2003-03-05 Roland McGrath <roland@frob.com>

	Make /hurd/magic support translator delegation via /servers/magic.
	* magic.c (struct magic): New structure.
	(magic, directory, dirbuf, dirbufsize): Variables removed,
	not members of struct magic.
	(trivfs_modify_stat, magic_getroot, trivfs_S_dir_readdir): Use a
	struct magic hanging off CNTL->hook rather than global variables.
	(trivfs_append_args): Likewise.
	(trivfs_S_dir_lookup): Likewise.  Let magic string be null to indicate
	prepending nothing in --directory mode.
	(parse_opt): Use struct magic in STATE->input instead of globals.
	If no argument, turn on --directory and leave M->magic null.
	(argp): New static variable, instead of auto in main.
	(main): Set both trivfs hook functions unconditionally.
	Use a struct magic, pass it to argp_parse and store it in FSYS->hook.
	Move directory buffer setup to ...
	(parse_opt): ... here, do it on ARGP_KEY_SUCCESS.
	(magic_open): Track users with a count.
	(magic_protid_destroy): New function to track users.
	(main): Set trivfs_protid_destroy_hook to that.
	(trivfs_goaway): Call ports_destroy_right if FSYS has no users.
	(all_fsys): New variable, list of all filesystems.
	(trivfs_clean_cntl): New function, exit if no filesystems left.
	(main): Put FSYS on that list.  On timeout with no RPCs, try
	trivfs_goaway on each filesystem on the list.
	(trivfs_S_fsys_forward): New function.
	(delegate): New variable.
	(options): New option -U/--use-server to set it.

1 files changed, 272 insertions, 87 deletions

diff --git a/trans/magic.c b/trans/magic.c
index 2febff68..2e47f911 100644
--- a/trans/magic.c
+++ b/trans/magic.c
@@ -1,6 +1,6 @@
 /* A translator for returning FS_RETRY_MAGIC strings.
 
-   Copyright (C) 1999,2001,02 Free Software Foundation, Inc.
+   Copyright (C) 1999,2001,02, 03 Free Software Foundation, Inc.
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
@@ -19,6 +19,7 @@
 #include <hurd.h>
 #include <hurd/ports.h>
 #include <hurd/trivfs.h>
+#include <hurd/fshelp.h>
 #include <hurd/fsys.h>
 #include <version.h>
 
@@ -36,23 +37,38 @@
 #include <assert.h>
 
 const char *argp_program_version = STANDARD_HURD_VERSION (magic);
-static char args_doc[] = "MAGIC";
-static char doc[] = "A translator that returns the magic retry result MAGIC.";
-static const struct argp_option options[] =
+
+/* This structure has all the state about one filesystem.
+   It hangs off trivfs_control->hook.  */
+struct magic
 {
-  {"directory",	'd', 0,		0, "Provide virtual (empty) directory node"},
-  {0}
-};
+  /* We chain all filesystems together so we can tell easily when they are
+     all unused.  */
+  struct trivfs_control *next;
+
+  /* The magic string we return for lookups.  */
+  char *magic;
 
-/* The magic string we return for lookups.  */
-static char *magic;
+  int directory;		/* --directory flag */
 
-static int directory;		/* --directory flag */
+  /* Pre-fab contents of dummy directory for dir_readdir.
+     Set up only under --directory.  */
+  void *dirbuf;
+  size_t dirbufsize;
 
-/* Pre-fab contents of dummy directory for dir_readdir.
-   Set up only under --directory.  */
-static void *dirbuf;
-static size_t dirbufsize;
+  unsigned int nusers;		/* Count of users, only with --directory.  */
+};
+
+static inline void
+free_magic (struct magic *m)
+{
+  free (m->magic);
+  if (m->dirbuf)
+    munmap (m->dirbuf, m->dirbufsize);
+  free (m);
+}
+
+static struct trivfs_control *all_fsys;
 
