Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752203AbaDVDEN (ORCPT ); Mon, 21 Apr 2014 23:04:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:4283 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751117AbaDVDEJ (ORCPT ); Mon, 21 Apr 2014 23:04:09 -0400 Date: Tue, 22 Apr 2014 11:01:58 +0800 From: Baoquan He To: Petr Tesarik Cc: Eric Biederman , Andrew Morton , Paul Mackerras , Fengguang Wu , Benjamin Herrenschmidt , Shaohua Li , Alexey Kardashevskiy , Sasha Levin , kexec@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Save PG_head_mask in VMCOREINFO Message-ID: <20140422030158.GJ8084@dhcp-16-105.nay.redhat.com> References: <20140411175039.00fa75ea@hananiah.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140411175039.00fa75ea@hananiah.suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/11/14 at 05:50pm, Petr Tesarik wrote: > To allow filtering of huge pages, makedumpfile must be able to > identify them in the dump. This can be done by checking the > appropriate page flag, so communicate its value to makedumpfile > through the VMCOREINFO interface. > > There's only one small catch. Depending on how many page flags > are available on a given architecture, this bit can be called > PG_head or PG_compound. > > I sent a similar patch back in 2012, but Eric Biederman did not > like using an #ifdef. So, this time I'm adding a common symbol > (PG_head_mask) instead. > > See https://lkml.org/lkml/2012/11/28/91 for the previous version. > > Signed-off-by: Petr Tesarik > --- > include/linux/page-flags.h | 3 +++ > kernel/kexec.c | 1 + > 2 files changed, 4 insertions(+) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index d1fe1a7..bc2007e 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -348,6 +348,9 @@ static inline void ClearPageCompound(struct page > *page) ClearPageHead(page); > } > #endif > + > +#define PG_head_mask ((1L << PG_head)) Hi Petr, I am fine with this trick which define one name PG_head_mask, but can stands for both PG_head and PG_compound. I guess Eric may suggest the implementation like it done in mm/memory-failure.c . In that file it explicitly defines both of them. Thanks Baoquan > + > #else > /* > * Reduce page flag use as much as possible by overlapping > diff --git a/kernel/kexec.c b/kernel/kexec.c > index c8380ad..e6f3aec 100644 > --- a/kernel/kexec.c > +++ b/kernel/kexec.c > @@ -1622,6 +1622,7 @@ static int __init crash_save_vmcoreinfo_init(void) > #ifdef CONFIG_MEMORY_FAILURE > VMCOREINFO_NUMBER(PG_hwpoison); > #endif > + VMCOREINFO_NUMBER(PG_head_mask); > VMCOREINFO_NUMBER(PAGE_BUDDY_MAPCOUNT_VALUE); > > arch_crash_save_vmcoreinfo(); > -- > 1.8.4.5 > > _______________________________________________ > kexec mailing list > kexec@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/