Re: [PATCH v1 2/9] mm/mmap: Abstract vma clean up from exit_mmap()

[Pedro Falcato <pfalcato@suse.de>]

On Tue, Sep 09, 2025 at 03:09:38PM -0400, Liam R. Howlett wrote:
> Create the new function tear_down_vmas() to remove a range of vmas.
> exit_mmap() will be removing all the vmas.
> 
> This is necessary for future patches.
> 
> No functional changes intended.
> 
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
> ---
>  mm/mmap.c | 37 ++++++++++++++++++++++++-------------
>  1 file changed, 24 insertions(+), 13 deletions(-)
> 
> diff --git a/mm/mmap.c b/mm/mmap.c
> index b07b3ec5e28f5..a290448a53bb2 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1250,6 +1250,29 @@ int vm_brk_flags(unsigned long addr, unsigned long request, vm_flags_t vm_flags)
>  }
>  EXPORT_SYMBOL(vm_brk_flags);
>  
> +static inline
> +unsigned long tear_down_vmas(struct mm_struct *mm, struct vma_iterator *vmi,
> +		struct vm_area_struct *vma, unsigned long max)
> +{
> +	unsigned long nr_accounted = 0;
> +	int count = 0;
> +
> +	mmap_assert_write_locked(mm);
> +	vma_iter_set(vmi, vma->vm_end);
> +	do {
> +		if (vma->vm_flags & VM_ACCOUNT)
> +			nr_accounted += vma_pages(vma);
> +		vma_mark_detached(vma);
> +		remove_vma(vma);
> +		count++;
> +		cond_resched();
> +		vma = vma_next(vmi);
> +	} while (vma && vma->vm_end <= max);

By not checking for XA_ZERO_ENTRY, we're technically breaking bisectability
here.

In any case,

Reviewed-by: Pedro Falcato <pfalcato@suse.de>

-- 
Pedro