 /* Trivfs hooks  */
 
@@ -68,7 +84,9 @@ int trivfs_allow_open = O_READ;
 void
 trivfs_modify_stat (struct trivfs_protid *cred, struct stat *st)
 {
-  st->st_size = dirbufsize;
+  struct magic *const m = cred->po->cntl->hook;
+
+  st->st_size = m->dirbufsize;
   st->st_blocks = getpagesize () / S_BLKSIZE;
 
   st->st_mode = ((st->st_mode & ~S_IFMT & ~ALLPERMS)
@@ -79,9 +97,45 @@ trivfs_modify_stat (struct trivfs_protid *cred, struct stat *st)
 error_t
 trivfs_goaway (struct trivfs_control *fsys, int flags)
 {
-  exit (0);
+  struct magic *const m = fsys->hook;
+
+  /* We are single-threaded, so no fancy stuff is needed here.  */
+
+  if (m->nusers > 0 && !(flags & FSYS_GOAWAY_FORCE))
+    return EBUSY;
+
+  /* No more communication with the parent filesystem.
+     This running RPC should now be the only ref keeping FSYS alive.  */
+  ports_destroy_right (fsys);
+  return 0;
 }
 
+
+/* Clean pointers in a struct trivfs_control when its last reference
+   vanishes before it's freed.  This overrides the libtrivfs version
+   so we can clean up our hook data.  */
+void
+trivfs_clean_cntl (void *arg)
+{
+  struct trivfs_control *cntl = arg;
+  struct magic *const m = cntl->hook;
+
+  /* Remove us from the list of all filesystems.  */
+  struct trivfs_control **lastp = &all_fsys;
+  while (*lastp != cntl)
+    lastp = &((struct magic *) (*lastp)->hook)->next;
+  *lastp = m->next;
+
+  if (all_fsys == 0)
+    /* Nothing more to do in this life.  */
+    exit (0);
+
+  mach_port_destroy (mach_task_self (), cntl->filesys_id);
+  mach_port_destroy (mach_task_self (), cntl->file_id);
+  mach_port_deallocate (mach_task_self (), cntl->underlying);
+
+  free_magic (m);
+}
 
 /* This hook is used when running without --directory;
    it circumvents basically all the trivfs machinery.  */
@@ -96,7 +150,12 @@ magic_getroot (struct trivfs_control *cntl,
 	       retry_type *do_retry, char *retry_name,
 	       mach_port_t *node, mach_msg_type_name_t *node_type)
 {
-  strcpy (retry_name, magic);
+  struct magic *const m = cntl->hook;
+
+  if (m->directory)
+    return EAGAIN;		/* Do normal trivfs getroot processing.  */
+
+  strcpy (retry_name, m->magic);
   *do_retry = FS_RETRY_MAGICAL;
   *node = MACH_PORT_NULL;
   *node_type = MACH_MSG_TYPE_COPY_SEND;
@@ -125,10 +184,20 @@ magic_open  (struct trivfs_control *cntl,
       assert_perror (err);
       err = mach_port_deallocate (mach_task_self (), dotdot);
       assert_perror (err);
+      struct magic *const m = cntl->hook;
+      m->nusers++;
     }
   return err;
 }
 
+/* We have this hook only for simple tracking of the live user ports.  */
+static void
+magic_protid_destroy (struct trivfs_protid *cred)
+{
+  struct magic *const m = cred->po->cntl->hook;
+  m->nusers--;
+}
+
 
 /* Do a directory lookup.  */
 
@@ -154,44 +223,49 @@ trivfs_S_dir_lookup (struct trivfs_protid *cred,
 
   if (name[0] != '\0')
     {
-      if (!directory)
+      struct magic *const m = cred->po->cntl->hook;
+
+      if (!m->directory)
 	return ENOTDIR;
-      else
-	{
-	  /* We have a real lookup in the dummy directory.
-	     Handle `.' and `..' specially, and anything else
-	     gets redirected to the magical retry.  */
 
