linux-kernel - Re: Extending mmu_notifiers to handle __xip

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Message-ID: <20080201121024.GN26420@sgi.com>
Date:	Fri, 1 Feb 2008 06:10:25 -0600
From:	Robin Holt <holt@....com>
To:	Christoph Lameter <clameter@....com>
Cc:	Andrea Arcangeli <andrea@...ranet.com>, 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>, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com
Subject: Re: Extending mmu_notifiers to handle __xip_unmap in a sleepable
	context?

Argh,

Here is the correct one.  Sorry

On Fri, Feb 01, 2008 at 05:58:41AM -0600, Robin Holt wrote:
> With this set of patches, I think we have enough to get xpmem working
> with most types of mappings.  In the past, we operated without any of
> these callouts by significantly restricting why types of mappings could
> remotely fault and what types of operations the user could do.  With
> this set, I am certain we can continue to meet the above assumptions.
> 
> That said, I would like to discuss __xip_unmap in more detail.
> 
> Currently, it is calling mmu_notifier _begin and _end under the
> i_mmap_lock.  I _THINK_ the following will make it so we could support
> __xip_unmap (although I don't recall ever seeing that done on ia64 and
> don't even know what the circumstances are for its use).

Index: mmu_notifiers-cl-v5/mm/filemap_xip.c
===================================================================
--- mmu_notifiers-cl-v5.orig/mm/filemap_xip.c	2008-02-01 05:38:32.000000000 -0600
+++ mmu_notifiers-cl-v5/mm/filemap_xip.c	2008-02-01 06:09:09.000000000 -0600
@@ -184,6 +184,10 @@ __xip_unmap (struct address_space * mapp
 	if (!page)
 		return;
 
+	if (unlikely(PageExternalRmap(page))) {
+		mmu_rmap_notifier(invalidate_page, page);
+		ClearPageExternalRmap(page);
+	}
 	spin_lock(&mapping->i_mmap_lock);
 	vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, pgoff) {
 		mm = vma->vm_mm;
--
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