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Date: Tue, 16 Feb 2016 13:14:50 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCHv2 17/28] thp: skip file huge pmd on copy_huge_pmd()
Message-ID: <20160216101450.GE46557@black.fi.intel.com>
References: <1455200516-132137-1-git-send-email-kirill.shutemov@linux.intel.com>
 <1455200516-132137-18-git-send-email-kirill.shutemov@linux.intel.com>
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To: Dave Hansen <dave.hansen@intel.com>
Cc: Hugh Dickins <hughd@google.com>, Andrea Arcangeli <aarcange@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Vlastimil Babka <vbabka@suse.cz>, Christoph Lameter <cl@gentwo.org>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>, Jerome Marchand <jmarchan@redhat.com>, Yang Shi <yang.shi@linaro.org>, Sasha Levin <sasha.levin@oracle.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org

On Fri, Feb 12, 2016 at 10:42:09AM -0800, Dave Hansen wrote:
> On 02/11/2016 06:21 AM, Kirill A. Shutemov wrote:
> > File pmds can be safely skip on copy_huge_pmd(), we can re-fault them
> > later. COW for file mappings handled on pte level.
> 
> Is this different from 4k pages?  I figured we might skip copying
> file-backed ptes on fork, but I couldn't find the code.

Currently, we only filter out on per-VMA basis. See first comment in
copy_page_range().

Here we handle PMD mapped file pages in COW mapping. File THP can be
mapped into COW mapping as result of read page fault.

-- 
 Kirill A. Shutemov

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