+      /* We have a real lookup in the dummy directory.
+	 Handle `.' and `..' specially, and anything else
+	 gets redirected to the magical retry.  */
+
+      while (*name == '/')
+	++name;
+      while (!strncmp (name, "./", 2))
+	{
+	  name += 2;
 	  while (*name == '/')
 	    ++name;
-	  while (!strncmp (name, "./", 2))
-	    {
-	      name += 2;
-	      while (*name == '/')
-		++name;
-	    }
+	}
 
-	  if (!strcmp (name, "..") || !strncmp (name, "../", 3))
-	    {
-	      name += 2;
-	      while (*name == '/')
-		++name;
-	      strcpy (retry_name, name);
-	      *retry_type = FS_RETRY_REAUTH;
-	      *retrypt = (mach_port_t) cred->po->hook;
-	      *retrypt_type = MACH_MSG_TYPE_COPY_SEND;
-	      return 0;
-	    }
-	  else if (name[0] != '\0' && strcmp (name, "."))
+      if (!strcmp (name, "..") || !strncmp (name, "../", 3))
+	{
+	  name += 2;
+	  while (*name == '/')
+	    ++name;
+	  strcpy (retry_name, name);
+	  *retry_type = FS_RETRY_REAUTH;
+	  *retrypt = (mach_port_t) cred->po->hook;
+	  *retrypt_type = MACH_MSG_TYPE_COPY_SEND;
+	  return 0;
+	}
+      else if (name[0] != '\0' && strcmp (name, "."))
+	{
+	  if (m->magic == 0)
+	    strcpy (retry_name, name);
+	  else
 	    {
-	      char *p = stpcpy (retry_name, magic);
+	      char *p = stpcpy (retry_name, m->magic);
 	      *p++ = '/';
 	      strcpy (p, name);
-	      *retry_type = FS_RETRY_MAGICAL;
-	      *retrypt = MACH_PORT_NULL;
-	      *retrypt_type = MACH_MSG_TYPE_COPY_SEND;
-	      return 0;
 	    }
+	  *retry_type = FS_RETRY_MAGICAL;
+	  *retrypt = MACH_PORT_NULL;
+	  *retrypt_type = MACH_MSG_TYPE_COPY_SEND;
+	  return 0;
 	}
     }
 
@@ -253,23 +327,25 @@ trivfs_S_dir_readdir (struct trivfs_protid *cred,
   if (!cred)
     return EOPNOTSUPP;
 
+  struct magic *const m = cred->po->cntl->hook;
+
   if (entry > 0)
     {
       void *p;
       int i;
       i = 0;
-      for (p = dirbuf; p < dirbuf + dirbufsize;
+      for (p = m->dirbuf; p < m->dirbuf + m->dirbufsize;
 	   p += ((struct dirent *) p)->d_reclen)
 	if (i++ == entry)
 	  break;
       *data = p;
-      *datalen = dirbuf + dirbufsize - p;
+      *datalen = m->dirbuf + m->dirbufsize - p;
       *amount = 2 - entry;
     }
   else
     {
-      *data = dirbuf;
-      *datalen = dirbufsize;
+      *data = m->dirbuf;
+      *datalen = m->dirbufsize;
       *amount = 2;
     }
 
@@ -278,32 +354,71 @@ trivfs_S_dir_readdir (struct trivfs_protid *cred,
 }
 
 
+#include <hurd/paths.h>
+#define _SERVERS_MAGIC _SERVERS "magic"
+
+/* To whom should we try to delegate on startup?  */
+static const char *delegate = _SERVERS_MAGIC;
+
+static const struct argp_option options[] =
+{
+  {"directory",	'd', 0,		0, "Provide virtual (empty) directory node"},
+  {"use-server", 'U', "NAME",	0,
+   "Delegate to server NAME instead of " _SERVERS_MAGIC},
+  {0}
+};
 
 static error_t
 parse_opt (int opt, char *arg, struct argp_state *state)
 {
+  struct magic *const m = state->input;
+
   switch (opt)
     {
-    case 'd':
-      directory = 1;
+    case 'U':
+      /* This is only valid for the startup options, not delegates.  */
+      if (all_fsys != 0)
+	return EINVAL;
+      delegate = arg;
       return 0;
 
