The patch titled
Subject: powerpc: assert_pte_locked() use pte_offset_map_nolock()
has been added to the -mm mm-unstable branch. Its filename is
powerpc-assert_pte_locked-use-pte_offset_map_nolock.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/powerpc-assert_pte_locked-use-pte_offset_map_nolock.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: powerpc: assert_pte_locked() use pte_offset_map_nolock()
Date: Tue, 11 Jul 2023 21:34:25 -0700 (PDT)
Instead of pte_lockptr(), use the recently added pte_offset_map_nolock()
in assert_pte_locked(). BUG if pte_offset_map_nolock() fails: this is
stricter than the previous implementation, which skipped when pmd_none()
(with a comment on khugepaged collapse transitions): but wouldn't we want
to know, if an assert_pte_locked() caller can be racing such transitions?
This mod might cause new crashes: which either expose my ignorance, or
indicate issues to be fixed, or limit the usage of assert_pte_locked().
Link: https://lkml.kernel.org/r/e8d56c95-c132-a82e-5f5f-7bb1b738b057@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Huang, Ying <ying.huang@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxx>
Cc: SeongJae Park <sj@xxxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Steven Price <steven.price@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vishal Moola (Oracle) <vishal.moola@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Zack Rusin <zackr@xxxxxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/mm/pgtable.c | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
--- a/arch/powerpc/mm/pgtable.c~powerpc-assert_pte_locked-use-pte_offset_map_nolock
+++ a/arch/powerpc/mm/pgtable.c
@@ -311,6 +311,8 @@ void assert_pte_locked(struct mm_struct
p4d_t *p4d;
pud_t *pud;
pmd_t *pmd;
+ pte_t *pte;
+ spinlock_t *ptl;
if (mm == &init_mm)
return;
@@ -321,16 +323,10 @@ void assert_pte_locked(struct mm_struct
pud = pud_offset(p4d, addr);
BUG_ON(pud_none(*pud));
pmd = pmd_offset(pud, addr);
- /*
- * khugepaged to collapse normal pages to hugepage, first set
- * pmd to none to force page fault/gup to take mmap_lock. After
- * pmd is set to none, we do a pte_clear which does this assertion
- * so if we find pmd none, return.
- */
- if (pmd_none(*pmd))
- return;
- BUG_ON(!pmd_present(*pmd));
- assert_spin_locked(pte_lockptr(mm, pmd));
+ pte = pte_offset_map_nolock(mm, pmd, addr, &ptl);
+ BUG_ON(!pte);
+ assert_spin_locked(ptl);
+ pte_unmap(pte);
}
#endif /* CONFIG_DEBUG_VM */
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
mm-userfaultfd-add-new-uffdio_poison-ioctl-fix.patch
mm-pgtable-add-rcu_read_lock-and-rcu_read_unlocks.patch
mm-pgtable-add-pae-safety-to-__pte_offset_map.patch
arm-adjust_pte-use-pte_offset_map_nolock.patch
powerpc-assert_pte_locked-use-pte_offset_map_nolock.patch
powerpc-add-pte_free_defer-for-pgtables-sharing-page.patch
sparc-add-pte_free_defer-for-pte_t-pgtable_t.patch
s390-add-pte_free_defer-for-pgtables-sharing-page.patch
mm-pgtable-add-pte_free_defer-for-pgtable-as-page.patch
mm-khugepaged-retract_page_tables-without-mmap-or-vma-lock.patch
mm-khugepaged-collapse_pte_mapped_thp-with-mmap_read_lock.patch
mm-khugepaged-delete-khugepaged_collapse_pte_mapped_thps.patch
mm-delete-mmap_write_trylock-and-vma_try_start_write.patch
mm-pgtable-notes-on-pte_offset_map.patch
