linux-kernel - Re: [PATCH 6/8] mm, hugetlb: remove vma_has

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Date:	Wed, 29 Jan 2014 11:24:16 -0800
From:	Davidlohr Bueso <davidlohr@...com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	akpm@...ux-foundation.org, iamjoonsoo.kim@....com, riel@...hat.com,
	mgorman@...e.de, mhocko@...e.cz, aneesh.kumar@...ux.vnet.ibm.com,
	kamezawa.hiroyu@...fujitsu.com, hughd@...gle.com,
	david@...son.dropbear.id.au, js1304@...il.com,
	liwanp@...ux.vnet.ibm.com, dhillf@...il.com, rientjes@...gle.com,
	aswin@...com, scott.norton@...com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/8] mm, hugetlb: remove vma_has_reserves

On Mon, 2014-01-27 at 16:04 -0500, Naoya Horiguchi wrote:
> On Sun, Jan 26, 2014 at 07:52:24PM -0800, Davidlohr Bueso wrote:
> > From: Joonsoo Kim <iamjoonsoo.kim@....com>
> > 
> > vma_has_reserves() can be substituted by using return value of
> > vma_needs_reservation(). If chg returned by vma_needs_reservation()
> > is 0, it means that vma has reserves. Otherwise, it means that vma don't
> > have reserves and need a hugepage outside of reserve pool. This definition
> > is perfectly same as vma_has_reserves(), so remove vma_has_reserves().
> 
> I'm concerned that this patch doesn't work when VM_NORESERVE is set.
> vma_needs_reservation() doesn't check VM_NORESERVE and this patch changes
> dequeue_huge_page_vma() not to check it. So no one seems to check it any more.

Good catch. I agree, this is new behavior and quite frankly not worth
changing just for a cleanup - the code is subtle enough as it is. I'm
dropping this patch and #7 which depends on this one, if Joonsoo wants
to later pursue this, he can.

Thanks,
Davidlohr

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