+    case 'd':
     case ARGP_KEY_NO_ARGS:
-      argp_usage (state);
-      return EINVAL;
+      m->directory = 1;
+      return 0;
 
-    case ARGP_KEY_ARGS:
-      if (state->next != state->argc - 1)
+    case ARGP_KEY_ARG:
+      if (m->magic != 0)
 	{
 	  argp_usage (state);
 	  return EINVAL;
 	}
-      else
+      m->magic = strdup (arg);
+      return m->magic == 0 ? ENOMEM : 0;
+
+    case ARGP_KEY_SUCCESS:
+      if (m->directory)
 	{
-	  magic = state->argv[state->next];
-	  return 0;
+	  inline struct dirent *add (struct dirent *d, const char *name)
+	    {
+	      d->d_fileno = 2;	/* random */
+	      d->d_type = DT_DIR;
+	      d->d_namlen = strlen (name);
+	      strcpy (d->d_name, name);
+	      d->d_name[d->d_namlen] = '\0';
+	      d->d_reclen = &d->d_name[d->d_namlen + 1] - (char *) d;
+	      d->d_reclen = ((d->d_reclen + __alignof (struct dirent) - 1)
+			     & ~(__alignof (struct dirent) - 1));
+	      return (struct dirent *) ((char *) d + d->d_reclen);
+	    }
+	  struct dirent *d;
+	  m->dirbuf = mmap (0, getpagesize (), PROT_READ|PROT_WRITE,
+			    MAP_ANON, 0, 0);
+	  d = add (m->dirbuf, ".");
+	  d = add (d, "..");
+	  m->dirbufsize = (char *) d - (char *) m->dirbuf;
 	}
-      break;
+      return 0;
     }
 
   return ARGP_ERR_UNKNOWN;
@@ -313,9 +428,16 @@ error_t
 trivfs_append_args (struct trivfs_control *fsys,
 		    char **argz, size_t *argz_len)
 {
-  return ((directory ? argz_add (argz, argz_len, "--directory") : 0)
-	  ?: argz_add (argz, argz_len, magic));
+  struct magic *const m = fsys->hook;
+  return ((m->directory ? argz_add (argz, argz_len, "--directory") : 0)
+	  ?: (m->magic ? argz_add (argz, argz_len, m->magic) : 0));
 }
+
+static struct argp argp =
+  {
+    options, parse_opt, "MAGIC",
+    "A translator that returns the magic retry result MAGIC."
+  };
 
 int
 main (int argc, char **argv)
@@ -323,48 +445,111 @@ main (int argc, char **argv)
   error_t err;
   mach_port_t bootstrap;
   struct trivfs_control *fsys;
-  struct argp argp = { options, parse_opt, args_doc, doc };
+  struct magic *m = calloc (1, sizeof *m);
 
-  argp_parse (&argp, argc, argv, 0, 0, 0);
+  argp_parse (&argp, argc, argv, 0, 0, m);
 
   task_get_bootstrap_port (mach_task_self (), &bootstrap);
   if (bootstrap == MACH_PORT_NULL)
     error (1, 0, "Must be started as a translator");
 
+  if (delegate != 0)
+    {
+      /* First, try to have the canonical server sitting on /servers/magic
+	 take over for us.  */
+      err = fshelp_delegate_translation (delegate, bootstrap, argv);
+      if (err == 0)
+	return 0;
+    }
+
+  /* Nope, we are doing it ourselves.  */
+
+  trivfs_getroot_hook = &magic_getroot;
+  trivfs_open_hook = &magic_open;
+  trivfs_protid_destroy_hook = &magic_protid_destroy;
+
   /* Reply to our parent */
   err = trivfs_startup (bootstrap, 0, 0, 0, 0, 0, &fsys);
   mach_port_deallocate (mach_task_self (), bootstrap);
   if (err)
     error (3, err, "Contacting parent");
+  fsys->hook = m;
+  all_fsys = fsys;
 
