Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752510Ab0GMDYf (ORCPT ); Mon, 12 Jul 2010 23:24:35 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:48226 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751708Ab0GMDYe (ORCPT ); Mon, 12 Jul 2010 23:24:34 -0400 X-SecurityPolicyCheck-FJ: OK by FujitsuOutboundMailChecker v1.3.1 Date: Tue, 13 Jul 2010 12:19:47 +0900 From: KAMEZAWA Hiroyuki To: Minchan Kim Cc: linux@arm.linux.org.uk, Yinghai Lu , "H. Peter Anvin" , Andrew Morton , Shaohua Li , Yakui Zhao , linux-kernel@vger.kernel.org, linux-mm@kvack.org, arm-kernel@lists.infradead.org, kgene.kim@samsung.com, Mel Gorman Subject: Re: [RFC] Tight check of pfn_valid on sparsemem Message-Id: <20100713121947.612bd656.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20100712155348.GA2815@barrios-desktop> References: <20100712155348.GA2815@barrios-desktop> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 3.0.3 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4058 Lines: 131 On Tue, 13 Jul 2010 00:53:48 +0900 Minchan Kim wrote: > Kukjin, Could you test below patch? > I don't have any sparsemem system. Sorry. > > -- CUT DOWN HERE -- > > Kukjin reported oops happen while he change min_free_kbytes > http://www.spinics.net/lists/arm-kernel/msg92894.html > It happen by memory map on sparsemem. > > The system has a memory map following as. > section 0 section 1 section 2 > 0x20000000-0x25000000, 0x40000000-0x50000000, 0x50000000-0x58000000 > SECTION_SIZE_BITS 28(256M) > > It means section 0 is an incompletely filled section. > Nontheless, current pfn_valid of sparsemem checks pfn loosely. > > It checks only mem_section's validation. > So in above case, pfn on 0x25000000 can pass pfn_valid's validation check. > It's not what we want. > > The Following patch adds check valid pfn range check on pfn_valid of sparsemem. > > Signed-off-by: Minchan Kim > Reported-by: Kukjin Kim > > P.S) > It is just RFC. If we agree with this, I will make the patch on mmotm. > > -- > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index b4d109e..6c2147a 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -979,6 +979,8 @@ struct mem_section { > struct page_cgroup *page_cgroup; > unsigned long pad; > #endif > + unsigned long start_pfn; > + unsigned long end_pfn; > }; > I have 2 concerns. 1. This makes mem_section twice. Wasting too much memory and not good for cache. But yes, you can put this under some CONFIG which has small number of mem_section[]. 2. This can't be help for a case where a section has multiple small holes. Then, my proposal for HOLES_IN_MEMMAP sparsemem is below. == Some architectures unmap memmap[] for memory holes even with SPARSEMEM. To handle that, pfn_valid() should check there are really memmap or not. For that purpose, __get_user() can be used. This idea is from ia64_pfn_valid(). Signed-off-by: KAMEZAWA Hiroyuki --- include/linux/mmzone.h | 12 ++++++++++++ mm/sparse.c | 17 +++++++++++++++++ 2 files changed, 29 insertions(+) Index: mmotm-2.6.35-0701/include/linux/mmzone.h =================================================================== --- mmotm-2.6.35-0701.orig/include/linux/mmzone.h +++ mmotm-2.6.35-0701/include/linux/mmzone.h @@ -1047,12 +1047,24 @@ static inline struct mem_section *__pfn_ return __nr_to_section(pfn_to_section_nr(pfn)); } +#ifndef CONFIG_ARCH_HAS_HOLES_IN_MEMMAP static inline int pfn_valid(unsigned long pfn) { if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS) return 0; return valid_section(__nr_to_section(pfn_to_section_nr(pfn))); } +#else +extern int pfn_valid_mapped(unsigned long pfn); +static inline int pfn_valid(unsigned long pfn) +{ + if (pfn_to_seciton_nr(pfn) >= NR_MEM_SECTIONS) + return 0; + if (!valid_section(__nr_to_section(pfn_to_section_nr(pfn)))) + return 0; + return pfn_valid_mapped(pfn); +} +#endif static inline int pfn_present(unsigned long pfn) { Index: mmotm-2.6.35-0701/mm/sparse.c =================================================================== --- mmotm-2.6.35-0701.orig/mm/sparse.c +++ mmotm-2.6.35-0701/mm/sparse.c @@ -799,3 +799,20 @@ void sparse_remove_one_section(struct zo free_section_usemap(memmap, usemap); } #endif + +#ifdef CONFIG_ARCH_HAS_HOLES_IN_MEMMAP +int pfn_valid_mapped(unsigned long pfn) +{ + struct page *page = pfn_to_page(pfn); + char *lastbyte = (char *)(page+1)-1; + char byte; + + if(__get_user(byte, page) != 0) + return 0; + + if ((((unsigned long)page) & PAGE_MASK) == + (((unsigned long)lastbyte) & PAGE_MASK)) + return 1; + return (__get_user(byte,lastbyte) == 0); +} +#endif -- 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/