[PATCH v1 8/9] mm/vma: Use unmap_desc in vms_clear_ptes() and exit_mmap()
Suren Baghdasaryan
surenb at google.com
Tue Sep 9 15:16:16 PDT 2025
On Tue, Sep 9, 2025 at 12:10 PM Liam R. Howlett <Liam.Howlett at oracle.com> wrote:
>
> vms_clear_ptes() is slightly different than other callers to
> unmap_region() and so had the unmapping open-coded. Using the new
> structure it is now possible to special-case the struct setup instead of
> having the open-coded function.
>
> exit_mmap() also calls unmap_vmas() with many arguemnts. Using the
> unmap_all_init() function to set the unmap descriptor for all vmas makes
> this a bit easier to read.
>
> Update to the vma test code is necessary to ensure testing continues to
> function.
>
> No functional changes intended.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett at oracle.com>
> ---
> include/linux/mm.h | 3 ---
> mm/internal.h | 3 +++
> mm/memory.c | 24 ++++++++------------
> mm/mmap.c | 5 +++-
> mm/vma.c | 39 ++++++++++++++++++--------------
> mm/vma.h | 14 ++++++++++++
> tools/testing/vma/vma_internal.h | 14 ++++--------
> 7 files changed, 56 insertions(+), 46 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 892fe5dbf9de0..23eb59d543390 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2450,9 +2450,6 @@ static inline void zap_vma_pages(struct vm_area_struct *vma)
> zap_page_range_single(vma, vma->vm_start,
> vma->vm_end - vma->vm_start, NULL);
> }
> -void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
> - struct vm_area_struct *start_vma, unsigned long start,
> - unsigned long end, unsigned long tree_end, bool mm_wr_locked);
>
> struct mmu_notifier_range;
>
> diff --git a/mm/internal.h b/mm/internal.h
> index d295252407fee..1239944f2830a 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -197,6 +197,9 @@ static inline void vma_close(struct vm_area_struct *vma)
> }
> }
>
> +/* unmap_vmas is in mm/memory.c */
> +void unmap_vmas(struct mmu_gather *tlb, struct unmap_desc *unmap);
> +
> #ifdef CONFIG_MMU
>
> /* Flags for folio_pte_batch(). */
> diff --git a/mm/memory.c b/mm/memory.c
> index 829cd94950182..8d4d976311037 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2084,12 +2084,7 @@ static void unmap_single_vma(struct mmu_gather *tlb,
> /**
> * unmap_vmas - unmap a range of memory covered by a list of vma's
> * @tlb: address of the caller's struct mmu_gather
> - * @mas: the maple state
> - * @vma: the starting vma
> - * @start_addr: virtual address at which to start unmapping
> - * @end_addr: virtual address at which to end unmapping
> - * @tree_end: The maximum index to check
> - * @mm_wr_locked: lock flag
> + * @unmap: The unmap_desc
> *
> * Unmap all pages in the vma list.
> *
> @@ -2102,11 +2097,9 @@ static void unmap_single_vma(struct mmu_gather *tlb,
> * ensure that any thus-far unmapped pages are flushed before unmap_vmas()
> * drops the lock and schedules.
> */
> -void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
> - struct vm_area_struct *vma, unsigned long start_addr,
> - unsigned long end_addr, unsigned long tree_end,
> - bool mm_wr_locked)
> +void unmap_vmas(struct mmu_gather *tlb, struct unmap_desc *unmap)
> {
> + struct vm_area_struct *vma;
> struct mmu_notifier_range range;
> struct zap_details details = {
> .zap_flags = ZAP_FLAG_DROP_MARKER | ZAP_FLAG_UNMAP,
> @@ -2114,17 +2107,18 @@ void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
> .even_cows = true,
> };
>
> + vma = unmap->first;
> mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, vma->vm_mm,
> - start_addr, end_addr);
> + unmap->vma_min, unmap->vma_max);
> mmu_notifier_invalidate_range_start(&range);
> do {
> - unsigned long start = start_addr;
> - unsigned long end = end_addr;
> + unsigned long start = unmap->vma_min;
> + unsigned long end = unmap->vma_max;
> hugetlb_zap_begin(vma, &start, &end);
> unmap_single_vma(tlb, vma, start, end, &details,
> - mm_wr_locked);
> + unmap->mm_wr_locked);
> hugetlb_zap_end(vma, &details);
> - vma = mas_find(mas, tree_end - 1);
> + vma = mas_find(unmap->mas, unmap->tree_max - 1);
> } while (vma);
> mmu_notifier_invalidate_range_end(&range);
> }
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 5c9bd3f20e53f..6011f62b0a294 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1280,10 +1280,12 @@ void exit_mmap(struct mm_struct *mm)
> struct vm_area_struct *vma;
> unsigned long nr_accounted = 0;
> VMA_ITERATOR(vmi, mm, 0);
> + struct unmap_desc unmap;
>
> /* mm's last user has gone, and its about to be pulled down */
> mmu_notifier_release(mm);
>
> + unmap.mm_wr_locked = false;
This will be reset by unmap_all_init() anyway, right?
