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Subject[PATCH 5.15 129/230] mm/memory-failure.c: fix race with changing page compound again
Date
From: Miaohe Lin <linmiaohe@huawei.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@linux-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@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.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


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