hurd: fix semantic of file_get_children

When first introduced as fsys_get_children, it made sense to return
the list of children using paths relative to the root of the
filesystem that was queried.  Making the get_children method part of
the fsys protocol was a mistake that has since been corrected in
9366d6b2.

Instead of returning paths relative to the root of the translator,
return paths relative to the path of the receiving node.

This fixes a problem with the mtab translator.  Previously, the mtab
translator invoked on a target that was not the root directory of a
translator would compute invalid paths, e.g.:

/hurd/mtab: /any/path/servers/socket/26 No such file or directory

* hurd/fs.defs (file_get_children): Update comment.
* libfshelp/translator-list.c (fshelp_get_active_translators): Add
argument PREFIX.  Filter entries not beginning with PREFIX if
non-NULL, and omit PREFIX from the returned paths.
* libfshelp/fshelp.h (fshelp_get_active_translators): Update comment
accordingly.  Also clarify that both FILTER and PREFIX can be NULL.
* libdiskfs/file-get-children.c (diskfs_S_file_get_children): Update
comment, pass prefix to fshelp_get_active_translators.
* libnetfs/file-get-children.c (netfs_S_file_get_children): Likewise.

1 files changed, 5 insertions, 4 deletions

diff --git a/libdiskfs/file-get-children.c b/libdiskfs/file-get-children.c
index 4581e4e0..98d5d60e 100644
--- a/libdiskfs/file-get-children.c
+++ b/libdiskfs/file-get-children.c
@@ -24,9 +24,9 @@
 
 #include <argz.h>
 
-/* Return any active translators bound to nodes of the receiving
-   filesystem.  CHILDREN is an argz vector containing file names
-   relative to the root of the receiving translator.  */
+/* Return any active translators bound to nodes below CRED.  CHILDREN
+   is an argz vector containing file names relative to the path of
+   CRED.  */
 error_t
 diskfs_S_file_get_children (struct protid *cred,
 			    char **children,
@@ -79,7 +79,8 @@ diskfs_S_file_get_children (struct protid *cred,
   char *c = NULL;
   size_t c_len = 0;
 
-  err = fshelp_get_active_translators (&c, &c_len, check_access);
+  err = fshelp_get_active_translators (&c, &c_len, check_access,
+				       cred->po->path);
   if (err)
     goto errout;