Re: [PATCH v4 6/6] mm/vmalloc: align vm_area so vmap() can batch mappings

[Uladzislau Rezki]

On Thu, Jun 18, 2026 at 04:47:26PM +0800, Wen Jiang wrote:
> From: "Barry Song (Xiaomi)" <baohua@xxxxxxxxxx>
> 
> Try to align the vmap virtual address to PMD_SHIFT or a
> larger PTE mapping size hinted by the architecture, so
> contiguous pages can be batch-mapped when setting PMD or
> PTE entries.
> 
> Add __get_vm_area_node_aligned_caller() as a wrapper over
> __get_vm_area_node() to simplify repeated calls with fixed
> arguments.
> 
> Signed-off-by: Barry Song (Xiaomi) <baohua@xxxxxxxxxx>
> Signed-off-by: Wen Jiang <jiangwen6@xxxxxxxxxx>
> Tested-by: Xueyuan Chen <xueyuan.chen21@xxxxxxxxx>
> ---
>  mm/vmalloc.c | 37 ++++++++++++++++++++++++++++++++++++-
>  1 file changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index fffb885cb2158..bc9fa93e2bdc6 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3628,6 +3628,41 @@ static int vmap_batched(unsigned long addr, unsigned long end,
>  	return err;
>  }
>  
> +static struct vm_struct *__get_vm_area_node_aligned_caller(unsigned long size,
> +		unsigned long align, unsigned long flags, const void *caller)
> +{
> +	return __get_vm_area_node(size, align, PAGE_SHIFT, flags,
> +			VMALLOC_START, VMALLOC_END,
> +			NUMA_NO_NODE, GFP_KERNEL, caller);
> +}
> +
> +static struct vm_struct *vmap_get_aligned_vm_area(unsigned long size,
> +		unsigned long flags, const void *caller)
> +{
> +	struct vm_struct *vm_area;
> +	unsigned int shift;
> +
> +	/* Try PMD alignment for large sizes */
> +	if (size >= PMD_SIZE) {
> +		vm_area = __get_vm_area_node_aligned_caller(size, PMD_SIZE,
> +				flags, caller);
> +		if (vm_area)
> +			return vm_area;
> +	}
> +
> +	/* Try CONT_PTE alignment */
> +	shift = arch_vmap_pte_supported_shift(size);
> +	if (shift > PAGE_SHIFT) {
> +		vm_area = __get_vm_area_node_aligned_caller(size, 1UL << shift,
> +				flags, caller);
> +		if (vm_area)
> +			return vm_area;
> +	}
> +
> +	/* Fall back to page alignment */
> +	return __get_vm_area_node_aligned_caller(size, PAGE_SIZE, flags, caller);
> +}
> +
>  /**
>   * vmap - map an array of pages into virtually contiguous space
>   * @pages: array of page pointers
> @@ -3666,7 +3701,7 @@ void *vmap(struct page **pages, unsigned int count,
>  		return NULL;
>  
>  	size = (unsigned long)count << PAGE_SHIFT;
> -	area = get_vm_area_caller(size, flags, __builtin_return_address(0));
> +	area = vmap_get_aligned_vm_area(size, flags, __builtin_return_address(0));
>  	if (!area)
>  		return NULL;
>  
> -- 
> 2.34.1
> 
Did intensive random mapping/unmaping, so i have not noticed any issues.

Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>

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Uladzislau Rezki