Re: [PATCH v4 18/66] xen: Use vma_lookup() in privcmd_ioctl_mmap()

[Vlastimil Babka]

On 12/1/21 15:29, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
> 
> vma_lookup() walks the VMA tree for a specific value, find_vma() will
> search the tree after walking to a specific value.  It is more efficient
> to only walk to the requested value as this case requires the address to
> equal the vm_start.

By that you mean the privcmd_ioctl_mmap() code checks msg->va !=
vma->vm_start and thus we know it's never interested the next vma, that
find_vma() can return if no vma covers the address?

> Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

> ---
>  drivers/xen/privcmd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
> index 3369734108af..ad17166b0ef6 100644
> --- a/drivers/xen/privcmd.c
> +++ b/drivers/xen/privcmd.c
> @@ -282,7 +282,7 @@ static long privcmd_ioctl_mmap(struct file *file, void __user *udata)
>  						     struct page, lru);
>  		struct privcmd_mmap_entry *msg = page_address(page);
>  
> -		vma = find_vma(mm, msg->va);
> +		vma = vma_lookup(mm, msg->va);
>  		rc = -EINVAL;
>  
>  		if (!vma || (msg->va != vma->vm_start) || vma->vm_private_data)