linux-kernel - Re: [PATCH v2] drivers/base/node.c: Simplify unregister_memory_block_under

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Message-Id: <13549413-C422-4661-9E7E-4DBC63B8997C@redhat.com>
Date:   Wed, 27 Nov 2019 23:55:42 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Michal Hocko <mhocko@...e.com>,
        Oscar Salvador <osalvador@...e.de>,
        Chris von Recklinghausen <crecklin@...hat.com>
Subject: Re: [PATCH v2] drivers/base/node.c: Simplify unregister_memory_block_under_nodes()



> Am 27.11.2019 um 23:15 schrieb Andrew Morton <akpm@...ux-foundation.org>:
> 
> On Wed, 27 Nov 2019 17:53:12 +0100 David Hildenbrand <david@...hat.com> wrote:
> 
>> Just a note that this was actually also a bugfix as noted by Chris.
>> 
>> If the memory we are removing was never onlined,
>> get_nid_for_pfn()->pfn_to_nid() will return garbage. Removing will
>> succeed but links will remain in place.
>> 
>> Can be triggered by
>> 
>> 1. hotplugging a DIMM to node 1
>> 2. not onlining the memory blocks
>> 3. unplugging it
>> 4. re-plugging it to node 1
>> 
>> We will trigger the BUG_ON(ret) in add_memory_resource(), because
>> link_mem_sections() will return with -EEXIST.
> 
> Oh.  In that case case we please redo the patch as a bugfix? 
> Appropriate title and changelog?  And perhaps the bugfix can be split
> from the cleanup, to make the former more backportable?

This is already upstream (d84f2f5a7552 ),so I‘m afraid we can‘t do anything about it. (When your cleanups turn into bugfixes ...).

I can still try to send stable patches, though ...