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

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Message-ID: <20160203030137.GA22446@hori1.linux.bs1.fc.nec.co.jp>
Date:	Wed, 3 Feb 2016 03:01:41 +0000
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Mike Kravetz <mike.kravetz@...cle.com>
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>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...e.cz>
Subject: Re: [PATCH] mm/hugetlb: fix gigantic page initialization/allocation

On Tue, Feb 02, 2016 at 03:17:10PM -0800, Mike Kravetz wrote:
> On 02/02/2016 02:59 PM, David Rientjes wrote:
> > On Tue, 2 Feb 2016, Mike Kravetz wrote:
> > 
> >> 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")
> >> Suggested-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
> >> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> > 
> > I'm not sure whether this should have a "From: Naoya Horiguchi" line with 
> > an accompanying sign-off or not, since Naoya debugged and wrote the actual 
> > fix to prep_compound_gigantic_page().
> 
> 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