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

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Message-ID: <614fe7d2-cc5d-61a2-6894-026e30498269@redhat.com>
Date:   Mon, 15 Apr 2019 15:55:41 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Anshuman Khandual <anshuman.khandual@....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

> +
> +#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.



> +		__remove_pgd_mapping(swapper_pg_dir,
> +					__phys_to_virt(start), size);
> +	return ret;
> +}
> +#endif
>  #endif
> 


-- 

Thanks,

David / dhildenb