if (PageHuge(p)) {
-- 
2.33.0