vfs: for usbfs, etc. internal vfsmounts ->mnt_sb->s_root == ->mnt_root

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index 89accc6..b2c65e0 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -2228,7 +2228,7 @@
 	/*
 	 * allocate a new dcache entry
 	 */
-	path.dentry = d_alloc(pfmfs_mnt->mnt_sb->s_root, &this);
+	path.dentry = d_alloc(pfmfs_mnt->mnt_root, &this);
 	if (!path.dentry) {
 		iput(inode);
 		return ERR_PTR(-ENOMEM);