Re: [PATCH v1 04/16] mm/memory: simplify calculation in unmap_mapping_range_tree()

Lorenzo Stoakes (Oracle)
2026-03-06T12:25:05Z

On Fri, Feb 27, 2026 at 09:08:35PM +0100, David Hildenbrand (Arm) wrote:
> Let's simplify the calculation a bit further to make it easier to get,
> reusing vma_last_pgoff() which we move from interval_tree.c to mm.h.
>
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>

Thanks, some crusty old code here much improved. LGTM, so:

Reviewed-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>

> ---
> include/linux/mm.h | 5 +++++
> mm/interval_tree.c | 5 -----
> mm/memory.c | 12 +++++-------
> 3 files changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index a8138ff7d1fa..d3ef586ee1c0 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -4000,6 +4000,11 @@ static inline unsigned long vma_pages(const struct vm_area_struct *vma)
> return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
> }
>
> +static inline unsigned long vma_last_pgoff(struct vm_area_struct *vma)
> +{
> + return vma->vm_pgoff + vma_pages(vma) - 1;
> +}
> +
> static inline unsigned long vma_desc_size(const struct vm_area_desc *desc)
> {
> return desc->end - desc->start;
> diff --git a/mm/interval_tree.c b/mm/interval_tree.c
> index 32e390c42c53..32bcfbfcf15f 100644
> --- a/mm/interval_tree.c
> +++ b/mm/interval_tree.c
> @@ -15,11 +15,6 @@ static inline unsigned long vma_start_pgoff(struct vm_area_struct *v)
> return v->vm_pgoff;
> }
>
> -static inline unsigned long vma_last_pgoff(struct vm_area_struct *v)
> -{
> - return v->vm_pgoff + vma_pages(v) - 1;
> -}
> -
> INTERVAL_TREE_DEFINE(struct vm_area_struct, shared.rb,
> unsigned long, shared.rb_subtree_last,
> vma_start_pgoff, vma_last_pgoff, /* empty */, vma_interval_tree)
> diff --git a/mm/memory.c b/mm/memory.c
> index 5c47309331f5..e4154f03feac 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4227,17 +4227,15 @@ static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
> struct zap_details *details)
> {
> struct vm_area_struct *vma;
> - pgoff_t vba, vea, zba, zea;
> unsigned long start, size;
> struct mmu_gather tlb;
>
> vma_interval_tree_foreach(vma, root, first_index, last_index) {
> - vba = vma->vm_pgoff;
> - vea = vba + vma_pages(vma) - 1;
> - zba = max(first_index, vba);
> - zea = min(last_index, vea);

These variable names... Lord.

> - start = ((zba - vba) << PAGE_SHIFT) + vma->vm_start;
> - size = (zea - zba + 1) << PAGE_SHIFT;
> + const pgoff_t start_idx = max(first_index, vma->vm_pgoff);
> + const pgoff_t end_idx = min(last_index, vma_last_pgoff(vma)) + 1;

I guess since 'end' is by-convention the +1 of last this is fine

> +
> + start = vma->vm_start + ((start_idx - vma->vm_pgoff) << PAGE_SHIFT);
> + size = (end_idx - start_idx) << PAGE_SHIFT;
>
> tlb_gather_mmu(&tlb, vma->vm_mm);
> zap_page_range_single_batched(&tlb, vma, start, size, details);
> --
> 2.43.0
>