[dragonfly.git] / sys / vfs / ufs / ffs_softdep.c

/*
 * Copyright 1998, 2000 Marshall Kirk McKusick. All Rights Reserved.
 *
 * The soft updates code is derived from the appendix of a University
 * of Michigan technical report (Gregory R. Ganger and Yale N. Patt,
 * "Soft Updates: A Solution to the Metadata Update Problem in File
 * Systems", CSE-TR-254-95, August 1995).
 *
 * Further information about soft updates can be obtained from:
 *
 *      Marshall Kirk McKusick          http://www.mckusick.com/softdep/
 *      1614 Oxford Street              mckusick@mckusick.com
 *      Berkeley, CA 94709-1608         +1-510-843-9542
 *      USA
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY MARSHALL KIRK MCKUSICK ``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 MARSHALL KIRK MCKUSICK 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.
 *
 *      from: @(#)ffs_softdep.c 9.59 (McKusick) 6/21/00
 * $FreeBSD: src/sys/ufs/ffs/ffs_softdep.c,v 1.57.2.11 2002/02/05 18:46:53 dillon Exp $
 * $DragonFly: src/sys/vfs/ufs/ffs_softdep.c,v 1.27 2005/07/31 22:25:46 dillon Exp $
 */

/*
 * For now we want the safety net that the DIAGNOSTIC and DEBUG flags provide.
 */
#ifndef DIAGNOSTIC
#define DIAGNOSTIC
#endif
#ifndef DEBUG
#define DEBUG
#endif

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/syslog.h>
#include <sys/vnode.h>
#include <sys/conf.h>
#include <sys/buf2.h>
#include "dir.h"
#include "quota.h"
#include "inode.h"
#include "ufsmount.h"
#include "fs.h"
#include "softdep.h"
#include "ffs_extern.h"
#include "ufs_extern.h"

#include <sys/thread2.h>

/*
 * These definitions need to be adapted to the system to which
 * this file is being ported.
 */
/*
 * malloc types defined for the softdep system.
 */
MALLOC_DEFINE(M_PAGEDEP, "pagedep","File page dependencies");
MALLOC_DEFINE(M_INODEDEP, "inodedep","Inode dependencies");
MALLOC_DEFINE(M_NEWBLK, "newblk","New block allocation");
MALLOC_DEFINE(M_BMSAFEMAP, "bmsafemap","Block or frag allocated from cyl group map");
MALLOC_DEFINE(M_ALLOCDIRECT, "allocdirect","Block or frag dependency for an inode");
MALLOC_DEFINE(M_INDIRDEP, "indirdep","Indirect block dependencies");
MALLOC_DEFINE(M_ALLOCINDIR, "allocindir","Block dependency for an indirect block");
MALLOC_DEFINE(M_FREEFRAG, "freefrag","Previously used frag for an inode");
MALLOC_DEFINE(M_FREEBLKS, "freeblks","Blocks freed from an inode");
MALLOC_DEFINE(M_FREEFILE, "freefile","Inode deallocated");
MALLOC_DEFINE(M_DIRADD, "diradd","New directory entry");
MALLOC_DEFINE(M_MKDIR, "mkdir","New directory");
MALLOC_DEFINE(M_DIRREM, "dirrem","Directory entry deleted");

#define M_SOFTDEP_FLAGS         (M_WAITOK | M_USE_RESERVE)

#define D_PAGEDEP       0
#define D_INODEDEP      1
#define D_NEWBLK        2
#define D_BMSAFEMAP     3
#define D_ALLOCDIRECT   4
#define D_INDIRDEP      5
#define D_ALLOCINDIR    6
#define D_FREEFRAG      7
#define D_FREEBLKS      8
#define D_FREEFILE      9
#define D_DIRADD        10
#define D_MKDIR         11
#define D_DIRREM        12
#define D_LAST          D_DIRREM

/* 
 * translate from workitem type to memory type
 * MUST match the defines above, such that memtype[D_XXX] == M_XXX
 */
static struct malloc_type *memtype[] = {
        M_PAGEDEP,
        M_INODEDEP,
        M_NEWBLK,
        M_BMSAFEMAP,
        M_ALLOCDIRECT,
        M_INDIRDEP,
        M_ALLOCINDIR,
        M_FREEFRAG,
        M_FREEBLKS,
        M_FREEFILE,
        M_DIRADD,
        M_MKDIR,
        M_DIRREM
};

#define DtoM(type) (memtype[type])

/*
 * Names of malloc types.
 */
#define TYPENAME(type)  \
        ((unsigned)(type) < D_LAST ? memtype[type]->ks_shortdesc : "???")
/*
 * End system adaptaion definitions.
 */

/*
 * Internal function prototypes.
 */
static  void softdep_error(char *, int);
static  void drain_output(struct vnode *, int);
static  int getdirtybuf(struct buf **, int);
static  void clear_remove(struct thread *);
static  void clear_inodedeps(struct thread *);
static  int flush_pagedep_deps(struct vnode *, struct mount *,
            struct diraddhd *);
static  int flush_inodedep_deps(struct fs *, ino_t);
static  int handle_written_filepage(struct pagedep *, struct buf *);
static  void diradd_inode_written(struct diradd *, struct inodedep *);
static  int handle_written_inodeblock(struct inodedep *, struct buf *);
static  void handle_allocdirect_partdone(struct allocdirect *);
static  void handle_allocindir_partdone(struct allocindir *);
static  void initiate_write_filepage(struct pagedep *, struct buf *);
static  void handle_written_mkdir(struct mkdir *, int);
static  void initiate_write_inodeblock(struct inodedep *, struct buf *);
static  void handle_workitem_freefile(struct freefile *);
static  void handle_workitem_remove(struct dirrem *);
static  struct dirrem *newdirrem(struct buf *, struct inode *,
            struct inode *, int, struct dirrem **);
static  void free_diradd(struct diradd *);
static  void free_allocindir(struct allocindir *, struct inodedep *);
static  int indir_trunc (struct inode *, ufs_daddr_t, int, ufs_lbn_t,
            long *);
static  void deallocate_dependencies(struct buf *, struct inodedep *);
static  void free_allocdirect(struct allocdirectlst *,
            struct allocdirect *, int);
static  int check_inode_unwritten(struct inodedep *);
static  int free_inodedep(struct inodedep *);
static  void handle_workitem_freeblocks(struct freeblks *);
static  void merge_inode_lists(struct inodedep *);
static  void setup_allocindir_phase2(struct buf *, struct inode *,
            struct allocindir *);
static  struct allocindir *newallocindir(struct inode *, int, ufs_daddr_t,
            ufs_daddr_t);
static  void handle_workitem_freefrag(struct freefrag *);
static  struct freefrag *newfreefrag(struct inode *, ufs_daddr_t, long);
static  void allocdirect_merge(struct allocdirectlst *,
            struct allocdirect *, struct allocdirect *);
static  struct bmsafemap *bmsafemap_lookup(struct buf *);
static  int newblk_lookup(struct fs *, ufs_daddr_t, int,
            struct newblk **);
static  int inodedep_lookup(struct fs *, ino_t, int, struct inodedep **);
static  int pagedep_lookup(struct inode *, ufs_lbn_t, int,
            struct pagedep **);
static  void pause_timer(void *);
static  int request_cleanup(int, int);
static  int process_worklist_item(struct mount *, int);
static  void add_to_worklist(struct worklist *);

/*
 * Exported softdep operations.
 */
static  void softdep_disk_io_initiation(struct buf *);
static  void softdep_disk_write_complete(struct buf *);
static  void softdep_deallocate_dependencies(struct buf *);
static  int softdep_fsync(struct vnode *);
static  int softdep_process_worklist(struct mount *);
static  void softdep_move_dependencies(struct buf *, struct buf *);
static  int softdep_count_dependencies(struct buf *bp, int);

static struct bio_ops softdep_bioops = {
        softdep_disk_io_initiation,             /* io_start */
        softdep_disk_write_complete,            /* io_complete */
        softdep_deallocate_dependencies,        /* io_deallocate */
        softdep_fsync,                          /* io_fsync */
        softdep_process_worklist,               /* io_sync */
        softdep_move_dependencies,              /* io_movedeps */
        softdep_count_dependencies,             /* io_countdeps */
};

/*
 * Locking primitives.
 *
 * For a uniprocessor, all we need to do is protect against disk
 * interrupts. For a multiprocessor, this lock would have to be
 * a mutex. A single mutex is used throughout this file, though
 * finer grain locking could be used if contention warranted it.
 *
 * For a multiprocessor, the sleep call would accept a lock and
 * release it after the sleep processing was complete. In a uniprocessor
 * implementation there is no such interlock, so we simple mark
 * the places where it needs to be done with the `interlocked' form
 * of the lock calls. Since the uniprocessor sleep already interlocks
 * the spl, there is nothing that really needs to be done.
 */
#ifndef /* NOT */ DEBUG
static struct lockit {
} lk = { 0 };
#define ACQUIRE_LOCK(lk)                crit_enter_id("softupdates");
#define FREE_LOCK(lk)                   crit_exit_id("softupdates");

#else /* DEBUG */
#define NOHOLDER        ((struct thread *)-1)
#define SPECIAL_FLAG    ((struct thread *)-2)
static struct lockit {
        int     lkt_spl;
        struct thread *lkt_held;
} lk = { 0, NOHOLDER };
static int lockcnt;

static  void acquire_lock(struct lockit *);
static  void free_lock(struct lockit *);
void    softdep_panic(char *);

#define ACQUIRE_LOCK(lk)                acquire_lock(lk)
#define FREE_LOCK(lk)                   free_lock(lk)

static void
acquire_lock(lk)
        struct lockit *lk;
{
        thread_t holder;

        if (lk->lkt_held != NOHOLDER) {
                holder = lk->lkt_held;
                FREE_LOCK(lk);
                if (holder == curthread)
                        panic("softdep_lock: locking against myself");
                else
                        panic("softdep_lock: lock held by %p", holder);
        }
        crit_enter_id("softupdates");
        lk->lkt_held = curthread;
        lockcnt++;
}

static void
free_lock(lk)
        struct lockit *lk;
{

        if (lk->lkt_held == NOHOLDER)
                panic("softdep_unlock: lock not held");
        lk->lkt_held = NOHOLDER;
        crit_exit_id("softupdates");
}

/*
 * Function to release soft updates lock and panic.
 */
void
softdep_panic(msg)
        char *msg;
{

        if (lk.lkt_held != NOHOLDER)
                FREE_LOCK(&lk);
        panic(msg);
}
#endif /* DEBUG */

static  int interlocked_sleep(struct lockit *, int, void *, int,
            const char *, int);

/*
 * When going to sleep, we must save our SPL so that it does
 * not get lost if some other process uses the lock while we
 * are sleeping. We restore it after we have slept. This routine
 * wraps the interlocking with functions that sleep. The list
 * below enumerates the available set of operations.
 */
#define UNKNOWN         0
#define SLEEP           1
#define LOCKBUF         2

static int
interlocked_sleep(lk, op, ident, flags, wmesg, timo)
        struct lockit *lk;
        int op;
        void *ident;
        int flags;
        const char *wmesg;
        int timo;
{
        thread_t holder;
        int s, retval;

        s = lk->lkt_spl;
#       ifdef DEBUG
        if (lk->lkt_held == NOHOLDER)
                panic("interlocked_sleep: lock not held");
        lk->lkt_held = NOHOLDER;
#       endif /* DEBUG */
        switch (op) {
        case SLEEP:
                retval = tsleep(ident, flags, wmesg, timo);
                break;
        case LOCKBUF:
                retval = BUF_LOCK((struct buf *)ident, flags);
                break;
        default:
                panic("interlocked_sleep: unknown operation");
        }
#       ifdef DEBUG
        if (lk->lkt_held != NOHOLDER) {
                holder = lk->lkt_held;
                FREE_LOCK(lk);
                if (holder == curthread)
                        panic("interlocked_sleep: locking against self");
                else
                        panic("interlocked_sleep: lock held by %p", holder);
        }
        lk->lkt_held = curthread;
        lockcnt++;
#       endif /* DEBUG */
        lk->lkt_spl = s;
        return (retval);
}

/*
 * Place holder for real semaphores.
 */
struct sema {
        int     value;
        thread_t holder;
        char    *name;
        int     prio;
        int     timo;
};
static  void sema_init(struct sema *, char *, int, int);
static  int sema_get(struct sema *, struct lockit *);
static  void sema_release(struct sema *);

static void
sema_init(semap, name, prio, timo)
        struct sema *semap;
        char *name;
        int prio, timo;
{

        semap->holder = NOHOLDER;
        semap->value = 0;
        semap->name = name;
        semap->prio = prio;
        semap->timo = timo;
}

static int
sema_get(semap, interlock)
        struct sema *semap;
        struct lockit *interlock;
{

        if (semap->value++ > 0) {
                if (interlock != NULL) {
                        interlocked_sleep(interlock, SLEEP, (caddr_t)semap,
                            semap->prio, semap->name, semap->timo);
                        FREE_LOCK(interlock);
                } else {
                        tsleep((caddr_t)semap, semap->prio, semap->name,
                            semap->timo);
                }
                return (0);
        }
        semap->holder = curthread;
        if (interlock != NULL)
                FREE_LOCK(interlock);
        return (1);
}

static void
sema_release(semap)
        struct sema *semap;
{

        if (semap->value <= 0 || semap->holder != curthread) {
                if (lk.lkt_held != NOHOLDER)
                        FREE_LOCK(&lk);
                panic("sema_release: not held");
        }
        if (--semap->value > 0) {
                semap->value = 0;
                wakeup(semap);
        }
        semap->holder = NOHOLDER;
}

/*
 * Worklist queue management.
 * These routines require that the lock be held.
 */
#ifndef /* NOT */ DEBUG
#define WORKLIST_INSERT(head, item) do {        \
        (item)->wk_state |= ONWORKLIST;         \
        LIST_INSERT_HEAD(head, item, wk_list);  \
} while (0)
#define WORKLIST_REMOVE(item) do {              \
        (item)->wk_state &= ~ONWORKLIST;        \
        LIST_REMOVE(item, wk_list);             \
} while (0)
#define WORKITEM_FREE(item, type) FREE(item, DtoM(type))

#else /* DEBUG */
static  void worklist_insert(struct workhead *, struct worklist *);
static  void worklist_remove(struct worklist *);
static  void workitem_free(struct worklist *, int);

#define WORKLIST_INSERT(head, item) worklist_insert(head, item)
#define WORKLIST_REMOVE(item) worklist_remove(item)
#define WORKITEM_FREE(item, type) workitem_free((struct worklist *)item, type)

static void
worklist_insert(head, item)
        struct workhead *head;
        struct worklist *item;
{

        if (lk.lkt_held == NOHOLDER)
                panic("worklist_insert: lock not held");
        if (item->wk_state & ONWORKLIST) {
                FREE_LOCK(&lk);
                panic("worklist_insert: already on list");
        }
        item->wk_state |= ONWORKLIST;
        LIST_INSERT_HEAD(head, item, wk_list);
}

static void
worklist_remove(item)
        struct worklist *item;
{

        if (lk.lkt_held == NOHOLDER)
                panic("worklist_remove: lock not held");
        if ((item->wk_state & ONWORKLIST) == 0) {
                FREE_LOCK(&lk);
                panic("worklist_remove: not on list");
        }
        item->wk_state &= ~ONWORKLIST;
        LIST_REMOVE(item, wk_list);
}

static void
workitem_free(item, type)
        struct worklist *item;
        int type;
{

        if (item->wk_state & ONWORKLIST) {
                if (lk.lkt_held != NOHOLDER)
                        FREE_LOCK(&lk);
                panic("workitem_free: still on list");
        }
        if (item->wk_type != type) {
                if (lk.lkt_held != NOHOLDER)
                        FREE_LOCK(&lk);
                panic("workitem_free: type mismatch");
        }
        FREE(item, DtoM(type));
}
#endif /* DEBUG */

/*
 * Workitem queue management
 */
static struct workhead softdep_workitem_pending;
static int num_on_worklist;     /* number of worklist items to be processed */
static int softdep_worklist_busy; /* 1 => trying to do unmount */
static int softdep_worklist_req; /* serialized waiters */
static int max_softdeps;        /* maximum number of structs before slowdown */
static int tickdelay = 2;       /* number of ticks to pause during slowdown */
static int *stat_countp;        /* statistic to count in proc_waiting timeout */
static int proc_waiting;        /* tracks whether we have a timeout posted */
static struct callout handle; /* handle on posted proc_waiting timeout */
static struct thread *filesys_syncer; /* proc of filesystem syncer process */
static int req_clear_inodedeps; /* syncer process flush some inodedeps */
#define FLUSH_INODES    1
static int req_clear_remove;    /* syncer process flush some freeblks */
#define FLUSH_REMOVE    2
/*
 * runtime statistics
 */
static int stat_worklist_push;  /* number of worklist cleanups */
static int stat_blk_limit_push; /* number of times block limit neared */
static int stat_ino_limit_push; /* number of times inode limit neared */
static int stat_blk_limit_hit;  /* number of times block slowdown imposed */
static int stat_ino_limit_hit;  /* number of times inode slowdown imposed */
static int stat_sync_limit_hit; /* number of synchronous slowdowns imposed */
static int stat_indir_blk_ptrs; /* bufs redirtied as indir ptrs not written */
static int stat_inode_bitmap;   /* bufs redirtied as inode bitmap not written */
static int stat_direct_blk_ptrs;/* bufs redirtied as direct ptrs not written */
static int stat_dir_entry;      /* bufs redirtied as dir entry cannot write */
#ifdef DEBUG
#include <vm/vm.h>
#include <sys/sysctl.h>
SYSCTL_INT(_debug, OID_AUTO, max_softdeps, CTLFLAG_RW, &max_softdeps, 0, "");
SYSCTL_INT(_debug, OID_AUTO, tickdelay, CTLFLAG_RW, &tickdelay, 0, "");
SYSCTL_INT(_debug, OID_AUTO, worklist_push, CTLFLAG_RW, &stat_worklist_push, 0,"");
SYSCTL_INT(_debug, OID_AUTO, blk_limit_push, CTLFLAG_RW, &stat_blk_limit_push, 0,"");
SYSCTL_INT(_debug, OID_AUTO, ino_limit_push, CTLFLAG_RW, &stat_ino_limit_push, 0,"");
SYSCTL_INT(_debug, OID_AUTO, blk_limit_hit, CTLFLAG_RW, &stat_blk_limit_hit, 0, "");
SYSCTL_INT(_debug, OID_AUTO, ino_limit_hit, CTLFLAG_RW, &stat_ino_limit_hit, 0, "");
SYSCTL_INT(_debug, OID_AUTO, sync_limit_hit, CTLFLAG_RW, &stat_sync_limit_hit, 0, "");
SYSCTL_INT(_debug, OID_AUTO, indir_blk_ptrs, CTLFLAG_RW, &stat_indir_blk_ptrs, 0, "");
SYSCTL_INT(_debug, OID_AUTO, inode_bitmap, CTLFLAG_RW, &stat_inode_bitmap, 0, "");
SYSCTL_INT(_debug, OID_AUTO, direct_blk_ptrs, CTLFLAG_RW, &stat_direct_blk_ptrs, 0, "");
SYSCTL_INT(_debug, OID_AUTO, dir_entry, CTLFLAG_RW, &stat_dir_entry, 0, "");
#endif /* DEBUG */

