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From: Zaslonko Mikhail <zaslonko@linux.bm.com>
To: Michal Hocko <mhocko@kernel.org>,
	Zaslonko Mikhail <zaslonko@linux.ibm.com>
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, Pavel.Tatashin@microsoft.com,
	schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com,
	gerald.schaefer@de.ibm.com
Subject: Re: [PATCH 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section
Date: Tue, 11 Dec 2018 16:18:02 +0100
Message-ID: <97b60ec7-2b95-91e5-80a6-aeae305cc696@linux.bm.com> (raw)
In-Reply-To: <20181210162410.GT1286@dhcp22.suse.cz>



On 10.12.2018 19:19, Michal Hocko wrote:
> On Mon 10-12-18 16:45:37, Zaslonko Mikhail wrote:
>> Hello,
>>
>> On 10.12.2018 14:24, Michal Hocko wrote:
> [...]
>>> Why do we need to restrict this to the highest zone? In other words, why
>>> cannot we do what I was suggesting earlier [1]. What does prevent other
>>> zones to have an incomplete section boundary?
>>
>> Well, as you were also suggesting earlier: 'If we do not have a zone which
>> spans the rest of the section'. I'm not sure how else we should verify that.
> 
> I am not sure I follow here. Why cannot we simply drop end_pfn check and
> keep the rest?
> 
>> Moreover, I was able to recreate the problem only with the highest zone
>> (memory end is not on the section boundary).
> 
> What exactly prevents exactmap memmap to generate these unfinished zones?

Probably you're right. I'm re-sending the patch V2.

> 
>>> [1] http://lkml.kernel.org/r/20181105183533.GQ4361@dhcp22.suse.cz
>>>
>>>> Signed-off-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
>>>> Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
>>>> Cc: <stable@vger.kernel.org>
>>>> ---
>>>>  mm/page_alloc.c | 15 +++++++++++++++
>>>>  1 file changed, 15 insertions(+)
>>>>
>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>> index 2ec9cc407216..41ef5508e5f1 100644
>>>> --- a/mm/page_alloc.c
>>>> +++ b/mm/page_alloc.c
>>>> @@ -5542,6 +5542,21 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
>>>>  			cond_resched();
>>>>  		}
>>>>  	}
>>>> +#ifdef CONFIG_SPARSEMEM
>>>> +	/*
>>>> +	 * If there is no zone spanning the rest of the section
>>>> +	 * then we should at least initialize those pages. Otherwise we
>>>> +	 * could blow up on a poisoned page in some paths which depend
>>>> +	 * on full sections being initialized (e.g. memory hotplug).
>>>> +	 */
>>>> +	if (end_pfn == max_pfn) {
>>>> +		while (end_pfn % PAGES_PER_SECTION) {
>>>> +			__init_single_page(pfn_to_page(end_pfn), end_pfn, zone,
>>>> +					   nid);
>>>> +			end_pfn++;
>>>> +		}
>>>> +	}
>>>> +#endif
>>>>  }
>>>>  
>>>>  #ifdef CONFIG_ZONE_DEVICE
>>>> -- 
>>>> 2.16.4
>>>
>>
>> Thanks,
>> Mikhail Zaslonko
> 

  reply index

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-12-10 13:07 [PATCH 0/1] Initialize struct pages for the full section Mikhail Zaslonko
2018-12-10 13:07 ` [PATCH 1/1] mm, memory_hotplug: Initialize struct pages for the full memory section Mikhail Zaslonko
2018-12-10 13:24   ` Michal Hocko
2018-12-10 15:45     ` Zaslonko Mikhail
2018-12-10 18:19       ` Michal Hocko
2018-12-11 15:18         ` Zaslonko Mikhail [this message]
2018-12-11  9:49     ` Wei Yang
2018-12-11 15:17       ` Zaslonko Mikhail
2018-12-11 22:24         ` Wei Yang
2018-12-10 15:10   ` Wei Yang
2018-12-10 16:14     ` Zaslonko Mikhail
2018-12-11  1:50       ` Wei Yang
2018-12-11 15:23         ` Zaslonko Mikhail
2018-12-11 22:14           ` Wei Yang
2018-12-10 21:09   ` Sasha Levin
2019-06-14 21:56   ` Sasha Levin

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