From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCHv2, RFC 00/30] Transparent huge page cache
Date: Mon, 18 Mar 2013 13:19:39 +0200 (EET)
Message-ID: <20130318111939.C8206E0085@blue.fi.intel.com>
References: <1363283435-7666-1-git-send-email-kirill.shutemov@linux.intel.com>
 <514691F5.2040204@gmail.com>
 <5146A4CC.3060306@gmail.com>
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Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
 Andrea Arcangeli <aarcange@redhat.com>,
 Andrew Morton <akpm@linux-foundation.org>,
 Al Viro <viro@zeniv.linux.org.uk>,
 Hugh Dickins <hughd@google.com>,
 Wu Fengguang <fengguang.wu@intel.com>,
 Jan Kara <jack@suse.cz>,
 Mel Gorman <mgorman@suse.de>,
 linux-mm@kvack.org,
 Andi Kleen <ak@linux.intel.com>,
 Matthew Wilcox <matthew.r.wilcox@intel.com>,
 "Kirill A. Shutemov" <kirill@shutemov.name>,
 Hillf Danton <dhillf@gmail.com>,
 linux-fsdevel@vger.kernel.org,
 linux-kernel@vger.kernel.org
To: Simon Jeons <simon.jeons@gmail.com>
Return-path: <owner-linux-mm@kvack.org>
In-Reply-To: <5146A4CC.3060306@gmail.com>
Sender: owner-linux-mm@kvack.org
List-Id: linux-fsdevel.vger.kernel.org

Simon Jeons wrote:
> On 03/18/2013 12:03 PM, Simon Jeons wrote:
> > Hi Kirill,
> > On 03/15/2013 01:50 AM, Kirill A. Shutemov wrote:
> >> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> >>
> >> Here's the second version of the patchset.
> >>
> >> The intend of the work is get code ready to enable transparent huge page
> >> cache for the most simple fs -- ramfs.
> >>
> >> We have read()/write()/mmap() functionality now. Still plenty work 
> >> ahead.
> >
> > One offline question.
> >
> > Why set PG_mlocked to page_tail which be splited in function 
> > __split_huge_page_refcount?

Not set, but copied from head page. Head page represents up-to-date sate
of compound page, we need to copy it to all tail pages on split.
 
> Also why can't find where _PAGE_SPLITTING and _PAGE_PSE flags are
> cleared in split_huge_page path?
 
The pmd is invalidated and replaced with reference to page table at the end
of __split_huge_page_map.
 
> Another offline question:
> Why don't clear tail page PG_tail flag in function
> __split_huge_page_refcount?

We do:

 page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP | __PG_HWPOISON;

-- 
 Kirill A. Shutemov

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