/*
 * Add an item to the end of the work queue.
 * This routine requires that the lock be held.
 * This is the only routine that adds items to the list.
 * The following routine is the only one that removes items
 * and does so in order from first to last.
 */
static void
add_to_worklist(wk)
        struct worklist *wk;
{
        static struct worklist *worklist_tail;

        if (wk->wk_state & ONWORKLIST) {
                if (lk.lkt_held != NOHOLDER)
                        FREE_LOCK(&lk);
                panic("add_to_worklist: already on list");
        }
        wk->wk_state |= ONWORKLIST;
        if (LIST_FIRST(&softdep_workitem_pending) == NULL)
                LIST_INSERT_HEAD(&softdep_workitem_pending, wk, wk_list);
        else
                LIST_INSERT_AFTER(worklist_tail, wk, wk_list);
        worklist_tail = wk;
        num_on_worklist += 1;
}

/*
 * Process that runs once per second to handle items in the background queue.
 *
 * Note that we ensure that everything is done in the order in which they
 * appear in the queue. The code below depends on this property to ensure
 * that blocks of a file are freed before the inode itself is freed. This
 * ordering ensures that no new <vfsid, inum, lbn> triples will be generated
 * until all the old ones have been purged from the dependency lists.
 */
static int 
softdep_process_worklist(matchmnt)
        struct mount *matchmnt;
{
        thread_t td = curthread;
        int matchcnt, loopcount;
        long starttime;

        /*
         * Record the process identifier of our caller so that we can give
         * this process preferential treatment in request_cleanup below.
         */
        filesys_syncer = td;
        matchcnt = 0;

        /*
         * There is no danger of having multiple processes run this
         * code, but we have to single-thread it when softdep_flushfiles()
         * is in operation to get an accurate count of the number of items
         * related to its mount point that are in the list.
         */
        if (matchmnt == NULL) {
                if (softdep_worklist_busy < 0)
                        return(-1);
                softdep_worklist_busy += 1;
        }

        /*
         * If requested, try removing inode or removal dependencies.
         */
        if (req_clear_inodedeps) {
                clear_inodedeps(td);
                req_clear_inodedeps -= 1;
                wakeup_one(&proc_waiting);
        }
        if (req_clear_remove) {
                clear_remove(td);
                req_clear_remove -= 1;
                wakeup_one(&proc_waiting);
        }
        loopcount = 1;
        starttime = time_second;
        while (num_on_worklist > 0) {
                matchcnt += process_worklist_item(matchmnt, 0);

                /*
                 * If a umount operation wants to run the worklist
                 * accurately, abort.
                 */
                if (softdep_worklist_req && matchmnt == NULL) {
                        matchcnt = -1;
                        break;
                }

                /*
                 * If requested, try removing inode or removal dependencies.
                 */
                if (req_clear_inodedeps) {
                        clear_inodedeps(td);
                        req_clear_inodedeps -= 1;
                        wakeup_one(&proc_waiting);
                }
                if (req_clear_remove) {
                        clear_remove(td);
                        req_clear_remove -= 1;
                        wakeup_one(&proc_waiting);
                }
                /*
                 * We do not generally want to stop for buffer space, but if
                 * we are really being a buffer hog, we will stop and wait.
                 */
                if (loopcount++ % 128 == 0)
                        bwillwrite();
                /*
                 * Never allow processing to run for more than one
                 * second. Otherwise the other syncer tasks may get
                 * excessively backlogged.
                 */
                if (starttime != time_second && matchmnt == NULL) {
                        matchcnt = -1;
                        break;
                }
        }
        if (matchmnt == NULL) {
                --softdep_worklist_busy;
                if (softdep_worklist_req && softdep_worklist_busy == 0)
                        wakeup(&softdep_worklist_req);
        }
        return (matchcnt);
}

/*
 * Process one item on the worklist.
 */
static int
process_worklist_item(matchmnt, flags)
        struct mount *matchmnt;
        int flags;
{
        struct worklist *wk;
        struct dirrem *dirrem;
        struct fs *matchfs;
        struct vnode *vp;
        int matchcnt = 0;

        matchfs = NULL;
        if (matchmnt != NULL)
                matchfs = VFSTOUFS(matchmnt)->um_fs;
        ACQUIRE_LOCK(&lk);
        /*
         * Normally we just process each item on the worklist in order.
         * However, if we are in a situation where we cannot lock any
         * inodes, we have to skip over any dirrem requests whose
         * vnodes are resident and locked.
         */
        LIST_FOREACH(wk, &softdep_workitem_pending, wk_list) {
                if ((flags & LK_NOWAIT) == 0 || wk->wk_type != D_DIRREM)
                        break;
                dirrem = WK_DIRREM(wk);
                vp = ufs_ihashlookup(VFSTOUFS(dirrem->dm_mnt)->um_dev,
                    dirrem->dm_oldinum);
                if (vp == NULL || !VOP_ISLOCKED(vp, curthread))
                        break;
        }
        if (wk == 0) {
                FREE_LOCK(&lk);
                return (0);
        }
        WORKLIST_REMOVE(wk);
        num_on_worklist -= 1;
        FREE_LOCK(&lk);
        switch (wk->wk_type) {

        case D_DIRREM:
                /* removal of a directory entry */
                if (WK_DIRREM(wk)->dm_mnt == matchmnt)
                        matchcnt += 1;
                handle_workitem_remove(WK_DIRREM(wk));
                break;

        case D_FREEBLKS:
                /* releasing blocks and/or fragments from a file */
                if (WK_FREEBLKS(wk)->fb_fs == matchfs)
                        matchcnt += 1;
                handle_workitem_freeblocks(WK_FREEBLKS(wk));
                break;

        case D_FREEFRAG:
                /* releasing a fragment when replaced as a file grows */
                if (WK_FREEFRAG(wk)->ff_fs == matchfs)
                        matchcnt += 1;
                handle_workitem_freefrag(WK_FREEFRAG(wk));
                break;

        case D_FREEFILE:
                /* releasing an inode when its link count drops to 0 */
                if (WK_FREEFILE(wk)->fx_fs == matchfs)
                        matchcnt += 1;
                handle_workitem_freefile(WK_FREEFILE(wk));
                break;

        default:
                panic("%s_process_worklist: Unknown type %s",
                    "softdep", TYPENAME(wk->wk_type));
                /* NOTREACHED */
        }
        return (matchcnt);
}

/*
 * Move dependencies from one buffer to another.
 */
static void
softdep_move_dependencies(oldbp, newbp)
        struct buf *oldbp;
        struct buf *newbp;
{
        struct worklist *wk, *wktail;

        if (LIST_FIRST(&newbp->b_dep) != NULL)
                panic("softdep_move_dependencies: need merge code");
        wktail = 0;
        ACQUIRE_LOCK(&lk);
        while ((wk = LIST_FIRST(&oldbp->b_dep)) != NULL) {
                LIST_REMOVE(wk, wk_list);
                if (wktail == 0)
                        LIST_INSERT_HEAD(&newbp->b_dep, wk, wk_list);
                else
                        LIST_INSERT_AFTER(wktail, wk, wk_list);
                wktail = wk;
        }
        FREE_LOCK(&lk);
}

/*
 * Purge the work list of all items associated with a particular mount point.
 */
int
softdep_flushfiles(struct mount *oldmnt, int flags, struct thread *td)
{
        struct vnode *devvp;
        int error, loopcnt;

        /*
         * Await our turn to clear out the queue, then serialize access.
         */
        while (softdep_worklist_busy != 0) {
                softdep_worklist_req += 1;
                tsleep(&softdep_worklist_req, 0, "softflush", 0);
                softdep_worklist_req -= 1;
        }
        softdep_worklist_busy = -1;

        if ((error = ffs_flushfiles(oldmnt, flags, td)) != 0) {
                softdep_worklist_busy = 0;
                if (softdep_worklist_req)
                        wakeup(&softdep_worklist_req);
                return (error);
        }
        /*
         * Alternately flush the block device associated with the mount
         * point and process any dependencies that the flushing
         * creates. In theory, this loop can happen at most twice,
         * but we give it a few extra just to be sure.
         */
        devvp = VFSTOUFS(oldmnt)->um_devvp;
        for (loopcnt = 10; loopcnt > 0; ) {
                if (softdep_process_worklist(oldmnt) == 0) {
                        loopcnt--;
                        /*
                         * Do another flush in case any vnodes were brought in
                         * as part of the cleanup operations.
                         */
                        if ((error = ffs_flushfiles(oldmnt, flags, td)) != 0)
                                break;
                        /*
                         * If we still found nothing to do, we are really done.
                         */
                        if (softdep_process_worklist(oldmnt) == 0)
                                break;
                }
                vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY, td);
                error = VOP_FSYNC(devvp, MNT_WAIT, td);
                VOP_UNLOCK(devvp, 0, td);
                if (error)
                        break;
        }
        softdep_worklist_busy = 0;
        if (softdep_worklist_req)
                wakeup(&softdep_worklist_req);

        /*
         * If we are unmounting then it is an error to fail. If we
         * are simply trying to downgrade to read-only, then filesystem
         * activity can keep us busy forever, so we just fail with EBUSY.
         */
        if (loopcnt == 0) {
                if (oldmnt->mnt_kern_flag & MNTK_UNMOUNT)
                        panic("softdep_flushfiles: looping");
                error = EBUSY;
        }
        return (error);
}

/*
 * Structure hashing.
 * 
 * There are three types of structures that can be looked up:
 *      1) pagedep structures identified by mount point, inode number,
 *         and logical block.
 *      2) inodedep structures identified by mount point and inode number.
 *      3) newblk structures identified by mount point and
 *         physical block number.
 *
 * The "pagedep" and "inodedep" dependency structures are hashed
 * separately from the file blocks and inodes to which they correspond.
 * This separation helps when the in-memory copy of an inode or
 * file block must be replaced. It also obviates the need to access
 * an inode or file page when simply updating (or de-allocating)
 * dependency structures. Lookup of newblk structures is needed to
 * find newly allocated blocks when trying to associate them with
 * their allocdirect or allocindir structure.
 *
 * The lookup routines optionally create and hash a new instance when
 * an existing entry is not found.
 */
#define DEPALLOC        0x0001  /* allocate structure if lookup fails */
#define NODELAY         0x0002  /* cannot do background work */

/*
 * Structures and routines associated with pagedep caching.
 */
LIST_HEAD(pagedep_hashhead, pagedep) *pagedep_hashtbl;
u_long  pagedep_hash;           /* size of hash table - 1 */
#define PAGEDEP_HASH(mp, inum, lbn) \
        (&pagedep_hashtbl[((((register_t)(mp)) >> 13) + (inum) + (lbn)) & \
            pagedep_hash])
static struct sema pagedep_in_progress;

/*
 * Look up a pagedep. Return 1 if found, 0 if not found.
 * If not found, allocate if DEPALLOC flag is passed.
 * Found or allocated entry is returned in pagedeppp.
 * This routine must be called with splbio interrupts blocked.
 */
static int
pagedep_lookup(ip, lbn, flags, pagedeppp)
        struct inode *ip;
        ufs_lbn_t lbn;
        int flags;
        struct pagedep **pagedeppp;
{
        struct pagedep *pagedep;
        struct pagedep_hashhead *pagedephd;
        struct mount *mp;
        int i;

#ifdef DEBUG
        if (lk.lkt_held == NOHOLDER)
                panic("pagedep_lookup: lock not held");
#endif
        mp = ITOV(ip)->v_mount;
        pagedephd = PAGEDEP_HASH(mp, ip->i_number, lbn);
top:
        LIST_FOREACH(pagedep, pagedephd, pd_hash)
                if (ip->i_number == pagedep->pd_ino &&
                    lbn == pagedep->pd_lbn &&
                    mp == pagedep->pd_mnt)
                        break;
        if (pagedep) {
                *pagedeppp = pagedep;
                return (1);
        }
        if ((flags & DEPALLOC) == 0) {
                *pagedeppp = NULL;
                return (0);
        }
        if (sema_get(&pagedep_in_progress, &lk) == 0) {
                ACQUIRE_LOCK(&lk);
                goto top;
        }
        MALLOC(pagedep, struct pagedep *, sizeof(struct pagedep), M_PAGEDEP,
                M_SOFTDEP_FLAGS);
        bzero(pagedep, sizeof(struct pagedep));
        pagedep->pd_list.wk_type = D_PAGEDEP;
        pagedep->pd_mnt = mp;
        pagedep->pd_ino = ip->i_number;
        pagedep->pd_lbn = lbn;
        LIST_INIT(&pagedep->pd_dirremhd);
        LIST_INIT(&pagedep->pd_pendinghd);
        for (i = 0; i < DAHASHSZ; i++)
                LIST_INIT(&pagedep->pd_diraddhd[i]);
        ACQUIRE_LOCK(&lk);
        LIST_INSERT_HEAD(pagedephd, pagedep, pd_hash);
        sema_release(&pagedep_in_progress);
        *pagedeppp = pagedep;
        return (0);
}

/*
 * Structures and routines associated with inodedep caching.
 */
LIST_HEAD(inodedep_hashhead, inodedep) *inodedep_hashtbl;
static u_long   inodedep_hash;  /* size of hash table - 1 */
static long     num_inodedep;   /* number of inodedep allocated */
#define INODEDEP_HASH(fs, inum) \
      (&inodedep_hashtbl[((((register_t)(fs)) >> 13) + (inum)) & inodedep_hash])
static struct sema inodedep_in_progress;

/*
 * Look up a inodedep. Return 1 if found, 0 if not found.
 * If not found, allocate if DEPALLOC flag is passed.
 * Found or allocated entry is returned in inodedeppp.
 * This routine must be called with splbio interrupts blocked.
 */
static int
inodedep_lookup(fs, inum, flags, inodedeppp)
        struct fs *fs;
        ino_t inum;
        int flags;
        struct inodedep **inodedeppp;
{
        struct inodedep *inodedep;
        struct inodedep_hashhead *inodedephd;
        int firsttry;

#ifdef DEBUG
        if (lk.lkt_held == NOHOLDER)
                panic("inodedep_lookup: lock not held");
#endif
        firsttry = 1;
        inodedephd = INODEDEP_HASH(fs, inum);
top:
        LIST_FOREACH(inodedep, inodedephd, id_hash)
                if (inum == inodedep->id_ino && fs == inodedep->id_fs)
                        break;
        if (inodedep) {
                *inodedeppp = inodedep;
                return (1);
        }
        if ((flags & DEPALLOC) == 0) {
                *inodedeppp = NULL;
                return (0);
        }
        /*
         * If we are over our limit, try to improve the situation.
         */
        if (num_inodedep > max_softdeps && firsttry && 
            speedup_syncer() == 0 && (flags & NODELAY) == 0 &&
            request_cleanup(FLUSH_INODES, 1)) {
                firsttry = 0;
                goto top;
        }
        if (sema_get(&inodedep_in_progress, &lk) == 0) {
                ACQUIRE_LOCK(&lk);
                goto top;
        }
        num_inodedep += 1;
        MALLOC(inodedep, struct inodedep *, sizeof(struct inodedep),
                M_INODEDEP, M_SOFTDEP_FLAGS);
        inodedep->id_list.wk_type = D_INODEDEP;
        inodedep->id_fs = fs;
        inodedep->id_ino = inum;
        inodedep->id_state = ALLCOMPLETE;
        inodedep->id_nlinkdelta = 0;
        inodedep->id_savedino = NULL;
        inodedep->id_savedsize = -1;
        inodedep->id_buf = NULL;
        LIST_INIT(&inodedep->id_pendinghd);
        LIST_INIT(&inodedep->id_inowait);
        LIST_INIT(&inodedep->id_bufwait);
        TAILQ_INIT(&inodedep->id_inoupdt);
        TAILQ_INIT(&inodedep->id_newinoupdt);
        ACQUIRE_LOCK(&lk);
        LIST_INSERT_HEAD(inodedephd, inodedep, id_hash);
        sema_release(&inodedep_in_progress);
        *inodedeppp = inodedep;
        return (0);
}

/*
 * Structures and routines associated with newblk caching.
 */
LIST_HEAD(newblk_hashhead, newblk) *newblk_hashtbl;
u_long  newblk_hash;            /* size of hash table - 1 */
#define NEWBLK_HASH(fs, inum) \
        (&newblk_hashtbl[((((register_t)(fs)) >> 13) + (inum)) & newblk_hash])
static struct sema newblk_in_progress;

/*
 * Look up a newblk. Return 1 if found, 0 if not found.
 * If not found, allocate if DEPALLOC flag is passed.
 * Found or allocated entry is returned in newblkpp.
 */
static int
newblk_lookup(fs, newblkno, flags, newblkpp)
        struct fs *fs;
        ufs_daddr_t newblkno;
        int flags;
        struct newblk **newblkpp;
{
        struct newblk *newblk;
        struct newblk_hashhead *newblkhd;

        newblkhd = NEWBLK_HASH(fs, newblkno);
top:
        LIST_FOREACH(newblk, newblkhd, nb_hash)
                if (newblkno == newblk->nb_newblkno && fs == newblk->nb_fs)
                        break;
        if (newblk) {
                *newblkpp = newblk;
                return (1);
        }
        if ((flags & DEPALLOC) == 0) {
                *newblkpp = NULL;
                return (0);
        }
        if (sema_get(&newblk_in_progress, 0) == 0)
                goto top;
        MALLOC(newblk, struct newblk *, sizeof(struct newblk),
                M_NEWBLK, M_SOFTDEP_FLAGS);
        newblk->nb_state = 0;
        newblk->nb_fs = fs;
        newblk->nb_newblkno = newblkno;
        LIST_INSERT_HEAD(newblkhd, newblk, nb_hash);
        sema_release(&newblk_in_progress);
        *newblkpp = newblk;
        return (0);
}

/*
 * Executed during filesystem system initialization before
 * mounting any filesystems.
 */
void 
softdep_initialize()
{
        callout_init(&handle);
        bioops = softdep_bioops;        /* XXX hack */

        LIST_INIT(&mkdirlisthd);
        LIST_INIT(&softdep_workitem_pending);
        max_softdeps = min(desiredvnodes * 8,
                M_INODEDEP->ks_limit / (2 * sizeof(struct inodedep)));
        pagedep_hashtbl = hashinit(desiredvnodes / 5, M_PAGEDEP,
            &pagedep_hash);
        sema_init(&pagedep_in_progress, "pagedep", 0, 0);
        inodedep_hashtbl = hashinit(desiredvnodes, M_INODEDEP, &inodedep_hash);
        sema_init(&inodedep_in_progress, "inodedep", 0, 0);
        newblk_hashtbl = hashinit(64, M_NEWBLK, &newblk_hash);
        sema_init(&newblk_in_progress, "newblk", 0, 0);
}

