Messages in this thread Patch in this message | | | Date | Mon, 15 Oct 2007 13:48:52 -0700 | From | Jeremy Fitzhardinge <> | Subject | [PATCH 12/12] xfs: eagerly remove vmap mappings to avoid upsetting Xen |
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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. David Chinner says this shouldn't have any performance impact on filesystems with default block sizes; it will only affect filesystems with large block sizes.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: David Chinner <dgc@sgi.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> 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)) { --
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