Date: Wed, 27 Feb 2008 16:14:08 -0800 (PST)
From: Christoph Lameter <clameter@sgi.com>
To: Andrea Arcangeli <andrea@qumranet.com>
cc: Nick Piggin <nickpiggin@yahoo.com.au>, akpm@linux-foundation.org,
       Robin Holt <holt@sgi.com>, Avi Kivity <avi@qumranet.com>,
       Izik Eidus <izike@qumranet.com>, kvm-devel@lists.sourceforge.net,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, general@lists.openfabrics.org,
       Steve Wise <swise@opengridcomputing.com>,
       Roland Dreier <rdreier@cisco.com>, Kanoj Sarcar <kanojsarcar@yahoo.com>,
       steiner@sgi.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       daniel.blueman@quadrics.com
Subject: Re: [patch 2/6] mmu_notifier: Callbacks to invalidate address ranges
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On Thu, 28 Feb 2008, Andrea Arcangeli wrote:

> > 3. Keep the refcount elevated until pages are freed in another execution 
> > context.
> 
> Page refcount is not enough (the mmu_notifier_release will run in
> another cpu the moment after i_mmap_lock is unlocked) but mm_users may
> prevent us to change the i_mmap_lock to a mutex, but it'll slowdown
> truncate as it'll have to drop the lock and restart the radix tree
> walk every time so a change like this better fits as a separate
> CONFIG_XPMEM IMHO.

Erm. This would also be needed by RDMA etc.

 
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