linux-kernel - Re: [PATCH v6 2/8] mm,memory_hotplug: Relax fully spanned sections check

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Message-Id: <59A04B1D-08D6-4E71-A382-F5503A6E0AF7@redhat.com>
Date:   Tue, 6 Apr 2021 22:43:01 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/8] mm,memory_hotplug: Relax fully spanned sections check


> Am 06.04.2021 um 18:34 schrieb Oscar Salvador <osalvador@...e.de>:
> 
> On 2021-04-06 17:32, David Hildenbrand wrote:
>> I'd only relax start_pfn. That way the function is pretty much
>> impossible to abuse for sub-section onlining/offlining.
>> if (WARN_ON_ONCE(!nr_pages ||
>>         !IS_ALIGNED(start_pfn, pageblock_nr_pages))
>>         !IS_ALIGNED(start_pfn + nr_pages, PAGES_PER_SECTION)))
> 
> But this is not going to work.
> When using memmap_on_memory, the nr of pages that online_pages() and offline_pages() get might be less than PAGES_PER_SECTION, so this check will always blow us up.

But not end_pfn as given in my version or what am I missing?


> -- 
> Oscar Salvador
> SUSE L3
>