linux-kernel - Re: [PATCH] mm/hugetlb: fix gigantic page initialization/allocation

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Date:	Fri, 5 Feb 2016 12:52:17 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Mike Kravetz <mike.kravetz@...cle.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	David Rientjes <rientjes@...gle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Jerome Marchand <jmarchan@...hat.com>,
	Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH] mm/hugetlb: fix gigantic page initialization/allocation

On 02/03/2016 05:15 AM, Mike Kravetz wrote:
> On 02/02/2016 07:01 PM, Naoya Horiguchi wrote:
>> On Tue, Feb 02, 2016 at 03:17:10PM -0800, Mike Kravetz wrote:
>>> I agree.  Naoya did debug and provide fix via e-mail exchange.  He did not
>>> sign-off and I could not tell if he was going to pursue.  My only intention
>>> was to fix ASAP.
>>>
>>> More than happy to give Naoya credit.
>>
>> Thank you! It's great if you append my signed-off below yours.
>>
>> Naoya
> 
> Adding Naoya's sign off and Acks received
> 
> mm/hugetlb: fix gigantic page initialization/allocation
> 
> Attempting to preallocate 1G gigantic huge pages at boot time with
> "hugepagesz=1G hugepages=1" on the kernel command line will prevent
> booting with the following:
> 
> kernel BUG at mm/hugetlb.c:1218!
> 
> When mapcount accounting was reworked, the setting of compound_mapcount_ptr
> in prep_compound_gigantic_page was overlooked.  As a result, the validation
> of mapcount in free_huge_page fails.
> 
> The "BUG_ON" checks in free_huge_page were also changed to "VM_BUG_ON_PAGE"
> to assist with debugging.
> 
> Fixes: af5642a8af ("mm: rework mapcount accounting to enable 4k mapping
> of THPs")
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Acked-by: David Rientjes <rientjes@...gle.com>

Tested-by: Vlastimil Babka <vbabka@...e.cz>