linux-kernel - Re: [PATCH v2 2/7] mm/swapfile.c: Replace some #ifdef with IS

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Message-ID: <ec1c459d-4366-8134-59d3-bc48d9fc5acd@linux.intel.com>
Date:   Wed, 18 Jul 2018 08:15:58 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     "Huang, Ying" <ying.huang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Shaohua Li <shli@...nel.org>, Hugh Dickins <hughd@...gle.com>,
        Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...hat.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH v2 2/7] mm/swapfile.c: Replace some #ifdef with
 IS_ENABLED()

On 07/17/2018 08:25 PM, Huang, Ying wrote:
>> 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;
>> 	}
> I totally agree with you that we should add more comments for THP swap
> to improve the code readability.  As for this specific case,
> VM_WARN_ON_ONCE() here is just to capture some programming error during
> development.  Do we really need comments here?

If it's code in mainline, we need to know what it is doing.

If it's not useful to have in mainline, then let's remove it.