Re: [PATCH v1 08/16] mm/memory: move adjusting of address range to unmap_vmas()

Lorenzo Stoakes (Oracle)
2026-03-06T21:18:31Z

On Fri, Feb 27, 2026 at 09:08:39PM +0100, David Hildenbrand (Arm) wrote:
> __zap_vma_range() has two callers, whereby
> zap_page_range_single_batched() documents that the range must fit into
> the VMA range.
>
> So move adjusting the range to unmap_vmas() where it is actually
> required and add a safety check in __zap_vma_range() instead. In
> unmap_vmas(), we'd never expect to have empty ranges (otherwise, why
> have the vma in there in the first place).
>
> __zap_vma_range() will no longer be called with start == end, so
> cleanup the function a bit. While at it, simplify the overly long
> comment to its core message.
>
> We will no longer call uprobe_munmap() for start == end, which actually
> seems to be the right thing to do.
>
> Note that hugetlb_zap_begin()->...->adjust_range_if_pmd_sharing_possible()
> cannot result in the range exceeding the vma range.
>
> Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>

LGTM, So:

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

> ---
> mm/memory.c | 58 +++++++++++++++++++++--------------------------------
> 1 file changed, 23 insertions(+), 35 deletions(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index f0aaec57a66b..fdcd2abf29c2 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2073,44 +2073,28 @@ static void unmap_page_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
> tlb_end_vma(tlb, vma);
> }
>
> -
> -static void __zap_vma_range(struct mmu_gather *tlb,
> - struct vm_area_struct *vma, unsigned long start_addr,
> - unsigned long end_addr, struct zap_details *details)
> +static void __zap_vma_range(struct mmu_gather *tlb, struct vm_area_struct *vma,
> + unsigned long start, unsigned long end,
> + struct zap_details *details)
> {
> - unsigned long start = max(vma->vm_start, start_addr);
> - unsigned long end;
> -
> - if (start >= vma->vm_end)
> - return;
> - end = min(vma->vm_end, end_addr);
> - if (end <= vma->vm_start)
> - return;
> + VM_WARN_ON_ONCE(start >= end || !range_in_vma(vma, start, end));
>
> if (vma->vm_file)
> uprobe_munmap(vma, start, end);
>
> - if (start != end) {
> - if (unlikely(is_vm_hugetlb_page(vma))) {
> - /*
> - * It is undesirable to test vma->vm_file as it
> - * should be non-null for valid hugetlb area.
> - * However, vm_file will be NULL in the error
> - * cleanup path of mmap_region. When
> - * hugetlbfs ->mmap method fails,
> - * mmap_region() nullifies vma->vm_file
> - * before calling this function to clean up.
> - * Since no pte has actually been setup, it is
> - * safe to do nothing in this case.
> - */
> - if (vma->vm_file) {
> - zap_flags_t zap_flags = details ?
> - details->zap_flags : 0;
> - __unmap_hugepage_range(tlb, vma, start, end,
> - NULL, zap_flags);
> - }
> - } else
> - unmap_page_range(tlb, vma, start, end, details);
> + if (unlikely(is_vm_hugetlb_page(vma))) {
> + zap_flags_t zap_flags = details ? details->zap_flags : 0;
> +
> + /*
> + * vm_file will be NULL when we fail early while instantiating
> + * a new mapping. In this case, no pages were mapped yet and
> + * there is nothing to do.
> + */
> + if (!vma->vm_file)
> + return;
> + __unmap_hugepage_range(tlb, vma, start, end, NULL, zap_flags);
> + } else {
> + unmap_page_range(tlb, vma, start, end, details);
> }
> }
>
> @@ -2174,8 +2158,9 @@ void unmap_vmas(struct mmu_gather *tlb, struct unmap_desc *unmap)
> unmap->vma_start, unmap->vma_end);
> mmu_notifier_invalidate_range_start(&range);
> do {
> - unsigned long start = unmap->vma_start;
> - unsigned long end = unmap->vma_end;
> + unsigned long start = max(vma->vm_start, unmap->vma_start);
> + unsigned long end = min(vma->vm_end, unmap->vma_end);
> +
> hugetlb_zap_begin(vma, &start, &end);
> __zap_vma_range(tlb, vma, start, end, &details);
> hugetlb_zap_end(vma, &details);
> @@ -2204,6 +2189,9 @@ void zap_page_range_single_batched(struct mmu_gather *tlb,
>
> VM_WARN_ON_ONCE(!tlb || tlb->mm != vma->vm_mm);
>
> + if (unlikely(!size))
> + return;
> +
> mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
> address, end);
> hugetlb_zap_begin(vma, &range.start, &range.end);
> --
> 2.43.0
>