Traverse translator hierarchies using the fsys protocol.

Previously, we used the fs protocol to traverse the translator
hierarchies.  This, however, is conceptually flawed, because
translators are bound to nodes, and a node can have zero or more links
in the file system.  Therefore, the previous method of returning a
list of paths to the client and expecting them to be able to follow
these to reach the child translators was always unreliable.

Fix this by using the fsys protocol to traverse the hierarchy, and
returning the control ports of all children.  This is more robust, and
also conceptually cleaner, because the fsys protocol is about
translator linkage, hence this is the point to implement traversal.

Also move the get source routine over.  A per-node source really
does not fit the reality of most translators, while a per-translator
source makes sense in many cases.

* hurd/fs.defs (file_get_children): Drop routine.
(file_get_source): Likewise.
* hurd/fsys.defs (fsys_get_children): New routine.
(fsys_get_source): Likewise.
* libdiskfs/Makefile (FSYSSRCS): Remove files, add files.
* libdiskfs/file-get-children.c: Remove file.
* libdiskfs/fsys-get-children.c: New file.
* libdiskfs/file-get-source.c: Remove file.
* libdiskfs/fsys-get-source.c: New file.
* libfshelp/fshelp.h (fshelp_filter): Remove type.
(fshelp_get_active_translators): Remove filter and prefix argument,
return list of control ports.
* libfshelp/translator-list.c (fshelp_get_active_translators):
Likewise.
* libnetfs/Makefile (FSSRCS): Move 'get-source.c' too OTHERSRCS.
(FSYSSRCS): Remove files, add files.
* libnetfs/file-get-children.c: Remove file.
* libnetfs/fsys-get-children.c: New file.
* libnetfs/file-get-source.c: Remove file.
* libnetfs/fsys-get-source.c: New file.
* libtrivfs/Makefile: Move 'get-source.c' too OTHERSRCS.
(FSYSSRCS): Remove files, add files.
* libtrivfs/file-get-children.c: Remove file.
* libtrivfs/fsys-get-children.c: New file.
* libtrivfs/file-get-source.c: Remove file.
* libtrivfs/fsys-get-source.c: Add file.
* trans/Makefile (mtab): Build client stubs until the libc has caught
on.
* trans/mtab.c (target_control): New variable.
(insecure): Drop variable.
(all_translators): Likewise.
(MAX_DEPTH): New macro.
(max_depth): New variable.
(options): Remove '--insecure' and '--all-translators', add '--depth'.
(parse_opt): Adapt accordingly.
(trivsfs_append_args): Likewise.
(main): Get the control port of the target translator, then drop
privileges.
(is_filesystem_translator): Remove function.
(mtab_mark_as_seen): Simplify.  Just check if the control port is
known.
(mtab_populate): Limit depth of recursion, adapt to traversing over
the control ports, simplify.
(open_hook): Remove scary comment, it is not applicable anymore
because we no longer dir_lookup child translators.

1 files changed, 39 insertions, 0 deletions

diff --git a/libnetfs/fsys-get-source.c b/libnetfs/fsys-get-source.c
new file mode 100644
index 00000000..bd33cb21
--- /dev/null
+++ b/libnetfs/fsys-get-source.c
@@ -0,0 +1,39 @@
+/* fsys_get_source
+
+   Copyright (C) 2017 Free Software Foundation, Inc.
+
+   This file is part of the GNU Hurd.
+
+   The GNU Hurd is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2, or (at your option)
+   any later version.
+
+   The GNU Hurd is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with the GNU Hurd.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "priv.h"
+#include "fsys_S.h"
+
+/* Return information about the source of the translator.  If the
+   concept of a source is applicable, SOURCE should refer to the
+   source of the translator and should be a description considered
+   appropriate in the context of the translator.  For example, if the
+   translator is a filesystem residing on a block device, then SOURCE
+   should be the file name of the underlying block device.  */
+error_t
+netfs_S_fsys_get_source (struct netfs_control *fsys,
+                         mach_port_t reply,
+                         mach_msg_type_name_t reply_type,
+			 char *source)
+{
+  if (! fsys)
+    return EOPNOTSUPP;
+
+  return netfs_get_source (source, 1024 /* XXX */);
+}