| Message ID | 20230125083851.27759-6-surenb@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | introduce vm_flags modifier functions | expand |
On Wed 25-01-23 00:38:50, Suren Baghdasaryan wrote: > In cases when VMA flags are modified after VMA was isolated and mmap_lock > was downgraded, flags modifications would result in an assertion because > mmap write lock is not held. > Introduce mod_vm_flags_nolock to be used in such situation. > Pass a hint to untrack_pfn to conditionally use mod_vm_flags_nolock for > flags modification and to avoid assertion. The changelog nor the documentation of mod_vm_flags_nolock really explain when it is safe to use it. This is really important for future potential users. > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > --- > arch/x86/mm/pat/memtype.c | 10 +++++++--- > include/linux/mm.h | 12 +++++++++--- > include/linux/pgtable.h | 5 +++-- > mm/memory.c | 13 +++++++------ > mm/memremap.c | 4 ++-- > mm/mmap.c | 16 ++++++++++------ > 6 files changed, 38 insertions(+), 22 deletions(-) > > diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c > index ae9645c900fa..d8adc0b42cf2 100644 > --- a/arch/x86/mm/pat/memtype.c > +++ b/arch/x86/mm/pat/memtype.c > @@ -1046,7 +1046,7 @@ 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 mm_wr_locked) > { > resource_size_t paddr; > unsigned long prot; > @@ -1065,8 +1065,12 @@ 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 (mm_wr_locked) > + 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 55335edd1373..48d49930c411 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -656,12 +656,18 @@ static inline void clear_vm_flags(struct vm_area_struct *vma, > vma->vm_flags &= ~flags; > } > > +static inline void mod_vm_flags_nolock(struct vm_area_struct *vma, > + unsigned long set, unsigned long clear) > +{ > + vma->vm_flags |= set; > + vma->vm_flags &= ~clear; > +} > + > static inline void mod_vm_flags(struct vm_area_struct *vma, > unsigned long set, unsigned long clear) > { > mmap_assert_write_locked(vma->vm_mm); > - vma->vm_flags |= set; > - vma->vm_flags &= ~clear; > + mod_vm_flags_nolock(vma, set, clear); > } > > static inline void vma_set_anonymous(struct vm_area_struct *vma) > @@ -2087,7 +2093,7 @@ static inline void zap_vma_pages(struct vm_area_struct *vma) > } > 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 mm_wr_locked); > > struct mmu_notifier_range; > > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > index 5fd45454c073..c63cd44777ec 100644 > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -1185,7 +1185,8 @@ 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 mm_wr_locked) > { > } > > @@ -1203,7 +1204,7 @@ 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 mm_wr_locked); > extern void untrack_pfn_moved(struct vm_area_struct *vma); > #endif > > diff --git a/mm/memory.c b/mm/memory.c > index d6902065e558..5b11b50e2c4a 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1613,7 +1613,7 @@ 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 mm_wr_locked) > { > unsigned long start = max(vma->vm_start, start_addr); > unsigned long end; > @@ -1628,7 +1628,7 @@ 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, mm_wr_locked); > > if (start != end) { > if (unlikely(is_vm_hugetlb_page(vma))) { > @@ -1675,7 +1675,7 @@ 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 mm_wr_locked) > { > struct mmu_notifier_range range; > struct zap_details details = { > @@ -1689,7 +1689,8 @@ 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, > + mm_wr_locked); > } while ((vma = mas_find(&mas, end_addr - 1)) != NULL); > mmu_notifier_invalidate_range_end(&range); > } > @@ -1723,7 +1724,7 @@ 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); > } > @@ -2492,7 +2493,7 @@ 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 2c6e9072e6a8..69d440997648 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -78,7 +78,7 @@ core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644); > static void unmap_region(struct mm_struct *mm, struct maple_tree *mt, > struct vm_area_struct *vma, struct vm_area_struct *prev, > struct vm_area_struct *next, unsigned long start, > - unsigned long end); > + unsigned long end, bool mm_wr_locked); > > static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags) > { > @@ -2136,14 +2136,14 @@ static inline void remove_mt(struct mm_struct *mm, struct ma_state *mas) > static void unmap_region(struct mm_struct *mm, struct maple_tree *mt, > struct vm_area_struct *vma, struct vm_area_struct *prev, > struct vm_area_struct *next, > - unsigned long start, unsigned long end) > + unsigned long start, unsigned long end, bool mm_wr_locked) > { > struct mmu_gather tlb; > > 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, mm_wr_locked); > free_pgtables(&tlb, mt, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS, > next ? next->vm_start : USER_PGTABLES_CEILING); > tlb_finish_mmu(&tlb); > @@ -2391,7 +2391,11 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, > mmap_write_downgrade(mm); > } > > - unmap_region(mm, &mt_detach, vma, prev, next, start, end); > + /* > + * We can free page tables without write-locking mmap_lock because VMAs > + * were isolated before we downgraded mmap_lock. > + */ > + unmap_region(mm, &mt_detach, vma, prev, next, start, end, !downgrade); > /* Statistics and freeing VMAs */ > mas_set(&mas_detach, start); > remove_mt(mm, &mas_detach); > @@ -2704,7 +2708,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, > > /* Undo any partial mapping done by a device driver. */ > unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start, > - vma->vm_end); > + vma->vm_end, true); > } > if (file && (vm_flags & VM_SHARED)) > mapping_unmap_writable(file->f_mapping); > @@ -3031,7 +3035,7 @@ 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); > > /* > -- > 2.39.1
diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c index ae9645c900fa..d8adc0b42cf2 100644 --- a/arch/x86/mm/pat/memtype.c +++ b/arch/x86/mm/pat/memtype.c @@ -1046,7 +1046,7 @@ 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 mm_wr_locked) { resource_size_t paddr; unsigned long prot; @@ -1065,8 +1065,12 @@ 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 (mm_wr_locked) + 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 55335edd1373..48d49930c411 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -656,12 +656,18 @@ static inline void clear_vm_flags(struct vm_area_struct *vma, vma->vm_flags &= ~flags; } +static inline void mod_vm_flags_nolock(struct vm_area_struct *vma, + unsigned long set, unsigned long clear) +{ + vma->vm_flags |= set; + vma->vm_flags &= ~clear; +} + static inline void mod_vm_flags(struct vm_area_struct *vma, unsigned long set, unsigned long clear) { mmap_assert_write_locked(vma->vm_mm); - vma->vm_flags |= set; - vma->vm_flags &= ~clear; + mod_vm_flags_nolock(vma, set, clear); } static inline void vma_set_anonymous(struct vm_area_struct *vma) @@ -2087,7 +2093,7 @@ static inline void zap_vma_pages(struct vm_area_struct *vma) } 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 mm_wr_locked); struct mmu_notifier_range; diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 5fd45454c073..c63cd44777ec 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -1185,7 +1185,8 @@ 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 mm_wr_locked) { } @@ -1203,7 +1204,7 @@ 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 mm_wr_locked); extern void untrack_pfn_moved(struct vm_area_struct *vma); #endif diff --git a/mm/memory.c b/mm/memory.c index d6902065e558..5b11b50e2c4a 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1613,7 +1613,7 @@ 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 mm_wr_locked) { unsigned long start = max(vma->vm_start, start_addr); unsigned long end; @@ -1628,7 +1628,7 @@ 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, mm_wr_locked); if (start != end) { if (unlikely(is_vm_hugetlb_page(vma))) { @@ -1675,7 +1675,7 @@ 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 mm_wr_locked) { struct mmu_notifier_range range; struct zap_details details = { @@ -1689,7 +1689,8 @@ 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, + mm_wr_locked); } while ((vma = mas_find(&mas, end_addr - 1)) != NULL); mmu_notifier_invalidate_range_end(&range); } @@ -1723,7 +1724,7 @@ 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); } @@ -2492,7 +2493,7 @@ 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 2c6e9072e6a8..69d440997648 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -78,7 +78,7 @@ core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644); static void unmap_region(struct mm_struct *mm, struct maple_tree *mt, struct vm_area_struct *vma, struct vm_area_struct *prev, struct vm_area_struct *next, unsigned long start, - unsigned long end); + unsigned long end, bool mm_wr_locked); static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags) { @@ -2136,14 +2136,14 @@ static inline void remove_mt(struct mm_struct *mm, struct ma_state *mas) static void unmap_region(struct mm_struct *mm, struct maple_tree *mt, struct vm_area_struct *vma, struct vm_area_struct *prev, struct vm_area_struct *next, - unsigned long start, unsigned long end) + unsigned long start, unsigned long end, bool mm_wr_locked) { struct mmu_gather tlb; 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, mm_wr_locked); free_pgtables(&tlb, mt, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS, next ? next->vm_start : USER_PGTABLES_CEILING); tlb_finish_mmu(&tlb); @@ -2391,7 +2391,11 @@ do_vmi_align_munmap(struct vma_iterator *vmi, struct vm_area_struct *vma, mmap_write_downgrade(mm); } - unmap_region(mm, &mt_detach, vma, prev, next, start, end); + /* + * We can free page tables without write-locking mmap_lock because VMAs + * were isolated before we downgraded mmap_lock. + */ + unmap_region(mm, &mt_detach, vma, prev, next, start, end, !downgrade); /* Statistics and freeing VMAs */ mas_set(&mas_detach, start); remove_mt(mm, &mas_detach); @@ -2704,7 +2708,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr, /* Undo any partial mapping done by a device driver. */ unmap_region(mm, &mm->mm_mt, vma, prev, next, vma->vm_start, - vma->vm_end); + vma->vm_end, true); } if (file && (vm_flags & VM_SHARED)) mapping_unmap_writable(file->f_mapping); @@ -3031,7 +3035,7 @@ 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); /*
In cases when VMA flags are modified after VMA was isolated and mmap_lock was downgraded, flags modifications would result in an assertion because mmap write lock is not held. Introduce mod_vm_flags_nolock to be used in such situation. Pass a hint to untrack_pfn to conditionally use mod_vm_flags_nolock for flags modification and to avoid assertion. Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- arch/x86/mm/pat/memtype.c | 10 +++++++--- include/linux/mm.h | 12 +++++++++--- include/linux/pgtable.h | 5 +++-- mm/memory.c | 13 +++++++------ mm/memremap.c | 4 ++-- mm/mmap.c | 16 ++++++++++------ 6 files changed, 38 insertions(+), 22 deletions(-)