[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Xen-devel] [PATCH 10/10] xfs: eagerly remove vmap mappings to avoid upsetting Xen



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@xxxxxxxxxxxxx>
Cc: XFS masters <xfs-masters@xxxxxxxxxxx>
Cc: Stable kernel <stable@xxxxxxxxxx>
Cc: Morten =?utf-8?q?B=C3=B8geskov?= <xen-users@xxxxxxxxxxxxxxxxxx>
Cc: Mark Williamson <mark.williamson@xxxxxxxxxxxx>

---
 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)) {

-- 


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel


 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.