[dragonfly.git] / sys / kern / vfs_sync.c

/*
 * (MPSAFE)
 *
 * 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.
 *
 *      @(#)vfs_subr.c  8.31 (Berkeley) 5/26/95
 * $FreeBSD: src/sys/kern/vfs_subr.c,v 1.249.2.30 2003/04/04 20:35:57 tegge Exp $
 * $DragonFly: src/sys/kern/vfs_sync.c,v 1.18 2008/05/18 05:54:25 dillon Exp $
 */

/*
 * External virtual filesystem routines
 */
#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/dirent.h>
#include <sys/domain.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/namei.h>
#include <sys/reboot.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>

#include <machine/limits.h>

#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vnode_pager.h>

#include <sys/buf2.h>
#include <sys/thread2.h>
#include <sys/mplock2.h>

/*
 * The workitem queue.
 */
#define SYNCER_MAXDELAY         32
static int syncer_maxdelay = SYNCER_MAXDELAY;   /* maximum delay time */
time_t syncdelay = 30;          /* max time to delay syncing data */
SYSCTL_INT(_kern, OID_AUTO, syncdelay, CTLFLAG_RW,
                &syncdelay, 0, "VFS data synchronization delay");
time_t filedelay = 30;          /* time to delay syncing files */
SYSCTL_INT(_kern, OID_AUTO, filedelay, CTLFLAG_RW,
                &filedelay, 0, "File synchronization delay");
time_t dirdelay = 29;           /* time to delay syncing directories */
SYSCTL_INT(_kern, OID_AUTO, dirdelay, CTLFLAG_RW,
                &dirdelay, 0, "Directory synchronization delay");
time_t metadelay = 28;          /* time to delay syncing metadata */
SYSCTL_INT(_kern, OID_AUTO, metadelay, CTLFLAG_RW,
                &metadelay, 0, "VFS metadata synchronization delay");
static int rushjob;                     /* number of slots to run ASAP */
static int stat_rush_requests;  /* number of times I/O speeded up */
SYSCTL_INT(_debug, OID_AUTO, rush_requests, CTLFLAG_RW,
                &stat_rush_requests, 0, "");

static int syncer_delayno = 0;
static long syncer_mask; 
static struct lwkt_token syncer_token;
LIST_HEAD(synclist, vnode);
static struct synclist *syncer_workitem_pending;

/*
 * Called from vfsinit()
 */
void
vfs_sync_init(void)
{
        syncer_workitem_pending = hashinit(syncer_maxdelay, M_DEVBUF,
                                            &syncer_mask);
        syncer_maxdelay = syncer_mask + 1;
        lwkt_token_init(&syncer_token, "syncer");
}

/*
 * 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 syncer 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]
 *
 */

/*
 * Add an item to the syncer work queue.
 *
 * WARNING: Cannot get vp->v_token here if not already held, we must
 *          depend on the syncer_token (which might already be held by
 *          the caller) to protect v_synclist and VONWORKLST.
 *
 * MPSAFE
 */
void
vn_syncer_add(struct vnode *vp, int delay)
{
        int slot;

        lwkt_gettoken(&syncer_token);

        if (vp->v_flag & VONWORKLST)
                LIST_REMOVE(vp, v_synclist);
        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);
        vsetflags(vp, VONWORKLST);

        lwkt_reltoken(&syncer_token);
}

/*
 * Removes the vnode from the syncer list.  Since we might block while
 * acquiring the syncer_token we have to recheck conditions.
 *
 * vp->v_token held on call
 */
void
vn_syncer_remove(struct vnode *vp)
{
        lwkt_gettoken(&syncer_token);

        if ((vp->v_flag & VONWORKLST) && RB_EMPTY(&vp->v_rbdirty_tree)) {
                vclrflags(vp, VONWORKLST);
                LIST_REMOVE(vp, v_synclist);
        }

        lwkt_reltoken(&syncer_token);
}

struct  thread *updatethread;

/*
 * System filesystem synchronizer daemon.
 */
static void
syncer_thread(void)
{
        struct thread *td = curthread;
        struct synclist *slp;
        struct vnode *vp;
        long starttime;

        EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc, td,
                              SHUTDOWN_PRI_LAST);
        for (;;) {
                kproc_suspend_loop();

                starttime = time_second;
                lwkt_gettoken(&syncer_token);

                /*
                 * Push files whose dirty time has expired.  Be careful
                 * of interrupt race on slp queue.
                 */
                slp = &syncer_workitem_pending[syncer_delayno];
                syncer_delayno += 1;
                if (syncer_delayno == syncer_maxdelay)
                        syncer_delayno = 0;

                while ((vp = LIST_FIRST(slp)) != NULL) {
                        if (vget(vp, LK_EXCLUSIVE | LK_NOWAIT) == 0) {
                                VOP_FSYNC(vp, MNT_LAZY, 0);
                                vput(vp);
                        }

                        /*
                         * vp is stale but can still be used if we can
                         * verify that it remains at the head of the list.
                         * Be careful not to try to get vp->v_token as
                         * vp can become stale if this blocks.
                         *
                         * If the vp is still at the head of the list were
                         * unable to completely flush it and move it to
                         * a later slot to give other vnodes a fair shot.
                         *
                         * Note that v_tag VT_VFS vnodes can remain on the
                         * worklist with no dirty blocks, but sync_fsync()
                         * moves it to a later slot so we will never see it
                         * here.
                         *
                         * It is possible to race a vnode with no dirty
                         * buffers being removed from the list.  If this
                         * occurs we will move the vnode in the synclist
                         * and then the other thread will remove it.  Do
                         * not try to remove it here.
                         */
                        if (LIST_FIRST(slp) == vp)
                                vn_syncer_add(vp, syncdelay);
                }
                lwkt_reltoken(&syncer_token);

