Date: Wed, 5 Apr 2017 10:48:52 -0500
From: Reza Arbab <arbab@linux.vnet.ibm.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>,
        Andrea Arcangeli <aarcange@redhat.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>,
        Zhang Zhen <zhenzhang.zhang@huawei.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>,
        Chris Metcalf <cmetcalf@mellanox.com>,
        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>
Subject: Re: [PATCH 0/6] mm: make movable onlining suck less
References: <20170403204213.rs7k2cvsnconel2z@arbab-laptop>
 <20170404072329.GA15132@dhcp22.suse.cz>
 <20170404073412.GC15132@dhcp22.suse.cz>
 <20170404082302.GE15132@dhcp22.suse.cz>
 <20170404160239.ftvuxklioo6zvuxl@arbab-laptop>
 <20170404164452.GQ15132@dhcp22.suse.cz>
 <20170404183012.a6biape5y7vu6cjm@arbab-laptop>
 <20170404194122.GS15132@dhcp22.suse.cz>
 <20170404214339.6o4c4uhwudyhzbbo@arbab-laptop>
 <20170405064239.GB6035@dhcp22.suse.cz>
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On Wed, Apr 05, 2017 at 08:42:39AM +0200, Michal Hocko wrote:
>On Tue 04-04-17 16:43:39, Reza Arbab wrote:
>> Okay, getting further. With this I can again repeatedly add and 
>> remove, but now I'm seeing a weird variation of that earlier issue:
>>
>> 1. add_memory(), online_movable
>>   /sys/devices/system/node/nodeX/memoryY symlinks are created.
>>
>> 2. offline, remove_memory()
>>   The node is offlined, since all memory has been removed, so all of
>>   /sys/devices/system/node/nodeX is gone. This is normal.
>>
>> 3. add_memory(), online_movable
>>   The node is onlined, so /sys/devices/system/node/nodeX is recreated,
>>   and the memory is added, but just like earlier in this email thread,
>>   the memoryY links are not there.
>
>Could you add some printks to see why the sysfs creation failed please?

Ah, simple enough. It's this, right at the top of 
register_mem_sect_under_node():

	if (!node_online(nid))
		return 0;

That being the case, I really don't understand why your patches make any 
difference. Is node_set_online() being called later than before somehow?

-- 
Reza Arbab