linux-kernel - [PATCH v1] mm, hwpoison: do not lock page again when me_huge

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Date:   Thu,  4 Mar 2021 15:44:37 +0900
From:   Naoya Horiguchi <nao.horiguchi@...il.com>
To:     linux-mm@...ck.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Oscar Salvador <osalvador@...e.de>,
        Tony Luck <tony.luck@...el.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v1] mm, hwpoison: do not lock page again when me_huge_page() successfully recovers

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

Currently me_huge_page() temporary unlocks page to perform some actions
then locks it again later. My testcase (which calls hard-offline on some
tail page in a hugetlb, then accesses the address of the hugetlb range)
showed that page allocation code detects the page lock on buddy page and
printed out "BUG: Bad page state" message.  PG_hwpoison does not prevent
it because PG_hwpoison flag is set on any subpage of the hugetlb page
but the 2nd page lock is on the head page.

This patch suggests to drop the 2nd page lock to fix the issue.

Fixes: commit 78bb920344b8 ("mm: hwpoison: dissolve in-use hugepage in unrecoverable memory error")
Cc: stable@...r.kernel.org
Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>
---
 mm/memory-failure.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git v5.11/mm/memory-failure.c v5.11_patched/mm/memory-failure.c
index e9481632fcd1..d8aba15295c5 100644
--- v5.11/mm/memory-failure.c
+++ v5.11_patched/mm/memory-failure.c
@@ -830,7 +830,6 @@ static int me_huge_page(struct page *p, unsigned long pfn)
 			page_ref_inc(p);
 			res = MF_RECOVERED;
 		}
-		lock_page(hpage);
 	}
 
 	return res;
@@ -1286,7 +1285,8 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
 
 	res = identify_page_state(pfn, p, page_flags);
 out:
-	unlock_page(head);
+	if (PageLocked(head))
+		unlock_page(head);
 	return res;
 }
 
-- 
2.25.1