linux-kernel - Re: [PATCH v4 1/2] memory-hotplug: add automatic onlining policy for the newly added memory

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Message-ID: <87io2v0yup.fsf@vitty.brq.redhat.com>
Date:	Fri, 15 Jan 2016 14:13:50 +0100
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	linux-mm@...ck.org, Jonathan Corbet <corbet@....net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Daniel Kiper <daniel.kiper@...cle.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	David Vrabel <david.vrabel@...rix.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Xishi Qiu <qiuxishi@...wei.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Igor Mammedov <imammedo@...hat.com>,
	Kay Sievers <kay@...y.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xenproject.org
Subject: Re: [PATCH v4 1/2] memory-hotplug: add automatic onlining policy for the newly added memory

David Rientjes <rientjes@...gle.com> writes:

> On Thu, 14 Jan 2016, Vitaly Kuznetsov wrote:
>
>> > My suggestion is to just simply document that auto-onlining can add the 
>> > memory but fail to online it and the failure is silent to userspace.  If 
>> > userspace cares, it can check the online status of the added memory blocks 
>> > itself.
>> 
>> The problem is not only that it's silent, but also that
>> /sys/devices/system/memory/*/state will lie as we create all memory
>> blocks in MEM_ONLINE state and from online_pages() error we can't figure
>> out which particular block failed. 'v5' which I sent yesterday is
>> supposed to fix the issue (blocks are onlined with
>> memory_block_change_state() which handles failures.
>> 
>
> Would you mind documenting that in the memory-hotplug.txt as an add-on 
> patch to your v5, which appears ready to go?

Sure,

I'll mention possible failures diring automatic onlining. It seems v5
wasn't picked by Andrew and I also have one nitpick in PATCH 2 to
address so I'll send v6.

Thanks,

-- 
  Vitaly