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    Subject[PATCH 38/41] mm: avoid assertion in untrack_pfn
    From
    untrack_pfn can be called after VMA was isolated and mmap_lock downgraded.
    An attempt to lock affected VMA would cause an assertion, therefore
    use mod_vm_flags_nolock in such situations.

    Signed-off-by: Suren Baghdasaryan <surenb@google.com>
    ---
    arch/x86/mm/pat/memtype.c | 10 +++++++---
    include/linux/mm.h | 2 +-
    include/linux/pgtable.h | 5 +++--
    mm/memory.c | 15 ++++++++-------
    mm/memremap.c | 4 ++--
    mm/mmap.c | 4 ++--
    6 files changed, 23 insertions(+), 17 deletions(-)

    diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
    index 9e490a372896..f71c8381430b 100644
    --- a/arch/x86/mm/pat/memtype.c
    +++ b/arch/x86/mm/pat/memtype.c
    @@ -1045,7 +1045,7 @@ void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, pfn_t pfn)
    * can be for the entire vma (in which case pfn, size are zero).
    */
    void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
    - unsigned long size)
    + unsigned long size, bool lock_vma)
    {
    resource_size_t paddr;
    unsigned long prot;
    @@ -1064,8 +1064,12 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
    size = vma->vm_end - vma->vm_start;
    }
    free_pfn_range(paddr, size);
    - if (vma)
    - clear_vm_flags(vma, VM_PAT);
    + if (vma) {
    + if (lock_vma)
    + clear_vm_flags(vma, VM_PAT);
    + else
    + mod_vm_flags_nolock(vma, 0, VM_PAT);
    + }
    }

    /*
    diff --git a/include/linux/mm.h b/include/linux/mm.h
    index 7d436a5027cc..3158f33e268c 100644
    --- a/include/linux/mm.h
    +++ b/include/linux/mm.h
    @@ -2135,7 +2135,7 @@ void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
    unsigned long size, struct zap_details *details);
    void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
    struct vm_area_struct *start_vma, unsigned long start,
    - unsigned long end);
    + unsigned long end, bool lock_vma);

    struct mmu_notifier_range;

    diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
    index 1159b25b0542..eaa831bd675d 100644
    --- a/include/linux/pgtable.h
    +++ b/include/linux/pgtable.h
    @@ -1214,7 +1214,8 @@ static inline int track_pfn_copy(struct vm_area_struct *vma)
    * can be for the entire vma (in which case pfn, size are zero).
    */
    static inline void untrack_pfn(struct vm_area_struct *vma,
    - unsigned long pfn, unsigned long size)
    + unsigned long pfn, unsigned long size,
    + bool lock_vma)
    {
    }

    @@ -1232,7 +1233,7 @@ extern void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
    pfn_t pfn);
    extern int track_pfn_copy(struct vm_area_struct *vma);
    extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
    - unsigned long size);
    + unsigned long size, bool lock_vma);
    extern void untrack_pfn_moved(struct vm_area_struct *vma);
    #endif

    diff --git a/mm/memory.c b/mm/memory.c
    index 12508f4d845a..5c7d5eaa60d8 100644
    --- a/mm/memory.c
    +++ b/mm/memory.c
    @@ -1610,7 +1610,7 @@ void unmap_page_range(struct mmu_gather *tlb,
    static void unmap_single_vma(struct mmu_gather *tlb,
    struct vm_area_struct *vma, unsigned long start_addr,
    unsigned long end_addr,
    - struct zap_details *details)
    + struct zap_details *details, bool lock_vma)
    {
    unsigned long start = max(vma->vm_start, start_addr);
    unsigned long end;
    @@ -1625,7 +1625,7 @@ static void unmap_single_vma(struct mmu_gather *tlb,
    uprobe_munmap(vma, start, end);

    if (unlikely(vma->vm_flags & VM_PFNMAP))
    - untrack_pfn(vma, 0, 0);
    + untrack_pfn(vma, 0, 0, lock_vma);