/*
 * Called at mount time to notify the dependency code that a
 * filesystem wishes to use it.
 */
int
softdep_mount(devvp, mp, fs)
        struct vnode *devvp;
        struct mount *mp;
        struct fs *fs;
{
        struct csum cstotal;
        struct cg *cgp;
        struct buf *bp;
        int error, cyl;

        mp->mnt_flag &= ~MNT_ASYNC;
        mp->mnt_flag |= MNT_SOFTDEP;
        /*
         * When doing soft updates, the counters in the
         * superblock may have gotten out of sync, so we have
         * to scan the cylinder groups and recalculate them.
         */
        if (fs->fs_clean != 0)
                return (0);
        bzero(&cstotal, sizeof cstotal);
        for (cyl = 0; cyl < fs->fs_ncg; cyl++) {
                if ((error = bread(devvp, fsbtodb(fs, cgtod(fs, cyl)),
                    fs->fs_cgsize, &bp)) != 0) {
                        brelse(bp);
                        return (error);
                }
                cgp = (struct cg *)bp->b_data;
                cstotal.cs_nffree += cgp->cg_cs.cs_nffree;
                cstotal.cs_nbfree += cgp->cg_cs.cs_nbfree;
                cstotal.cs_nifree += cgp->cg_cs.cs_nifree;
                cstotal.cs_ndir += cgp->cg_cs.cs_ndir;
                fs->fs_cs(fs, cyl) = cgp->cg_cs;
                brelse(bp);
        }
#ifdef DEBUG
        if (bcmp(&cstotal, &fs->fs_cstotal, sizeof cstotal))
                printf("ffs_mountfs: superblock updated for soft updates\n");
#endif
        bcopy(&cstotal, &fs->fs_cstotal, sizeof cstotal);
        return (0);
}

/*
 * Protecting the freemaps (or bitmaps).
 * 
 * To eliminate the need to execute fsck before mounting a filesystem
 * after a power failure, one must (conservatively) guarantee that the
 * on-disk copy of the bitmaps never indicate that a live inode or block is
 * free.  So, when a block or inode is allocated, the bitmap should be
 * updated (on disk) before any new pointers.  When a block or inode is
 * freed, the bitmap should not be updated until all pointers have been
 * reset.  The latter dependency is handled by the delayed de-allocation
 * approach described below for block and inode de-allocation.  The former
 * dependency is handled by calling the following procedure when a block or
 * inode is allocated. When an inode is allocated an "inodedep" is created
 * with its DEPCOMPLETE flag cleared until its bitmap is written to disk.
 * Each "inodedep" is also inserted into the hash indexing structure so
 * that any additional link additions can be made dependent on the inode
 * allocation.
 * 
 * The ufs filesystem maintains a number of free block counts (e.g., per
 * cylinder group, per cylinder and per <cylinder, rotational position> pair)
 * in addition to the bitmaps.  These counts are used to improve efficiency
 * during allocation and therefore must be consistent with the bitmaps.
 * There is no convenient way to guarantee post-crash consistency of these
 * counts with simple update ordering, for two main reasons: (1) The counts
 * and bitmaps for a single cylinder group block are not in the same disk
 * sector.  If a disk write is interrupted (e.g., by power failure), one may
 * be written and the other not.  (2) Some of the counts are located in the
 * superblock rather than the cylinder group block. So, we focus our soft
 * updates implementation on protecting the bitmaps. When mounting a
 * filesystem, we recompute the auxiliary counts from the bitmaps.
 */

/*
 * Called just after updating the cylinder group block to allocate an inode.
 */
void
softdep_setup_inomapdep(bp, ip, newinum)
        struct buf *bp;         /* buffer for cylgroup block with inode map */
        struct inode *ip;       /* inode related to allocation */
        ino_t newinum;          /* new inode number being allocated */
{
        struct inodedep *inodedep;
        struct bmsafemap *bmsafemap;

        /*
         * Create a dependency for the newly allocated inode.
         * Panic if it already exists as something is seriously wrong.
         * Otherwise add it to the dependency list for the buffer holding
         * the cylinder group map from which it was allocated.
         */
        ACQUIRE_LOCK(&lk);
        if ((inodedep_lookup(ip->i_fs, newinum, DEPALLOC|NODELAY, &inodedep))) {
                FREE_LOCK(&lk);
                panic("softdep_setup_inomapdep: found inode");
        }
        inodedep->id_buf = bp;
        inodedep->id_state &= ~DEPCOMPLETE;
        bmsafemap = bmsafemap_lookup(bp);
        LIST_INSERT_HEAD(&bmsafemap->sm_inodedephd, inodedep, id_deps);
        FREE_LOCK(&lk);
}

/*
 * Called just after updating the cylinder group block to
 * allocate block or fragment.
 */
void
softdep_setup_blkmapdep(bp, fs, newblkno)
        struct buf *bp;         /* buffer for cylgroup block with block map */
        struct fs *fs;          /* filesystem doing allocation */
        ufs_daddr_t newblkno;   /* number of newly allocated block */
{
        struct newblk *newblk;
        struct bmsafemap *bmsafemap;

        /*
         * Create a dependency for the newly allocated block.
         * Add it to the dependency list for the buffer holding
         * the cylinder group map from which it was allocated.
         */
        if (newblk_lookup(fs, newblkno, DEPALLOC, &newblk) != 0)
                panic("softdep_setup_blkmapdep: found block");
        ACQUIRE_LOCK(&lk);
        newblk->nb_bmsafemap = bmsafemap = bmsafemap_lookup(bp);
        LIST_INSERT_HEAD(&bmsafemap->sm_newblkhd, newblk, nb_deps);
        FREE_LOCK(&lk);
}

/*
 * Find the bmsafemap associated with a cylinder group buffer.
 * If none exists, create one. The buffer must be locked when
 * this routine is called and this routine must be called with
 * splbio interrupts blocked.
 */
static struct bmsafemap *
bmsafemap_lookup(bp)
        struct buf *bp;
{
        struct bmsafemap *bmsafemap;
        struct worklist *wk;

#ifdef DEBUG
        if (lk.lkt_held == NOHOLDER)
                panic("bmsafemap_lookup: lock not held");
#endif
        LIST_FOREACH(wk, &bp->b_dep, wk_list)
                if (wk->wk_type == D_BMSAFEMAP)
                        return (WK_BMSAFEMAP(wk));
        FREE_LOCK(&lk);
        MALLOC(bmsafemap, struct bmsafemap *, sizeof(struct bmsafemap),
                M_BMSAFEMAP, M_SOFTDEP_FLAGS);
        bmsafemap->sm_list.wk_type = D_BMSAFEMAP;
        bmsafemap->sm_list.wk_state = 0;
        bmsafemap->sm_buf = bp;
        LIST_INIT(&bmsafemap->sm_allocdirecthd);
        LIST_INIT(&bmsafemap->sm_allocindirhd);
        LIST_INIT(&bmsafemap->sm_inodedephd);
        LIST_INIT(&bmsafemap->sm_newblkhd);
        ACQUIRE_LOCK(&lk);
        WORKLIST_INSERT(&bp->b_dep, &bmsafemap->sm_list);
        return (bmsafemap);
}

/*
 * Direct block allocation dependencies.
 * 
 * When a new block is allocated, the corresponding disk locations must be
 * initialized (with zeros or new data) before the on-disk inode points to
 * them.  Also, the freemap from which the block was allocated must be
 * updated (on disk) before the inode's pointer. These two dependencies are
 * independent of each other and are needed for all file blocks and indirect
 * blocks that are pointed to directly by the inode.  Just before the
 * "in-core" version of the inode is updated with a newly allocated block
 * number, a procedure (below) is called to setup allocation dependency
 * structures.  These structures are removed when the corresponding
 * dependencies are satisfied or when the block allocation becomes obsolete
 * (i.e., the file is deleted, the block is de-allocated, or the block is a
 * fragment that gets upgraded).  All of these cases are handled in
 * procedures described later.
 * 
 * When a file extension causes a fragment to be upgraded, either to a larger
 * fragment or to a full block, the on-disk location may change (if the
 * previous fragment could not simply be extended). In this case, the old
 * fragment must be de-allocated, but not until after the inode's pointer has
 * been updated. In most cases, this is handled by later procedures, which
 * will construct a "freefrag" structure to be added to the workitem queue
 * when the inode update is complete (or obsolete).  The main exception to
 * this is when an allocation occurs while a pending allocation dependency
 * (for the same block pointer) remains.  This case is handled in the main
 * allocation dependency setup procedure by immediately freeing the
 * unreferenced fragments.
 */ 
void 
softdep_setup_allocdirect(ip, lbn, newblkno, oldblkno, newsize, oldsize, bp)
        struct inode *ip;       /* inode to which block is being added */
        ufs_lbn_t lbn;          /* block pointer within inode */
        ufs_daddr_t newblkno;   /* disk block number being added */
        ufs_daddr_t oldblkno;   /* previous block number, 0 unless frag */
        long newsize;           /* size of new block */
        long oldsize;           /* size of new block */
        struct buf *bp;         /* bp for allocated block */
{
        struct allocdirect *adp, *oldadp;
        struct allocdirectlst *adphead;
        struct bmsafemap *bmsafemap;
        struct inodedep *inodedep;
        struct pagedep *pagedep;
        struct newblk *newblk;

        MALLOC(adp, struct allocdirect *, sizeof(struct allocdirect),
                M_ALLOCDIRECT, M_SOFTDEP_FLAGS);
        bzero(adp, sizeof(struct allocdirect));
        adp->ad_list.wk_type = D_ALLOCDIRECT;
        adp->ad_lbn = lbn;
        adp->ad_newblkno = newblkno;
        adp->ad_oldblkno = oldblkno;
        adp->ad_newsize = newsize;
        adp->ad_oldsize = oldsize;
        adp->ad_state = ATTACHED;
        if (newblkno == oldblkno)
                adp->ad_freefrag = NULL;
        else
                adp->ad_freefrag = newfreefrag(ip, oldblkno, oldsize);

        if (newblk_lookup(ip->i_fs, newblkno, 0, &newblk) == 0)
                panic("softdep_setup_allocdirect: lost block");

        ACQUIRE_LOCK(&lk);
        inodedep_lookup(ip->i_fs, ip->i_number, DEPALLOC | NODELAY, &inodedep);
        adp->ad_inodedep = inodedep;

        if (newblk->nb_state == DEPCOMPLETE) {
                adp->ad_state |= DEPCOMPLETE;
                adp->ad_buf = NULL;
        } else {
                bmsafemap = newblk->nb_bmsafemap;
                adp->ad_buf = bmsafemap->sm_buf;
                LIST_REMOVE(newblk, nb_deps);
                LIST_INSERT_HEAD(&bmsafemap->sm_allocdirecthd, adp, ad_deps);
        }
        LIST_REMOVE(newblk, nb_hash);
        FREE(newblk, M_NEWBLK);

        WORKLIST_INSERT(&bp->b_dep, &adp->ad_list);
        if (lbn >= NDADDR) {
                /* allocating an indirect block */
                if (oldblkno != 0) {
                        FREE_LOCK(&lk);
                        panic("softdep_setup_allocdirect: non-zero indir");
                }
        } else {
                /*
                 * Allocating a direct block.
                 *
                 * If we are allocating a directory block, then we must
                 * allocate an associated pagedep to track additions and
                 * deletions.
                 */
                if ((ip->i_mode & IFMT) == IFDIR &&
                    pagedep_lookup(ip, lbn, DEPALLOC, &pagedep) == 0)
                        WORKLIST_INSERT(&bp->b_dep, &pagedep->pd_list);
        }
        /*
         * The list of allocdirects must be kept in sorted and ascending
         * order so that the rollback routines can quickly determine the
         * first uncommitted block (the size of the file stored on disk
         * ends at the end of the lowest committed fragment, or if there
         * are no fragments, at the end of the highest committed block).
         * Since files generally grow, the typical case is that the new
         * block is to be added at the end of the list. We speed this
         * special case by checking against the last allocdirect in the
         * list before laboriously traversing the list looking for the
         * insertion point.
         */
        adphead = &inodedep->id_newinoupdt;
        oldadp = TAILQ_LAST(adphead, allocdirectlst);
        if (oldadp == NULL || oldadp->ad_lbn <= lbn) {
                /* insert at end of list */
                TAILQ_INSERT_TAIL(adphead, adp, ad_next);
                if (oldadp != NULL && oldadp->ad_lbn == lbn)
                        allocdirect_merge(adphead, adp, oldadp);
                FREE_LOCK(&lk);
                return;
        }
        TAILQ_FOREACH(oldadp, adphead, ad_next) {
                if (oldadp->ad_lbn >= lbn)
                        break;
        }
        if (oldadp == NULL) {
                FREE_LOCK(&lk);
                panic("softdep_setup_allocdirect: lost entry");
        }
        /* insert in middle of list */
        TAILQ_INSERT_BEFORE(oldadp, adp, ad_next);
        if (oldadp->ad_lbn == lbn)
                allocdirect_merge(adphead, adp, oldadp);
        FREE_LOCK(&lk);
}

/*
 * Replace an old allocdirect dependency with a newer one.
 * This routine must be called with splbio interrupts blocked.
 */
static void
allocdirect_merge(adphead, newadp, oldadp)
        struct allocdirectlst *adphead; /* head of list holding allocdirects */
        struct allocdirect *newadp;     /* allocdirect being added */
        struct allocdirect *oldadp;     /* existing allocdirect being checked */
{
        struct freefrag *freefrag;

#ifdef DEBUG
        if (lk.lkt_held == NOHOLDER)
                panic("allocdirect_merge: lock not held");
#endif
        if (newadp->ad_oldblkno != oldadp->ad_newblkno ||
            newadp->ad_oldsize != oldadp->ad_newsize ||
            newadp->ad_lbn >= NDADDR) {
                FREE_LOCK(&lk);
                panic("allocdirect_check: old %d != new %d || lbn %ld >= %d",
                    newadp->ad_oldblkno, oldadp->ad_newblkno, newadp->ad_lbn,
                    NDADDR);
        }
        newadp->ad_oldblkno = oldadp->ad_oldblkno;
        newadp->ad_oldsize = oldadp->ad_oldsize;
        /*
         * If the old dependency had a fragment to free or had never
         * previously had a block allocated, then the new dependency
         * can immediately post its freefrag and adopt the old freefrag.
         * This action is done by swapping the freefrag dependencies.
         * The new dependency gains the old one's freefrag, and the
         * old one gets the new one and then immediately puts it on
         * the worklist when it is freed by free_allocdirect. It is
         * not possible to do this swap when the old dependency had a
         * non-zero size but no previous fragment to free. This condition
         * arises when the new block is an extension of the old block.
         * Here, the first part of the fragment allocated to the new
         * dependency is part of the block currently claimed on disk by
         * the old dependency, so cannot legitimately be freed until the
         * conditions for the new dependency are fulfilled.
         */
        if (oldadp->ad_freefrag != NULL || oldadp->ad_oldblkno == 0) {
                freefrag = newadp->ad_freefrag;
                newadp->ad_freefrag = oldadp->ad_freefrag;
                oldadp->ad_freefrag = freefrag;
        }
        free_allocdirect(adphead, oldadp, 0);
}
                
/*
 * Allocate a new freefrag structure if needed.
 */
static struct freefrag *
newfreefrag(ip, blkno, size)
        struct inode *ip;
        ufs_daddr_t blkno;
        long size;
{
        struct freefrag *freefrag;
        struct fs *fs;

        if (blkno == 0)
                return (NULL);
        fs = ip->i_fs;
        if (fragnum(fs, blkno) + numfrags(fs, size) > fs->fs_frag)
                panic("newfreefrag: frag size");
        MALLOC(freefrag, struct freefrag *, sizeof(struct freefrag),
                M_FREEFRAG, M_SOFTDEP_FLAGS);
        freefrag->ff_list.wk_type = D_FREEFRAG;
        freefrag->ff_state = ip->i_uid & ~ONWORKLIST;   /* XXX - used below */
        freefrag->ff_inum = ip->i_number;
        freefrag->ff_fs = fs;
        freefrag->ff_devvp = ip->i_devvp;
        freefrag->ff_blkno = blkno;
        freefrag->ff_fragsize = size;
        return (freefrag);
}

/*
 * This workitem de-allocates fragments that were replaced during
 * file block allocation.
 */
static void 
handle_workitem_freefrag(freefrag)
        struct freefrag *freefrag;
{
        struct inode tip;

        tip.i_fs = freefrag->ff_fs;
        tip.i_devvp = freefrag->ff_devvp;
        tip.i_dev = freefrag->ff_devvp->v_rdev;
        tip.i_number = freefrag->ff_inum;
        tip.i_uid = freefrag->ff_state & ~ONWORKLIST;   /* XXX - set above */
        ffs_blkfree(&tip, freefrag->ff_blkno, freefrag->ff_fragsize);
        FREE(freefrag, M_FREEFRAG);
}

/*
 * Indirect block allocation dependencies.
 * 
 * The same dependencies that exist for a direct block also exist when
 * a new block is allocated and pointed to by an entry in a block of
 * indirect pointers. The undo/redo states described above are also
 * used here. Because an indirect block contains many pointers that
 * may have dependencies, a second copy of the entire in-memory indirect
 * block is kept. The buffer cache copy is always completely up-to-date.
 * The second copy, which is used only as a source for disk writes,
 * contains only the safe pointers (i.e., those that have no remaining
 * update dependencies). The second copy is freed when all pointers
 * are safe. The cache is not allowed to replace indirect blocks with
 * pending update dependencies. If a buffer containing an indirect
 * block with dependencies is written, these routines will mark it
 * dirty again. It can only be successfully written once all the
 * dependencies are removed. The ffs_fsync routine in conjunction with
 * softdep_sync_metadata work together to get all the dependencies
 * removed so that a file can be successfully written to disk. Three
 * procedures are used when setting up indirect block pointer
 * dependencies. The division is necessary because of the organization
 * of the "balloc" routine and because of the distinction between file
 * pages and file metadata blocks.
 */

/*
 * Allocate a new allocindir structure.
 */
static struct allocindir *
newallocindir(ip, ptrno, newblkno, oldblkno)
        struct inode *ip;       /* inode for file being extended */
        int ptrno;              /* offset of pointer in indirect block */
        ufs_daddr_t newblkno;   /* disk block number being added */
        ufs_daddr_t oldblkno;   /* previous block number, 0 if none */
{
        struct allocindir *aip;

        MALLOC(aip, struct allocindir *, sizeof(struct allocindir),
                M_ALLOCINDIR, M_SOFTDEP_FLAGS);
        bzero(aip, sizeof(struct allocindir));
        aip->ai_list.wk_type = D_ALLOCINDIR;
        aip->ai_state = ATTACHED;
        aip->ai_offset = ptrno;
        aip->ai_newblkno = newblkno;
        aip->ai_oldblkno = oldblkno;
        aip->ai_freefrag = newfreefrag(ip, oldblkno, ip->i_fs->fs_bsize);
        return (aip);
}

