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Subject: Re: [PATCH v2 2/7] mm/swapfile.c: Replace some #ifdef with
 IS_ENABLED()
References: <20180717005556.29758-1-ying.huang@intel.com>
 <20180717005556.29758-3-ying.huang@intel.com>
 <10878744-8db0-1d2c-e899-7c132d78e153@linux.intel.com>
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From: Dave Hansen <dave.hansen@linux.intel.com>
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Date: Wed, 18 Jul 2018 08:15:58 -0700
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To: "Huang, Ying" <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Michal Hocko <mhocko@suse.com>, Johannes Weiner <hannes@cmpxchg.org>, Shaohua Li <shli@kernel.org>, Hugh Dickins <hughd@google.com>, Minchan Kim <minchan@kernel.org>, Rik van Riel <riel@redhat.com>, Daniel Jordan <daniel.m.jordan@oracle.com>, Dan Williams <dan.j.williams@intel.com>

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.