| Message ID | 20230125083851.27759-1-surenb@google.com |
|---|---|
| Headers | show |
| Series | introduce vm_flags modifier functions | expand |
On Wed 25-01-23 00:38:46, Suren Baghdasaryan wrote: > vm_flags are among VMA attributes which affect decisions like VMA merging > and splitting. Therefore all vm_flags modifications are performed after > taking exclusive mmap_lock to prevent vm_flags updates racing with such > operations. Introduce modifier functions for vm_flags to be used whenever > flags are updated. This way we can better check and control correct > locking behavior during these updates. > > Signed-off-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Michal Hocko <mhocko@suse.com> > --- > include/linux/mm.h | 37 +++++++++++++++++++++++++++++++++++++ > include/linux/mm_types.h | 8 +++++++- > 2 files changed, 44 insertions(+), 1 deletion(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index c2f62bdce134..b71f2809caac 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -627,6 +627,43 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm) > INIT_LIST_HEAD(&vma->anon_vma_chain); > } > > +/* Use when VMA is not part of the VMA tree and needs no locking */ > +static inline void init_vm_flags(struct vm_area_struct *vma, > + unsigned long flags) > +{ > + vma->vm_flags = flags; > +} > + > +/* Use when VMA is part of the VMA tree and modifications need coordination */ > +static inline void reset_vm_flags(struct vm_area_struct *vma, > + unsigned long flags) > +{ > + mmap_assert_write_locked(vma->vm_mm); > + init_vm_flags(vma, flags); > +} > + > +static inline void set_vm_flags(struct vm_area_struct *vma, > + unsigned long flags) > +{ > + mmap_assert_write_locked(vma->vm_mm); > + vma->vm_flags |= flags; > +} > + > +static inline void clear_vm_flags(struct vm_area_struct *vma, > + unsigned long flags) > +{ > + mmap_assert_write_locked(vma->vm_mm); > + vma->vm_flags &= ~flags; > +} > + > +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; > +} > + > static inline void vma_set_anonymous(struct vm_area_struct *vma) > { > vma->vm_ops = NULL; > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 2d6d790d9bed..6c7c70bf50dd 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -491,7 +491,13 @@ struct vm_area_struct { > * See vmf_insert_mixed_prot() for discussion. > */ > pgprot_t vm_page_prot; > - unsigned long vm_flags; /* Flags, see mm.h. */ > + > + /* > + * Flags, see mm.h. > + * WARNING! Do not modify directly. > + * Use {init|reset|set|clear|mod}_vm_flags() functions instead. > + */ > + unsigned long vm_flags; > > /* > * For areas with an address space and backing store, > -- > 2.39.1
On Wed, Jan 25, 2023 at 12:38:46AM -0800, Suren Baghdasaryan wrote: > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 2d6d790d9bed..6c7c70bf50dd 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -491,7 +491,13 @@ struct vm_area_struct { > * See vmf_insert_mixed_prot() for discussion. > */ > pgprot_t vm_page_prot; > - unsigned long vm_flags; /* Flags, see mm.h. */ > + > + /* > + * Flags, see mm.h. > + * WARNING! Do not modify directly. > + * Use {init|reset|set|clear|mod}_vm_flags() functions instead. > + */ > + unsigned long vm_flags; We have __private and ACCESS_PRIVATE() to help with enforcing this.
