linux-kernel - Re: [PATCHv4 14/39] thp, mm: rewrite delete_from_page

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Message-Id: <20130610174146.8C1CFE0090@blue.fi.intel.com>
Date:	Mon, 10 Jun 2013 20:41:46 +0300 (EEST)
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Dave Hansen <dave@...1.net>
Cc:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Hugh Dickins <hughd@...gle.com>,
	Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
	Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
	Andi Kleen <ak@...ux.intel.com>,
	Matthew Wilcox <matthew.r.wilcox@...el.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Hillf Danton <dhillf@...il.com>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 14/39] thp, mm: rewrite delete_from_page_cache() to
 support huge pages

Dave Hansen wrote:
> On 06/07/2013 08:10 AM, Kirill A. Shutemov wrote:
> > +	/*
> > +	 * When we add a huge page to page cache we take only reference to head
> > +	 * page, but on split we need to take addition reference to all tail
> > +	 * pages since they are still in page cache after splitting.
> > +	 */
> > +	init_tail_refcount = PageAnon(page) ? 0 : 1;
> 
> What's the "init" for in the name?

initial_tail_refcount?

> In add_to_page_cache_locked() in patch 12/39, you do
> > +       spin_lock_irq(&mapping->tree_lock);
> > +       for (i = 0; i < nr; i++) {
> > +               page_cache_get(page + i);
> 
> That looks to me to be taking references to the tail pages.  What gives? :)

The point is to drop this from add_to_page_cache_locked() and make distribution
on split.

-- 
 Kirill A. Shutemov
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