linux-kernel - Re: [PATCH 05/10] ksm: no debug in page_dup

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Message-ID: <4A64B342.8070002@redhat.com>
Date:	Mon, 20 Jul 2009 14:11:14 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Izik Eidus <ieidus@...hat.com>
CC:	akpm@...ux-foundation.org, hugh.dickins@...cali.co.uk,
	aarcange@...hat.com, chrisw@...hat.com, avi@...hat.com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	nickpiggin@...oo.com.au, Nick Piggin <npiggin@...e.de>
Subject: Re: [PATCH 05/10] ksm: no debug in page_dup_rmap()

Izik Eidus wrote:
> From: Hugh Dickins <hugh.dickins@...cali.co.uk>
> 
> page_dup_rmap(), used on each mapped page when forking,  was originally
> just an inline atomic_inc of mapcount.  2.6.22 added CONFIG_DEBUG_VM
> out-of-line checks to it, which would need to be ever-so-slightly
> complicated to allow for the PageKsm() we're about to define.
> 
> But I think these checks never caught anything.  And if it's coding
> errors we're worried about, such checks should be in page_remove_rmap()
> too, not just when forking; whereas if it's pagetable corruption we're
> worried about, then they shouldn't be limited to CONFIG_DEBUG_VM.

Acked-by: Rik van Riel <riel@...hat.com>

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