On Wed 25-01-23 00:38:49, Suren Baghdasaryan wrote: > Replace indirect modifications to vma->vm_flags with calls to modifier > functions to be able to track flag changes and to keep vma locking > correctness. Add a BUG_ON check in ksm_madvise() to catch indirect > vm_flags modification attempts. Those BUG_ONs scream to much IMHO. KSM is an MM internal code so I gueess we should be willing to trust it. > Signed-off-by: Suren Baghdasaryan <surenb@google.com> Acked-by: Michal Hocko <mhocko@suse.com>
On Wed, Jan 25, 2023 at 1:42 AM Michal Hocko <mhocko@suse.com> wrote: > > 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. True. I'll add clarification in the comments and in the changelog. Thanks! > > > 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 > > -- > Michal Hocko > SUSE Labs
On Wed, Jan 25, 2023 at 9:08 AM Michal Hocko <mhocko@suse.com> wrote: > > On Wed 25-01-23 08:57:48, Suren Baghdasaryan wrote: > > On Wed, Jan 25, 2023 at 1:38 AM 'Michal Hocko' via kernel-team > > <kernel-team@android.com> wrote: > > > > > > On Wed 25-01-23 00:38:49, Suren Baghdasaryan wrote: > > > > Replace indirect modifications to vma->vm_flags with calls to modifier > > > > functions to be able to track flag changes and to keep vma locking > > > > correctness. Add a BUG_ON check in ksm_madvise() to catch indirect > > > > vm_flags modification attempts. > > > > > > Those BUG_ONs scream to much IMHO. KSM is an MM internal code so I > > > gueess we should be willing to trust it. > > > > Yes, but I really want to prevent an indirect misuse since it was not > > easy to find these. If you feel strongly about it I will remove them > > or if you have a better suggestion I'm all for it. > > You can avoid that by making flags inaccesible directly, right? Ah, you mean Peter's suggestion of using __private? I guess that would cover it. I'll drop these BUG_ONs in the next version. Thanks! > > -- > Michal Hocko > SUSE Labs
On Wed, Jan 25, 2023 at 08:49:50AM -0800, Suren Baghdasaryan wrote: > On Wed, Jan 25, 2023 at 1:10 AM Peter Zijlstra <peterz@infradead.org> wrote: > > > + /* > > > + * Flags, see mm.h. > > > + * WARNING! Do not modify directly. > > > + * Use {init|reset|set|clear|mod}_vm_flags() functions instead. > > > + */ > > > + unsigned long vm_flags; > > > > We have __private and ACCESS_PRIVATE() to help with enforcing this. > > Thanks for pointing this out, Peter! I guess for that I'll need to > convert all read accesses and provide get_vm_flags() too? That will > cause some additional churt (a quick search shows 801 hits over 248 > files) but maybe it's worth it? I think Michal suggested that too in > another patch. Should I do that while we are at it? Here's a trick I saw somewhere in the VFS: union { const vm_flags_t vm_flags; vm_flags_t __private __vm_flags; }; Now it can be read by anybody but written only by those using ACCESS_PRIVATE.
On Wed, Jan 25, 2023 at 10:33 AM Matthew Wilcox <willy@infradead.org> wrote: > > On Wed, Jan 25, 2023 at 12:38:46AM -0800, Suren Baghdasaryan wrote: > > +/* Use when VMA is not part of the VMA tree and needs no locking */ > > +static inline void init_vm_flags(struct vm_area_struct *vma, > > + unsigned long flags) > > +{ > > + vma->vm_flags = flags; > > vm_flags are supposed to have type vm_flags_t. That's not been > fully realised yet, but perhaps we could avoid making it worse? > > > pgprot_t vm_page_prot; > > - unsigned long vm_flags; /* Flags, see mm.h. */ > > + > > + /* > > + * Flags, see mm.h. > > + * WARNING! Do not modify directly. > > + * Use {init|reset|set|clear|mod}_vm_flags() functions instead. > > + */ > > + unsigned long vm_flags; > > Including changing this line to vm_flags_t Good point. Will make the change. Thanks!
On Wed, Jan 25, 2023 at 12:38:46AM -0800, Suren Baghdasaryan wrote: > vm_flags are among VMA attributes which affect decisions like VMA merging > and splitting. Therefore all vm_flags modifications are performed after > taking exclusive mmap_lock to prevent vm_flags updates racing with such > operations. Introduce modifier functions for vm_flags to be used whenever > flags are updated. This way we can better check and control correct > locking behavior during these updates. > > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > --- > include/linux/mm.h | 37 +++++++++++++++++++++++++++++++++++++ > include/linux/mm_types.h | 8 +++++++- > 2 files changed, 44 insertions(+), 1 deletion(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index c2f62bdce134..b71f2809caac 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -627,6 +627,43 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm) > INIT_LIST_HEAD(&vma->anon_vma_chain); > } > > +/* Use when VMA is not part of the VMA tree and needs no locking */ > +static inline void init_vm_flags(struct vm_area_struct *vma, > + unsigned long flags) I'd suggest to make it vm_flags_init() etc. Except that Acked-by: Mike