linux-kernel - Re: [PATCH] thp: tail page refcounting fix

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Message-ID: <20110823165453.GB23870@redhat.com>
Date:	Tue, 23 Aug 2011 18:54:53 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Michel Lespinasse <walken@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
	Johannes Weiner <jweiner@...hat.com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Shaohua Li <shaohua.li@...el.com>
Subject: Re: [PATCH] thp: tail page refcounting fix

On Wed, Aug 24, 2011 at 01:45:15AM +0900, Minchan Kim wrote:
> Nice idea!

Thanks! It felt natural to account the tail refcounts in
page_tail->_count, so they were already there and it was enough to add
the page_mapcount(head_page) to the page_tail->_count. But there's no
particular reason we had to do the tail_page refcounting in the
->_page field before the split...

> Reviewed-by: Minchan Kim <minchan.kim@...il.com>
> 
> The code looks good to me.

Thanks a lot for the quick review.

> The nitpick is about naming 'foll'.
> What does it mean? 'follow'?
> If it is, I hope we use full name.
> Regardless of renaming it, I am okay the patch.

Ok the name comes from FOLL_GET. Only code  paths marked by checking
FOLL_GET are allowed to call get_page_foll(). Anything else can't.

mm/*memory.c:

	 if (flags & FOLL_GET)
	    get_page_foll(page);
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