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Date: Fri, 31 Mar 2017 08:50:02 +0200
From: Michal Hocko <mhocko@kernel.org>
Subject: Re: [PATCH 5/6] mm, memory_hotplug: do not associate hotadded memory
 to zones until online
Message-ID: <20170331065002.GD27098@dhcp22.suse.cz>
References: <20170330115454.32154-1-mhocko@kernel.org>
 <20170330115454.32154-6-mhocko@kernel.org>
 <04c901d2a9e6$91968a20$b4c39e60$@alibaba-inc.com>
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To: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: linux-mm@kvack.org, 'Andrew Morton' <akpm@linux-foundation.org>, 'Mel Gorman' <mgorman@suse.de>, 'Vlastimil Babka' <vbabka@suse.cz>, 'Andrea Arcangeli' <aarcange@redhat.com>, 'Reza Arbab' <arbab@linux.vnet.ibm.com>, 'Yasuaki Ishimatsu' <yasu.isimatu@gmail.com>, 'Tang Chen' <tangchen@cn.fujitsu.com>, qiuxishi@huawei.com, 'Kani Toshimitsu' <toshi.kani@hpe.com>, slaoub@gmail.com, 'Joonsoo Kim' <js1304@gmail.com>, 'Andi Kleen' <ak@linux.intel.com>, 'David Rientjes' <rientjes@google.com>, 'Daniel Kiper' <daniel.kiper@oracle.com>, 'Igor Mammedov' <imammedo@redhat.com>, 'Vitaly Kuznetsov' <vkuznets@redhat.com>, 'LKML' <linux-kernel@vger.kernel.org>, 'Dan Williams' <dan.j.williams@gmail.com>, 'Heiko Carstens' <heiko.carstens@de.ibm.com>, 'Lai Jiangshan' <laijs@cn.fujitsu.com>, 'Martin Schwidefsky' <schwidefsky@de.ibm.com>

On Fri 31-03-17 14:18:08, Hillf Danton wrote:
> 
> On March 30, 2017 7:55 PM Michal Hocko wrote:
> > 
> > +static void __meminit resize_zone_range(struct zone *zone, unsigned long start_pfn,
> > +		unsigned long nr_pages)
> > +{
> > +	unsigned long old_end_pfn = zone_end_pfn(zone);
> > +
> > +	if (start_pfn < zone->zone_start_pfn)
> > +		zone->zone_start_pfn = start_pfn;
> > +
> > +	zone->spanned_pages = max(start_pfn + nr_pages, old_end_pfn) - zone->zone_start_pfn;
> > +}
> The implementation above implies zone can only go bigger.

yes, we do not shrink zones currently and I see no poit in doing that
right now.

> Can we resize zone with the given data?

Why couldn't we?

-- 
Michal Hocko
SUSE Labs

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