Rapoport (IBM) <rppt@kernel.org> > +{ > + vma->vm_flags = flags; > +} > + > +/* Use when VMA is part of the VMA tree and modifications need coordination */ > +static inline void reset_vm_flags(struct vm_area_struct *vma, > + unsigned long flags) > +{ > + mmap_assert_write_locked(vma->vm_mm); > + init_vm_flags(vma, flags); > +} > + > +static inline void set_vm_flags(struct vm_area_struct *vma, > + unsigned long flags) > +{ > + mmap_assert_write_locked(vma->vm_mm); > + vma->vm_flags |= flags; > +} > + > +static inline void clear_vm_flags(struct vm_area_struct *vma, > + unsigned long flags) > +{ > + mmap_assert_write_locked(vma->vm_mm); > + vma->vm_flags &= ~flags; > +} > + > +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; > +} > + > static inline void vma_set_anonymous(struct vm_area_struct *vma) > { > vma->vm_ops = NULL; > diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h > index 2d6d790d9bed..6c7c70bf50dd 100644 > --- a/include/linux/mm_types.h > +++ b/include/linux/mm_types.h > @@ -491,7 +491,13 @@ struct vm_area_struct { > * See vmf_insert_mixed_prot() for discussion. > */ > pgprot_t vm_page_prot; > - unsigned long vm_flags; /* Flags, see mm.h. */ > + > + /* > + * Flags, see mm.h. > + * WARNING! Do not modify directly. > + * Use {init|reset|set|clear|mod}_vm_flags() functions instead. > + */ > + unsigned long vm_flags; > > /* > * For areas with an address space and backing store, > -- > 2.39.1 > >
On Wed, Jan 25, 2023 at 12:38:50AM -0800, 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. vm_flags_mod_nolock? > 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(-) > > 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 > >
On Thu, Jan 26, 2023 at 11:17:09AM +0200, Mike Rapoport wrote: > On Wed, Jan 25, 2023 at 12:38:46AM -0800, Suren Baghdasaryan wrote: > > vm_flags are among VMA attributes which affect decisions like VMA merging > > and splitting. Therefore all vm_flags modifications are performed after > > taking exclusive mmap_lock to prevent vm_flags updates racing with such > > operations. Introduce modifier functions for vm_flags to be used whenever > > flags are updated. This way we can better check and control correct > > locking behavior during these updates. > > > > Signed-off-by: Suren Baghdasaryan <surenb@google.com> > > --- > > include/linux/mm.h | 37 +++++++++++++++++++++++++++++++++++++ > > include/linux/mm_types.h | 8 +++++++- > > 2 files changed, 44 insertions(+), 1 deletion(-) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index c2f62bdce134..b71f2809caac 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -627,6 +627,43 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm) > > INIT_LIST_HEAD(&vma->anon_vma_chain); > > } > > > > +/* Use when VMA is not part of the VMA tree and needs no locking */ > > +static inline void init_vm_flags(struct vm_area_struct *vma, > > + unsigned long flags) > > I'd suggest to make it vm_flags_init() etc. Thinking more about it, it will be even clearer to name these vma_flags_xyz() > Except that > > Acked-by: Mike Rapoport (IBM) <rppt@kernel.org> > -- Sincerely yours, Mike.
On Thu, Jan 26, 2023 at 04:50:59PM +0200, Mike Rapoport wrote: > On Thu, Jan 26, 2023 at 11:17:09AM +0200, Mike Rapoport wrote: > > On Wed, Jan 25, 2023 at 12:38:46AM -0800, Suren Baghdasaryan wrote: > > > +/* Use when VMA is not part of the VMA tree and needs no locking */ > > > +static inline void init_vm_flags(struct vm_area_struct *vma, > > > + unsigned long flags) > > > > I'd suggest to make it vm_flags_init() etc. > > Thinking more about it, it will be even clearer to name these vma_flags_xyz() Perhaps vma_VERB_flags()? vma_init_flags() vma_reset_flags() vma_set_flags() vma_clear_flags() vma_mod_flags()
On Thu, Jan 26, 2023 at 7:09 AM Matthew Wilcox <willy@infradead.org> wrote: > > On Thu, Jan 26, 2023 at 04:50:59PM +0200, Mike Rapoport wrote: > > On Thu, Jan 26, 2023 at 11:17:09AM +0200, Mike Rapoport wrote: > > > On Wed, Jan 25, 2023 at 12:38:46AM -0800, Suren Baghdasaryan wrote: > > > > +/* Use when VMA is not part of the VMA tree and needs no locking */ > > > > +static inline void init_vm_flags(struct vm_area_struct *vma, > > > > + unsigned long flags) > > > > > > I'd suggest to make it vm_flags_init() etc. > > > > Thinking more about it, it will be even clearer to name these vma_flags_xyz() > > Perhaps vma_VERB_flags()? > > vma_init_flags() > vma_reset_flags() > vma_set_flags() > vma_clear_flags() > vma_mod_flags() Due to excessive email bouncing I posted the v3 of this patchset using the original per-VMA patchset's distribution list. That might have dropped Mike from the list. Sorry about that Mike, I'll add you to my usual list of suspects :) The v3 is here: https://lore.kernel.org/all/20230125233554.153109-1-surenb@google.com/ and Andrew did suggest the same renames, so I'll be posting v4 with those changes later today. Thanks for the feedback! >