[PATCH 6/8] libfshelp: fix the api of fshelp_set_active_translator

[Justus Winter]

To detect if an active translator goes away, we need to register for
dead name notifications. Those notifications have to be sent to a port
known to the ports library, as the ports library handles the dead name
notifications. The most straight forward way is to use the port to the
underlying node for that. To that end, a reference to the port_info
struct is handed in and kept in the list of active translators.

This commit also moves the registration of dead name notifications to
libfshelp.

* libfshelp/fshelp.h (fshelp_set_active_translator): Add port_info argument.
* libfshelp/translator-list.c (struct translator): Add port_info pointer.
(translator_ihash_cleanup): Dereference port_info object.
(fshelp_set_active_translator): Register dead name notifications.
* libdiskfs/file-set-trans.c (diskfs_S_file_set_translator): Update
  accordingly.
* libnetfs/file-set-translator.c (netfs_S_file_set_translator): Likewise.
---
 libdiskfs/file-set-trans.c     | 18 +++---------------
 libfshelp/fshelp.h             | 18 ++++++++++++------
 libfshelp/translator-list.c    | 43 +++++++++++++++++++++++++++++++++++-------
 libnetfs/file-set-translator.c | 19 ++++---------------
 4 files changed, 55 insertions(+), 43 deletions(-)

diff --git a/libdiskfs/file-set-trans.c b/libdiskfs/file-set-trans.c
index 8de2e64..58f6255 100644
--- a/libdiskfs/file-set-trans.c
+++ b/libdiskfs/file-set-trans.c
@@ -1,5 +1,5 @@
 /* libdiskfs implementation of fs.defs: file_set_translator
-   Copyright (C) 1992,93,94,95,96,99,2001,02,13
+   Copyright (C) 1992,93,94,95,96,99,2001,02,13,14
      Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or
@@ -208,20 +208,8 @@ diskfs_S_file_set_translator (struct protid *cred,
 
   pthread_mutex_unlock (&np->lock);
 
-  if (! error && cred->po->path)
-    error = fshelp_set_active_translator (cred->po->path, active);
-
-  if (! error && active != MACH_PORT_NULL)
-    {
-      mach_port_t old;
-      error = mach_port_request_notification (mach_task_self (), active,
-                                             MACH_NOTIFY_DEAD_NAME, 0,
-                                             cred->pi.port_right,
-                                             MACH_MSG_TYPE_MAKE_SEND_ONCE,
-                                             &old);
-      if (old != MACH_PORT_NULL)
-       mach_port_deallocate (mach_task_self (), old);
-    }
+  if (! error && cred->po->path && active_flags & FS_TRANS_SET)
+    error = fshelp_set_active_translator (&cred->pi, cred->po->path, active);
 
   return error;
 }
diff --git a/libfshelp/fshelp.h b/libfshelp/fshelp.h
index a7702ca..5d3a0ce 100644
--- a/libfshelp/fshelp.h
+++ b/libfshelp/fshelp.h
@@ -1,5 +1,5 @@
 /* FS helper library definitions
-   Copyright (C) 1994,95,96,97,98,99,2000,01,02,13
+   Copyright (C) 1994,95,96,97,98,99,2000,01,02,13,14
      Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or
@@ -34,14 +34,20 @@
 
 
 /* Keeping track of active translators */
-/* These routines keep a list of active translators.  They are
-   self-contained and do not require multi threading or the ports
-   library.  */
+/* These routines keep a list of active translators.  They do not
+   require multi threading but depend on the ports library.  */
+
+struct port_info;
 
 /* Record an active translator being bound to the given file name
-   NAME.  ACTIVE is the control port of the translator.  */
+   NAME.  ACTIVE is the control port of the translator.  PI references
+   a receive port that is used to request dead name notifications,
+   typically the port for the underlying node passed to the
+   translator.  */
 error_t
-fshelp_set_active_translator (const char *name, mach_port_t active);
+fshelp_set_active_translator (struct port_info *pi,
+                              const char *name,
+                              mach_port_t active);
 
 /* Remove the active translator specified by its control port ACTIVE.
    If there is no active translator with the given control port, this
diff --git a/libfshelp/translator-list.c b/libfshelp/translator-list.c
index 87dcb21..3ece711 100644
--- a/libfshelp/translator-list.c
+++ b/libfshelp/translator-list.c
@@ -1,6 +1,6 @@
 /* A list of active translators.
 
