path: root/sys/kern/vfs_sync.c

/*       $OpenBSD: vfs_sync.c,v 1.3 1998/03/14 19:32:59 millert Exp $  */


/*
 *  Portions of this code are:
 *
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * Syncer daemon
 */

#include <sys/queue.h>
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/vnode.h>
#include <sys/buf.h>
#include <sys/malloc.h>

#include <sys/kernel.h>

/*
 * The workitem queue.
 */ 
#define SYNCER_MAXDELAY	32
int syncer_maxdelay = SYNCER_MAXDELAY;	/* maximum delay time */
time_t syncdelay = 30;			/* time to delay syncing vnodes */
int rushjob;				/* number of slots to run ASAP */
 
static int syncer_delayno = 0;
static long syncer_mask;
LIST_HEAD(synclist, vnode);
static struct synclist *syncer_workitem_pending;

extern struct simplelock mountlist_slock;

/*
 * The workitem queue.
 * 
 * It is useful to delay writes of file data and filesystem metadata
 * for tens of seconds so that quickly created and deleted files need
 * not waste disk bandwidth being created and removed. To realize this,
 * we append vnodes to a "workitem" queue. When running with a soft
 * updates implementation, most pending metadata dependencies should
 * not wait for more than a few seconds. Thus, mounted on block devices
 * are delayed only about a half the time that file data is delayed.
 * Similarly, directory updates are more critical, so are only delayed
 * about a third the time that file data is delayed. Thus, there are
 * SYNCER_MAXDELAY queues that are processed round-robin at a rate of
 * one each second (driven off the filesystem syner process). The
 * syncer_delayno variable indicates the next queue that is to be processed.
 * Items that need to be processed soon are placed in this queue:
 *
 *	syncer_workitem_pending[syncer_delayno]
 *
 * A delay of fifteen seconds is done by placing the request fifteen
 * entries later in the queue:
 *
 *	syncer_workitem_pending[(syncer_delayno + 15) & syncer_mask]
 *
 */

void
vn_initialize_syncerd()

{
	syncer_workitem_pending = hashinit(syncer_maxdelay, M_VNODE,
					   &syncer_mask);
	syncer_maxdelay = syncer_mask + 1;
}

/*
 * Add an item to the syncer work queue.
 */
void
vn_syncer_add_to_worklist(vp, delay)
	struct vnode *vp;
	int delay;
{
	int s, slot;

	s = splbio();
	if (delay > syncer_maxdelay - 2)
		delay = syncer_maxdelay - 2;
	slot = (syncer_delayno + delay) & syncer_mask;
	LIST_INSERT_HEAD(&syncer_workitem_pending[slot], vp, v_synclist);
	splx(s);
}

/*
 * System filesystem synchronizer daemon.
 */


extern int lbolt;

void 
sched_sync(p)
	struct proc *p;
{
	struct synclist *slp;
	struct vnode *vp;
	long starttime;
	int s;

	for (;;) {
		starttime = time.tv_sec;

		/*
		 * Push files whose dirty time has expired.
		 */
		s = splbio();
		slp = &syncer_workitem_pending[syncer_delayno];
		syncer_delayno += 1;
		if (syncer_delayno == syncer_maxdelay)
			syncer_delayno = 0;
		splx(s);
		while ((vp = LIST_FIRST(slp)) != NULL) {
			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, p);
			(void) VOP_FSYNC(vp, p->p_ucred, MNT_LAZY, p);
			VOP_UNLOCK(vp, 0, p);
			if (LIST_FIRST(slp) == vp) {
				if (LIST_FIRST(&vp->v_dirtyblkhd) == NULL)
					panic("sched_sync: fsync failed");
				/*
				 * Move ourselves to the back of the sync list.
				 */
				LIST_REMOVE(vp, v_synclist);
				vn_syncer_add_to_worklist(vp, syncdelay);
			}
		}

		/*
		 * Do soft update processing.
		 */
		if (bioops.io_sync)
			(*bioops.io_sync)(NULL);

		/*
		 * The variable rushjob allows the kernel to speed up the
		 * processing of the filesystem syncer process. A rushjob
		 * value of N tells the filesystem syncer to process the next
		 * N seconds worth of work on its queue ASAP. Currently rushjob
		 * is used by the soft update code to speed up the filesystem
		 * syncer process when the incore state is getting so far
		 * ahead of the disk that the kernel memory pool is being
		 * threatened with exhaustion.
		 */
		if (rushjob > 0) {
			rushjob -= 1;
			continue;
		}
		/*
		 * If it has taken us less than a second to process the
		 * current work, then wait. Otherwise start right over
		 * again. We can still lose time if any single round
		 * takes more than two seconds, but it does not really
		 * matter as we are just trying to generally pace the
		 * filesystem activity.
		 */
		if (time.tv_sec == starttime)
			tsleep(&lbolt, PPAUSE, "syncer", 0);
	}
}


