linux-kernel - Re: [PATCH 2 of 8] Moves all mmu notifier methods outside the PT lock (first and not last

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Message-ID: <Pine.LNX.4.64.0804021459560.31247@schroedinger.engr.sgi.com>
Date:	Wed, 2 Apr 2008 15:03:12 -0700 (PDT)
From:	Christoph Lameter <clameter@....com>
To:	Andrea Arcangeli <andrea@...ranet.com>
cc:	akpm@...ux-foundation.org, Jack Steiner <steiner@....com>,
	Nick Piggin <npiggin@...e.de>, Robin Holt <holt@....com>,
	Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	general@...ts.openfabrics.org,
	Steve Wise <swise@...ngridcomputing.com>,
	Roland Dreier <rdreier@...co.com>,
	Kanoj Sarcar <kanojsarcar@...oo.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2 of 8] Moves all mmu notifier methods outside the PT
 lock (first and not last

On Wed, 2 Apr 2008, Andrea Arcangeli wrote:

> diff --git a/mm/memory.c b/mm/memory.c
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1626,9 +1626,10 @@
>  			 */
>  			page_table = pte_offset_map_lock(mm, pmd, address,
>  							 &ptl);
> -			page_cache_release(old_page);
> +			new_page = NULL;
>  			if (!pte_same(*page_table, orig_pte))
>  				goto unlock;
> +			page_cache_release(old_page);
>  
>  			page_mkwrite = 1;
>  		}

This is deferring frees and not moving the callouts. KVM specific? What 
exactly is this doing?

A significant portion of this seems to be undoing what the first patch 
did.
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