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Date: Mon, 1 Jul 2019 14:47:17 +0200
From: Michal Hocko <mhocko@kernel.org>
To: David Hildenbrand <david@redhat.com>
Subject: Re: [PATCH v3 03/11] s390x/mm: Implement arch_remove_memory()
Message-ID: <20190701124717.GU6376@dhcp22.suse.cz>
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Cc: Oscar Salvador <osalvador@suse.com>, linux-s390@vger.kernel.org,
 linux-ia64@vger.kernel.org, Vasily Gorbik <gor@linux.ibm.com>,
 linux-sh@vger.kernel.org, Heiko Carstens <heiko.carstens@de.ibm.com>,
 linux-kernel@vger.kernel.org, Wei Yang <richard.weiyang@gmail.com>,
 linux-mm@kvack.org, Mike Rapoport <rppt@linux.vnet.ibm.com>,
 Martin Schwidefsky <schwidefsky@de.ibm.com>,
 Igor Mammedov <imammedo@redhat.com>, akpm@linux-foundation.org,
 linuxppc-dev@lists.ozlabs.org, Dan Williams <dan.j.williams@intel.com>,
 linux-arm-kernel@lists.infradead.org
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 <linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org>

On Mon 01-07-19 09:45:03, Michal Hocko wrote:
> On Mon 27-05-19 13:11:44, David Hildenbrand wrote:
> > Will come in handy when wanting to handle errors after
> > arch_add_memory().
> 
> I do not understand this. Why do you add a code for something that is
> not possible on this HW (based on the comment - is it still valid btw?)

Same as the previous patch (drop it).

> > Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
> > Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Michal Hocko <mhocko@suse.com>
> > Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
> > Cc: David Hildenbrand <david@redhat.com>
> > Cc: Vasily Gorbik <gor@linux.ibm.com>
> > Cc: Oscar Salvador <osalvador@suse.com>
> > Signed-off-by: David Hildenbrand <david@redhat.com>
> > ---
> >  arch/s390/mm/init.c | 13 +++++++------
> >  1 file changed, 7 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> > index d552e330fbcc..14955e0a9fcf 100644
> > --- a/arch/s390/mm/init.c
> > +++ b/arch/s390/mm/init.c
> > @@ -243,12 +243,13 @@ int arch_add_memory(int nid, u64 start, u64 size,
> >  void arch_remove_memory(int nid, u64 start, u64 size,
> >  			struct vmem_altmap *altmap)
> >  {
> > -	/*
> > -	 * There is no hardware or firmware interface which could trigger a
> > -	 * hot memory remove on s390. So there is nothing that needs to be
> > -	 * implemented.
> > -	 */
> > -	BUG();
> > +	unsigned long start_pfn = start >> PAGE_SHIFT;
> > +	unsigned long nr_pages = size >> PAGE_SHIFT;
> > +	struct zone *zone;
> > +
> > +	zone = page_zone(pfn_to_page(start_pfn));
> > +	__remove_pages(zone, start_pfn, nr_pages, altmap);
> > +	vmem_remove_mapping(start, size);
> >  }
> >  #endif
> >  #endif /* CONFIG_MEMORY_HOTPLUG */
> > -- 
> > 2.20.1
> > 
> 
> -- 
> Michal Hocko
> SUSE Labs

-- 
Michal Hocko
SUSE Labs