/*
 * Routine to create and manage a filesystem syncer vnode.
 */
#define sync_close nullop
int   sync_fsync __P((void *));
int   sync_inactive __P((void *));
#define sync_reclaim nullop
#define sync_lock vop_nolock
#define sync_unlock vop_nounlock
int   sync_print __P((void *));
#define sync_islocked vop_noislocked
 
int (**sync_vnodeop_p) __P((void *));
struct vnodeopv_entry_desc sync_vnodeop_entries[] = {
      { &vop_default_desc, vn_default_error },
      { &vop_close_desc, sync_close },                /* close */
      { &vop_fsync_desc, sync_fsync },                /* fsync */
      { &vop_inactive_desc, sync_inactive },          /* inactive */
      { &vop_reclaim_desc, sync_reclaim },            /* reclaim */
      { &vop_lock_desc, sync_lock },                  /* lock */
      { &vop_unlock_desc, sync_unlock },              /* unlock */
      { &vop_print_desc, sync_print },                /* print */
      { &vop_islocked_desc, sync_islocked },          /* islocked */
      { (struct vnodeop_desc*)NULL, (int(*) __P((void *)))NULL }
};
struct vnodeopv_desc sync_vnodeop_opv_desc =
      { &sync_vnodeop_p, sync_vnodeop_entries };

/*
 * Create a new filesystem syncer vnode for the specified mount point.
 */
int
vfs_allocate_syncvnode(mp)
      struct mount *mp;
{
      struct vnode *vp;
      static long start, incr, next;
      int error;

      /* Allocate a new vnode */
      if ((error = getnewvnode(VT_VFS, mp, sync_vnodeop_p, &vp)) != 0) {
              mp->mnt_syncer = NULL;
              return (error);
      }
      vp->v_writecount = 1;
      vp->v_type = VNON;
      /*
       * Place the vnode onto the syncer worklist. We attempt to
       * scatter them about on the list so that they will go off
       * at evenly distributed times even if all the filesystems
       * are mounted at once.
       */
      next += incr;
      if (next == 0 || next > syncer_maxdelay) {
              start /= 2;
              incr /= 2;
              if (start == 0) {
                      start = syncer_maxdelay / 2;
                      incr = syncer_maxdelay;
              }
              next = start;
      }
      vn_syncer_add_to_worklist(vp, next);
      mp->mnt_syncer = vp;
      return (0);
}

/*
 * Do a lazy sync of the filesystem.
 */
int
sync_fsync(v)
	void *v;
{
      struct vop_fsync_args /* {
              struct vnode *a_vp;
              struct ucred *a_cred;
              int a_waitfor;
              struct proc *a_p;
      } */ *ap = v;

      struct vnode *syncvp = ap->a_vp;
      struct mount *mp = syncvp->v_mount;
      int asyncflag;

      /*
       * We only need to do something if this is a lazy evaluation.
       */
      if (ap->a_waitfor != MNT_LAZY)
              return (0);

      /*
       * Move ourselves to the back of the sync list.
       */
      LIST_REMOVE(syncvp, v_synclist);
      vn_syncer_add_to_worklist(syncvp, syncdelay);

      /*
       * Walk the list of vnodes pushing all that are dirty and
       * not already on the sync list.
       */
      simple_lock(&mountlist_slock);
      if (vfs_busy(mp, LK_NOWAIT, &mountlist_slock, ap->a_p) == 0) {
              asyncflag = mp->mnt_flag & MNT_ASYNC;
              mp->mnt_flag &= ~MNT_ASYNC;
              VFS_SYNC(mp, MNT_LAZY, ap->a_cred, ap->a_p);
              if (asyncflag)
                      mp->mnt_flag |= MNT_ASYNC;
              vfs_unbusy(mp, ap->a_p);
      }
      return (0);
}

/*
 * The syncer vnode is no longer needed and is being decommissioned.
 */
int
sync_inactive(v)
	void *v;
	
{
      struct vop_inactive_args /* {
               struct vnode *a_vp;
               struct proc *a_p;
      } */ *ap = v;

      struct vnode *vp = ap->a_vp;

      if (vp->v_usecount == 0)
              return (0);
      vp->v_mount->mnt_syncer = NULL;
      LIST_REMOVE(vp, v_synclist);
      vp->v_writecount = 0;
      vput(vp);
      return (0);
}

/*
 * Print out a syncer vnode.
 */
int
sync_print(v)
	void *v;

{
      struct vop_print_args /* {
              struct vnode *a_vp;
      } */ *ap = v;
      struct vnode *vp = ap->a_vp;

      printf("syncer vnode");
      if (vp->v_vnlock != NULL)
              lockmgr_printinfo(vp->v_vnlock);
      printf("\n");
      return (0);
}