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Date: Thu, 7 May 2009 10:46:56 +0800
From: Wu Fengguang <fengguang.wu@intel.com>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Andi Kleen <andi@firstfloor.org>, Matt Mackall <mpm@selenic.com>,
       Alexey Dobriyan <adobriyan@gmail.com>,
       "linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH 4/7] proc: export more page flags in /proc/kpageflags
Message-ID: <20090507024656.GA12828@localhost>
References: <20090507012116.996644836@intel.com> <20090507014914.364045992@intel.com> <20090507114016.40ee6577.minchan.kim@barrios-desktop>
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On Thu, May 07, 2009 at 10:40:16AM +0800, Minchan Kim wrote:
> On Thu, 07 May 2009 09:21:21 +0800
> Wu Fengguang <fengguang.wu@intel.com> wrote:
> 
> > +	 * pseudo flags for the well known (anonymous) memory mapped pages
> > +	 */
> > +	if (!PageSlab(page) && page_mapped(page))
> > +		u |= 1 << KPF_MMAP;
> > +	if (PageAnon(page))
> > +		u |= 1 << KPF_ANON;
> 
> Why do you check PageSlab on user pages ?
> Is there any case that PageSlab == true && page_mapped == true ?

Yes at least for SLUB: it reuses page->_mapcount, so page_mapped() is
meaningless for slab pages.