Re: [PATCH v2 2/7] mm/swapfile.c: Replace some #ifdef with IS_ENABLED()

[Dave Hansen]

> @@ -878,6 +877,11 @@ static int swap_alloc_cluster(struct swap_info_struct 
> *si, swp_entry_t *slot)
>       unsigned long offset, i;
>       unsigned char *map;
>  
> +     if (!IS_ENABLED(CONFIG_THP_SWAP)) {
> +             VM_WARN_ON_ONCE(1);
> +             return 0;
> +     }

I see you seized the opportunity to keep this code gloriously
unencumbered by pesky comments.  This seems like a time when you might
have slipped up and been temped to add a comment or two.  Guess not. :)

Seriously, though, does it hurt us to add a comment or two to say
something like:

        /*
         * Should not even be attempting cluster allocations when
         * huge page swap is disabled.  Warn and fail the allocation.
         */
        if (!IS_ENABLED(CONFIG_THP_SWAP)) {
                VM_WARN_ON_ONCE(1);
                return 0;
        }