Re: [PATCH v6 6/6] mm/vmalloc: align vm_area so vmap() can batch mappings

[Dev Jain]

On 09/07/26 1:08 pm, 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. We do not expect any significant overhead for
> this.
> 
> 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>
> Tested-by: Leo Yan <leo.yan@xxxxxxx>
> Reviewed-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> ---

Reviewed-by: Dev Jain <dev.jain@xxxxxxx>


>  mm/vmalloc.c | 35 ++++++++++++++++++++++++++++++++++-
>  1 file changed, 34 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index db0492151ad08..2ac805cdf18ad 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3314,6 +3314,14 @@ struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
>  				  NUMA_NO_NODE, GFP_KERNEL, caller);
>  }
>  
> +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);
> +}
> +
>  /**
>   * find_vm_area - find a continuous kernel virtual area
>   * @addr:	  base address
> @@ -3626,6 +3634,30 @@ static int vmap_pages_range_batched(unsigned long addr, unsigned long end,
>  	return err;
>  }
>  
> +static struct vm_struct *vmap_get_aligned_vm_area(unsigned long size,
> +		unsigned long flags, pgprot_t prot, const void *caller)
> +{
> +	struct vm_struct *vm_area;
> +	unsigned int shift;
> +
> +	if (arch_vmap_pmd_supported(prot) && size >= PMD_SIZE) {
> +		vm_area = __get_vm_area_node_aligned_caller(size, PMD_SIZE,
> +				flags, caller);
> +		if (vm_area)
> +			return vm_area;
> +	}
> +
> +	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;
> +	}
> +
> +	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
> @@ -3664,7 +3696,8 @@ 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, prot,
> +				__builtin_return_address(0));
>  	if (!area)
>  		return NULL;
>