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Date: Mon, 30 Mar 2015 18:20:51 +0300
From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Dave Hansen <dave.hansen@intel.com>, Hugh Dickins <hughd@google.com>,
        Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
        Vlastimil Babka <vbabka@suse.cz>, Christoph Lameter <cl@gentwo.org>,
        Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
        Steve Capper <steve.capper@linaro.org>,
        Johannes Weiner <hannes@cmpxchg.org>, Michal Hocko <mhocko@suse.cz>,
        Jerome Marchand <jmarchan@redhat.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCHv4 18/24] thp, mm: split_huge_page(): caller need to lock
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On Mon, Mar 30, 2015 at 07:40:29PM +0530, Aneesh Kumar K.V wrote:
> "Kirill A. Shutemov" <kirill.shutemov@linux.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@linux.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