/*
 * Called just before setting an indirect block pointer
 * to a newly allocated file page.
 */
void
softdep_setup_allocindir_page(ip, lbn, bp, ptrno, newblkno, oldblkno, nbp)
        struct inode *ip;       /* inode for file being extended */
        ufs_lbn_t lbn;          /* allocated block number within file */
        struct buf *bp;         /* buffer with indirect blk referencing page */
        int ptrno;              /* offset of pointer in indirect block */
        ufs_daddr_t newblkno;   /* disk block number being added */
        ufs_daddr_t oldblkno;   /* previous block number, 0 if none */
        struct buf *nbp;        /* buffer holding allocated page */
{
        struct allocindir *aip;
        struct pagedep *pagedep;

        aip = newallocindir(ip, ptrno, newblkno, oldblkno);
        ACQUIRE_LOCK(&lk);
        /*
         * If we are allocating a directory page, then we must
         * allocate an associated pagedep to track additions and
         * deletions.
         */
        if ((ip->i_mode & IFMT) == IFDIR &&
            pagedep_lookup(ip, lbn, DEPALLOC, &pagedep) == 0)
                WORKLIST_INSERT(&nbp->b_dep, &pagedep->pd_list);
        WORKLIST_INSERT(&nbp->b_dep, &aip->ai_list);
        FREE_LOCK(&lk);
        setup_allocindir_phase2(bp, ip, aip);
}

/*
 * Called just before setting an indirect block pointer to a
 * newly allocated indirect block.
 */
void
softdep_setup_allocindir_meta(nbp, ip, bp, ptrno, newblkno)
        struct buf *nbp;        /* newly allocated indirect block */
        struct inode *ip;       /* inode for file being extended */
        struct buf *bp;         /* indirect block referencing allocated block */
        int ptrno;              /* offset of pointer in indirect block */
        ufs_daddr_t newblkno;   /* disk block number being added */
{
        struct allocindir *aip;

        aip = newallocindir(ip, ptrno, newblkno, 0);
        ACQUIRE_LOCK(&lk);
        WORKLIST_INSERT(&nbp->b_dep, &aip->ai_list);
        FREE_LOCK(&lk);
        setup_allocindir_phase2(bp, ip, aip);
}

/*
 * Called to finish the allocation of the "aip" allocated
 * by one of the two routines above.
 */
static void 
setup_allocindir_phase2(bp, ip, aip)
        struct buf *bp;         /* in-memory copy of the indirect block */
        struct inode *ip;       /* inode for file being extended */
        struct allocindir *aip; /* allocindir allocated by the above routines */
{
        struct worklist *wk;
        struct indirdep *indirdep, *newindirdep;
        struct bmsafemap *bmsafemap;
        struct allocindir *oldaip;
        struct freefrag *freefrag;
        struct newblk *newblk;

        if (bp->b_lblkno >= 0)
                panic("setup_allocindir_phase2: not indir blk");
        for (indirdep = NULL, newindirdep = NULL; ; ) {
                ACQUIRE_LOCK(&lk);
                LIST_FOREACH(wk, &bp->b_dep, wk_list) {
                        if (wk->wk_type != D_INDIRDEP)
                                continue;
                        indirdep = WK_INDIRDEP(wk);
                        break;
                }
                if (indirdep == NULL && newindirdep) {
                        indirdep = newindirdep;
                        WORKLIST_INSERT(&bp->b_dep, &indirdep->ir_list);
                        newindirdep = NULL;
                }
                FREE_LOCK(&lk);
                if (indirdep) {
                        if (newblk_lookup(ip->i_fs, aip->ai_newblkno, 0,
                            &newblk) == 0)
                                panic("setup_allocindir: lost block");
                        ACQUIRE_LOCK(&lk);
                        if (newblk->nb_state == DEPCOMPLETE) {
                                aip->ai_state |= DEPCOMPLETE;
                                aip->ai_buf = NULL;
                        } else {
                                bmsafemap = newblk->nb_bmsafemap;
                                aip->ai_buf = bmsafemap->sm_buf;
                                LIST_REMOVE(newblk, nb_deps);
                                LIST_INSERT_HEAD(&bmsafemap->sm_allocindirhd,
                                    aip, ai_deps);
                        }
                        LIST_REMOVE(newblk, nb_hash);
                        FREE(newblk, M_NEWBLK);
                        aip->ai_indirdep = indirdep;
                        /*
                         * Check to see if there is an existing dependency
                         * for this block. If there is, merge the old
                         * dependency into the new one.
                         */
                        if (aip->ai_oldblkno == 0)
                                oldaip = NULL;
                        else

                                LIST_FOREACH(oldaip, &indirdep->ir_deplisthd, ai_next)
                                        if (oldaip->ai_offset == aip->ai_offset)
                                                break;
                        if (oldaip != NULL) {
                                if (oldaip->ai_newblkno != aip->ai_oldblkno) {
                                        FREE_LOCK(&lk);
                                        panic("setup_allocindir_phase2: blkno");
                                }
                                aip->ai_oldblkno = oldaip->ai_oldblkno;
                                freefrag = oldaip->ai_freefrag;
                                oldaip->ai_freefrag = aip->ai_freefrag;
                                aip->ai_freefrag = freefrag;
                                free_allocindir(oldaip, NULL);
                        }
                        LIST_INSERT_HEAD(&indirdep->ir_deplisthd, aip, ai_next);
                        ((ufs_daddr_t *)indirdep->ir_savebp->b_data)
                            [aip->ai_offset] = aip->ai_oldblkno;
                        FREE_LOCK(&lk);
                }
                if (newindirdep) {
                        /*
                         * Avoid any possibility of data corruption by 
                         * ensuring that our old version is thrown away.
                         */
                        newindirdep->ir_savebp->b_flags |= B_INVAL | B_NOCACHE;
                        brelse(newindirdep->ir_savebp);
                        WORKITEM_FREE((caddr_t)newindirdep, D_INDIRDEP);
                }
                if (indirdep)
                        break;
                MALLOC(newindirdep, struct indirdep *, sizeof(struct indirdep),
                        M_INDIRDEP, M_SOFTDEP_FLAGS);
                newindirdep->ir_list.wk_type = D_INDIRDEP;
                newindirdep->ir_state = ATTACHED;
                LIST_INIT(&newindirdep->ir_deplisthd);
                LIST_INIT(&newindirdep->ir_donehd);
                if (bp->b_blkno == bp->b_lblkno) {
                        VOP_BMAP(bp->b_vp, bp->b_lblkno, NULL, &bp->b_blkno,
                                NULL, NULL);
                }
                newindirdep->ir_savebp =
                    getblk(ip->i_devvp, bp->b_blkno, bp->b_bcount, 0, 0);
                BUF_KERNPROC(newindirdep->ir_savebp);
                bcopy(bp->b_data, newindirdep->ir_savebp->b_data, bp->b_bcount);
        }
}

/*
 * Block de-allocation dependencies.
 * 
 * When blocks are de-allocated, the on-disk pointers must be nullified before
 * the blocks are made available for use by other files.  (The true
 * requirement is that old pointers must be nullified before new on-disk
 * pointers are set.  We chose this slightly more stringent requirement to
 * reduce complexity.) Our implementation handles this dependency by updating
 * the inode (or indirect block) appropriately but delaying the actual block
 * de-allocation (i.e., freemap and free space count manipulation) until
 * after the updated versions reach stable storage.  After the disk is
 * updated, the blocks can be safely de-allocated whenever it is convenient.
 * This implementation handles only the common case of reducing a file's
 * length to zero. Other cases are handled by the conventional synchronous
 * write approach.
 *
 * The ffs implementation with which we worked double-checks
 * the state of the block pointers and file size as it reduces
 * a file's length.  Some of this code is replicated here in our
 * soft updates implementation.  The freeblks->fb_chkcnt field is
 * used to transfer a part of this information to the procedure
 * that eventually de-allocates the blocks.
 *
 * This routine should be called from the routine that shortens
 * a file's length, before the inode's size or block pointers
 * are modified. It will save the block pointer information for
 * later release and zero the inode so that the calling routine
 * can release it.
 */
struct softdep_setup_freeblocks_info {
        struct fs *fs;
        struct inode *ip;
};

static int softdep_setup_freeblocks_bp(struct buf *bp, void *data);

void
softdep_setup_freeblocks(ip, length)
        struct inode *ip;       /* The inode whose length is to be reduced */
        off_t length;           /* The new length for the file */
{
        struct softdep_setup_freeblocks_info info;
        struct freeblks *freeblks;
        struct inodedep *inodedep;
        struct allocdirect *adp;
        struct vnode *vp;
        struct buf *bp;
        struct fs *fs;
        int i, error, delay;
        int count;

        fs = ip->i_fs;
        if (length != 0)
                panic("softde_setup_freeblocks: non-zero length");
        MALLOC(freeblks, struct freeblks *, sizeof(struct freeblks),
                M_FREEBLKS, M_SOFTDEP_FLAGS);
        bzero(freeblks, sizeof(struct freeblks));
        freeblks->fb_list.wk_type = D_FREEBLKS;
        freeblks->fb_state = ATTACHED;
        freeblks->fb_uid = ip->i_uid;
        freeblks->fb_previousinum = ip->i_number;
        freeblks->fb_devvp = ip->i_devvp;
        freeblks->fb_fs = fs;
        freeblks->fb_oldsize = ip->i_size;
        freeblks->fb_newsize = length;
        freeblks->fb_chkcnt = ip->i_blocks;
        for (i = 0; i < NDADDR; i++) {
                freeblks->fb_dblks[i] = ip->i_db[i];
                ip->i_db[i] = 0;
        }
        for (i = 0; i < NIADDR; i++) {
                freeblks->fb_iblks[i] = ip->i_ib[i];
                ip->i_ib[i] = 0;
        }
        ip->i_blocks = 0;
        ip->i_size = 0;
        /*
         * Push the zero'ed inode to to its disk buffer so that we are free
         * to delete its dependencies below. Once the dependencies are gone
         * the buffer can be safely released.
         */
        if ((error = bread(ip->i_devvp,
            fsbtodb(fs, ino_to_fsba(fs, ip->i_number)),
            (int)fs->fs_bsize, &bp)) != 0)
                softdep_error("softdep_setup_freeblocks", error);
        *((struct dinode *)bp->b_data + ino_to_fsbo(fs, ip->i_number)) =
            ip->i_din;
        /*
         * Find and eliminate any inode dependencies.
         */
        ACQUIRE_LOCK(&lk);
        (void) inodedep_lookup(fs, ip->i_number, DEPALLOC, &inodedep);
        if ((inodedep->id_state & IOSTARTED) != 0) {
                FREE_LOCK(&lk);
                panic("softdep_setup_freeblocks: inode busy");
        }
        /*
         * Add the freeblks structure to the list of operations that
         * must await the zero'ed inode being written to disk. If we
         * still have a bitmap dependency (delay == 0), then the inode
         * has never been written to disk, so we can process the
         * freeblks below once we have deleted the dependencies.
         */
        delay = (inodedep->id_state & DEPCOMPLETE);
        if (delay)
                WORKLIST_INSERT(&inodedep->id_bufwait, &freeblks->fb_list);
        /*
         * Because the file length has been truncated to zero, any
         * pending block allocation dependency structures associated
         * with this inode are obsolete and can simply be de-allocated.
         * We must first merge the two dependency lists to get rid of
         * any duplicate freefrag structures, then purge the merged list.
         */
        merge_inode_lists(inodedep);
        while ((adp = TAILQ_FIRST(&inodedep->id_inoupdt)) != 0)
                free_allocdirect(&inodedep->id_inoupdt, adp, 1);
        FREE_LOCK(&lk);
        bdwrite(bp);
        /*
         * We must wait for any I/O in progress to finish so that
         * all potential buffers on the dirty list will be visible.
         * Once they are all there, walk the list and get rid of
         * any dependencies.
         */
        vp = ITOV(ip);
        ACQUIRE_LOCK(&lk);
        drain_output(vp, 1);

        info.fs = fs;
        info.ip = ip;
        do {
                count = RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, NULL, 
                                softdep_setup_freeblocks_bp, &info);
        } while (count > 0);
        if (inodedep_lookup(fs, ip->i_number, 0, &inodedep) != 0)
                (void)free_inodedep(inodedep);

        if (delay) {
                freeblks->fb_state |= DEPCOMPLETE;
                /*
                 * If the inode with zeroed block pointers is now on disk
                 * we can start freeing blocks. Add freeblks to the worklist
                 * instead of calling  handle_workitem_freeblocks directly as
                 * it is more likely that additional IO is needed to complete
                 * the request here than in the !delay case.
                 */
                if ((freeblks->fb_state & ALLCOMPLETE) == ALLCOMPLETE)
                        add_to_worklist(&freeblks->fb_list);
        }

        FREE_LOCK(&lk);
        /*
         * If the inode has never been written to disk (delay == 0),
         * then we can process the freeblks now that we have deleted
         * the dependencies.
         */
        if (!delay)
                handle_workitem_freeblocks(freeblks);
}

static int
softdep_setup_freeblocks_bp(struct buf *bp, void *data)
{
        struct softdep_setup_freeblocks_info *info = data;
        struct inodedep *inodedep;

        if (getdirtybuf(&bp, MNT_WAIT) == 0)
                return(-1);
        (void) inodedep_lookup(info->fs, info->ip->i_number, 0, &inodedep);
        deallocate_dependencies(bp, inodedep);
        bp->b_flags |= B_INVAL | B_NOCACHE;
        FREE_LOCK(&lk);
        brelse(bp);
        ACQUIRE_LOCK(&lk);
        return(1);
}

/*
 * Reclaim any dependency structures from a buffer that is about to
 * be reallocated to a new vnode. The buffer must be locked, thus,
 * no I/O completion operations can occur while we are manipulating
 * its associated dependencies. The mutex is held so that other I/O's
 * associated with related dependencies do not occur.
 */
static void
deallocate_dependencies(bp, inodedep)
        struct buf *bp;
        struct inodedep *inodedep;
{
        struct worklist *wk;
        struct indirdep *indirdep;
        struct allocindir *aip;
        struct pagedep *pagedep;
        struct dirrem *dirrem;
        struct diradd *dap;
        int i;

        while ((wk = LIST_FIRST(&bp->b_dep)) != NULL) {
                switch (wk->wk_type) {

                case D_INDIRDEP:
                        indirdep = WK_INDIRDEP(wk);
                        /*
                         * None of the indirect pointers will ever be visible,
                         * so they can simply be tossed. GOINGAWAY ensures
                         * that allocated pointers will be saved in the buffer
                         * cache until they are freed. Note that they will
                         * only be able to be found by their physical address
                         * since the inode mapping the logical address will
                         * be gone. The save buffer used for the safe copy
                         * was allocated in setup_allocindir_phase2 using
                         * the physical address so it could be used for this
                         * purpose. Hence we swap the safe copy with the real
                         * copy, allowing the safe copy to be freed and holding
                         * on to the real copy for later use in indir_trunc.
                         */
                        if (indirdep->ir_state & GOINGAWAY) {
                                FREE_LOCK(&lk);
                                panic("deallocate_dependencies: already gone");
                        }
                        indirdep->ir_state |= GOINGAWAY;
                        while ((aip = LIST_FIRST(&indirdep->ir_deplisthd)) != 0)
                                free_allocindir(aip, inodedep);
                        if (bp->b_lblkno >= 0 ||
                            bp->b_blkno != indirdep->ir_savebp->b_lblkno) {
                                FREE_LOCK(&lk);
                                panic("deallocate_dependencies: not indir");
                        }
                        bcopy(bp->b_data, indirdep->ir_savebp->b_data,
                            bp->b_bcount);
                        WORKLIST_REMOVE(wk);
                        WORKLIST_INSERT(&indirdep->ir_savebp->b_dep, wk);
                        continue;

                case D_PAGEDEP:
                        pagedep = WK_PAGEDEP(wk);
                        /*
                         * None of the directory additions will ever be
                         * visible, so they can simply be tossed.
                         */
                        for (i = 0; i < DAHASHSZ; i++)
                                while ((dap =
                                    LIST_FIRST(&pagedep->pd_diraddhd[i])))
                                        free_diradd(dap);
                        while ((dap = LIST_FIRST(&pagedep->pd_pendinghd)) != 0)
                                free_diradd(dap);
                        /*
                         * Copy any directory remove dependencies to the list
                         * to be processed after the zero'ed inode is written.
                         * If the inode has already been written, then they 
                         * can be dumped directly onto the work list.
                         */
                        LIST_FOREACH(dirrem, &pagedep->pd_dirremhd, dm_next) {
                                LIST_REMOVE(dirrem, dm_next);
                                dirrem->dm_dirinum = pagedep->pd_ino;
                                if (inodedep == NULL ||
                                    (inodedep->id_state & ALLCOMPLETE) ==
                                     ALLCOMPLETE)
                                        add_to_worklist(&dirrem->dm_list);
                                else
                                        WORKLIST_INSERT(&inodedep->id_bufwait,
                                            &dirrem->dm_list);
                        }
                        WORKLIST_REMOVE(&pagedep->pd_list);
                        LIST_REMOVE(pagedep, pd_hash);
                        WORKITEM_FREE(pagedep, D_PAGEDEP);
                        continue;

                case D_ALLOCINDIR:
                        free_allocindir(WK_ALLOCINDIR(wk), inodedep);
                        continue;

                case D_ALLOCDIRECT:
                case D_INODEDEP:
                        FREE_LOCK(&lk);
                        panic("deallocate_dependencies: Unexpected type %s",
                            TYPENAME(wk->wk_type));
                        /* NOTREACHED */

                default:
                        FREE_LOCK(&lk);
                        panic("deallocate_dependencies: Unknown type %s",
                            TYPENAME(wk->wk_type));
                        /* NOTREACHED */
                }
        }
}

/*
 * Free an allocdirect. Generate a new freefrag work request if appropriate.
 * This routine must be called with splbio interrupts blocked.
 */
static void
free_allocdirect(adphead, adp, delay)
        struct allocdirectlst *adphead;
        struct allocdirect *adp;
        int delay;
{

#ifdef DEBUG
        if (lk.lkt_held == NOHOLDER)
                panic("free_allocdirect: lock not held");
#endif
        if ((adp->ad_state & DEPCOMPLETE) == 0)
                LIST_REMOVE(adp, ad_deps);
        TAILQ_REMOVE(adphead, adp, ad_next);
        if ((adp->ad_state & COMPLETE) == 0)
                WORKLIST_REMOVE(&adp->ad_list);
        if (adp->ad_freefrag != NULL) {
                if (delay)
                        WORKLIST_INSERT(&adp->ad_inodedep->id_bufwait,
                            &adp->ad_freefrag->ff_list);
                else
                        add_to_worklist(&adp->ad_freefrag->ff_list);
        }
        WORKITEM_FREE(adp, D_ALLOCDIRECT);
}

/*
 * Prepare an inode to be freed. The actual free operation is not
 * done until the zero'ed inode has been written to disk.
 */
void
softdep_freefile(pvp, ino, mode)
                struct vnode *pvp;
                ino_t ino;
                int mode;
{
        struct inode *ip = VTOI(pvp);
        struct inodedep *inodedep;
        struct freefile *freefile;

