Re: [PATCH v12 1/5] mm/vmalloc: extract vm_area_free_pages() helper from vfree()

[Uladzislau Rezki <urezki@gmail.com>]

On Tue, Apr 28, 2026 at 01:54:16AM +0530, Shivam Kalra via B4 Relay wrote:
> From: Shivam Kalra <shivamkalra98@zohomail.in>
> 
> Extract page freeing and NR_VMALLOC stat accounting from
> vfree() into a reusable vm_area_free_pages() helper.
> The helper operates on a range [start_idx, end_idx) of pages
> from a vm_struct, making it suitable for both full free (vfree)
> and partial free (upcoming vrealloc shrink).
> 
> Freed page pointers in vm->pages[] are set to NULL
> to prevent stale references when the vm_struct outlives the
> free (as in vrealloc shrink).
> 
> Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
> ---
>  mm/vmalloc.c | 34 +++++++++++++++++++++++++++-------
>  1 file changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 878c5b7bf837..1073abb6094e 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3416,6 +3416,32 @@ void vfree_atomic(const void *addr)
>  		schedule_work(&p->wq);
>  }
>  
> +/*
> + * vm_area_free_pages - free a range of pages from a vmalloc allocation
> + * @vm: the vm_struct containing the pages
> + * @start_idx: first page index to free (inclusive)
> + * @end_idx: last page index to free (exclusive)
> + *
> + * Free pages [start_idx, end_idx) updating NR_VMALLOC stat accounting.
> + * Freed vm->pages[] entries are set to NULL.
> + * Caller is responsible for unmapping (vunmap_range) and KASAN
> + * poisoning before calling this.
> + */
> +static void vm_area_free_pages(struct vm_struct *vm, unsigned int start_idx,
> +			       unsigned int end_idx)
> +{
> +	unsigned int i;
> +
> +	if (!(vm->flags & VM_MAP_PUT_PAGES)) {
> +		for (i = start_idx; i < end_idx; i++)
> +			mod_lruvec_page_state(vm->pages[i], NR_VMALLOC, -1);
> +	}
> +	free_pages_bulk(vm->pages + start_idx, end_idx - start_idx);
> +
> +	for (i = start_idx; i < end_idx; i++)
> +		vm->pages[i] = NULL;
> +}
> +
>  /**
>   * vfree - Release memory allocated by vmalloc()
>   * @addr:  Memory base address
> @@ -3436,7 +3462,6 @@ void vfree_atomic(const void *addr)
>  void vfree(const void *addr)
>  {
>  	struct vm_struct *vm;
> -	int i;
>  
>  	if (unlikely(in_interrupt())) {
>  		vfree_atomic(addr);
> @@ -3460,12 +3485,7 @@ void vfree(const void *addr)
>  	if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS))
>  		vm_reset_perms(vm);
>  
> -	if (!(vm->flags & VM_MAP_PUT_PAGES)) {
> -		for (i = 0; i < vm->nr_pages; i++)
> -			mod_lruvec_page_state(vm->pages[i], NR_VMALLOC, -1);
> -	}
> -	free_pages_bulk(vm->pages, vm->nr_pages);
> -
> +	vm_area_free_pages(vm, 0, vm->nr_pages);
>  	kvfree(vm->pages);
>  	kfree(vm);
>  }
> 
> -- 
> 2.43.0
> 
> 
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Uladzislau Rezki