Re: [PATCH] mm/swap_slots.c: Remove unnecessary NULL pointer check

[Matthew Wilcox]

On Sat, Jan 09, 2021 at 03:09:43AM -0500, Miaohe Lin wrote:
> The cache->slots and cache->slots_ret is already checked before we try to
> drain it. And kvfree can handle the NULL pointer itself. So remove the
> NULL pointer check here.

> @@ -178,7 +178,7 @@ static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
>  		swapcache_free_entries(cache->slots + cache->cur, cache->nr);
>  		cache->cur = 0;
>  		cache->nr = 0;
> -		if (free_slots && cache->slots) {
> +		if (free_slots) {

Prove that swapcache_free_entries() doesn't change cache->slots.

> @@ -188,13 +188,12 @@ static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
>  		spin_lock_irq(&cache->free_lock);
>  		swapcache_free_entries(cache->slots_ret, cache->n_ret);
>  		cache->n_ret = 0;
> -		if (free_slots && cache->slots_ret) {
> +		if (free_slots) {

... or ->slots_ret

> -		if (slots)
> -			kvfree(slots);
> +		kvfree(slots);

This is fine.