linux-kernel - Re: [PATCH V2 2/2] arm64/mm: Enable memory hot remove

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Message-ID: <eeff6d30-f6c9-733b-5a27-76d2a80c649d@arm.com>
Date:   Tue, 16 Apr 2019 15:22:28 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, will.deacon@....com,
        catalin.marinas@....com
Cc:     mhocko@...e.com, mgorman@...hsingularity.net, james.morse@....com,
        mark.rutland@....com, robin.murphy@....com, cpandya@...eaurora.org,
        arunks@...eaurora.org, dan.j.williams@...el.com, osalvador@...e.de,
        cai@....pw, logang@...tatee.com, ira.weiny@...el.com
Subject: Re: [PATCH V2 2/2] arm64/mm: Enable memory hot remove



On 04/15/2019 07:25 PM, David Hildenbrand wrote:
>> +
>> +#ifdef CONFIG_MEMORY_HOTREMOVE
>> +int 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 = page_zone(pfn_to_page(start_pfn));
>> +	int ret;
>> +
>> +	ret = __remove_pages(zone, start_pfn, nr_pages, altmap);
>> +	if (!ret)
> Please note that I posted patches that remove all error handling
> from arch_remove_memory and __remove_pages(). They are already in next/master
> 
> So this gets a lot simpler and more predictable.
> 
> 
> Author: David Hildenbrand <david@...hat.com>
> Date:   Wed Apr 10 11:02:27 2019 +1000
> 
>     mm/memory_hotplug: make __remove_pages() and arch_remove_memory() never fail
>     
>     All callers of arch_remove_memory() ignore errors.  And we should really
>     try to remove any errors from the memory removal path.  No more errors are
>     reported from __remove_pages().  BUG() in s390x code in case
>     arch_remove_memory() is triggered.  We may implement that properly later.
>     WARN in case powerpc code failed to remove the section mapping, which is
>     better than ignoring the error completely right now

Sure will follow suit next time around.