-   Copyright (C) 2013 Free Software Foundation, Inc.
+   Copyright (C) 2013,14 Free Software Foundation, Inc.
 
    Written by Justus Winter <4winter@informatik.uni-hamburg.de>
 
@@ -22,6 +22,7 @@
 #include <argz.h>
 #include <hurd/fsys.h>
 #include <hurd/ihash.h>
+#include <hurd/ports.h>
 #include <mach.h>
 #include <mach/notify.h>
 #include <pthread.h>
@@ -33,6 +34,7 @@
 
 struct translator
 {
+  struct port_info *pi;
   char *name;
   mach_port_t active;
 };
@@ -49,8 +51,10 @@ translator_ihash_cleanup (void *element, void *arg)
 {
   struct translator *translator = element;
 
-  /* No need to deallocate port, we only keep the name of the
-     port, not a reference.  */
+  if (translator->pi)
+    ports_port_deref (translator->pi);
+  /* No need to deallocate translator->active, we only keep the name of
+     the port, not a reference.  */
   free (translator->name);
   free (translator);
 }
@@ -58,7 +62,9 @@ translator_ihash_cleanup (void *element, void *arg)
 /* Record an active translator being bound to the given file name
    NAME.  ACTIVE is the control port of the translator.  */
 error_t
-fshelp_set_active_translator (const char *name, mach_port_t active)
+fshelp_set_active_translator (struct port_info *pi,
+                             const char *name,
+                             mach_port_t active)
 {
   error_t err = 0;
   pthread_mutex_lock (&translator_ihash_lock);
@@ -79,6 +85,7 @@ fshelp_set_active_translator (const char *name, mach_port_t 
active)
     return ENOMEM;
 
   t->active = MACH_PORT_NULL;
+  t->pi = NULL;
   t->name = strdup (name);
   if (! t->name)
     {
@@ -93,9 +100,31 @@ fshelp_set_active_translator (const char *name, mach_port_t 
active)
 
  update:
   if (active)
-    /* No need to increment the reference count, we only keep the
-       name, not a reference.  */
-    t->active = active;
+    {
+      if (t->pi != pi)
+       {
+         mach_port_t old;
+         err = mach_port_request_notification (mach_task_self (), active,
+                                               MACH_NOTIFY_DEAD_NAME, 0,
+                                               pi->port_right,
+                                               MACH_MSG_TYPE_MAKE_SEND_ONCE,
+                                               &old);
+         if (err)
+           return err;
+         if (old != MACH_PORT_NULL)
+           mach_port_deallocate (mach_task_self (), old);
+
+         if (t->pi)
+           ports_port_deref (t->pi);
+
+         ports_port_ref (pi);
+         t->pi = pi;
+       }
+
+      /* No need to increment the reference count, we only keep the
+        name, not a reference.  */
+      t->active = active;
+    }
   else
     hurd_ihash_remove (&translator_ihash, (hurd_ihash_key_t) t);
 
diff --git a/libnetfs/file-set-translator.c b/libnetfs/file-set-translator.c
index a9883a3..b46eb02 100644
--- a/libnetfs/file-set-translator.c
+++ b/libnetfs/file-set-translator.c
@@ -1,5 +1,6 @@
 /*
-   Copyright (C) 1996, 1997, 1999, 2001, 2013 Free Software Foundation, Inc.
+   Copyright (C) 1996, 1997, 1999, 2001, 2013, 2014
+     Free Software Foundation, Inc.
    Written by Michael I. Bushnell, p/BSG.
 
    This file is part of the GNU Hurd.
@@ -175,20 +176,8 @@ netfs_S_file_set_translator (struct protid *user,
        }
     }
 
-  if (! err && user->po->path)
-    err = fshelp_set_active_translator (user->po->path, active);
-
-  if (! err && active != MACH_PORT_NULL)
-    {
-      mach_port_t old;
-      err = mach_port_request_notification (mach_task_self (), active,
-                                           MACH_NOTIFY_DEAD_NAME, 0,
-                                           user->pi.port_right,
-                                           MACH_MSG_TYPE_MAKE_SEND_ONCE,
-                                           &old);
-      if (old != MACH_PORT_NULL)
-       mach_port_deallocate (mach_task_self (), old);
-    }
+  if (! err && user->po->path && active_flags & FS_TRANS_SET)
+    err = fshelp_set_active_translator (&user->pi, user->po->path, active);
 
  out:
   pthread_mutex_unlock (&np->lock);
-- 
1.8.5.2