linux-kernel - Re: [patch 2/4] mmu_notifier: Callbacks to invalidate address ranges

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Message-ID: <20080201104959.GJ26420@sgi.com>
Date:	Fri, 1 Feb 2008 04:49:59 -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: [patch 2/4] mmu_notifier: Callbacks to invalidate address
	ranges

do_wp_page can reach the _end callout without passing the _begin
callout.  This prevents making the _end unles the _begin has also
been made.

Index: mmu_notifiers-cl-v5/mm/memory.c
===================================================================
--- mmu_notifiers-cl-v5.orig/mm/memory.c	2008-02-01 04:44:03.000000000 -0600
+++ mmu_notifiers-cl-v5/mm/memory.c	2008-02-01 04:46:18.000000000 -0600
@@ -1564,7 +1564,7 @@ static int do_wp_page(struct mm_struct *
 {
 	struct page *old_page, *new_page;
 	pte_t entry;
-	int reuse = 0, ret = 0;
+	int reuse = 0, ret = 0, invalidate_started = 0;
 	int page_mkwrite = 0;
 	struct page *dirty_page = NULL;
 
@@ -1649,6 +1649,8 @@ gotten:
 
 	mmu_notifier(invalidate_range_begin, mm, address,
 				address + PAGE_SIZE, 0);
+	invalidate_started = 1;
+
 	/*
 	 * Re-check the pte - we dropped the lock
 	 */
@@ -1687,7 +1689,8 @@ gotten:
 		page_cache_release(old_page);
 unlock:
 	pte_unmap_unlock(page_table, ptl);
-	mmu_notifier(invalidate_range_end, mm,
+	if (invalidate_started)
+		mmu_notifier(invalidate_range_end, mm,
 				address, address + PAGE_SIZE, 0);
 	if (dirty_page) {
 		if (vma->vm_file)
--
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