        /*
         * This sets up the inode de-allocation dependency.
         */
        MALLOC(freefile, struct freefile *, sizeof(struct freefile),
                M_FREEFILE, M_SOFTDEP_FLAGS);
        freefile->fx_list.wk_type = D_FREEFILE;
        freefile->fx_list.wk_state = 0;
        freefile->fx_mode = mode;
        freefile->fx_oldinum = ino;
        freefile->fx_devvp = ip->i_devvp;
        freefile->fx_fs = ip->i_fs;

        /*
         * If the inodedep does not exist, then the zero'ed inode has
         * been written to disk. If the allocated inode has never been
         * written to disk, then the on-disk inode is zero'ed. In either
         * case we can free the file immediately.
         */
        ACQUIRE_LOCK(&lk);
        if (inodedep_lookup(ip->i_fs, ino, 0, &inodedep) == 0 ||
            check_inode_unwritten(inodedep)) {
                FREE_LOCK(&lk);
                handle_workitem_freefile(freefile);
                return;
        }
        WORKLIST_INSERT(&inodedep->id_inowait, &freefile->fx_list);
        FREE_LOCK(&lk);
}

/*
 * Check to see if an inode has never been written to disk. If
 * so free the inodedep and return success, otherwise return failure.
 * This routine must be called with splbio interrupts blocked.
 *
 * If we still have a bitmap dependency, then the inode has never
 * been written to disk. Drop the dependency as it is no longer
 * necessary since the inode is being deallocated. We set the
 * ALLCOMPLETE flags since the bitmap now properly shows that the
 * inode is not allocated. Even if the inode is actively being
 * written, it has been rolled back to its zero'ed state, so we
 * are ensured that a zero inode is what is on the disk. For short
 * lived files, this change will usually result in removing all the
 * dependencies from the inode so that it can be freed immediately.
 */
static int
check_inode_unwritten(inodedep)
        struct inodedep *inodedep;
{

        if ((inodedep->id_state & DEPCOMPLETE) != 0 ||
            LIST_FIRST(&inodedep->id_pendinghd) != NULL ||
            LIST_FIRST(&inodedep->id_bufwait) != NULL ||
            LIST_FIRST(&inodedep->id_inowait) != NULL ||
            TAILQ_FIRST(&inodedep->id_inoupdt) != NULL ||
            TAILQ_FIRST(&inodedep->id_newinoupdt) != NULL ||
            inodedep->id_nlinkdelta != 0)
                return (0);
        inodedep->id_state |= ALLCOMPLETE;
        LIST_REMOVE(inodedep, id_deps);
        inodedep->id_buf = NULL;
        if (inodedep->id_state & ONWORKLIST)
                WORKLIST_REMOVE(&inodedep->id_list);
        if (inodedep->id_savedino != NULL) {
                FREE(inodedep->id_savedino, M_INODEDEP);
                inodedep->id_savedino = NULL;
        }
        if (free_inodedep(inodedep) == 0) {
                FREE_LOCK(&lk);
                panic("check_inode_unwritten: busy inode");
        }
        return (1);
}

/*
 * Try to free an inodedep structure. Return 1 if it could be freed.
 */
static int
free_inodedep(inodedep)
        struct inodedep *inodedep;
{

        if ((inodedep->id_state & ONWORKLIST) != 0 ||
            (inodedep->id_state & ALLCOMPLETE) != ALLCOMPLETE ||
            LIST_FIRST(&inodedep->id_pendinghd) != NULL ||
            LIST_FIRST(&inodedep->id_bufwait) != NULL ||
            LIST_FIRST(&inodedep->id_inowait) != NULL ||
            TAILQ_FIRST(&inodedep->id_inoupdt) != NULL ||
            TAILQ_FIRST(&inodedep->id_newinoupdt) != NULL ||
            inodedep->id_nlinkdelta != 0 || inodedep->id_savedino != NULL)
                return (0);
        LIST_REMOVE(inodedep, id_hash);
        WORKITEM_FREE(inodedep, D_INODEDEP);
        num_inodedep -= 1;
        return (1);
}

/*
 * This workitem routine performs the block de-allocation.
 * The workitem is added to the pending list after the updated
 * inode block has been written to disk.  As mentioned above,
 * checks regarding the number of blocks de-allocated (compared
 * to the number of blocks allocated for the file) are also
 * performed in this function.
 */
static void
handle_workitem_freeblocks(freeblks)
        struct freeblks *freeblks;
{
        struct inode tip;
        ufs_daddr_t bn;
        struct fs *fs;
        int i, level, bsize;
        long nblocks, blocksreleased = 0;
        int error, allerror = 0;
        ufs_lbn_t baselbns[NIADDR], tmpval;

        tip.i_number = freeblks->fb_previousinum;
        tip.i_devvp = freeblks->fb_devvp;
        tip.i_dev = freeblks->fb_devvp->v_rdev;
        tip.i_fs = freeblks->fb_fs;
        tip.i_size = freeblks->fb_oldsize;
        tip.i_uid = freeblks->fb_uid;
        fs = freeblks->fb_fs;
        tmpval = 1;
        baselbns[0] = NDADDR;
        for (i = 1; i < NIADDR; i++) {
                tmpval *= NINDIR(fs);
                baselbns[i] = baselbns[i - 1] + tmpval;
        }
        nblocks = btodb(fs->fs_bsize);
        blocksreleased = 0;
        /*
         * Indirect blocks first.
         */
        for (level = (NIADDR - 1); level >= 0; level--) {
                if ((bn = freeblks->fb_iblks[level]) == 0)
                        continue;
                if ((error = indir_trunc(&tip, fsbtodb(fs, bn), level,
                    baselbns[level], &blocksreleased)) == 0)
                        allerror = error;
                ffs_blkfree(&tip, bn, fs->fs_bsize);
                blocksreleased += nblocks;
        }
        /*
         * All direct blocks or frags.
         */
        for (i = (NDADDR - 1); i >= 0; i--) {
                if ((bn = freeblks->fb_dblks[i]) == 0)
                        continue;
                bsize = blksize(fs, &tip, i);
                ffs_blkfree(&tip, bn, bsize);
                blocksreleased += btodb(bsize);
        }

#ifdef DIAGNOSTIC
        if (freeblks->fb_chkcnt != blocksreleased)
                printf("handle_workitem_freeblocks: block count\n");
        if (allerror)
                softdep_error("handle_workitem_freeblks", allerror);
#endif /* DIAGNOSTIC */
        WORKITEM_FREE(freeblks, D_FREEBLKS);
}

/*
 * Release blocks associated with the inode ip and stored in the indirect
 * block dbn. If level is greater than SINGLE, the block is an indirect block
 * and recursive calls to indirtrunc must be used to cleanse other indirect
 * blocks.
 */
static int
indir_trunc(ip, dbn, level, lbn, countp)
        struct inode *ip;
        ufs_daddr_t dbn;
        int level;
        ufs_lbn_t lbn;
        long *countp;
{
        struct buf *bp;
        ufs_daddr_t *bap;
        ufs_daddr_t nb;
        struct fs *fs;
        struct worklist *wk;
        struct indirdep *indirdep;
        int i, lbnadd, nblocks;
        int error, allerror = 0;

        fs = ip->i_fs;
        lbnadd = 1;
        for (i = level; i > 0; i--)
                lbnadd *= NINDIR(fs);
        /*
         * Get buffer of block pointers to be freed. This routine is not
         * called until the zero'ed inode has been written, so it is safe
         * to free blocks as they are encountered. Because the inode has
         * been zero'ed, calls to bmap on these blocks will fail. So, we
         * have to use the on-disk address and the block device for the
         * filesystem to look them up. If the file was deleted before its
         * indirect blocks were all written to disk, the routine that set
         * us up (deallocate_dependencies) will have arranged to leave
         * a complete copy of the indirect block in memory for our use.
         * Otherwise we have to read the blocks in from the disk.
         */
        ACQUIRE_LOCK(&lk);
        if ((bp = incore(ip->i_devvp, dbn)) != NULL &&
            (wk = LIST_FIRST(&bp->b_dep)) != NULL) {
                if (wk->wk_type != D_INDIRDEP ||
                    (indirdep = WK_INDIRDEP(wk))->ir_savebp != bp ||
                    (indirdep->ir_state & GOINGAWAY) == 0) {
                        FREE_LOCK(&lk);
                        panic("indir_trunc: lost indirdep");
                }
                WORKLIST_REMOVE(wk);
                WORKITEM_FREE(indirdep, D_INDIRDEP);
                if (LIST_FIRST(&bp->b_dep) != NULL) {
                        FREE_LOCK(&lk);
                        panic("indir_trunc: dangling dep");
                }
                FREE_LOCK(&lk);
        } else {
                FREE_LOCK(&lk);
                error = bread(ip->i_devvp, dbn, (int)fs->fs_bsize, &bp);
                if (error)
                        return (error);
        }
        /*
         * Recursively free indirect blocks.
         */
        bap = (ufs_daddr_t *)bp->b_data;
        nblocks = btodb(fs->fs_bsize);
        for (i = NINDIR(fs) - 1; i >= 0; i--) {
                if ((nb = bap[i]) == 0)
                        continue;
                if (level != 0) {
                        if ((error = indir_trunc(ip, fsbtodb(fs, nb),
                             level - 1, lbn + (i * lbnadd), countp)) != 0)
                                allerror = error;
                }
                ffs_blkfree(ip, nb, fs->fs_bsize);
                *countp += nblocks;
        }
        bp->b_flags |= B_INVAL | B_NOCACHE;
        brelse(bp);
        return (allerror);
}

/*
 * Free an allocindir.
 * This routine must be called with splbio interrupts blocked.
 */
static void
free_allocindir(aip, inodedep)
        struct allocindir *aip;
        struct inodedep *inodedep;
{
        struct freefrag *freefrag;

#ifdef DEBUG
        if (lk.lkt_held == NOHOLDER)
                panic("free_allocindir: lock not held");
#endif
        if ((aip->ai_state & DEPCOMPLETE) == 0)
                LIST_REMOVE(aip, ai_deps);
        if (aip->ai_state & ONWORKLIST)
                WORKLIST_REMOVE(&aip->ai_list);
        LIST_REMOVE(aip, ai_next);
        if ((freefrag = aip->ai_freefrag) != NULL) {
                if (inodedep == NULL)
                        add_to_worklist(&freefrag->ff_list);
                else
                        WORKLIST_INSERT(&inodedep->id_bufwait,
                            &freefrag->ff_list);
        }
        WORKITEM_FREE(aip, D_ALLOCINDIR);
}

/*
 * Directory entry addition dependencies.
 * 
 * When adding a new directory entry, the inode (with its incremented link
 * count) must be written to disk before the directory entry's pointer to it.
 * Also, if the inode is newly allocated, the corresponding freemap must be
 * updated (on disk) before the directory entry's pointer. These requirements
 * are met via undo/redo on the directory entry's pointer, which consists
 * simply of the inode number.
 * 
 * As directory entries are added and deleted, the free space within a
 * directory block can become fragmented.  The ufs filesystem will compact
 * a fragmented directory block to make space for a new entry. When this
 * occurs, the offsets of previously added entries change. Any "diradd"
 * dependency structures corresponding to these entries must be updated with
 * the new offsets.
 */

/*
 * This routine is called after the in-memory inode's link
 * count has been incremented, but before the directory entry's
 * pointer to the inode has been set.
 */
void 
softdep_setup_directory_add(bp, dp, diroffset, newinum, newdirbp)
        struct buf *bp;         /* buffer containing directory block */
        struct inode *dp;       /* inode for directory */
        off_t diroffset;        /* offset of new entry in directory */
        ino_t newinum;          /* inode referenced by new directory entry */
        struct buf *newdirbp;   /* non-NULL => contents of new mkdir */
{
        int offset;             /* offset of new entry within directory block */
        ufs_lbn_t lbn;          /* block in directory containing new entry */
        struct fs *fs;
        struct diradd *dap;
        struct pagedep *pagedep;
        struct inodedep *inodedep;
        struct mkdir *mkdir1, *mkdir2;

        /*
         * Whiteouts have no dependencies.
         */
        if (newinum == WINO) {
                if (newdirbp != NULL)
                        bdwrite(newdirbp);
                return;
        }

        fs = dp->i_fs;
        lbn = lblkno(fs, diroffset);
        offset = blkoff(fs, diroffset);
        MALLOC(dap, struct diradd *, sizeof(struct diradd), M_DIRADD,
            M_SOFTDEP_FLAGS);
        bzero(dap, sizeof(struct diradd));
        dap->da_list.wk_type = D_DIRADD;
        dap->da_offset = offset;
        dap->da_newinum = newinum;
        dap->da_state = ATTACHED;
        if (newdirbp == NULL) {
                dap->da_state |= DEPCOMPLETE;
                ACQUIRE_LOCK(&lk);
        } else {
                dap->da_state |= MKDIR_BODY | MKDIR_PARENT;
                MALLOC(mkdir1, struct mkdir *, sizeof(struct mkdir), M_MKDIR,
                    M_SOFTDEP_FLAGS);
                mkdir1->md_list.wk_type = D_MKDIR;
                mkdir1->md_state = MKDIR_BODY;
                mkdir1->md_diradd = dap;
                MALLOC(mkdir2, struct mkdir *, sizeof(struct mkdir), M_MKDIR,
                    M_SOFTDEP_FLAGS);
                mkdir2->md_list.wk_type = D_MKDIR;
                mkdir2->md_state = MKDIR_PARENT;
                mkdir2->md_diradd = dap;
                /*
                 * Dependency on "." and ".." being written to disk.
                 */
                mkdir1->md_buf = newdirbp;
                ACQUIRE_LOCK(&lk);
                LIST_INSERT_HEAD(&mkdirlisthd, mkdir1, md_mkdirs);
                WORKLIST_INSERT(&newdirbp->b_dep, &mkdir1->md_list);
                FREE_LOCK(&lk);
                bdwrite(newdirbp);
                /*
                 * Dependency on link count increase for parent directory
                 */
                ACQUIRE_LOCK(&lk);
                if (inodedep_lookup(dp->i_fs, dp->i_number, 0, &inodedep) == 0
                    || (inodedep->id_state & ALLCOMPLETE) == ALLCOMPLETE) {
                        dap->da_state &= ~MKDIR_PARENT;
                        WORKITEM_FREE(mkdir2, D_MKDIR);
                } else {
                        LIST_INSERT_HEAD(&mkdirlisthd, mkdir2, md_mkdirs);
                        WORKLIST_INSERT(&inodedep->id_bufwait,&mkdir2->md_list);
                }
        }
        /*
         * Link into parent directory pagedep to await its being written.
         */
        if (pagedep_lookup(dp, lbn, DEPALLOC, &pagedep) == 0)
                WORKLIST_INSERT(&bp->b_dep, &pagedep->pd_list);
        dap->da_pagedep = pagedep;
        LIST_INSERT_HEAD(&pagedep->pd_diraddhd[DIRADDHASH(offset)], dap,
            da_pdlist);
        /*
         * Link into its inodedep. Put it on the id_bufwait list if the inode
         * is not yet written. If it is written, do the post-inode write
         * processing to put it on the id_pendinghd list.
         */
        (void) inodedep_lookup(fs, newinum, DEPALLOC, &inodedep);
        if ((inodedep->id_state & ALLCOMPLETE) == ALLCOMPLETE)
                diradd_inode_written(dap, inodedep);
        else
                WORKLIST_INSERT(&inodedep->id_bufwait, &dap->da_list);
        FREE_LOCK(&lk);
}

/*
 * This procedure is called to change the offset of a directory
 * entry when compacting a directory block which must be owned
 * exclusively by the caller. Note that the actual entry movement
 * must be done in this procedure to ensure that no I/O completions
 * occur while the move is in progress.
 */
void 
softdep_change_directoryentry_offset(dp, base, oldloc, newloc, entrysize)
        struct inode *dp;       /* inode for directory */
        caddr_t base;           /* address of dp->i_offset */
        caddr_t oldloc;         /* address of old directory location */
        caddr_t newloc;         /* address of new directory location */
        int entrysize;          /* size of directory entry */
{
        int offset, oldoffset, newoffset;
        struct pagedep *pagedep;
        struct diradd *dap;
        ufs_lbn_t lbn;

        ACQUIRE_LOCK(&lk);
        lbn = lblkno(dp->i_fs, dp->i_offset);
        offset = blkoff(dp->i_fs, dp->i_offset);
        if (pagedep_lookup(dp, lbn, 0, &pagedep) == 0)
                goto done;
        oldoffset = offset + (oldloc - base);
        newoffset = offset + (newloc - base);

        LIST_FOREACH(dap, &pagedep->pd_diraddhd[DIRADDHASH(oldoffset)], da_pdlist) {
                if (dap->da_offset != oldoffset)
                        continue;
                dap->da_offset = newoffset;
                if (DIRADDHASH(newoffset) == DIRADDHASH(oldoffset))
                        break;
                LIST_REMOVE(dap, da_pdlist);
                LIST_INSERT_HEAD(&pagedep->pd_diraddhd[DIRADDHASH(newoffset)],
                    dap, da_pdlist);
                break;
        }
        if (dap == NULL) {

                LIST_FOREACH(dap, &pagedep->pd_pendinghd, da_pdlist) {
                        if (dap->da_offset == oldoffset) {
                                dap->da_offset = newoffset;
                                break;
                        }
                }
        }
done:
        bcopy(oldloc, newloc, entrysize);
        FREE_LOCK(&lk);
}

/*
 * Free a diradd dependency structure. This routine must be called
 * with splbio interrupts blocked.
 */
static void
free_diradd(dap)
        struct diradd *dap;
{
        struct dirrem *dirrem;
        struct pagedep *pagedep;
        struct inodedep *inodedep;
        struct mkdir *mkdir, *nextmd;

#ifdef DEBUG
        if (lk.lkt_held == NOHOLDER)
                panic("free_diradd: lock not held");
#endif
        WORKLIST_REMOVE(&dap->da_list);
        LIST_REMOVE(dap, da_pdlist);
        if ((dap->da_state & DIRCHG) == 0) {
                pagedep = dap->da_pagedep;
        } else {
                dirrem = dap->da_previous;
                pagedep = dirrem->dm_pagedep;
                dirrem->dm_dirinum = pagedep->pd_ino;
                add_to_worklist(&dirrem->dm_list);
        }
        if (inodedep_lookup(VFSTOUFS(pagedep->pd_mnt)->um_fs, dap->da_newinum,
            0, &inodedep) != 0)
                (void) free_inodedep(inodedep);
        if ((dap->da_state & (MKDIR_PARENT | MKDIR_BODY)) != 0) {
                for (mkdir = LIST_FIRST(&mkdirlisthd); mkdir; mkdir = nextmd) {
                        nextmd = LIST_NEXT(mkdir, md_mkdirs);
                        if (mkdir->md_diradd != dap)
                                continue;
                        dap->da_state &= ~mkdir->md_state;
                        WORKLIST_REMOVE(&mkdir->md_list);
                        LIST_REMOVE(mkdir, md_mkdirs);
                        WORKITEM_FREE(mkdir, D_MKDIR);
                }
                if ((dap->da_state & (MKDIR_PARENT | MKDIR_BODY)) != 0) {
                        FREE_LOCK(&lk);
                        panic("free_diradd: unfound ref");
                }
        }
        WORKITEM_FREE(dap, D_DIRADD);
}

