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From: Jeremy Fitzhardinge <jeremy@goop.org>
To: LKML <linux-kernel@vger.kernel.org>
Cc: "Andi Kleen" <ak@muc.de>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	virtualization@lists.osdl.org, xen-devel@lists.xensource.com,
	"Chris Wright" <chrisw@sous-sol.org>,
	"Keir Fraser" <keir@xensource.com>,
	"XFS masters" <xfs-masters@oss.sgi.com>,
	"Stable kernel" <stable@kernel.org>,
	"Morten Bøgeskov" <xen-users@morten.bogeskov.dk>,
	"Mark Williamson" <mark.williamson@cl.cam.ac.uk>
Subject: [PATCH 10/10] xfs: eagerly remove vmap mappings to avoid upsetting Xen
Date: Fri, 12 Oct 2007 14:11:42 -0700	[thread overview]
Message-ID: <20071012211148.864500000@goop.org> (raw)
In-Reply-To: <20071012211132.198718000@goop.org>

[-- Attachment #1: xen-xfs-unmap.patch --]
[-- Type: text/plain, Size: 1514 bytes --]

XFS leaves stray mappings around when it vmaps memory to make it
virtually contigious.  This upsets Xen if one of those pages is being
recycled into a pagetable, since it finds an extra writable mapping of
the page.

This patch solves the problem in a brute force way, by making XFS
always eagerly unmap its mappings.

[ Stable: This works around a bug in 2.6.23.  We may come up with a
better solution for mainline, but this seems like a low-impact fix for
the stable kernel. ]

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: XFS masters <xfs-masters@oss.sgi.com>
Cc: Stable kernel <stable@kernel.org>
Cc: Morten =?utf-8?q?B=C3=B8geskov?= <xen-users@morten.bogeskov.dk>
Cc: Mark Williamson <mark.williamson@cl.cam.ac.uk>

---
 fs/xfs/linux-2.6/xfs_buf.c |   13 +++++++++++++
 1 file changed, 13 insertions(+)

===================================================================
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -186,6 +186,19 @@ free_address(
 	void		*addr)
 {
 	a_list_t	*aentry;
+
+#ifdef CONFIG_XEN
+	/*
+	 * Xen needs to be able to make sure it can get an exclusive
+	 * RO mapping of pages it wants to turn into a pagetable.  If
+	 * a newly allocated page is also still being vmap()ed by xfs,
+	 * it will cause pagetable construction to fail.  This is a
+	 * quick workaround to always eagerly unmap pages so that Xen
+	 * is happy.
+	 */
+	vunmap(addr);
+	return;
+#endif
 
 	aentry = kmalloc(sizeof(a_list_t), GFP_NOWAIT);
 	if (likely(aentry)) {

-- 


  parent reply	other threads:[~2007-10-12 21:47 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-10-12 21:11 [PATCH 00/10] REVIEW: Xen patches for 2.6.24 Jeremy Fitzhardinge
2007-10-12 21:11 ` [PATCH 01/10] remove dead code in pgtable_cache_init Jeremy Fitzhardinge
2007-10-12 21:11 ` [PATCH 02/10] Clean up duplicate includes in arch/i386/xen/ Jeremy Fitzhardinge
2007-10-12 21:11 ` [PATCH 03/10] xen: yield to IPI target if necessary Jeremy Fitzhardinge
2007-10-12 21:11 ` [PATCH 04/10] xen: add batch completion callbacks Jeremy Fitzhardinge
2007-11-13 22:50   ` patch xen-multicall-callbacks.patch queued to -stable tree gregkh
2007-10-12 21:11 ` [PATCH 05/10] xen: deal with stale cr3 values when unpinning pagetables Jeremy Fitzhardinge
2007-11-13 22:50   ` patch xen-handle-lazy-cr3-on-unpin.patch queued to -stable tree gregkh
2007-10-12 21:11 ` [PATCH 06/10] xen: lock pte pages while pinning/unpinning Jeremy Fitzhardinge
2007-10-12 21:11 ` [PATCH 07/10] xen: ask the hypervisor how much space it needs reserved Jeremy Fitzhardinge
2007-10-12 21:11 ` [PATCH 08/10] xen: fix incorrect vcpu_register_vcpu_info hypercall argument Jeremy Fitzhardinge
2007-11-13 22:50   ` patch xen-fix-register_vcpu_info.patch queued to -stable tree gregkh
2007-10-12 21:11 ` [PATCH 09/10] xen: add some debug output for failed multicalls Jeremy Fitzhardinge
2007-10-12 21:11 ` Jeremy Fitzhardinge [this message]
2007-11-13 22:50   ` patch xen-xfs-unmap.patch queued to -stable tree gregkh

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