Re: [PATCH v2 1/2] mm/vmalloc: extract vmalloc_free_pages() helper from vfree()

[Uladzislau Rezki <urezki@gmail.com>]

On Wed, Mar 04, 2026 at 08:23:15PM +0530, Shivam Kalra via B4 Relay wrote:
> From: Shivam Kalra <shivamkalra98@zohomail.in>
> 
> Extract the page-freeing loop and NR_VMALLOC stat accounting from
> vfree() into a reusable vmalloc_free_pages() helper. The helper operates
> on a range [start, end) of pages from a vm_struct, making it suitable
> for both full free (vfree) and partial free (upcoming vrealloc shrink).
> 
> No functional change.
> 
> Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
> ---
>  mm/vmalloc.c | 42 ++++++++++++++++++++++++++++--------------
>  1 file changed, 28 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index c607307c657a..e2aef0a79f2e 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3416,6 +3416,32 @@ void vfree_atomic(const void *addr)
>  		schedule_work(&p->wq);
>  }
>  
> +/*
> + * vmalloc_free_pages - free a range of pages from a vmalloc allocation
> + * @vm: the vm_struct containing the pages
> + * @start: first page index to free (inclusive)
> + * @end: last page index to free (exclusive)
> + *
> + * Free pages [start, end) updating NR_VMALLOC stat accounting.
> + * Caller is responsible for unmapping (vunmap_range) and KASAN
> + * poisoning before calling this.
> + */
> +static void vmalloc_free_pages(struct vm_struct *vm, unsigned int start,
> +			       unsigned int end)
> +{
> +	unsigned int i;
> +
> +	for (i = start; i < end; i++) {
> +		struct page *page = vm->pages[i];
> +
> +		BUG_ON(!page);
> +		if (!(vm->flags & VM_MAP_PUT_PAGES))
> +			mod_lruvec_page_state(page, NR_VMALLOC, -1);
> +		__free_page(page);
> +		cond_resched();
> +	}
> +}
> +
>  /**
>   * 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);
> @@ -3459,19 +3484,8 @@ void vfree(const void *addr)
>  
>  	if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS))
>  		vm_reset_perms(vm);
> -	for (i = 0; i < vm->nr_pages; i++) {
> -		struct page *page = vm->pages[i];
> -
> -		BUG_ON(!page);
> -		/*
> -		 * High-order allocs for huge vmallocs are split, so
> -		 * can be freed as an array of order-0 allocations
> -		 */
> -		if (!(vm->flags & VM_MAP_PUT_PAGES))
> -			mod_lruvec_page_state(page, NR_VMALLOC, -1);
> -		__free_page(page);
> -		cond_resched();
> -	}
> +	if (vm->nr_pages)
> +		vmalloc_free_pages(vm, 0, vm->nr_pages);
>  	kvfree(vm->pages);
>
probably we should move "if (vm->nr_pages)" condition inside the
vmalloc_free_pages(). 

I think, the function name should also be renamed to something like
vm_area_free_pages() so we align with vm_area_alloc_pages() helper.

--
Uladzislau Rezki