-  if (directory)
+  /* Launch. */
+  while (1)
     {
-      inline struct dirent *add (struct dirent *d, const char *name)
+      ports_manage_port_operations_one_thread (fsys->pi.bucket, trivfs_demuxer,
+					       10 * 60 * 1000);
+
+      /* That returns when 10 minutes pass without an RPC.  Try shutting down
+	 as if sent fsys_goaway; if we have any users who need us to stay
+	 around, this returns EBUSY and we loop to service more RPCs.  */
+
+      struct trivfs_control *fs = all_fsys;
+      do
 	{
-	  d->d_fileno = 2;	/* random */
-	  d->d_type = DT_DIR;
-	  d->d_namlen = strlen (name);
-	  strcpy (d->d_name, name);
-	  d->d_name[d->d_namlen] = '\0';
-	  d->d_reclen = &d->d_name[d->d_namlen + 1] - (char *) d;
-	  d->d_reclen = ((d->d_reclen + __alignof (struct dirent) - 1)
-			 & ~(__alignof (struct dirent) - 1));
-	  return (struct dirent *) ((char *) d + d->d_reclen);
-	}
-      struct dirent *d;
-      dirbuf = mmap (0, getpagesize (), PROT_READ|PROT_WRITE, MAP_ANON, 0, 0);
-      d = add (dirbuf, ".");
-      d = add (d, "..");
-      dirbufsize = (char *) d - (char *) dirbuf;
+	  struct magic *const m = fs->hook;
+	  struct trivfs_control *const next = m->next;
+	  trivfs_goaway (fs, 0);
+	  fs = next;
+	} while (fs != 0);
+    }
+
+  return 0;
+}
+
 
-      trivfs_open_hook = &magic_open;
+/* Handle delegated filesystems.  */
+error_t
+trivfs_S_fsys_forward (mach_port_t server,
+		       mach_port_t reply,
+		       mach_msg_type_name_t replytype,
+		       mach_port_t requestor,
+		       char *argz, size_t argz_len)
+{
+  struct trivfs_protid *cred
+    = ports_lookup_port (all_fsys->pi.bucket, server,
+			 trivfs_protid_portclasses[0]);
+  if (!cred)
+    return EOPNOTSUPP;
+  ports_port_deref (cred);
+
+  /* Allocate a new structure for parameters, and parse the arguments
+     to fill it in.  */
+  struct magic *m = calloc (1, sizeof *m);
+  if (!m)
+    return ENOMEM;
+
+  int argc = argz_count (argz, argz_len);
+  char *argv[argc + 1];
+  argz_extract (argz, argz_len, argv);
+  error_t err = argp_parse (&argp, argc, argv,
+			    ARGP_NO_ERRS | ARGP_NO_HELP, 0, m);
+  if (err)
+    {
+      free_magic (m);
+      return err;
     }
-  else
-    trivfs_getroot_hook = &magic_getroot;
 
-  /* Launch. */
-  ports_manage_port_operations_one_thread (fsys->pi.bucket, trivfs_demuxer,
-					   2 * 60 * 1000);
+  /* Now we are ready to start up the filesystem.  Contact the parent.  */
+  struct trivfs_control *fsys;
+  err = trivfs_startup (requestor, 0,
+			trivfs_cntl_portclasses[0], all_fsys->pi.bucket,
+			trivfs_protid_portclasses[0], all_fsys->pi.bucket,
+			&fsys);
+  if (err)
+    {
+      free_magic (m);
+      return err;
+    }
+  mach_port_deallocate (mach_task_self (), requestor);
+
+  /* The new filesystem is all hooked up.
+     Put it on the list of all filesystems we are serving.  */
+  m->next = all_fsys;
+  fsys->hook = m;
+  all_fsys = fsys;
 
   return 0;
 }