                /*
                 * Do sync processing for each mount.
                 */
                bio_ops_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) {
                        atomic_subtract_int(&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_second == starttime)
                        tsleep(&lbolt_syncer, 0, "syncer", 0);
        }
}

static struct kproc_desc up_kp = {
        "syncer",
        syncer_thread,
        &updatethread
};
SYSINIT(syncer, SI_SUB_KTHREAD_UPDATE, SI_ORDER_FIRST, kproc_start, &up_kp)

/*
 * Request the syncer daemon to speed up its work.
 * We never push it to speed up more than half of its
 * normal turn time, otherwise it could take over the cpu.
 */
int
speedup_syncer(void)
{
        /*
         * Don't bother protecting the test.  unsleep_and_wakeup_thread()
         * will only do something real if the thread is in the right state.
         */
        wakeup(&lbolt_syncer);
        if (rushjob < syncdelay / 2) {
                atomic_add_int(&rushjob, 1);
                stat_rush_requests += 1;
                return (1);
        }
        return(0);
}

/*
 * Routine to create and manage a filesystem syncer vnode.
 */
static int sync_close(struct vop_close_args *);
static int sync_fsync(struct vop_fsync_args *);
static int sync_inactive(struct vop_inactive_args *);
static int sync_reclaim (struct vop_reclaim_args *);
static int sync_print(struct vop_print_args *);

static struct vop_ops sync_vnode_vops = {
        .vop_default =  vop_eopnotsupp,
        .vop_close =    sync_close,
        .vop_fsync =    sync_fsync,
        .vop_inactive = sync_inactive,
        .vop_reclaim =  sync_reclaim,
        .vop_print =    sync_print,
};

static struct vop_ops *sync_vnode_vops_p = &sync_vnode_vops;

VNODEOP_SET(sync_vnode_vops);

/*
 * Create a new filesystem syncer vnode for the specified mount point.
 * This vnode is placed on the worklist and is responsible for sync'ing
 * the filesystem.
 *
 * NOTE: read-only mounts are also placed on the worklist.  The filesystem
 * sync code is also responsible for cleaning up vnodes.
 */
int
vfs_allocate_syncvnode(struct mount *mp)
{
        struct vnode *vp;
        static long start, incr, next;
        int error;

        /* Allocate a new vnode */
        error = getspecialvnode(VT_VFS, mp, &sync_vnode_vops_p, &vp, 0, 0);
        if (error) {
                mp->mnt_syncer = NULL;
                return (error);
        }
        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(vp, syncdelay > 0 ? next % syncdelay : 0);

        /*
         * The mnt_syncer field inherits the vnode reference, which is
         * held until later decomissioning.
         */
        mp->mnt_syncer = vp;
        vx_unlock(vp);
        return (0);
}

static int
sync_close(struct vop_close_args *ap)
{
        return (0);
}

/*
 * Do a lazy sync of the filesystem.
 *
 * sync_fsync { struct vnode *a_vp, int a_waitfor }
 */
static int
sync_fsync(struct vop_fsync_args *ap)
{
        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) == 0)
                return (0);

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

        /*
         * Walk the list of vnodes pushing all that are dirty and
         * not already on the sync list, and freeing vnodes which have
         * no refs and whos VM objects are empty.  vfs_msync() handles
         * the VM issues and must be called whether the mount is readonly
         * or not.
         */
        if (vfs_busy(mp, LK_NOWAIT) != 0)
                return (0);
        if (mp->mnt_flag & MNT_RDONLY) {
                vfs_msync(mp, MNT_NOWAIT);
        } else {
                asyncflag = mp->mnt_flag & MNT_ASYNC;
                mp->mnt_flag &= ~MNT_ASYNC;     /* ZZZ hack */
                vfs_msync(mp, MNT_NOWAIT);
                VFS_SYNC(mp, MNT_NOWAIT | MNT_LAZY);
                if (asyncflag)
                        mp->mnt_flag |= MNT_ASYNC;
        }
        vfs_unbusy(mp);
        return (0);
}

/*
 * The syncer vnode is no longer referenced.
 *
 * sync_inactive { struct vnode *a_vp, struct proc *a_p }
 */
static int
sync_inactive(struct vop_inactive_args *ap)
{
        vgone_vxlocked(ap->a_vp);
        return (0);
}

/*
 * The syncer vnode is no longer needed and is being decommissioned.
 * This can only occur when the last reference has been released on
 * mp->mnt_syncer, so mp->mnt_syncer had better be NULL.
 *
 * Modifications to the worklist must be protected with a critical
 * section.
 *
 *      sync_reclaim { struct vnode *a_vp }
 */
static int
sync_reclaim(struct vop_reclaim_args *ap)
{
        struct vnode *vp = ap->a_vp;

        lwkt_gettoken(&syncer_token);
        KKASSERT(vp->v_mount->mnt_syncer != vp);
        if (vp->v_flag & VONWORKLST) {
                LIST_REMOVE(vp, v_synclist);
                vclrflags(vp, VONWORKLST);
        }
        lwkt_reltoken(&syncer_token);

        return (0);
}

/*
 * Print out a syncer vnode.
 *
 *      sync_print { struct vnode *a_vp }
 */
static int
sync_print(struct vop_print_args *ap)
{
        struct vnode *vp = ap->a_vp;

        kprintf("syncer vnode");
        lockmgr_printinfo(&vp->v_lock);
        kprintf("\n");
        return (0);
}