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

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Message-ID: <b294506a-9007-be11-f477-5b2a0011b2ba@microsoft.com>
Date:   Thu, 30 Aug 2018 22:17:35 +0000
From:   Pasha Tatashin <Pavel.Tatashin@...rosoft.com>
To:     David Hildenbrand <david@...hat.com>,
        Oscar Salvador <osalvador@...hadventures.net>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.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 8/16/18 7:00 AM, David Hildenbrand wrote:
> On 16.08.2018 12:47, Oscar Salvador wrote:
>> 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
> 
> Right, I missed that function.
> 
>>
>> 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.

I am OK with that, but will wait for a patch to review.

Pavel