diff mbox series

[31/31] perf/core: Allow pte_offset_map() to fail

Message ID a4616d9b-20d-fdd7-ae7a-7c8af451a1a@google.com (mailing list archive)
State New
Headers show
Series mm: allow pte_offset_map[_lock]() to fail | expand

Commit Message

Hugh Dickins May 22, 2023, 5:29 a.m. UTC 
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@google.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 mbox series

Patch

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);