linux-kernel - Re: [PATCH v2 1/7] mm,memory_hotplug: Allocate memmap from the added memory range

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d02e77cf-fd23-2ccd-612e-b857a8140a1c@redhat.com>
Date:   Mon, 1 Mar 2021 09:30:17 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>, VlastimilBabkavbabka@...e.cz,
        pasha.tatashin@...een.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH v2 1/7] mm,memory_hotplug: Allocate memmap from the added
 memory range

>>> +		(*online_page_callback)(pfn_to_page(pfn), pageblock_order);
>>> +		pfn += 1 << pageblock_order;
>>
>> pfn += pageblock_nr_pages;
>>
>> Can you add a comment why we can be sure that we are off by  a single pageblock? What about s390x where a MAX_ORDER_NR_PAGES == 4 * pageblock_nr_pages?
>>
>> Would it make thing simpler to just do a
>>
>> while (!IS_ALIGNED(pfn, MAX_ORDER_NR_PAGES)) {
>> 	(*online_page_callback)(pfn_to_page(pfn), 0);
>> 	pfn++;
>> }
> 
> Honestly, I did not spend much time thinking on other platforms other
> than arm64/x86_64.
> But I think that that would be the universal solution as we do not make
> any assumptions.
> 
> I will replace it.

I think you could also go with

while (!IS_ALIGNED(pfn, MAX_ORDER_NR_PAGES)) {
     (*online_page_callback)(pfn_to_page(pfn), pageblock_order);
  	pageblock_nr_pages;
}

And maybe add a comment why we can be sure it has to be aligned to 
pageblocks. Or maybe rather add

VM_BUG_ON(IS_ALIGNED(pfn, pageblock_nr_pages));

-- 
Thanks,

David / dhildenb