Re: [kvm-unit-tests PATCH v2 03/11] lib/vmalloc: add some asserts and improvements

[Janosch Frank <frankja@linux.ibm.com>]

On 1/15/21 1:37 PM, Claudio Imbrenda wrote:
> Add some asserts to make sure the state is consistent.
> 
> Simplify and improve the readability of vm_free.
> 
> If a NULL pointer is freed, no operation is performed.
> 
> Fixes: 3f6fee0d4da4 ("lib/vmalloc: vmalloc support for handling allocation metadata")
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

Acked-by: Janosch Frank <frankja@de.ibm.com>

> ---
>  lib/vmalloc.c | 22 +++++++++++++---------
>  1 file changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/lib/vmalloc.c b/lib/vmalloc.c
> index 986a34c..6b52790 100644
> --- a/lib/vmalloc.c
> +++ b/lib/vmalloc.c
> @@ -162,13 +162,16 @@ static void *vm_memalign(size_t alignment, size_t size)
>  static void vm_free(void *mem)
>  {
>  	struct metadata *m;
> -	uintptr_t ptr, end;
> +	uintptr_t ptr, page, i;
>  
> +	if (!mem)
> +		return;
>  	/* the pointer is not page-aligned, it was a single-page allocation */
>  	if (!IS_ALIGNED((uintptr_t)mem, PAGE_SIZE)) {
>  		assert(GET_MAGIC(mem) == VM_MAGIC);
> -		ptr = virt_to_pte_phys(page_root, mem) & PAGE_MASK;
> -		free_page(phys_to_virt(ptr));
> +		page = virt_to_pte_phys(page_root, mem) & PAGE_MASK;
> +		assert(page);
> +		free_page(phys_to_virt(page));
>  		return;
>  	}
>  
> @@ -176,13 +179,14 @@ static void vm_free(void *mem)
>  	m = GET_METADATA(mem);
>  	assert(m->magic == VM_MAGIC);
>  	assert(m->npages > 0);
> +	assert(m->npages < BIT_ULL(BITS_PER_LONG - PAGE_SHIFT));
>  	/* free all the pages including the metadata page */
> -	ptr = (uintptr_t)mem - PAGE_SIZE;
> -	end = ptr + m->npages * PAGE_SIZE;
> -	for ( ; ptr < end; ptr += PAGE_SIZE)
> -		free_page(phys_to_virt(virt_to_pte_phys(page_root, (void *)ptr)));
> -	/* free the last one separately to avoid overflow issues */
> -	free_page(phys_to_virt(virt_to_pte_phys(page_root, (void *)ptr)));
> +	ptr = (uintptr_t)m & PAGE_MASK;
> +	for (i = 0 ; i < m->npages + 1; i++, ptr += PAGE_SIZE) {

s/i < m->npages + 1/i <= m->npages/ ?

> +		page = virt_to_pte_phys(page_root, (void *)ptr) & PAGE_MASK;
> +		assert(page);
> +		free_page(phys_to_virt(page));
> +	}
>  }
>  
>  static struct alloc_ops vmalloc_ops = {
>