From: Jeremy Fitzhardinge Subject: [PATCH 10/10] xfs: eagerly remove vmap mappings to avoid upsetting Xen Date: Fri, 12 Oct 2007 14:11:42 -0700 Message-ID: <20071012211148.864500000@goop.org> References: <20071012211132.198718000@goop.org> Return-path: Content-Disposition: inline; filename=xen-xfs-unmap.patch List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: LKML Cc: xen-devel@lists.xensource.com, virtualization@lists.osdl.org, Mark Williamson , XFS masters , Chris Wright , Andi Kleen , Morten =?utf-8?q?B=C3=B8geskov?= , Andrew Morton , Keir Fraser , Stable kernel List-Id: virtualization@lists.linuxfoundation.org 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 Cc: XFS masters Cc: Stable kernel Cc: Morten =?utf-8?q?B=C3=B8geskov?= Cc: Mark Williamson --- 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)) { --