From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752751AbcAZX3o (ORCPT ); Tue, 26 Jan 2016 18:29:44 -0500 Received: from mail-pa0-f49.google.com ([209.85.220.49]:33011 "EHLO mail-pa0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752642AbcAZX3k (ORCPT ); Tue, 26 Jan 2016 18:29:40 -0500 Date: Tue, 26 Jan 2016 15:29:38 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Heiko Carstens cc: Christian Borntraeger , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH/RFC 3/3] s390: query dynamic DEBUG_PAGEALLOC setting In-Reply-To: <20160126181903.GB4671@osiris> Message-ID: References: <1453799905-10941-1-git-send-email-borntraeger@de.ibm.com> <1453799905-10941-4-git-send-email-borntraeger@de.ibm.com> <20160126181903.GB4671@osiris> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 26 Jan 2016, Heiko Carstens wrote: > On Tue, Jan 26, 2016 at 10:18:25AM +0100, Christian Borntraeger wrote: > > We can use debug_pagealloc_enabled() to check if we can map > > the identity mapping with 1MB/2GB pages as well as to print > > the current setting in dump_stack. > > > > Signed-off-by: Christian Borntraeger > > --- > > arch/s390/kernel/dumpstack.c | 4 +++- > > arch/s390/mm/vmem.c | 10 ++++------ > > 2 files changed, 7 insertions(+), 7 deletions(-) > > > > diff --git a/arch/s390/kernel/dumpstack.c b/arch/s390/kernel/dumpstack.c > > index dc8e204..a1c0530 100644 > > --- a/arch/s390/kernel/dumpstack.c > > +++ b/arch/s390/kernel/dumpstack.c > > @@ -11,6 +11,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > @@ -186,7 +187,8 @@ void die(struct pt_regs *regs, const char *str) > > printk("SMP "); > > #endif > > #ifdef CONFIG_DEBUG_PAGEALLOC > > - printk("DEBUG_PAGEALLOC"); > > + printk("DEBUG_PAGEALLOC(%s)", > > + debug_pagealloc_enabled() ? "enabled" : "disabled"); > > #endif > > I'd prefer if you change this to > > if (debug_pagealloc_enabled()) > printk("DEBUG_PAGEALLOC"); > > That way we can get rid of yet another ifdef. Having > "DEBUG_PAGEALLOC(disabled)" doesn't seem to be very helpful. > I'd agree if CONFIG_DEBUG_PAGEALLOC only did anything when debug_pagealloc_enabled() is true, but that doesn't seem to be the case. When CONFIG_DEBUG_SLAB is enabled, for instance, CONFIG_DEBUG_PAGEALLOC also enables stackinfo storing and poisoning and it's not guarded by debug_pagealloc_enabled(). It seems like CONFIG_DEBUG_PAGEALLOC enables debugging functionality outside the scope of the debug_pagealloc=on kernel parameter, so DEBUG_PAGEALLOC(disabled) actually does mean something.