1 files changed, 131 insertions, 0 deletions
diff --git a/libdiskfs/sync-interval.c b/libdiskfs/sync-interval.c
new file mode 100644
index 00000000..8167fc4a
--- /dev/null
+++ b/libdiskfs/sync-interval.c
@@ -0,0 +1,131 @@
+/* Support for periodic syncing
+
+   Copyright (C) 1995, 96, 99 Free Software Foundation, Inc.
+
+   Written by Miles Bader <miles@gnu.ai.mit.edu>
+
+   This program 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.
+
+   This program 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 this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
+
+#include <errno.h>
+#include <cthreads.h>
+#include <unistd.h>
+
+#include <hurd/fsys.h>
+
+#include "priv.h"
+
+/* A user-readable variable reflecting the last set sync interval.  */
+int diskfs_sync_interval = 0;
+
+/* The thread that's doing the syncing.  */
+static cthread_t periodic_sync_thread;
+
+/* This port represents the periodic sync service as if it were
+   an RPC.  We can use ports_inhibit_port_rpcs on this port to guarantee
+   that the periodic_sync_thread is quiescent.  */
+static struct port_info *pi;
+
+static void periodic_sync ();
+
+/* Establish a thread to sync the filesystem every INTERVAL seconds, or
+   never, if INTERVAL is zero.  If an error occurs creating the thread, it is
+   returned, otherwise 0.  Subsequent calls will create a new thread and
+   (eventually) get rid of the old one; the old thread won't do any more
+   syncs, regardless.  */
+error_t
+diskfs_set_sync_interval (int interval)
+{
+  error_t err = 0;
+
+  if (! pi)
+    {
+      err = ports_create_port (diskfs_control_class, diskfs_port_bucket,
+			       sizeof (struct port_info), &pi);
+      if (err)
+	return err;
+    }
+
+  err = ports_inhibit_port_rpcs (pi);
+  if (err)
+    return err;
+
+  /* Here we just set the new thread; any existing thread will notice when it
+     wakes up and go away silently.  */
+  if (interval == 0)
+    periodic_sync_thread = 0;
+  else
+    {
+      periodic_sync_thread =
+	cthread_fork ((cthread_fn_t)periodic_sync, (any_t)interval);
+      if (periodic_sync_thread)
+	cthread_detach (periodic_sync_thread);
+      else
+	err = ENOMEM;
+    }
+
+  if (!err)
+    diskfs_sync_interval = interval;
+
+  ports_resume_port_rpcs (pi);
+
+  return err;
+}
+
+/* ---------------------------------------------------------------- */
+
+/* Sync the filesystem (pointed to by the variable CONTROL_PORT above) every
+   INTERVAL seconds, as long as it's in the thread pointed to by the global
+   variable PERIODIC_SYNC_THREAD.   */
+static void
+periodic_sync (int interval)
+{
+  for (;;)
+    {
+      error_t err;
+      struct rpc_info link;
+
+      /* This acts as a lock against creation of a new sync thread
+	 while we are in the process of syncing.  */
+      err = ports_begin_rpc (pi, 0, &link);
+
+      if (periodic_sync_thread != cthread_self ())
+	{
+	  /* We've been superseded as the sync thread.  Just die silently.  */
+	  ports_end_rpc (pi, &link);
+	  return;
+	}
+
+      if (! err)
+	{
+	  if (! diskfs_readonly)
+	    {
+	      rwlock_reader_lock (&diskfs_fsys_lock);
+	      /* Only sync if we need to, to avoid clearing the clean flag
+		 when it's just been set.  Any other thread doing a sync
+		 will have held the lock while it did its work.  */
+	      if (_diskfs_diskdirty)
+		{
+		  diskfs_sync_everything (0);
+		  diskfs_set_hypermetadata (0, 0);
+		}
+	      rwlock_reader_unlock (&diskfs_fsys_lock);
+	    }
+	  ports_end_rpc (pi, &link);
+	}
+
+      /* Wait until next time.  */
+      sleep (interval);
+    }
+}