nfs: make nfs_path() work without vfsmount

part 3: now we have everything to get nfs_path() just by dentry -
just follow to (disconnected) root and pick the rest of the thing
there.

Start killing propagation of struct vfsmount * on the paths that
used to bring it to nfs_path().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/nfs/super.c b/fs/nfs/super.c
index 1d81032..a6ab483 100644
--- a/fs/nfs/super.c
+++ b/fs/nfs/super.c
@@ -2771,16 +2771,15 @@
 	return root_mnt;
 }
 
-static void nfs_fix_devname(const struct path *path, struct vfsmount *mnt)
+static void nfs_fix_devname(struct dentry *dentry, struct vfsmount *mnt)
 {
 	char *page = (char *) __get_free_page(GFP_KERNEL);
 	char *devname, *tmp;
+	char *dummy;
 
 	if (page == NULL)
 		return;
-	devname = nfs_path(path->mnt->mnt_devname,
-			path->mnt->mnt_root, path->dentry,
-			page, PAGE_SIZE);
+	devname = nfs_path(&dummy, dentry, page, PAGE_SIZE);
 	if (IS_ERR(devname))
 		goto out_freepage;
 	tmp = kstrdup(devname, GFP_KERNEL);
@@ -2894,7 +2893,7 @@
 	mnt_target->mnt_root = dget(nd->path.dentry);
 
 	/* Correct the device pathname */
-	nfs_fix_devname(&nd->path, mnt_target);
+	nfs_fix_devname(nd->path.dentry, mnt_target);
 
 	path_put(&nd->path);
 	kfree(nd);