    if (start != end) {
    if (unlikely(is_vm_hugetlb_page(vma))) {
    @@ -1672,7 +1672,7 @@ static void unmap_single_vma(struct mmu_gather *tlb,
    */
    void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
    struct vm_area_struct *vma, unsigned long start_addr,
    - unsigned long end_addr)
    + unsigned long end_addr, bool lock_vma)
    {
    struct mmu_notifier_range range;
    struct zap_details details = {
    @@ -1686,7 +1686,8 @@ void unmap_vmas(struct mmu_gather *tlb, struct maple_tree *mt,
    start_addr, end_addr);
    mmu_notifier_invalidate_range_start(&range);
    do {
    - unmap_single_vma(tlb, vma, start_addr, end_addr, &details);
    + unmap_single_vma(tlb, vma, start_addr, end_addr, &details,
    + lock_vma);
    } while ((vma = mas_find(&mas, end_addr - 1)) != NULL);
    mmu_notifier_invalidate_range_end(&range);
    }
    @@ -1715,7 +1716,7 @@ void zap_page_range(struct vm_area_struct *vma, unsigned long start,
    update_hiwater_rss(vma->vm_mm);
    mmu_notifier_invalidate_range_start(&range);
    do {
    - unmap_single_vma(&tlb, vma, start, range.end, NULL);
    + unmap_single_vma(&tlb, vma, start, range.end, NULL, false);
    } while ((vma = mas_find(&mas, end - 1)) != NULL);
    mmu_notifier_invalidate_range_end(&range);
    tlb_finish_mmu(&tlb);
    @@ -1750,7 +1751,7 @@ void zap_page_range_single(struct vm_area_struct *vma, unsigned long address,
    * unmap 'address-end' not 'range.start-range.end' as range
    * could have been expanded for hugetlb pmd sharing.
    */
    - unmap_single_vma(&tlb, vma, address, end, details);
    + unmap_single_vma(&tlb, vma, address, end, details, false);
    mmu_notifier_invalidate_range_end(&range);
    tlb_finish_mmu(&tlb);
    }
    @@ -2519,7 +2520,7 @@ int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,

    err = remap_pfn_range_notrack(vma, addr, pfn, size, prot);
    if (err)
    - untrack_pfn(vma, pfn, PAGE_ALIGN(size));
    + untrack_pfn(vma, pfn, PAGE_ALIGN(size), true);
    return err;
    }
    EXPORT_SYMBOL(remap_pfn_range);
    diff --git a/mm/memremap.c b/mm/memremap.c
    index 08cbf54fe037..2f88f43d4a01 100644
    --- a/mm/memremap.c
    +++ b/mm/memremap.c
    @@ -129,7 +129,7 @@ static void pageunmap_range(struct dev_pagemap *pgmap, int range_id)
    }
    mem_hotplug_done();

    - untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range));
    + untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range), true);
    pgmap_array_delete(range);
    }

    @@ -276,7 +276,7 @@ static int pagemap_range(struct dev_pagemap *pgmap, struct mhp_params *params,
    if (!is_private)
    kasan_remove_zero_shadow(__va(range->start), range_len(range));
    err_kasan:
    - untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range));
    + untrack_pfn(NULL, PHYS_PFN(range->start), range_len(range), true);
    err_pfn_remap:
    pgmap_array_delete(range);
    return error;
    diff --git a/mm/mmap.c b/mm/mmap.c
    index a256deca0bc0..332af383f7cd 100644
    --- a/mm/mmap.c
    +++ b/mm/mmap.c
    @@ -2209,7 +2209,7 @@ static void unmap_region(struct mm_struct *mm, struct maple_tree *mt,
    lru_add_drain();
    tlb_gather_mmu(&tlb, mm);
    update_hiwater_rss(mm);
    - unmap_vmas(&tlb, mt, vma, start, end);
    + unmap_vmas(&tlb, mt, vma, start, end, lock_vma);
    free_pgtables(&tlb, mt, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
    next ? next->vm_start : USER_PGTABLES_CEILING,
    lock_vma);
    @@ -3127,7 +3127,7 @@ void exit_mmap(struct mm_struct *mm)
    tlb_gather_mmu_fullmm(&tlb, mm);
    /* update_hiwater_rss(mm) here? but nobody should be looking */
    /* Use ULONG_MAX here to ensure all VMAs in the mm are unmapped */
    - unmap_vmas(&tlb, &mm->mm_mt, vma, 0, ULONG_MAX);
    + unmap_vmas(&tlb, &mm->mm_mt, vma, 0, ULONG_MAX, false);
    mmap_read_unlock(mm);

    /*
    --
    2.39.0
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