From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id 49B7D6B03BD for ; Wed, 8 Mar 2017 02:51:27 -0500 (EST) Received: by mail-wm0-f71.google.com with SMTP id g8so8650323wmg.7 for ; Tue, 07 Mar 2017 23:51:27 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id x61si3223145wrb.294.2017.03.07.23.51.25 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 07 Mar 2017 23:51:25 -0800 (PST) Subject: Re: [PATCH] mm: Do not use double negation for testing page flags References: <1488868597-32222-1-git-send-email-minchan@kernel.org> <8b5c4679-484e-fe7f-844b-af5fd41b01e0@linux.vnet.ibm.com> <20170308052555.GB11206@bbox> From: Vlastimil Babka Message-ID: <6f9274f7-6d2e-60a6-c36a-78f8f79004aa@suse.cz> Date: Wed, 8 Mar 2017 08:51:23 +0100 MIME-Version: 1.0 In-Reply-To: <20170308052555.GB11206@bbox> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim , Anshuman Khandual Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@lge.com, Michal Hocko , "Kirill A . Shutemov" , Johannes Weiner , Chen Gang On 03/08/2017 06:25 AM, Minchan Kim wrote: > Hi Anshuman, > > On Tue, Mar 07, 2017 at 09:31:18PM +0530, Anshuman Khandual wrote: >> On 03/07/2017 12:06 PM, Minchan Kim wrote: >>> With the discussion[1], I found it seems there are every PageFlags >>> functions return bool at this moment so we don't need double >>> negation any more. >>> Although it's not a problem to keep it, it makes future users >>> confused to use dobule negation for them, too. >>> >>> Remove such possibility. >> >> A quick search of '!!Page' in the source tree does not show any other >> place having this double negation. So I guess this is all which need >> to be fixed. > > Yeb. That's the why my patch includes only khugepagd part but my > concern is PageFlags returns int type not boolean so user might > be confused easily and tempted to use dobule negation. > > Other side is they who create new custom PageXXX(e.g., PageMovable) > should keep it in mind that they should return 0 or 1 although > fucntion prototype's return value is int type. > It shouldn't be > documented nowhere. Was this double negation intentional? :P > Although we can add a little description > somewhere in page-flags.h, I believe changing to boolean is more > clear/not-error-prone so Chen's work is enough worth, I think. Agree, unless some arches benefit from the int by performance for some reason (no idea if it's possible). Anyway, to your original patch: Acked-by: Vlastimil Babka -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org