/*
 * Directory entry removal dependencies.
 * 
 * When removing a directory entry, the entry's inode pointer must be
 * zero'ed on disk before the corresponding inode's link count is decremented
 * (possibly freeing the inode for re-use). This dependency is handled by
 * updating the directory entry but delaying the inode count reduction until
 * after the directory block has been written to disk. After this point, the
 * inode count can be decremented whenever it is convenient.
 */

/*
 * This routine should be called immediately after removing
 * a directory entry.  The inode's link count should not be
 * decremented by the calling procedure -- the soft updates
 * code will do this task when it is safe.
 */
void 
softdep_setup_remove(bp, dp, ip, isrmdir)
        struct buf *bp;         /* buffer containing directory block */
        struct inode *dp;       /* inode for the directory being modified */
        struct inode *ip;       /* inode for directory entry being removed */
        int isrmdir;            /* indicates if doing RMDIR */
{
        struct dirrem *dirrem, *prevdirrem;

        /*
         * Allocate a new dirrem if appropriate and ACQUIRE_LOCK.
         */
        dirrem = newdirrem(bp, dp, ip, isrmdir, &prevdirrem);

        /*
         * If the COMPLETE flag is clear, then there were no active
         * entries and we want to roll back to a zeroed entry until
         * the new inode is committed to disk. If the COMPLETE flag is
         * set then we have deleted an entry that never made it to
         * disk. If the entry we deleted resulted from a name change,
         * then the old name still resides on disk. We cannot delete
         * its inode (returned to us in prevdirrem) until the zeroed
         * directory entry gets to disk. The new inode has never been
         * referenced on the disk, so can be deleted immediately.
         */
        if ((dirrem->dm_state & COMPLETE) == 0) {
                LIST_INSERT_HEAD(&dirrem->dm_pagedep->pd_dirremhd, dirrem,
                    dm_next);
                FREE_LOCK(&lk);
        } else {
                if (prevdirrem != NULL)
                        LIST_INSERT_HEAD(&dirrem->dm_pagedep->pd_dirremhd,
                            prevdirrem, dm_next);
                dirrem->dm_dirinum = dirrem->dm_pagedep->pd_ino;
                FREE_LOCK(&lk);
                handle_workitem_remove(dirrem);
        }
}

/*
 * Allocate a new dirrem if appropriate and return it along with
 * its associated pagedep. Called without a lock, returns with lock.
 */
static long num_dirrem;         /* number of dirrem allocated */
static struct dirrem *
newdirrem(bp, dp, ip, isrmdir, prevdirremp)
        struct buf *bp;         /* buffer containing directory block */
        struct inode *dp;       /* inode for the directory being modified */
        struct inode *ip;       /* inode for directory entry being removed */
        int isrmdir;            /* indicates if doing RMDIR */
        struct dirrem **prevdirremp; /* previously referenced inode, if any */
{
        int offset;
        ufs_lbn_t lbn;
        struct diradd *dap;
        struct dirrem *dirrem;
        struct pagedep *pagedep;

        /*
         * Whiteouts have no deletion dependencies.
         */
        if (ip == NULL)
                panic("newdirrem: whiteout");
        /*
         * If we are over our limit, try to improve the situation.
         * Limiting the number of dirrem structures will also limit
         * the number of freefile and freeblks structures.
         */
        if (num_dirrem > max_softdeps / 2 && speedup_syncer() == 0)
                (void) request_cleanup(FLUSH_REMOVE, 0);
        num_dirrem += 1;
        MALLOC(dirrem, struct dirrem *, sizeof(struct dirrem),
                M_DIRREM, M_SOFTDEP_FLAGS);
        bzero(dirrem, sizeof(struct dirrem));
        dirrem->dm_list.wk_type = D_DIRREM;
        dirrem->dm_state = isrmdir ? RMDIR : 0;
        dirrem->dm_mnt = ITOV(ip)->v_mount;
        dirrem->dm_oldinum = ip->i_number;
        *prevdirremp = NULL;

        ACQUIRE_LOCK(&lk);
        lbn = lblkno(dp->i_fs, dp->i_offset);
        offset = blkoff(dp->i_fs, dp->i_offset);
        if (pagedep_lookup(dp, lbn, DEPALLOC, &pagedep) == 0)
                WORKLIST_INSERT(&bp->b_dep, &pagedep->pd_list);
        dirrem->dm_pagedep = pagedep;
        /*
         * Check for a diradd dependency for the same directory entry.
         * If present, then both dependencies become obsolete and can
         * be de-allocated. Check for an entry on both the pd_dirraddhd
         * list and the pd_pendinghd list.
         */

        LIST_FOREACH(dap, &pagedep->pd_diraddhd[DIRADDHASH(offset)], da_pdlist)
                if (dap->da_offset == offset)
                        break;
        if (dap == NULL) {

                LIST_FOREACH(dap, &pagedep->pd_pendinghd, da_pdlist)
                        if (dap->da_offset == offset)
                                break;
                if (dap == NULL)
                        return (dirrem);
        }
        /*
         * Must be ATTACHED at this point.
         */
        if ((dap->da_state & ATTACHED) == 0) {
                FREE_LOCK(&lk);
                panic("newdirrem: not ATTACHED");
        }
        if (dap->da_newinum != ip->i_number) {
                FREE_LOCK(&lk);
                panic("newdirrem: inum %d should be %d",
                    ip->i_number, dap->da_newinum);
        }
        /*
         * If we are deleting a changed name that never made it to disk,
         * then return the dirrem describing the previous inode (which
         * represents the inode currently referenced from this entry on disk).
         */
        if ((dap->da_state & DIRCHG) != 0) {
                *prevdirremp = dap->da_previous;
                dap->da_state &= ~DIRCHG;
                dap->da_pagedep = pagedep;
        }
        /*
         * We are deleting an entry that never made it to disk.
         * Mark it COMPLETE so we can delete its inode immediately.
         */
        dirrem->dm_state |= COMPLETE;
        free_diradd(dap);
        return (dirrem);
}

/*
 * Directory entry change dependencies.
 * 
 * Changing an existing directory entry requires that an add operation
 * be completed first followed by a deletion. The semantics for the addition
 * are identical to the description of adding a new entry above except
 * that the rollback is to the old inode number rather than zero. Once
 * the addition dependency is completed, the removal is done as described
 * in the removal routine above.
 */

/*
 * This routine should be called immediately after changing
 * a directory entry.  The inode's link count should not be
 * decremented by the calling procedure -- the soft updates
 * code will perform this task when it is safe.
 */
void 
softdep_setup_directory_change(bp, dp, ip, newinum, isrmdir)
        struct buf *bp;         /* buffer containing directory block */
        struct inode *dp;       /* inode for the directory being modified */
        struct inode *ip;       /* inode for directory entry being removed */
        ino_t newinum;          /* new inode number for changed entry */
        int isrmdir;            /* indicates if doing RMDIR */
{
        int offset;
        struct diradd *dap = NULL;
        struct dirrem *dirrem, *prevdirrem;
        struct pagedep *pagedep;
        struct inodedep *inodedep;

        offset = blkoff(dp->i_fs, dp->i_offset);

        /*
         * Whiteouts do not need diradd dependencies.
         */
        if (newinum != WINO) {
                MALLOC(dap, struct diradd *, sizeof(struct diradd),
                    M_DIRADD, M_SOFTDEP_FLAGS);
                bzero(dap, sizeof(struct diradd));
                dap->da_list.wk_type = D_DIRADD;
                dap->da_state = DIRCHG | ATTACHED | DEPCOMPLETE;
                dap->da_offset = offset;
                dap->da_newinum = newinum;
        }

        /*
         * Allocate a new dirrem and ACQUIRE_LOCK.
         */
        dirrem = newdirrem(bp, dp, ip, isrmdir, &prevdirrem);
        pagedep = dirrem->dm_pagedep;
        /*
         * The possible values for isrmdir:
         *      0 - non-directory file rename
         *      1 - directory rename within same directory
         *   inum - directory rename to new directory of given inode number
         * When renaming to a new directory, we are both deleting and
         * creating a new directory entry, so the link count on the new
         * directory should not change. Thus we do not need the followup
         * dirrem which is usually done in handle_workitem_remove. We set
         * the DIRCHG flag to tell handle_workitem_remove to skip the 
         * followup dirrem.
         */
        if (isrmdir > 1)
                dirrem->dm_state |= DIRCHG;

        /*
         * Whiteouts have no additional dependencies,
         * so just put the dirrem on the correct list.
         */
        if (newinum == WINO) {
                if ((dirrem->dm_state & COMPLETE) == 0) {
                        LIST_INSERT_HEAD(&pagedep->pd_dirremhd, dirrem,
                            dm_next);
                } else {
                        dirrem->dm_dirinum = pagedep->pd_ino;
                        add_to_worklist(&dirrem->dm_list);
                }
                FREE_LOCK(&lk);
                return;
        }

        /*
         * If the COMPLETE flag is clear, then there were no active
         * entries and we want to roll back to the previous inode until
         * the new inode is committed to disk. If the COMPLETE flag is
         * set, then we have deleted an entry that never made it to disk.
         * If the entry we deleted resulted from a name change, then the old
         * inode reference still resides on disk. Any rollback that we do
         * needs to be to that old inode (returned to us in prevdirrem). If
         * the entry we deleted resulted from a create, then there is
         * no entry on the disk, so we want to roll back to zero rather
         * than the uncommitted inode. In either of the COMPLETE cases we
         * want to immediately free the unwritten and unreferenced inode.
         */
        if ((dirrem->dm_state & COMPLETE) == 0) {
                dap->da_previous = dirrem;
        } else {
                if (prevdirrem != NULL) {
                        dap->da_previous = prevdirrem;
                } else {
                        dap->da_state &= ~DIRCHG;
                        dap->da_pagedep = pagedep;
                }
                dirrem->dm_dirinum = pagedep->pd_ino;
                add_to_worklist(&dirrem->dm_list);
        }
        /*
         * Link into its inodedep. Put it on the id_bufwait list if the inode
         * is not yet written. If it is written, do the post-inode write
         * processing to put it on the id_pendinghd list.
         */
        if (inodedep_lookup(dp->i_fs, newinum, DEPALLOC, &inodedep) == 0 ||
            (inodedep->id_state & ALLCOMPLETE) == ALLCOMPLETE) {
                dap->da_state |= COMPLETE;
                LIST_INSERT_HEAD(&pagedep->pd_pendinghd, dap, da_pdlist);
                WORKLIST_INSERT(&inodedep->id_pendinghd, &dap->da_list);
        } else {
                LIST_INSERT_HEAD(&pagedep->pd_diraddhd[DIRADDHASH(offset)],
                    dap, da_pdlist);
                WORKLIST_INSERT(&inodedep->id_bufwait, &dap->da_list);
        }
        FREE_LOCK(&lk);
}

/*
 * Called whenever the link count on an inode is changed.
 * It creates an inode dependency so that the new reference(s)
 * to the inode cannot be committed to disk until the updated
 * inode has been written.
 */
void
softdep_change_linkcnt(ip)
        struct inode *ip;       /* the inode with the increased link count */
{
        struct inodedep *inodedep;

        ACQUIRE_LOCK(&lk);
        (void) inodedep_lookup(ip->i_fs, ip->i_number, DEPALLOC, &inodedep);
        if (ip->i_nlink < ip->i_effnlink) {
                FREE_LOCK(&lk);
                panic("softdep_change_linkcnt: bad delta");
        }
        inodedep->id_nlinkdelta = ip->i_nlink - ip->i_effnlink;
        FREE_LOCK(&lk);
}

/*
 * This workitem decrements the inode's link count.
 * If the link count reaches zero, the file is removed.
 */
static void 
handle_workitem_remove(dirrem)
        struct dirrem *dirrem;
{
        struct thread *td = curthread;  /* XXX */
        struct inodedep *inodedep;
        struct vnode *vp;
        struct inode *ip;
        ino_t oldinum;
        int error;

        if ((error = VFS_VGET(dirrem->dm_mnt, dirrem->dm_oldinum, &vp)) != 0) {
                softdep_error("handle_workitem_remove: vget", error);
                return;
        }
        ip = VTOI(vp);
        ACQUIRE_LOCK(&lk);
        if ((inodedep_lookup(ip->i_fs, dirrem->dm_oldinum, 0, &inodedep)) == 0){
                FREE_LOCK(&lk);
                panic("handle_workitem_remove: lost inodedep");
        }
        /*
         * Normal file deletion.
         */
        if ((dirrem->dm_state & RMDIR) == 0) {
                ip->i_nlink--;
                ip->i_flag |= IN_CHANGE;
                if (ip->i_nlink < ip->i_effnlink) {
                        FREE_LOCK(&lk);
                        panic("handle_workitem_remove: bad file delta");
                }
                inodedep->id_nlinkdelta = ip->i_nlink - ip->i_effnlink;
                FREE_LOCK(&lk);
                vput(vp);
                num_dirrem -= 1;
                WORKITEM_FREE(dirrem, D_DIRREM);
                return;
        }
        /*
         * Directory deletion. Decrement reference count for both the
         * just deleted parent directory entry and the reference for ".".
         * Next truncate the directory to length zero. When the
         * truncation completes, arrange to have the reference count on
         * the parent decremented to account for the loss of "..".
         */
        ip->i_nlink -= 2;
        ip->i_flag |= IN_CHANGE;
        if (ip->i_nlink < ip->i_effnlink) {
                FREE_LOCK(&lk);
                panic("handle_workitem_remove: bad dir delta");
        }
        inodedep->id_nlinkdelta = ip->i_nlink - ip->i_effnlink;
        FREE_LOCK(&lk);
        if ((error = UFS_TRUNCATE(vp, (off_t)0, 0, proc0.p_ucred, td)) != 0)
                softdep_error("handle_workitem_remove: truncate", error);
        /*
         * Rename a directory to a new parent. Since, we are both deleting
         * and creating a new directory entry, the link count on the new
         * directory should not change. Thus we skip the followup dirrem.
         */
        if (dirrem->dm_state & DIRCHG) {
                vput(vp);
                num_dirrem -= 1;
                WORKITEM_FREE(dirrem, D_DIRREM);
                return;
        }
        /*
         * If the inodedep does not exist, then the zero'ed inode has
         * been written to disk. If the allocated inode has never been
         * written to disk, then the on-disk inode is zero'ed. In either
         * case we can remove the file immediately.
         */
        ACQUIRE_LOCK(&lk);
        dirrem->dm_state = 0;
        oldinum = dirrem->dm_oldinum;
        dirrem->dm_oldinum = dirrem->dm_dirinum;
        if (inodedep_lookup(ip->i_fs, oldinum, 0, &inodedep) == 0 ||
            check_inode_unwritten(inodedep)) {
                FREE_LOCK(&lk);
                vput(vp);
                handle_workitem_remove(dirrem);
                return;
        }
        WORKLIST_INSERT(&inodedep->id_inowait, &dirrem->dm_list);
        FREE_LOCK(&lk);
        vput(vp);
}

/*
 * Inode de-allocation dependencies.
 * 
 * When an inode's link count is reduced to zero, it can be de-allocated. We
 * found it convenient to postpone de-allocation until after the inode is
 * written to disk with its new link count (zero).  At this point, all of the
 * on-disk inode's block pointers are nullified and, with careful dependency
 * list ordering, all dependencies related to the inode will be satisfied and
 * the corresponding dependency structures de-allocated.  So, if/when the
 * inode is reused, there will be no mixing of old dependencies with new
 * ones.  This artificial dependency is set up by the block de-allocation
 * procedure above (softdep_setup_freeblocks) and completed by the
 * following procedure.
 */
static void 
handle_workitem_freefile(freefile)
        struct freefile *freefile;
{
        struct vnode vp;
        struct inode tip;
        struct inodedep *idp;
        int error;

#ifdef DEBUG
        ACQUIRE_LOCK(&lk);
        error = inodedep_lookup(freefile->fx_fs, freefile->fx_oldinum, 0, &idp);
        FREE_LOCK(&lk);
        if (error)
                panic("handle_workitem_freefile: inodedep survived");
#endif
        tip.i_devvp = freefile->fx_devvp;
        tip.i_dev = freefile->fx_devvp->v_rdev;
        tip.i_fs = freefile->fx_fs;
        vp.v_data = &tip;
        if ((error = ffs_freefile(&vp, freefile->fx_oldinum, freefile->fx_mode)) != 0)
                softdep_error("handle_workitem_freefile", error);
        WORKITEM_FREE(freefile, D_FREEFILE);
}

/*
 * Disk writes.
 * 
 * The dependency structures constructed above are most actively used when file
 * system blocks are written to disk.  No constraints are placed on when a
 * block can be written, but unsatisfied update dependencies are made safe by
 * modifying (or replacing) the source memory for the duration of the disk
 * write.  When the disk write completes, the memory block is again brought
 * up-to-date.
 *
 * In-core inode structure reclamation.
 * 
 * Because there are a finite number of "in-core" inode structures, they are
 * reused regularly.  By transferring all inode-related dependencies to the
 * in-memory inode block and indexing them separately (via "inodedep"s), we
 * can allow "in-core" inode structures to be reused at any time and avoid
 * any increase in contention.
 *
 * Called just before entering the device driver to initiate a new disk I/O.
 * The buffer must be locked, thus, no I/O completion operations can occur
 * while we are manipulating its associated dependencies.
 */
static void 
softdep_disk_io_initiation(bp)
        struct buf *bp;         /* structure describing disk write to occur */
{
        struct worklist *wk, *nextwk;
        struct indirdep *indirdep;

        /*
         * We only care about write operations. There should never
         * be dependencies for reads.
         */
        if (bp->b_flags & B_READ)
                panic("softdep_disk_io_initiation: read");
        /*
         * Do any necessary pre-I/O processing.
         */
        for (wk = LIST_FIRST(&bp->b_dep); wk; wk = nextwk) {
                nextwk = LIST_NEXT(wk, wk_list);
                switch (wk->wk_type) {

                case D_PAGEDEP:
                        initiate_write_filepage(WK_PAGEDEP(wk), bp);
                        continue;

                case D_INODEDEP:
                        initiate_write_inodeblock(WK_INODEDEP(wk), bp);
                        continue;

                case D_INDIRDEP:
                        indirdep = WK_INDIRDEP(wk);
                        if (indirdep->ir_state & GOINGAWAY)
                                panic("disk_io_initiation: indirdep gone");
                        /*
                         * If there are no remaining dependencies, this
                         * will be writing the real pointers, so the
                         * dependency can be freed.
                         */
                        if (LIST_FIRST(&indirdep->ir_deplisthd) == NULL) {
                                indirdep->ir_savebp->b_flags |= B_INVAL | B_NOCACHE;
                                brelse(indirdep->ir_savebp);
                                /* inline expand WORKLIST_REMOVE(wk); */
                                wk->wk_state &= ~ONWORKLIST;
                                LIST_REMOVE(wk, wk_list);
                                WORKITEM_FREE(indirdep, D_INDIRDEP);
                                continue;
                        }
                        /*
                         * Replace up-to-date version with safe version.
                         */
                        MALLOC(indirdep->ir_saveddata, caddr_t, bp->b_bcount,
                            M_INDIRDEP, M_SOFTDEP_FLAGS);
                        ACQUIRE_LOCK(&lk);
                        indirdep->ir_state &= ~ATTACHED;
                        indirdep->ir_state |= UNDONE;
                        bcopy(bp->b_data, indirdep->ir_saveddata, bp->b_bcount);
                        bcopy(indirdep->ir_savebp->b_data, bp->b_data,
                            bp->b_bcount);
                        FREE_LOCK(&lk);
                        continue;

                case D_MKDIR:
                case D_BMSAFEMAP:
                case D_ALLOCDIRECT:
                case D_ALLOCINDIR:
                        continue;

                default:
                        panic("handle_disk_io_initiation: Unexpected type %s",
                            TYPENAME(wk->wk_type));
                        /* NOTREACHED */
                }
        }
}

