+ powerpc-assert_pte_locked-use-pte_offset_map_nolock-fix.patch added to mm-unstable branch

+ powerpc-assert_pte_locked-use-pte_offset_map_nolock-fix.patch added to mm-unstable branch

[Andrew Morton]

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The patch titled
     Subject: powerpc: assert_pte_locked() use pte_offset_map_nolock(): fix
has been added to the -mm mm-unstable branch.  Its filename is
     powerpc-assert_pte_locked-use-pte_offset_map_nolock-fix.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-fix.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@google.com>
Subject: powerpc: assert_pte_locked() use pte_offset_map_nolock(): fix
Date: Sun, 23 Jul 2023 15:26:02 -0700 (PDT)

Aneesh points out that assert_pte_locked() still needs the pmd_none()
check, to stop crashing in khugepaged: restore that comment and check.

Link: https://lkml.kernel.org/r/c73d1543-532c-3da2-8cf2-a95363a14116@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Huang, Ying <ying.huang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lorenzo Stoakes <lstoakes@gmail.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Ralph Campbell <rcampbell@nvidia.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <song@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Zack Rusin <zackr@vmware.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/powerpc/mm/pgtable.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/arch/powerpc/mm/pgtable.c~powerpc-assert_pte_locked-use-pte_offset_map_nolock-fix
+++ a/arch/powerpc/mm/pgtable.c
@@ -323,6 +323,14 @@ 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;
 	pte = pte_offset_map_nolock(mm, pmd, addr, &ptl);
 	BUG_ON(!pte);
 	assert_spin_locked(ptl);
_

Patches currently in -mm which might be from hughd@google.com are

tmpfs-fix-documentation-of-noswap-and-huge-mount-options.patch
shmem-minor-fixes-to-splice-read-implementation.patch
mm-pagewalk-fix-efi_pgt_dump-of-espfix-area.patch
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-assert_pte_locked-use-pte_offset_map_nolock-fix.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
s390-add-pte_free_defer-for-pgtables-sharing-page-fix.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-collapse_pte_mapped_thp-with-mmap_read_lock-fix.patch
mm-khugepaged-delete-khugepaged_collapse_pte_mapped_thps.patch
mm-khugepaged-delete-khugepaged_collapse_pte_mapped_thps-fix.patch
mm-delete-mmap_write_trylock-and-vma_try_start_write.patch
mm-pgtable-notes-on-pte_offset_map.patch