From: Minchan Kim <minchan@kernel.org> To: Vlastimil Babka <vbabka@suse.cz> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>, Andrew Morton <akpm@linux-foundation.org>, <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>, <kernel-team@lge.com>, Michal Hocko <mhocko@suse.com>, "Kirill A . Shutemov" <kirill@shutemov.name>, Johannes Weiner <hannes@cmpxchg.org>, Chen Gang <gang.chen.5i5j@gmail.com> Subject: Re: [PATCH] mm: Do not use double negation for testing page flags Date: Thu, 9 Mar 2017 15:42:24 +0900 [thread overview] Message-ID: <20170309064224.GD854@bbox> (raw) In-Reply-To: <6f9274f7-6d2e-60a6-c36a-78f8f79004aa@suse.cz> Hi Vlastimil, On Wed, Mar 08, 2017 at 08:51:23AM +0100, Vlastimil Babka wrote: > 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 Nice catch! It seems you have a crystal ball. ;-) > > > 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 <vbabka@suse.cz> Thanks!
WARNING: multiple messages have this Message-ID (diff)
From: Minchan Kim <minchan@kernel.org> To: Vlastimil Babka <vbabka@suse.cz> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>, Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@lge.com, Michal Hocko <mhocko@suse.com>, "Kirill A . Shutemov" <kirill@shutemov.name>, Johannes Weiner <hannes@cmpxchg.org>, Chen Gang <gang.chen.5i5j@gmail.com> Subject: Re: [PATCH] mm: Do not use double negation for testing page flags Date: Thu, 9 Mar 2017 15:42:24 +0900 [thread overview] Message-ID: <20170309064224.GD854@bbox> (raw) In-Reply-To: <6f9274f7-6d2e-60a6-c36a-78f8f79004aa@suse.cz> Hi Vlastimil, On Wed, Mar 08, 2017 at 08:51:23AM +0100, Vlastimil Babka wrote: > 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 Nice catch! It seems you have a crystal ball. ;-) > > > 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 <vbabka@suse.cz> Thanks! -- 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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-03-09 6:42 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-03-07 6:36 [PATCH] mm: Do not use double negation for testing page flags Minchan Kim 2017-03-07 6:36 ` Minchan Kim 2017-03-07 16:01 ` Anshuman Khandual 2017-03-07 16:01 ` Anshuman Khandual 2017-03-08 5:25 ` Minchan Kim 2017-03-08 5:25 ` Minchan Kim 2017-03-08 7:51 ` Vlastimil Babka 2017-03-08 7:51 ` Vlastimil Babka 2017-03-08 9:18 ` Michal Hocko 2017-03-08 9:18 ` Michal Hocko 2017-03-09 6:42 ` Minchan Kim [this message] 2017-03-09 6:42 ` Minchan Kim 2017-03-07 17:39 ` Johannes Weiner 2017-03-07 17:39 ` Johannes Weiner
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