From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oa0-f47.google.com (mail-oa0-f47.google.com [209.85.219.47]) by kanga.kvack.org (Postfix) with ESMTP id 332986B0031 for ; Tue, 24 Jun 2014 11:21:55 -0400 (EDT) Received: by mail-oa0-f47.google.com with SMTP id n16so511789oag.34 for ; Tue, 24 Jun 2014 08:21:54 -0700 (PDT) Received: from g4t3425.houston.hp.com (g4t3425.houston.hp.com. [15.201.208.53]) by mx.google.com with ESMTPS id uq9si789683obc.92.2014.06.24.08.21.54 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 24 Jun 2014 08:21:54 -0700 (PDT) Message-ID: <1403622753.25108.12.camel@misato.fc.hp.com> Subject: Re: [PATCH 2/2] x86,mem-hotplug: modify PGD entry when removing memory From: Toshi Kani Date: Tue, 24 Jun 2014 09:12:33 -0600 In-Reply-To: <53A8C6F6.2060906@jp.fujitsu.com> References: <53A132E2.9000605@jp.fujitsu.com> <53A133ED.2090005@jp.fujitsu.com> <1403289003.25108.3.camel@misato.fc.hp.com> <53A8C6F6.2060906@jp.fujitsu.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Yasuaki Ishimatsu Cc: akpm@linux-foundation.org, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, tangchen@cn.fujitsu.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, guz.fnst@cn.fujitsu.com, zhangyanfei@cn.fujitsu.com On Tue, 2014-06-24 at 09:31 +0900, Yasuaki Ishimatsu wrote: > (2014/06/21 3:30), Toshi Kani wrote: > > On Wed, 2014-06-18 at 15:38 +0900, Yasuaki Ishimatsu wrote: > > : > >> @@ -186,7 +186,12 @@ void sync_global_pgds(unsigned long start, unsigned long end) > >> const pgd_t *pgd_ref = pgd_offset_k(address); > >> struct page *page; > >> > >> - if (pgd_none(*pgd_ref)) > >> + /* > >> + * When it is called after memory hot remove, pgd_none() > >> + * returns true. In this case (removed == 1), we must clear > >> + * the PGD entries in the local PGD level page. > >> + */ > >> + if (pgd_none(*pgd_ref) && !removed) > >> continue; > >> > >> spin_lock(&pgd_lock); > >> @@ -199,12 +204,18 @@ void sync_global_pgds(unsigned long start, unsigned long end) > >> pgt_lock = &pgd_page_get_mm(page)->page_table_lock; > >> spin_lock(pgt_lock); > >> > >> - if (pgd_none(*pgd)) > >> - set_pgd(pgd, *pgd_ref); > >> - else > > >> + if (!pgd_none(*pgd_ref) && !pgd_none(*pgd)) > >> BUG_ON(pgd_page_vaddr(*pgd) > >> != pgd_page_vaddr(*pgd_ref)); > >> > >> + if (removed) { > > > > Shouldn't this condition be "else if"? > > The first if sentence checks whether PGDs hit to BUG_ON. And the second > if sentence checks whether the function was called after hot-removing memory. > I think that the first if sentence and the second if sentence check different > things. So I think the condition should be "if" sentence. When the 1st if sentence is true, you have no additional operation and the 2nd if sentence is redundant. But I agree that the two ifs can be logically separated. So: Acked-by: Toshi Kani Thanks, -Toshi -- 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