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Message-ID: <a4616d9b-20d-fdd7-ae7a-7c8af451a1a@google.com>
Date: Sun, 21 May 2023 22:29:07 -0700 (PDT)
From: Hugh Dickins <hughd@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Mike Kravetz <mike.kravetz@...cle.com>,
Mike Rapoport <rppt@...nel.org>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
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Suren Baghdasaryan <surenb@...gle.com>,
Qi Zheng <zhengqi.arch@...edance.com>,
Yang Shi <shy828301@...il.com>,
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Peter Xu <peterx@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
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SeongJae Park <sj@...nel.org>,
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Minchan Kim <minchan@...nel.org>,
Christoph Hellwig <hch@...radead.org>,
Song Liu <song@...nel.org>,
Thomas Hellstrom <thomas.hellstrom@...ux.intel.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 31/31] perf/core: Allow pte_offset_map() to fail
In rare transient cases, not yet made possible, pte_offset_map() and
pte_offet_map_lock() may not find a page table: handle appropriately.
Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
This is a perf patch, not an mm patch, and it will want to go in through
the tip tree in due course; but keep it in this series for now, so that
it's not missed, and not submitted before mm review.
kernel/events/core.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index db016e418931..174be710f3b3 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7490,6 +7490,7 @@ static u64 perf_get_pgtable_size(struct mm_struct *mm, unsigned long addr)
return pud_leaf_size(pud);
pmdp = pmd_offset_lockless(pudp, pud, addr);
+again:
pmd = pmdp_get_lockless(pmdp);
if (!pmd_present(pmd))
return 0;
@@ -7498,6 +7499,9 @@ static u64 perf_get_pgtable_size(struct mm_struct *mm, unsigned long addr)
return pmd_leaf_size(pmd);
ptep = pte_offset_map(&pmd, addr);
+ if (!ptep)
+ goto again;
+
pte = ptep_get_lockless(ptep);
if (pte_present(pte))
size = pte_leaf_size(pte);
--
2.35.3
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