linux-kernel - Re: [PATCHv4 18/24] thp, mm: split_huge

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Message-ID: <20150330152051.GA5849@node.dhcp.inet.fi>
Date:	Mon, 30 Mar 2015 18:20:51 +0300
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Hugh Dickins <hughd@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Christoph Lameter <cl@...two.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Steve Capper <steve.capper@...aro.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Jerome Marchand <jmarchan@...hat.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv4 18/24] thp, mm: split_huge_page(): caller need to lock
 page

On Mon, Mar 30, 2015 at 07:40:29PM +0530, Aneesh Kumar K.V wrote:
> "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> writes:
> 
> > We're going to use migration entries instead of compound_lock() to
> > stabilize page refcounts. Setup and remove migration entries require
> > page to be locked.
> >
> > Some of split_huge_page() callers already have the page locked. Let's
> > require everybody to lock the page before calling split_huge_page().
> >
> > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> 
> Why not have split_huge_page_locked/unlocked, and call the one which
> takes lock internally every where ?

We could do that, but it's not obvoius for me what is benefit. Couple of
lines on caller side?

-- 
 Kirill A. Shutemov
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