linux-kernel - [PATCH 5.15 129/230] mm/memory-failure.c: fix race with changing page compound again

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Date:   Mon, 11 Jul 2022 11:06:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Miaohe Lin <linmiaohe@...wei.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Tony Luck <tony.luck@...el.com>,
        Borislav Petkov <bp@...en8.de>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Yang Shi <shy828301@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.15 129/230] mm/memory-failure.c: fix race with changing page compound again

From: Miaohe Lin <linmiaohe@...wei.com>

[ Upstream commit 888af2701db79b9b27c7e37f9ede528a5ca53b76 ]

Patch series "A few fixup patches for memory failure", v2.

This series contains a few patches to fix the race with changing page
compound page, make non-LRU movable pages unhandlable and so on.  More
details can be found in the respective changelogs.

There is a race window where we got the compound_head, the hugetlb page
could be freed to buddy, or even changed to another compound page just
before we try to get hwpoison page.  Think about the below race window:

  CPU 1					  CPU 2
  memory_failure_hugetlb
  struct page *head = compound_head(p);
					  hugetlb page might be freed to
					  buddy, or even changed to another
					  compound page.

  get_hwpoison_page -- page is not what we want now...

If this race happens, just bail out.  Also MF_MSG_DIFFERENT_PAGE_SIZE is
introduced to record this event.

[akpm@...ux-foundation.org: s@/**@/*@, per Naoya Horiguchi]

Link: https://lkml.kernel.org/r/20220312074613.4798-1-linmiaohe@huawei.com
Link: https://lkml.kernel.org/r/20220312074613.4798-2-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@....com>
Cc: Tony Luck <tony.luck@...el.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Mike Kravetz <mike.kravetz@...cle.com>
Cc: Yang Shi <shy828301@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/linux/mm.h      |  1 +
 include/ras/ras_event.h |  1 +
 mm/memory-failure.c     | 12 ++++++++++++
 3 files changed, 14 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 85205adcdd0d..7a80a08eec84 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3167,6 +3167,7 @@ enum mf_action_page_type {
 	MF_MSG_BUDDY_2ND,
 	MF_MSG_DAX,
 	MF_MSG_UNSPLIT_THP,
+	MF_MSG_DIFFERENT_PAGE_SIZE,
 	MF_MSG_UNKNOWN,
 };
 
diff --git a/include/ras/ras_event.h b/include/ras/ras_event.h
index 0bdbc0d17d2f..cac13ff1d6eb 100644
--- a/include/ras/ras_event.h
+++ b/include/ras/ras_event.h
@@ -376,6 +376,7 @@ TRACE_EVENT(aer_event,
 	EM ( MF_MSG_BUDDY_2ND, "free buddy page (2nd try)" )		\
 	EM ( MF_MSG_DAX, "dax page" )					\
 	EM ( MF_MSG_UNSPLIT_THP, "unsplit thp" )			\
+	EM ( MF_MSG_DIFFERENT_PAGE_SIZE, "different page size" )	\
 	EMe ( MF_MSG_UNKNOWN, "unknown page" )
 
 /*
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 5664bafd5e77..a4d70c21c146 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -741,6 +741,7 @@ static const char * const action_page_types[] = {
 	[MF_MSG_BUDDY_2ND]		= "free buddy page (2nd try)",
 	[MF_MSG_DAX]			= "dax page",
 	[MF_MSG_UNSPLIT_THP]		= "unsplit thp",
+	[MF_MSG_DIFFERENT_PAGE_SIZE]	= "different page size",
 	[MF_MSG_UNKNOWN]		= "unknown page",
 };
 
@@ -1461,6 +1462,17 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
 	}
 
 	lock_page(head);
+
+	/*
+	 * The page could have changed compound pages due to race window.
+	 * If this happens just bail out.
+	 */
+	if (!PageHuge(p) || compound_head(p) != head) {
+		action_result(pfn, MF_MSG_DIFFERENT_PAGE_SIZE, MF_IGNORED);
+		res = -EBUSY;
+		goto out;
+	}
+
 	page_flags = head->flags;
 
 	/*
-- 
2.35.1