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mm: khugepaged: collapse_pte_mapped_thp() use pte_offset_map_rw_nolock()

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In collapse_pte_mapped_thp(), we may modify the pte and pmd entry after
acquiring the ptl, so convert it to using pte_offset_map_rw_nolock().  At
this time, the pte_same() check is not performed after the PTL held.  So
we should get pgt_pmd and do pmd_same() check after the ptl held.

Link: https://lkml.kernel.org/r/055e42db68da00ac8ecab94bd2633c7cd965eb1c.1727332572.git.zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Qi Zheng 2024-09-26 14:46:20 +08:00 committed by Andrew Morton
parent d9c1ddf37b
commit 6dfd0d2cb3
1 changed files with 13 additions and 5 deletions
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16
mm/khugepaged.c
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@ -1608,7 +1608,7 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
if (userfaultfd_armed(vma) && !(vma->vm_flags & VM_SHARED))
pml = pmd_lock(mm, pmd);
start_pte = pte_offset_map_nolock(mm, pmd, haddr, &ptl);
start_pte = pte_offset_map_rw_nolock(mm, pmd, haddr, &pgt_pmd, &ptl);
if (!start_pte) /* mmap_lock + page lock should prevent this */
goto abort;
if (!pml)
@ -1616,6 +1616,9 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
else if (ptl != pml)
spin_lock_nested(ptl, SINGLE_DEPTH_NESTING);
if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd))))
goto abort;
/* step 2: clear page table and adjust rmap */
for (i = 0, addr = haddr, pte = start_pte;
i < HPAGE_PMD_NR; i++, addr += PAGE_SIZE, pte++) {
@ -1648,7 +1651,6 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
nr_ptes++;
}
pte_unmap(start_pte);
if (!pml)
spin_unlock(ptl);
@ -1661,13 +1663,18 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
/* step 4: remove empty page table */
if (!pml) {
pml = pmd_lock(mm, pmd);
if (ptl != pml)
if (ptl != pml) {
spin_lock_nested(ptl, SINGLE_DEPTH_NESTING);
if (unlikely(!pmd_same(pgt_pmd, pmdp_get_lockless(pmd)))) {
flush_tlb_mm(mm);
goto unlock;
}
}
}
pgt_pmd = pmdp_collapse_flush(vma, haddr, pmd);
pmdp_get_lockless_sync();
pte_unmap_unlock(start_pte, ptl);
if (ptl != pml)
spin_unlock(ptl);
spin_unlock(pml);
mmu_notifier_invalidate_range_end(&range);
@ -1688,6 +1695,7 @@ int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr,
folio_ref_sub(folio, nr_ptes);
add_mm_counter(mm, mm_counter_file(folio), -nr_ptes);
}
unlock:
if (start_pte)
pte_unmap_unlock(start_pte, ptl);
if (pml && pml != ptl)