linux-kernel - Re: [PATCH v3 6/9] mm, memory_hotplug: do not associate hotadded memory to zones until online

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Message-ID: <54f98d7c-2a7a-b81a-0e8b-85a4b55ebe9b@suse.cz>
Date:   Thu, 20 Apr 2017 12:51:42 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Michal Hocko <mhocko@...nel.org>,
        Dan Williams <dan.j.williams@...il.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
        slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Lai Jiangshan <laijs@...fujitsu.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: [PATCH v3 6/9] mm, memory_hotplug: do not associate hotadded
 memory to zones until online

On 04/20/2017 11:06 AM, Michal Hocko wrote:
> On Thu 20-04-17 10:25:27, Vlastimil Babka wrote:
>>> + * intersection with the given zone
>>> + */
>>> +static inline bool zone_intersects(struct zone *zone,
>>> +		unsigned long start_pfn, unsigned long nr_pages)
>>> +{
>>
>> I'm looking at your current mmotm tree branch, which looks like this:
>>
>> + * Return true if [start_pfn, start_pfn + nr_pages) range has a non-mpty
>> + * intersection with the given zone
>> + */
>> +static inline bool zone_intersects(struct zone *zone,
>> +               unsigned long start_pfn, unsigned long nr_pages)
>> +{
>> +       if (zone_is_empty(zone))
>> +               return false;
>> +       if (zone->zone_start_pfn <= start_pfn && start_pfn < zone_end_pfn(zone))
>> +               return true;
>> +       if (start_pfn + nr_pages > zone->zone_start_pfn)
>> +               return true;
>>
>> A false positive is possible here, when start_pfn >= zone_end_pfn(zone)?
> 
> Ohh, right. Looks better?

Yeah.

You can add for the whole patch

Acked-by: Vlastimil Babka <vbabka@...e.cz>

But I can't guarantee some corner case won't surface. The hotplug code
is far from straightforward :(