/*
 * Called from within the procedure above to deal with unsatisfied
 * allocation dependencies in a directory. The buffer must be locked,
 * thus, no I/O completion operations can occur while we are
 * manipulating its associated dependencies.
 */
static void
initiate_write_filepage(pagedep, bp)
        struct pagedep *pagedep;
        struct buf *bp;
{
        struct diradd *dap;
        struct direct *ep;
        int i;

        if (pagedep->pd_state & IOSTARTED) {
                /*
                 * This can only happen if there is a driver that does not
                 * understand chaining. Here biodone will reissue the call
                 * to strategy for the incomplete buffers.
                 */
                printf("initiate_write_filepage: already started\n");
                return;
        }
        pagedep->pd_state |= IOSTARTED;
        ACQUIRE_LOCK(&lk);
        for (i = 0; i < DAHASHSZ; i++) {
                LIST_FOREACH(dap, &pagedep->pd_diraddhd[i], da_pdlist) {
                        ep = (struct direct *)
                            ((char *)bp->b_data + dap->da_offset);
                        if (ep->d_ino != dap->da_newinum) {
                                FREE_LOCK(&lk);
                                panic("%s: dir inum %d != new %d",
                                    "initiate_write_filepage",
                                    ep->d_ino, dap->da_newinum);
                        }
                        if (dap->da_state & DIRCHG)
                                ep->d_ino = dap->da_previous->dm_oldinum;
                        else
                                ep->d_ino = 0;
                        dap->da_state &= ~ATTACHED;
                        dap->da_state |= UNDONE;
                }
        }
        FREE_LOCK(&lk);
}

/*
 * Called from within the procedure above to deal with unsatisfied
 * allocation dependencies in an inodeblock. The buffer must be
 * locked, thus, no I/O completion operations can occur while we
 * are manipulating its associated dependencies.
 */
static void 
initiate_write_inodeblock(inodedep, bp)
        struct inodedep *inodedep;
        struct buf *bp;                 /* The inode block */
{
        struct allocdirect *adp, *lastadp;
        struct dinode *dp;
        struct fs *fs;
        ufs_lbn_t prevlbn = 0;
        int i, deplist;

        if (inodedep->id_state & IOSTARTED)
                panic("initiate_write_inodeblock: already started");
        inodedep->id_state |= IOSTARTED;
        fs = inodedep->id_fs;
        dp = (struct dinode *)bp->b_data +
            ino_to_fsbo(fs, inodedep->id_ino);
        /*
         * If the bitmap is not yet written, then the allocated
         * inode cannot be written to disk.
         */
        if ((inodedep->id_state & DEPCOMPLETE) == 0) {
                if (inodedep->id_savedino != NULL)
                        panic("initiate_write_inodeblock: already doing I/O");
                MALLOC(inodedep->id_savedino, struct dinode *,
                    sizeof(struct dinode), M_INODEDEP, M_SOFTDEP_FLAGS);
                *inodedep->id_savedino = *dp;
                bzero((caddr_t)dp, sizeof(struct dinode));
                return;
        }
        /*
         * If no dependencies, then there is nothing to roll back.
         */
        inodedep->id_savedsize = dp->di_size;
        if (TAILQ_FIRST(&inodedep->id_inoupdt) == NULL)
                return;
        /*
         * Set the dependencies to busy.
         */
        ACQUIRE_LOCK(&lk);
        for (deplist = 0, adp = TAILQ_FIRST(&inodedep->id_inoupdt); adp;
             adp = TAILQ_NEXT(adp, ad_next)) {
#ifdef DIAGNOSTIC
                if (deplist != 0 && prevlbn >= adp->ad_lbn) {
                        FREE_LOCK(&lk);
                        panic("softdep_write_inodeblock: lbn order");
                }
                prevlbn = adp->ad_lbn;
                if (adp->ad_lbn < NDADDR &&
                    dp->di_db[adp->ad_lbn] != adp->ad_newblkno) {
                        FREE_LOCK(&lk);
                        panic("%s: direct pointer #%ld mismatch %d != %d",
                            "softdep_write_inodeblock", adp->ad_lbn,
                            dp->di_db[adp->ad_lbn], adp->ad_newblkno);
                }
                if (adp->ad_lbn >= NDADDR &&
                    dp->di_ib[adp->ad_lbn - NDADDR] != adp->ad_newblkno) {
                        FREE_LOCK(&lk);
                        panic("%s: indirect pointer #%ld mismatch %d != %d",
                            "softdep_write_inodeblock", adp->ad_lbn - NDADDR,
                            dp->di_ib[adp->ad_lbn - NDADDR], adp->ad_newblkno);
                }
                deplist |= 1 << adp->ad_lbn;
                if ((adp->ad_state & ATTACHED) == 0) {
                        FREE_LOCK(&lk);
                        panic("softdep_write_inodeblock: Unknown state 0x%x",
                            adp->ad_state);
                }
#endif /* DIAGNOSTIC */
                adp->ad_state &= ~ATTACHED;
                adp->ad_state |= UNDONE;
        }
        /*
         * The on-disk inode cannot claim to be any larger than the last
         * fragment that has been written. Otherwise, the on-disk inode
         * might have fragments that were not the last block in the file
         * which would corrupt the filesystem.
         */
        for (lastadp = NULL, adp = TAILQ_FIRST(&inodedep->id_inoupdt); adp;
             lastadp = adp, adp = TAILQ_NEXT(adp, ad_next)) {
                if (adp->ad_lbn >= NDADDR)
                        break;
                dp->di_db[adp->ad_lbn] = adp->ad_oldblkno;
                /* keep going until hitting a rollback to a frag */
                if (adp->ad_oldsize == 0 || adp->ad_oldsize == fs->fs_bsize)
                        continue;
                dp->di_size = fs->fs_bsize * adp->ad_lbn + adp->ad_oldsize;
                for (i = adp->ad_lbn + 1; i < NDADDR; i++) {
#ifdef DIAGNOSTIC
                        if (dp->di_db[i] != 0 && (deplist & (1 << i)) == 0) {
                                FREE_LOCK(&lk);
                                panic("softdep_write_inodeblock: lost dep1");
                        }
#endif /* DIAGNOSTIC */
                        dp->di_db[i] = 0;
                }
                for (i = 0; i < NIADDR; i++) {
#ifdef DIAGNOSTIC
                        if (dp->di_ib[i] != 0 &&
                            (deplist & ((1 << NDADDR) << i)) == 0) {
                                FREE_LOCK(&lk);
                                panic("softdep_write_inodeblock: lost dep2");
                        }
#endif /* DIAGNOSTIC */
                        dp->di_ib[i] = 0;
                }
                FREE_LOCK(&lk);
                return;
        }
        /*
         * If we have zero'ed out the last allocated block of the file,
         * roll back the size to the last currently allocated block.
         * We know that this last allocated block is a full-sized as
         * we already checked for fragments in the loop above.
         */
        if (lastadp != NULL &&
            dp->di_size <= (lastadp->ad_lbn + 1) * fs->fs_bsize) {
                for (i = lastadp->ad_lbn; i >= 0; i--)
                        if (dp->di_db[i] != 0)
                                break;
                dp->di_size = (i + 1) * fs->fs_bsize;
        }
        /*
         * The only dependencies are for indirect blocks.
         *
         * The file size for indirect block additions is not guaranteed.
         * Such a guarantee would be non-trivial to achieve. The conventional
         * synchronous write implementation also does not make this guarantee.
         * Fsck should catch and fix discrepancies. Arguably, the file size
         * can be over-estimated without destroying integrity when the file
         * moves into the indirect blocks (i.e., is large). If we want to
         * postpone fsck, we are stuck with this argument.
         */
        for (; adp; adp = TAILQ_NEXT(adp, ad_next))
                dp->di_ib[adp->ad_lbn - NDADDR] = 0;
        FREE_LOCK(&lk);
}

/*
 * This routine is called during the completion interrupt
 * service routine for a disk write (from the procedure called
 * by the device driver to inform the filesystem caches of
 * a request completion).  It should be called early in this
 * procedure, before the block is made available to other
 * processes or other routines are called.
 */
static void 
softdep_disk_write_complete(bp)
        struct buf *bp;         /* describes the completed disk write */
{
        struct worklist *wk;
        struct workhead reattach;
        struct newblk *newblk;
        struct allocindir *aip;
        struct allocdirect *adp;
        struct indirdep *indirdep;
        struct inodedep *inodedep;
        struct bmsafemap *bmsafemap;

#ifdef DEBUG
        if (lk.lkt_held != NOHOLDER)
                panic("softdep_disk_write_complete: lock is held");
        lk.lkt_held = SPECIAL_FLAG;
#endif
        LIST_INIT(&reattach);
        while ((wk = LIST_FIRST(&bp->b_dep)) != NULL) {
                WORKLIST_REMOVE(wk);
                switch (wk->wk_type) {

                case D_PAGEDEP:
                        if (handle_written_filepage(WK_PAGEDEP(wk), bp))
                                WORKLIST_INSERT(&reattach, wk);
                        continue;

                case D_INODEDEP:
                        if (handle_written_inodeblock(WK_INODEDEP(wk), bp))
                                WORKLIST_INSERT(&reattach, wk);
                        continue;

                case D_BMSAFEMAP:
                        bmsafemap = WK_BMSAFEMAP(wk);
                        while ((newblk = LIST_FIRST(&bmsafemap->sm_newblkhd))) {
                                newblk->nb_state |= DEPCOMPLETE;
                                newblk->nb_bmsafemap = NULL;
                                LIST_REMOVE(newblk, nb_deps);
                        }
                        while ((adp =
                           LIST_FIRST(&bmsafemap->sm_allocdirecthd))) {
                                adp->ad_state |= DEPCOMPLETE;
                                adp->ad_buf = NULL;
                                LIST_REMOVE(adp, ad_deps);
                                handle_allocdirect_partdone(adp);
                        }
                        while ((aip =
                            LIST_FIRST(&bmsafemap->sm_allocindirhd))) {
                                aip->ai_state |= DEPCOMPLETE;
                                aip->ai_buf = NULL;
                                LIST_REMOVE(aip, ai_deps);
                                handle_allocindir_partdone(aip);
                        }
                        while ((inodedep =
                             LIST_FIRST(&bmsafemap->sm_inodedephd)) != NULL) {
                                inodedep->id_state |= DEPCOMPLETE;
                                LIST_REMOVE(inodedep, id_deps);
                                inodedep->id_buf = NULL;
                        }
                        WORKITEM_FREE(bmsafemap, D_BMSAFEMAP);
                        continue;

                case D_MKDIR:
                        handle_written_mkdir(WK_MKDIR(wk), MKDIR_BODY);
                        continue;

                case D_ALLOCDIRECT:
                        adp = WK_ALLOCDIRECT(wk);
                        adp->ad_state |= COMPLETE;
                        handle_allocdirect_partdone(adp);
                        continue;

                case D_ALLOCINDIR:
                        aip = WK_ALLOCINDIR(wk);
                        aip->ai_state |= COMPLETE;
                        handle_allocindir_partdone(aip);
                        continue;

                case D_INDIRDEP:
                        indirdep = WK_INDIRDEP(wk);
                        if (indirdep->ir_state & GOINGAWAY) {
                                lk.lkt_held = NOHOLDER;
                                panic("disk_write_complete: indirdep gone");
                        }
                        bcopy(indirdep->ir_saveddata, bp->b_data, bp->b_bcount);
                        FREE(indirdep->ir_saveddata, M_INDIRDEP);
                        indirdep->ir_saveddata = 0;
                        indirdep->ir_state &= ~UNDONE;
                        indirdep->ir_state |= ATTACHED;
                        while ((aip = LIST_FIRST(&indirdep->ir_donehd)) != 0) {
                                handle_allocindir_partdone(aip);
                                if (aip == LIST_FIRST(&indirdep->ir_donehd)) {
                                        lk.lkt_held = NOHOLDER;
                                        panic("disk_write_complete: not gone");
                                }
                        }
                        WORKLIST_INSERT(&reattach, wk);
                        if ((bp->b_flags & B_DELWRI) == 0)
                                stat_indir_blk_ptrs++;
                        bdirty(bp);
                        continue;

                default:
                        lk.lkt_held = NOHOLDER;
                        panic("handle_disk_write_complete: Unknown type %s",
                            TYPENAME(wk->wk_type));
                        /* NOTREACHED */
                }
        }
        /*
         * Reattach any requests that must be redone.
         */
        while ((wk = LIST_FIRST(&reattach)) != NULL) {
                WORKLIST_REMOVE(wk);
                WORKLIST_INSERT(&bp->b_dep, wk);
        }
#ifdef DEBUG
        if (lk.lkt_held != SPECIAL_FLAG)
                panic("softdep_disk_write_complete: lock lost");
        lk.lkt_held = NOHOLDER;
#endif
}

/*
 * Called from within softdep_disk_write_complete above. Note that
 * this routine is always called from interrupt level with further
 * splbio interrupts blocked.
 */
static void 
handle_allocdirect_partdone(adp)
        struct allocdirect *adp;        /* the completed allocdirect */
{
        struct allocdirect *listadp;
        struct inodedep *inodedep;
        long bsize;

        if ((adp->ad_state & ALLCOMPLETE) != ALLCOMPLETE)
                return;
        if (adp->ad_buf != NULL) {
                lk.lkt_held = NOHOLDER;
                panic("handle_allocdirect_partdone: dangling dep");
        }
        /*
         * The on-disk inode cannot claim to be any larger than the last
         * fragment that has been written. Otherwise, the on-disk inode
         * might have fragments that were not the last block in the file
         * which would corrupt the filesystem. Thus, we cannot free any
         * allocdirects after one whose ad_oldblkno claims a fragment as
         * these blocks must be rolled back to zero before writing the inode.
         * We check the currently active set of allocdirects in id_inoupdt.
         */
        inodedep = adp->ad_inodedep;
        bsize = inodedep->id_fs->fs_bsize;
        TAILQ_FOREACH(listadp, &inodedep->id_inoupdt, ad_next) {
                /* found our block */
                if (listadp == adp)
                        break;
                /* continue if ad_oldlbn is not a fragment */
                if (listadp->ad_oldsize == 0 ||
                    listadp->ad_oldsize == bsize)
                        continue;
                /* hit a fragment */
                return;
        }
        /*
         * If we have reached the end of the current list without
         * finding the just finished dependency, then it must be
         * on the future dependency list. Future dependencies cannot
         * be freed until they are moved to the current list.
         */
        if (listadp == NULL) {
#ifdef DEBUG
                TAILQ_FOREACH(listadp, &inodedep->id_newinoupdt, ad_next)
                        /* found our block */
                        if (listadp == adp)
                                break;
                if (listadp == NULL) {
                        lk.lkt_held = NOHOLDER;
                        panic("handle_allocdirect_partdone: lost dep");
                }
#endif /* DEBUG */
                return;
        }
        /*
         * If we have found the just finished dependency, then free
         * it along with anything that follows it that is complete.
         */
        for (; adp; adp = listadp) {
                listadp = TAILQ_NEXT(adp, ad_next);
                if ((adp->ad_state & ALLCOMPLETE) != ALLCOMPLETE)
                        return;
                free_allocdirect(&inodedep->id_inoupdt, adp, 1);
        }
}

/*
 * Called from within softdep_disk_write_complete above. Note that
 * this routine is always called from interrupt level with further
 * splbio interrupts blocked.
 */
static void
handle_allocindir_partdone(aip)
        struct allocindir *aip;         /* the completed allocindir */
{
        struct indirdep *indirdep;

        if ((aip->ai_state & ALLCOMPLETE) != ALLCOMPLETE)
                return;
        if (aip->ai_buf != NULL) {
                lk.lkt_held = NOHOLDER;
                panic("handle_allocindir_partdone: dangling dependency");
        }
        indirdep = aip->ai_indirdep;
        if (indirdep->ir_state & UNDONE) {
                LIST_REMOVE(aip, ai_next);
                LIST_INSERT_HEAD(&indirdep->ir_donehd, aip, ai_next);
                return;
        }
        ((ufs_daddr_t *)indirdep->ir_savebp->b_data)[aip->ai_offset] =
            aip->ai_newblkno;
        LIST_REMOVE(aip, ai_next);
        if (aip->ai_freefrag != NULL)
                add_to_worklist(&aip->ai_freefrag->ff_list);
        WORKITEM_FREE(aip, D_ALLOCINDIR);
}

