linux-kernel - Re: [PATCH v3 04/11] arm64/mm: Add temporary arch_remove

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Message-ID: <20190701124809.GV6376@dhcp22.suse.cz>
Date:   Mon, 1 Jul 2019 14:48:09 +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>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Chintan Pandya <cpandya@...eaurora.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Jun Yao <yaojun8558363@...il.com>, Yu Zhao <yuzhao@...gle.com>,
        Robin Murphy <robin.murphy@....com>,
        Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH v3 04/11] arm64/mm: Add temporary arch_remove_memory()
 implementation

On Mon 27-05-19 13:11:45, David Hildenbrand wrote:
> A proper arch_remove_memory() implementation is on its way, which also
> cleanly removes page tables in arch_add_memory() in case something goes
> wrong.
> 
> As we want to use arch_remove_memory() in case something goes wrong
> during memory hotplug after arch_add_memory() finished, let's add
> a temporary hack that is sufficient enough until we get a proper
> implementation that cleans up page table entries.
> 
> We will remove CONFIG_MEMORY_HOTREMOVE around this code in follow up
> patches.

I would drop this one as well (like s390 counterpart).
 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
> Cc: Chintan Pandya <cpandya@...eaurora.org>
> Cc: Mike Rapoport <rppt@...ux.ibm.com>
> Cc: Jun Yao <yaojun8558363@...il.com>
> Cc: Yu Zhao <yuzhao@...gle.com>
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Anshuman Khandual <anshuman.khandual@....com>
> Signed-off-by: David Hildenbrand <david@...hat.com>
> ---
>  arch/arm64/mm/mmu.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index a1bfc4413982..e569a543c384 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -1084,4 +1084,23 @@ int arch_add_memory(int nid, u64 start, u64 size,
>  	return __add_pages(nid, start >> PAGE_SHIFT, size >> PAGE_SHIFT,
>  			   restrictions);
>  }
> +#ifdef CONFIG_MEMORY_HOTREMOVE
> +void arch_remove_memory(int nid, u64 start, u64 size,
> +			struct vmem_altmap *altmap)
> +{
> +	unsigned long start_pfn = start >> PAGE_SHIFT;
> +	unsigned long nr_pages = size >> PAGE_SHIFT;
> +	struct zone *zone;
> +
> +	/*
> +	 * FIXME: Cleanup page tables (also in arch_add_memory() in case
> +	 * adding fails). Until then, this function should only be used
> +	 * during memory hotplug (adding memory), not for memory
> +	 * unplug. ARCH_ENABLE_MEMORY_HOTREMOVE must not be
> +	 * unlocked yet.
> +	 */
> +	zone = page_zone(pfn_to_page(start_pfn));
> +	__remove_pages(zone, start_pfn, nr_pages, altmap);
> +}
> +#endif
>  #endif
> -- 
> 2.20.1

-- 
Michal Hocko
SUSE Labs