Re: [PATCH v4 63/66] i915: Use the VMA iterator

[Vlastimil Babka]

On 12/1/21 15:30, Liam Howlett wrote:
> From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
> 
> Replace the O(n.log(n)) loop with an O(n) loop.

Not true?

> Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>  drivers/gpu/drm/i915/gem/i915_gem_userptr.c | 14 +++++---------
>  1 file changed, 5 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> index 3173c9f9a040..39960973c130 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_userptr.c
> @@ -425,12 +425,11 @@ static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = {
>  static int
>  probe_range(struct mm_struct *mm, unsigned long addr, unsigned long len)
>  {
> -	const unsigned long end = addr + len;
> +	VMA_ITERATOR(vmi, mm, addr);
>  	struct vm_area_struct *vma;
> -	int ret = -EFAULT;
>  
>  	mmap_read_lock(mm);
> -	for (vma = find_vma(mm, addr); vma; vma = vma->vm_next) {
> +	for_each_vma_range(vmi, vma, addr + len) {
>  		/* Check for holes, note that we also update the addr below */
>  		if (vma->vm_start > addr)
>  			break;
> @@ -438,16 +437,13 @@ probe_range(struct mm_struct *mm, unsigned long addr, unsigned long len)
>  		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
>  			break;
>  
> -		if (vma->vm_end >= end) {
> -			ret = 0;
> -			break;
> -		}
> -
>  		addr = vma->vm_end;
>  	}
>  	mmap_read_unlock(mm);
>  
> -	return ret;
> +	if (vma)
> +		return -EFAULT;
> +	return 0;
>  }
>  
>  /*