linux-kernel - Re: [PATCH v3 03/11] s390x/mm: Implement arch_remove

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Message-ID: <20190701074503.GD6376@dhcp22.suse.cz>
Date:   Mon, 1 Jul 2019 09:45:03 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-ia64@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, akpm@...ux-foundation.org,
        Dan Williams <dan.j.williams@...el.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Oscar Salvador <osalvador@...e.com>
Subject: Re: [PATCH v3 03/11] s390x/mm: Implement arch_remove_memory()

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?)

> Cc: Martin Schwidefsky <schwidefsky@...ibm.com>
> Cc: Heiko Carstens <heiko.carstens@...ibm.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Mike Rapoport <rppt@...ux.vnet.ibm.com>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Vasily Gorbik <gor@...ux.ibm.com>
> Cc: Oscar Salvador <osalvador@...e.com>
> Signed-off-by: David Hildenbrand <david@...hat.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