From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx180.postini.com [74.125.245.180]) by kanga.kvack.org (Postfix) with SMTP id 30C486B0068 for ; Fri, 28 Sep 2012 04:05:11 -0400 (EDT) Received: by pbbrq2 with SMTP id rq2so5347326pbb.14 for ; Fri, 28 Sep 2012 01:05:10 -0700 (PDT) Message-ID: <50655A29.1050303@gmail.com> Date: Fri, 28 Sep 2012 16:04:57 +0800 From: Ni zhan Chen MIME-Version: 1.0 Subject: Re: [PATCH 3/3] memory_hotplug: Don't modify the zone_start_pfn outside of zone_span_writelock() References: <1348728470-5580-1-git-send-email-laijs@cn.fujitsu.com> <1348728470-5580-4-git-send-email-laijs@cn.fujitsu.com> <5064525E.5080901@gmail.com> <506551CF.9090009@cn.fujitsu.com> In-Reply-To: <506551CF.9090009@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, Mel Gorman , Andrew Morton , Jiang Liu , Xishi Qiu , Mel Gorman , Minchan Kim , KAMEZAWA Hiroyuki , Michal Hocko , linux-mm@kvack.org On 09/28/2012 03:29 PM, Lai Jiangshan wrote: > Hi, Chen, > > On 09/27/2012 09:19 PM, Ni zhan Chen wrote: >> On 09/27/2012 02:47 PM, Lai Jiangshan wrote: >>> The __add_zone() maybe call sleep-able init_currently_empty_zone() >>> to init wait_table, >>> >>> But this function also modifies the zone_start_pfn without any lock. >>> It is bugy. >>> >>> So we move this modification out, and we ensure the modification >>> of zone_start_pfn is only done with zone_span_writelock() held or in booting. >>> >>> Since zone_start_pfn is not modified by init_currently_empty_zone() >>> grow_zone_span() needs to check zone_start_pfn before update it. >>> >>> CC: Mel Gorman >>> Signed-off-by: Lai Jiangshan >>> Reported-by: Yasuaki ISIMATU >>> Tested-by: Wen Congyang >>> --- >>> mm/memory_hotplug.c | 2 +- >>> mm/page_alloc.c | 3 +-- >>> 2 files changed, 2 insertions(+), 3 deletions(-) >>> >>> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c >>> index b62d429b..790561f 100644 >>> --- a/mm/memory_hotplug.c >>> +++ b/mm/memory_hotplug.c >>> @@ -205,7 +205,7 @@ static void grow_zone_span(struct zone *zone, unsigned long start_pfn, >>> zone_span_writelock(zone); >>> old_zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages; >>> - if (start_pfn < zone->zone_start_pfn) >>> + if (!zone->zone_start_pfn || start_pfn < zone->zone_start_pfn) >>> zone->zone_start_pfn = start_pfn; >>> zone->spanned_pages = max(old_zone_end_pfn, end_pfn) - >>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c >>> index c13ea75..2545013 100644 >>> --- a/mm/page_alloc.c >>> +++ b/mm/page_alloc.c >>> @@ -3997,8 +3997,6 @@ int __meminit init_currently_empty_zone(struct zone *zone, >>> return ret; >>> pgdat->nr_zones = zone_idx(zone) + 1; >>> - zone->zone_start_pfn = zone_start_pfn; >>> - >> then how can mminit_dprintk print zone->zone_start_pfn ? always print 0 make no sense. > > The full code here: > > mminit_dprintk(MMINIT_TRACE, "memmap_init", > "Initialising map node %d zone %lu pfns %lu -> %lu\n", > pgdat->node_id, > (unsigned long)zone_idx(zone), > zone_start_pfn, (zone_start_pfn + size)); > > > It doesn't always print 0, it still behaves as I expected. > Could you elaborate? Yeah, you are right. I mean mminit_dprintk is called after zone->zone_start_pfn initialized to show initialising state, but after this patch applied zone->zone_start_pfn will not be initialized before this print point. > > Thanks, > Lai > > >>> mminit_dprintk(MMINIT_TRACE, "memmap_init", >>> "Initialising map node %d zone %lu pfns %lu -> %lu\n", >>> pgdat->node_id, >>> @@ -4465,6 +4463,7 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat, >>> ret = init_currently_empty_zone(zone, zone_start_pfn, >>> size, MEMMAP_EARLY); >>> BUG_ON(ret); >>> + zone->zone_start_pfn = zone_start_pfn; >>> memmap_init(size, nid, j, zone_start_pfn); >>> zone_start_pfn += size; >>> } >> > -- 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