linux-kernel - Re: [PATCH v1 3/5] mm/memory_hotplug: check if sections are already online/offline

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Message-ID: <20180816104736.GA16861@techadventures.net>
Date:   Thu, 16 Aug 2018 12:47:36 +0200
From:   Oscar Salvador <osalvador@...hadventures.net>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Kemi Wang <kemi.wang@...el.com>,
        David Rientjes <rientjes@...gle.com>,
        Jia He <jia.he@...-semitech.com>,
        Oscar Salvador <osalvador@...e.de>,
        Petr Tesarik <ptesarik@...e.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Mathieu Malaterre <malat@...ian.org>,
        Baoquan He <bhe@...hat.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Ross Zwisler <zwisler@...nel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [PATCH v1 3/5] mm/memory_hotplug: check if sections are already
 online/offline

On Thu, Aug 16, 2018 at 12:06:26PM +0200, David Hildenbrand wrote:

> +
> +/* check if all mem sections are offline */
> +bool mem_sections_offline(unsigned long pfn, unsigned long end_pfn)
> +{
> +	for (; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
> +		unsigned long section_nr = pfn_to_section_nr(pfn);
> +
> +		if (WARN_ON(!valid_section_nr(section_nr)))
> +			continue;
> +		if (online_section_nr(section_nr))
> +			return false;
> +	}
> +	return true;
> +}

AFAICS pages_correctly_probed will catch this first.
pages_correctly_probed checks for the section to be:

- present
- valid
- !online

Maybe it makes sense to rename it, and write another pages_correctly_probed routine
for the offline case.

So all checks would stay in memory_block_action level, and we would not need
the mem_sections_offline/online stuff.

Thanks
-- 
Oscar Salvador
SUSE L3