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/* 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);
}
}
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