> mmap_read_lock(mm);
> arch_exit_mmap(mm);
>
> @@ -1295,11 +1297,12 @@ void exit_mmap(struct mm_struct *mm)
> goto destroy;
> }
>
> + unmap_all_init(&unmap, &vmi, vma);
Can we use a macro, something like DEFINE_UNMAP_ALL_REGIONS() instead
of unmap_all_init()?
> flush_cache_mm(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, &vmi.mas, vma, 0, ULONG_MAX, ULONG_MAX, false);
> + unmap_vmas(&tlb, &unmap);
> mmap_read_unlock(mm);
>
> /*
> diff --git a/mm/vma.c b/mm/vma.c
> index c92384975cbb2..ad64cd9795ef3 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -481,8 +481,7 @@ void unmap_region(struct unmap_desc *desc)
>
> tlb_gather_mmu(&tlb, mm);
> update_hiwater_rss(mm);
> - unmap_vmas(&tlb, mas, desc->first, desc->vma_min, desc->vma_max,
> - desc->vma_max, desc->mm_wr_locked);
> + unmap_vmas(&tlb, desc);
> mas_set(mas, desc->tree_reset);
> free_pgtables(&tlb, mas, desc->first, desc->first_pgaddr,
> desc->last_pgaddr, desc->tree_max,
> @@ -1213,26 +1212,32 @@ int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,
> static inline void vms_clear_ptes(struct vma_munmap_struct *vms,
> struct ma_state *mas_detach, bool mm_wr_locked)
> {
> - struct mmu_gather tlb;
> + struct unmap_desc unmap = {
> + .mas = mas_detach,
> + .first = vms->vma,
> + /* start and end may be different if there is no prev or next vma. */
> + .first_pgaddr = vms->unmap_start,
> + .last_pgaddr = vms->unmap_end,
> + .vma_min = vms->start,
> + .vma_max = vms->end,
> + /*
> + * The tree limits and reset differ from the normal case since it's a
> + * side-tree
> + */
> + .tree_reset = 1,
> + .tree_max = vms->vma_count,
> + /*
> + * We can free page tables without write-locking mmap_lock because VMAs
> + * were isolated before we downgraded mmap_lock.
> + */
> + .mm_wr_locked = mm_wr_locked,
> + };
>
> if (!vms->clear_ptes) /* Nothing to do */
> return;
>
> - /*
> - * We can free page tables without write-locking mmap_lock because VMAs
> - * were isolated before we downgraded mmap_lock.
> - */
> mas_set(mas_detach, 1);
> - tlb_gather_mmu(&tlb, vms->vma->vm_mm);
> - update_hiwater_rss(vms->vma->vm_mm);
> - unmap_vmas(&tlb, mas_detach, vms->vma, vms->start, vms->end,
> - vms->vma_count, mm_wr_locked);
> -
> - mas_set(mas_detach, 1);
> - /* start and end may be different if there is no prev or next vma. */
> - free_pgtables(&tlb, mas_detach, vms->vma, vms->unmap_start,
> - vms->unmap_end, vms->unmap_end, mm_wr_locked);
> - tlb_finish_mmu(&tlb);
> + unmap_region(&unmap);
> vms->clear_ptes = false;
> }
>
> diff --git a/mm/vma.h b/mm/vma.h
> index 4edd5d26ffcfc..8b55a0c73d097 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -164,6 +164,20 @@ struct unmap_desc {
> bool mm_wr_locked; /* If the mmap write lock is held */
> };
>
> +static inline void unmap_all_init(struct unmap_desc *desc,
> + struct vma_iterator *vmi, struct vm_area_struct *vma)
> +{
> + desc->mas = &vmi->mas;
> + desc->first = vma;
> + desc->first_pgaddr = FIRST_USER_ADDRESS;
> + desc->last_pgaddr = USER_PGTABLES_CEILING;
> + desc->vma_min = 0;
> + desc->vma_max = ULONG_MAX;
> + desc->tree_max = ULONG_MAX;
> + desc->tree_reset = vma->vm_end;
> + desc->mm_wr_locked = false;
> +}
> +
> #define UNMAP_REGION(name, _vmi, _vma, _vma_min, _vma_max, _prev, _next) \
> struct unmap_desc name = { \
> .mas = &(_vmi)->mas, \
> diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h
> index 823d379e1fac2..d73ad4747d40a 100644
> --- a/tools/testing/vma/vma_internal.h
> +++ b/tools/testing/vma/vma_internal.h
> @@ -884,18 +884,12 @@ static inline void update_hiwater_vm(struct mm_struct *)
> {
> }
>
> -static inline void unmap_vmas(struct mmu_gather *tlb, struct ma_state *mas,
> - struct vm_area_struct *vma, unsigned long start_addr,
> - unsigned long end_addr, unsigned long tree_end,
> - bool mm_wr_locked)
> +struct unmap_desc;
> +
> +static inline void unmap_vmas(struct mmu_gather *tlb, struct unmap_desc *unmap)
> {
> (void)tlb;
> - (void)mas;
> - (void)vma;
> - (void)start_addr;
> - (void)end_addr;
> - (void)tree_end;
> - (void)mm_wr_locked;
> + (void)unmap;
> }
>
> static inline void free_pgtables(struct mmu_gather *tlb, struct ma_state *mas,
> --
> 2.47.2
>
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