Re: [PATCH 6/6] s390/zcrypt: replace get_zeroed_page() with kzalloc()

[Harald Freudenberger <freude@linux.ibm.com>]

On 2026-05-28 09:09, Mike Rapoport (Microsoft) wrote:
> zcrypt_rng_device_add() allocates a buffer for the software random
> number generator data cache.
> 
> This buffer can be allocated with kmalloc() as there's nothing special
> about it to go directly to the page allocator.
> 
> kmalloc() provides a better API that does not require ugly casts and
> kfree() does not need to know the size of the freed object.
> 
> Performance difference between kmalloc() and __get_free_pages() is not
> measurable as both allocators take an object/page from a per-CPU list 
> for
> fast path allocations.
> 
> For the slow path the performance is anyway determined by the amount of
> reclaim involved rather than by what allocator is used.
> 
> Replace use of get_zeroed_page() with kzalloc() and free_page() with
> kfree().
> 
> Link:
> https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>  drivers/s390/crypto/zcrypt_api.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/s390/crypto/zcrypt_api.c 
> b/drivers/s390/crypto/zcrypt_api.c
> index d6a455df228d..f57189c2b839 100644
> --- a/drivers/s390/crypto/zcrypt_api.c
> +++ b/drivers/s390/crypto/zcrypt_api.c
> @@ -1782,7 +1782,7 @@ int zcrypt_rng_device_add(void)
> 
>  	mutex_lock(&zcrypt_rng_mutex);
>  	if (zcrypt_rng_device_count == 0) {
> -		zcrypt_rng_buffer = (u32 *)get_zeroed_page(GFP_KERNEL);
> +		zcrypt_rng_buffer = kzalloc(PAGE_SIZE, GFP_KERNEL);
>  		if (!zcrypt_rng_buffer) {
>  			rc = -ENOMEM;
>  			goto out;
> @@ -1799,7 +1799,7 @@ int zcrypt_rng_device_add(void)
>  	return 0;
> 
>  out_free:
> -	free_page((unsigned long)zcrypt_rng_buffer);
> +	kfree(zcrypt_rng_buffer);
>  out:
>  	mutex_unlock(&zcrypt_rng_mutex);
>  	return rc;
> @@ -1811,7 +1811,7 @@ void zcrypt_rng_device_remove(void)
>  	zcrypt_rng_device_count--;
>  	if (zcrypt_rng_device_count == 0) {
>  		hwrng_unregister(&zcrypt_rng_dev);
> -		free_page((unsigned long)zcrypt_rng_buffer);
> +		kfree(zcrypt_rng_buffer);
>  	}
>  	mutex_unlock(&zcrypt_rng_mutex);
>  }

Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>