linux-kernel - Re: [PATCH 1/6] pagemap: avoid splitting thp when reading /proc/pid/pagemap

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Message-ID: <20120115120605.GI3236@redhat.com>
Date:	Sun, 15 Jan 2012 13:06:05 +0100
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Andi Kleen <andi@...stfloor.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/6] pagemap: avoid splitting thp when reading
 /proc/pid/pagemap

On Sat, Jan 14, 2012 at 06:00:26PM +0100, Andrea Arcangeli wrote:
> Why don't you pass the pmd and then do "if (pmd_present(pmd))
> page_to_pfn(pmd_page(pmd)) ? What's the argument for the cast. I'm

Of course I meant pmd_pfn above... in short as a replacement of the
pte_pfn in your patch.

About the _stable function, I was now thinking maybe _lock suffix is
more appropriate than _stable, because that function effectively has
the objective of taking the page_table_lock in the most efficient way,
and not much else other than taking the lock. Adding a comment that
it's only safe to call with the mmap_sem held in the inline version in
the .h file (the one that then would call the __ version in the .c
file).
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