linux-kernel - Re: [PATCH v3] resource: Merge resources on a node when hot-adding memory

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Message-ID: <41eb4fc8-3b57-478b-05b4-88bed24ed66e@suse.cz>
Date:   Fri, 10 Aug 2018 10:28:26 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Rashmica Gupta <rashmica.g@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     toshi.kani@....com, tglx@...utronix.de, bp@...e.de,
        brijesh.singh@....com, thomas.lendacky@....com, jglisse@...hat.com,
        gregkh@...uxfoundation.org, baiyaowei@...s.chinamobile.com,
        dan.j.williams@...el.com, mhocko@...e.com, iamjoonsoo.kim@....com,
        malat@...ian.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        osalvador@...hadventures.net, yasu.isimatu@...il.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>
Subject: Re: [PATCH v3] resource: Merge resources on a node when hot-adding
 memory

On 08/10/2018 08:55 AM, Rashmica Gupta wrote:
> On Fri, Aug 10, 2018 at 11:12 AM, Andrew Morton
> <akpm@...ux-foundation.org> wrote:
>>
>> What is the end-user impact of this patch?
>>
> 
> Only architectures/setups that allow the user to remove and add memory of
> different sizes or different start addresses from the kernel at runtime will
> potentially encounter the resource fragmentation.
> 
> Trying to remove memory that overlaps iomem resources the first time
> gives us this warning: "Unable to release resource <%pa-%pa>".
> 
> Attempting a second time results in a kernel oops (on ppc at least).

An oops? I think that should be investigated and fixed, even if resource
merging prevents it. Do you have the details?

Thanks,
Vlastimil