/*
 * Called from within softdep_disk_write_complete above to restore
 * in-memory inode block contents to their most up-to-date state. Note
 * that this routine is always called from interrupt level with further
 * splbio interrupts blocked.
 */
static int 
handle_written_inodeblock(inodedep, bp)
        struct inodedep *inodedep;
        struct buf *bp;         /* buffer containing the inode block */
{
        struct worklist *wk, *filefree;
        struct allocdirect *adp, *nextadp;
        struct dinode *dp;
        int hadchanges;

        if ((inodedep->id_state & IOSTARTED) == 0) {
                lk.lkt_held = NOHOLDER;
                panic("handle_written_inodeblock: not started");
        }
        inodedep->id_state &= ~IOSTARTED;
        inodedep->id_state |= COMPLETE;
        dp = (struct dinode *)bp->b_data +
            ino_to_fsbo(inodedep->id_fs, inodedep->id_ino);
        /*
         * If we had to rollback the inode allocation because of
         * bitmaps being incomplete, then simply restore it.
         * Keep the block dirty so that it will not be reclaimed until
         * all associated dependencies have been cleared and the
         * corresponding updates written to disk.
         */
        if (inodedep->id_savedino != NULL) {
                *dp = *inodedep->id_savedino;
                FREE(inodedep->id_savedino, M_INODEDEP);
                inodedep->id_savedino = NULL;
                if ((bp->b_flags & B_DELWRI) == 0)
                        stat_inode_bitmap++;
                bdirty(bp);
                return (1);
        }
        /*
         * Roll forward anything that had to be rolled back before 
         * the inode could be updated.
         */
        hadchanges = 0;
        for (adp = TAILQ_FIRST(&inodedep->id_inoupdt); adp; adp = nextadp) {
                nextadp = TAILQ_NEXT(adp, ad_next);
                if (adp->ad_state & ATTACHED) {
                        lk.lkt_held = NOHOLDER;
                        panic("handle_written_inodeblock: new entry");
                }
                if (adp->ad_lbn < NDADDR) {
                        if (dp->di_db[adp->ad_lbn] != adp->ad_oldblkno) {
                                lk.lkt_held = NOHOLDER;
                                panic("%s: %s #%ld mismatch %d != %d",
                                    "handle_written_inodeblock",
                                    "direct pointer", adp->ad_lbn,
                                    dp->di_db[adp->ad_lbn], adp->ad_oldblkno);
                        }
                        dp->di_db[adp->ad_lbn] = adp->ad_newblkno;
                } else {
                        if (dp->di_ib[adp->ad_lbn - NDADDR] != 0) {
                                lk.lkt_held = NOHOLDER;
                                panic("%s: %s #%ld allocated as %d",
                                    "handle_written_inodeblock",
                                    "indirect pointer", adp->ad_lbn - NDADDR,
                                    dp->di_ib[adp->ad_lbn - NDADDR]);
                        }
                        dp->di_ib[adp->ad_lbn - NDADDR] = adp->ad_newblkno;
                }
                adp->ad_state &= ~UNDONE;
                adp->ad_state |= ATTACHED;
                hadchanges = 1;
        }
        if (hadchanges && (bp->b_flags & B_DELWRI) == 0)
                stat_direct_blk_ptrs++;
        /*
         * Reset the file size to its most up-to-date value.
         */
        if (inodedep->id_savedsize == -1) {
                lk.lkt_held = NOHOLDER;
                panic("handle_written_inodeblock: bad size");
        }
        if (dp->di_size != inodedep->id_savedsize) {
                dp->di_size = inodedep->id_savedsize;
                hadchanges = 1;
        }
        inodedep->id_savedsize = -1;
        /*
         * If there were any rollbacks in the inode block, then it must be
         * marked dirty so that its will eventually get written back in
         * its correct form.
         */
        if (hadchanges)
                bdirty(bp);
        /*
         * Process any allocdirects that completed during the update.
         */
        if ((adp = TAILQ_FIRST(&inodedep->id_inoupdt)) != NULL)
                handle_allocdirect_partdone(adp);
        /*
         * Process deallocations that were held pending until the
         * inode had been written to disk. Freeing of the inode
         * is delayed until after all blocks have been freed to
         * avoid creation of new <vfsid, inum, lbn> triples
         * before the old ones have been deleted.
         */
        filefree = NULL;
        while ((wk = LIST_FIRST(&inodedep->id_bufwait)) != NULL) {
                WORKLIST_REMOVE(wk);
                switch (wk->wk_type) {

                case D_FREEFILE:
                        /*
                         * We defer adding filefree to the worklist until
                         * all other additions have been made to ensure
                         * that it will be done after all the old blocks
                         * have been freed.
                         */
                        if (filefree != NULL) {
                                lk.lkt_held = NOHOLDER;
                                panic("handle_written_inodeblock: filefree");
                        }
                        filefree = wk;
                        continue;

                case D_MKDIR:
                        handle_written_mkdir(WK_MKDIR(wk), MKDIR_PARENT);
                        continue;

                case D_DIRADD:
                        diradd_inode_written(WK_DIRADD(wk), inodedep);
                        continue;

                case D_FREEBLKS:
                        wk->wk_state |= COMPLETE;
                        if ((wk->wk_state  & ALLCOMPLETE) != ALLCOMPLETE)
                                continue;
                        /* -- fall through -- */
                case D_FREEFRAG:
                case D_DIRREM:
                        add_to_worklist(wk);
                        continue;

                default:
                        lk.lkt_held = NOHOLDER;
                        panic("handle_written_inodeblock: Unknown type %s",
                            TYPENAME(wk->wk_type));
                        /* NOTREACHED */
                }
        }
        if (filefree != NULL) {
                if (free_inodedep(inodedep) == 0) {
                        lk.lkt_held = NOHOLDER;
                        panic("handle_written_inodeblock: live inodedep");
                }
                add_to_worklist(filefree);
                return (0);
        }

        /*
         * If no outstanding dependencies, free it.
         */
        if (free_inodedep(inodedep) || TAILQ_FIRST(&inodedep->id_inoupdt) == 0)
                return (0);
        return (hadchanges);
}

/*
 * Process a diradd entry after its dependent inode has been written.
 * This routine must be called with splbio interrupts blocked.
 */
static void
diradd_inode_written(dap, inodedep)
        struct diradd *dap;
        struct inodedep *inodedep;
{
        struct pagedep *pagedep;

        dap->da_state |= COMPLETE;
        if ((dap->da_state & ALLCOMPLETE) == ALLCOMPLETE) {
                if (dap->da_state & DIRCHG)
                        pagedep = dap->da_previous->dm_pagedep;
                else
                        pagedep = dap->da_pagedep;
                LIST_REMOVE(dap, da_pdlist);
                LIST_INSERT_HEAD(&pagedep->pd_pendinghd, dap, da_pdlist);
        }
        WORKLIST_INSERT(&inodedep->id_pendinghd, &dap->da_list);
}

/*
 * Handle the completion of a mkdir dependency.
 */
static void
handle_written_mkdir(mkdir, type)
        struct mkdir *mkdir;
        int type;
{
        struct diradd *dap;
        struct pagedep *pagedep;

        if (mkdir->md_state != type) {
                lk.lkt_held = NOHOLDER;
                panic("handle_written_mkdir: bad type");
        }
        dap = mkdir->md_diradd;
        dap->da_state &= ~type;
        if ((dap->da_state & (MKDIR_PARENT | MKDIR_BODY)) == 0)
                dap->da_state |= DEPCOMPLETE;
        if ((dap->da_state & ALLCOMPLETE) == ALLCOMPLETE) {
                if (dap->da_state & DIRCHG)
                        pagedep = dap->da_previous->dm_pagedep;
                else
                        pagedep = dap->da_pagedep;
                LIST_REMOVE(dap, da_pdlist);
                LIST_INSERT_HEAD(&pagedep->pd_pendinghd, dap, da_pdlist);
        }
        LIST_REMOVE(mkdir, md_mkdirs);
        WORKITEM_FREE(mkdir, D_MKDIR);
}

/*
 * Called from within softdep_disk_write_complete above.
 * A write operation was just completed. Removed inodes can
 * now be freed and associated block pointers may be committed.
 * Note that this routine is always called from interrupt level
 * with further splbio interrupts blocked.
 */
static int 
handle_written_filepage(pagedep, bp)
        struct pagedep *pagedep;
        struct buf *bp;         /* buffer containing the written page */
{
        struct dirrem *dirrem;
        struct diradd *dap, *nextdap;
        struct direct *ep;
        int i, chgs;

        if ((pagedep->pd_state & IOSTARTED) == 0) {
                lk.lkt_held = NOHOLDER;
                panic("handle_written_filepage: not started");
        }
        pagedep->pd_state &= ~IOSTARTED;
        /*
         * Process any directory removals that have been committed.
         */
        while ((dirrem = LIST_FIRST(&pagedep->pd_dirremhd)) != NULL) {
                LIST_REMOVE(dirrem, dm_next);
                dirrem->dm_dirinum = pagedep->pd_ino;
                add_to_worklist(&dirrem->dm_list);
        }
        /*
         * Free any directory additions that have been committed.
         */
        while ((dap = LIST_FIRST(&pagedep->pd_pendinghd)) != NULL)
                free_diradd(dap);
        /*
         * Uncommitted directory entries must be restored.
         */
        for (chgs = 0, i = 0; i < DAHASHSZ; i++) {
                for (dap = LIST_FIRST(&pagedep->pd_diraddhd[i]); dap;
                     dap = nextdap) {
                        nextdap = LIST_NEXT(dap, da_pdlist);
                        if (dap->da_state & ATTACHED) {
                                lk.lkt_held = NOHOLDER;
                                panic("handle_written_filepage: attached");
                        }
                        ep = (struct direct *)
                            ((char *)bp->b_data + dap->da_offset);
                        ep->d_ino = dap->da_newinum;
                        dap->da_state &= ~UNDONE;
                        dap->da_state |= ATTACHED;
                        chgs = 1;
                        /*
                         * If the inode referenced by the directory has
                         * been written out, then the dependency can be
                         * moved to the pending list.
                         */
                        if ((dap->da_state & ALLCOMPLETE) == ALLCOMPLETE) {
                                LIST_REMOVE(dap, da_pdlist);
                                LIST_INSERT_HEAD(&pagedep->pd_pendinghd, dap,
                                    da_pdlist);
                        }
                }
        }
        /*
         * If there were any rollbacks in the directory, then it must be
         * marked dirty so that its will eventually get written back in
         * its correct form.
         */
        if (chgs) {
                if ((bp->b_flags & B_DELWRI) == 0)
                        stat_dir_entry++;
                bdirty(bp);
        }
        /*
         * If no dependencies remain, the pagedep will be freed.
         * Otherwise it will remain to update the page before it
         * is written back to disk.
         */
        if (LIST_FIRST(&pagedep->pd_pendinghd) == 0) {
                for (i = 0; i < DAHASHSZ; i++)
                        if (LIST_FIRST(&pagedep->pd_diraddhd[i]) != NULL)
                                break;
                if (i == DAHASHSZ) {
                        LIST_REMOVE(pagedep, pd_hash);
                        WORKITEM_FREE(pagedep, D_PAGEDEP);
                        return (0);
                }
        }
        return (1);
}

/*
 * Writing back in-core inode structures.
 * 
 * The filesystem only accesses an inode's contents when it occupies an
 * "in-core" inode structure.  These "in-core" structures are separate from
 * the page frames used to cache inode blocks.  Only the latter are
 * transferred to/from the disk.  So, when the updated contents of the
 * "in-core" inode structure are copied to the corresponding in-memory inode
 * block, the dependencies are also transferred.  The following procedure is
 * called when copying a dirty "in-core" inode to a cached inode block.
 */

/*
 * Called when an inode is loaded from disk. If the effective link count
 * differed from the actual link count when it was last flushed, then we
 * need to ensure that the correct effective link count is put back.
 */
void 
softdep_load_inodeblock(ip)
        struct inode *ip;       /* the "in_core" copy of the inode */
{
        struct inodedep *inodedep;

        /*
         * Check for alternate nlink count.
         */
        ip->i_effnlink = ip->i_nlink;
        ACQUIRE_LOCK(&lk);
        if (inodedep_lookup(ip->i_fs, ip->i_number, 0, &inodedep) == 0) {
                FREE_LOCK(&lk);
                return;
        }
        ip->i_effnlink -= inodedep->id_nlinkdelta;
        FREE_LOCK(&lk);
}

/*
 * This routine is called just before the "in-core" inode
 * information is to be copied to the in-memory inode block.
 * Recall that an inode block contains several inodes. If
 * the force flag is set, then the dependencies will be
 * cleared so that the update can always be made. Note that
 * the buffer is locked when this routine is called, so we
 * will never be in the middle of writing the inode block 
 * to disk.
 */
void 
softdep_update_inodeblock(ip, bp, waitfor)
        struct inode *ip;       /* the "in_core" copy of the inode */
        struct buf *bp;         /* the buffer containing the inode block */
        int waitfor;            /* nonzero => update must be allowed */
{
        struct inodedep *inodedep;
        struct worklist *wk;
        int error, gotit;

        /*
         * If the effective link count is not equal to the actual link
         * count, then we must track the difference in an inodedep while
         * the inode is (potentially) tossed out of the cache. Otherwise,
         * if there is no existing inodedep, then there are no dependencies
         * to track.
         */
        ACQUIRE_LOCK(&lk);
        if (inodedep_lookup(ip->i_fs, ip->i_number, 0, &inodedep) == 0) {
                FREE_LOCK(&lk);
                if (ip->i_effnlink != ip->i_nlink)
                        panic("softdep_update_inodeblock: bad link count");
                return;
        }
        if (inodedep->id_nlinkdelta != ip->i_nlink - ip->i_effnlink) {
                FREE_LOCK(&lk);
                panic("softdep_update_inodeblock: bad delta");
        }
        /*
         * Changes have been initiated. Anything depending on these
         * changes cannot occur until this inode has been written.
         */
        inodedep->id_state &= ~COMPLETE;
        if ((inodedep->id_state & ONWORKLIST) == 0)
                WORKLIST_INSERT(&bp->b_dep, &inodedep->id_list);
        /*
         * Any new dependencies associated with the incore inode must 
         * now be moved to the list associated with the buffer holding
         * the in-memory copy of the inode. Once merged process any
         * allocdirects that are completed by the merger.
         */
        merge_inode_lists(inodedep);
        if (TAILQ_FIRST(&inodedep->id_inoupdt) != NULL)
                handle_allocdirect_partdone(TAILQ_FIRST(&inodedep->id_inoupdt));
        /*
         * Now that the inode has been pushed into the buffer, the
         * operations dependent on the inode being written to disk
         * can be moved to the id_bufwait so that they will be
         * processed when the buffer I/O completes.
         */
        while ((wk = LIST_FIRST(&inodedep->id_inowait)) != NULL) {
                WORKLIST_REMOVE(wk);
                WORKLIST_INSERT(&inodedep->id_bufwait, wk);
        }
        /*
         * Newly allocated inodes cannot be written until the bitmap
         * that allocates them have been written (indicated by
         * DEPCOMPLETE being set in id_state). If we are doing a
         * forced sync (e.g., an fsync on a file), we force the bitmap
         * to be written so that the update can be done.
         */
        if ((inodedep->id_state & DEPCOMPLETE) != 0 || waitfor == 0) {
                FREE_LOCK(&lk);
                return;
        }
        gotit = getdirtybuf(&inodedep->id_buf, MNT_WAIT);
        FREE_LOCK(&lk);
        if (gotit &&
            (error = VOP_BWRITE(inodedep->id_buf->b_vp, inodedep->id_buf)) != 0)
                softdep_error("softdep_update_inodeblock: bwrite", error);
        if ((inodedep->id_state & DEPCOMPLETE) == 0)
                panic("softdep_update_inodeblock: update failed");
}

/*
 * Merge the new inode dependency list (id_newinoupdt) into the old
 * inode dependency list (id_inoupdt). This routine must be called
 * with splbio interrupts blocked.
 */
static void
merge_inode_lists(inodedep)
        struct inodedep *inodedep;
{
        struct allocdirect *listadp, *newadp;

        newadp = TAILQ_FIRST(&inodedep->id_newinoupdt);
        for (listadp = TAILQ_FIRST(&inodedep->id_inoupdt); listadp && newadp;) {
                if (listadp->ad_lbn < newadp->ad_lbn) {
                        listadp = TAILQ_NEXT(listadp, ad_next);
                        continue;
                }
                TAILQ_REMOVE(&inodedep->id_newinoupdt, newadp, ad_next);
                TAILQ_INSERT_BEFORE(listadp, newadp, ad_next);
                if (listadp->ad_lbn == newadp->ad_lbn) {
                        allocdirect_merge(&inodedep->id_inoupdt, newadp,
                            listadp);
                        listadp = newadp;
                }
                newadp = TAILQ_FIRST(&inodedep->id_newinoupdt);
        }
        while ((newadp = TAILQ_FIRST(&inodedep->id_newinoupdt)) != NULL) {
                TAILQ_REMOVE(&inodedep->id_newinoupdt, newadp, ad_next);
                TAILQ_INSERT_TAIL(&inodedep->id_inoupdt, newadp, ad_next);
        }
}

/*
 * If we are doing an fsync, then we must ensure that any directory
 * entries for the inode have been written after the inode gets to disk.
 */
static int
softdep_fsync(vp)
        struct vnode *vp;       /* the "in_core" copy of the inode */
{
        struct inodedep *inodedep;
        struct pagedep *pagedep;
        struct worklist *wk;
        struct diradd *dap;
        struct mount *mnt;
        struct vnode *pvp;
        struct inode *ip;
        struct buf *bp;
        struct fs *fs;
        struct thread *td = curthread;          /* XXX */
        int error, flushparent;
        ino_t parentino;
        ufs_lbn_t lbn;

        ip = VTOI(vp);
        fs = ip->i_fs;
        ACQUIRE_LOCK(&lk);
        if (inodedep_lookup(fs, ip->i_number, 0, &inodedep) == 0) {
                FREE_LOCK(&lk);
                return (0);
        }
        if (LIST_FIRST(&inodedep->id_inowait) != NULL ||
            LIST_FIRST(&inodedep->id_bufwait) != NULL ||
            TAILQ_FIRST(&inodedep->id_inoupdt) != NULL ||
            TAILQ_FIRST(&inodedep->id_newinoupdt) != NULL) {
                FREE_LOCK(&lk);
                panic("softdep_fsync: pending ops");
        }
        for (error = 0, flushparent = 0; ; ) {
                if ((wk = LIST_FIRST(&inodedep->id_pendinghd)) == NULL)
                        break;
                if (wk->wk_type != D_DIRADD) {
                        FREE_LOCK(&lk);
                        panic("softdep_fsync: Unexpected type %s",
                            TYPENAME(wk->wk_type));
                }
                dap = WK_DIRADD(wk);
                /*
                 * Flush our parent if this directory entry
                 * has a MKDIR_PARENT dependency.
                 */
                if (dap->da_state & DIRCHG)
                        pagedep = dap->da_previous->dm_pagedep;
                else
                        pagedep = dap->da_pagedep;
                mnt = pagedep->pd_mnt;
                parentino = pagedep->pd_ino;
                lbn = pagedep->pd_lbn;
                if ((dap->da_state & (MKDIR_BODY | COMPLETE)) != COMPLETE) {
                        FREE_LOCK(&lk);
                        panic("softdep_fsync: dirty");
                }
                flushparent = dap->da_state & MKDIR_PARENT;
                /*
                 * If we are being fsync'ed as part of vgone'ing this vnode,
                 * then we will not be able to release and recover the
                 * vnode below, so we just have to give up on writing its
                 * directory entry out. It will eventually be written, just
                 * not now, but then the user was not asking to have it
                 * written, so we are not breaking any promises.
                 */
                if (vp->v_flag & VRECLAIMED)
                        break;
                /*
                 * We prevent deadlock by always fetching inodes from the
                 * root, moving down the directory tree. Thus, when fetching
                 * our parent directory, we must unlock ourselves before
                 * requesting the lock on our parent. See the comment in
                 * ufs_lookup for details on possible races.
                 */
                FREE_LOCK(&lk);
                VOP_UNLOCK(vp, 0, td);
                error = VFS_VGET(mnt, parentino, &pvp);
                vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
                if (error != 0)
                        return (error);
                if (flushparent) {
                        if ((error = UFS_UPDATE(pvp, 1)) != 0) {
                                vput(pvp);
                                return (error);
                        }
                }
                /*
                 * Flush directory page containing the inode's name.
                 */
                error = bread(pvp, lbn, blksize(fs, VTOI(pvp), lbn), &bp);
                if (error == 0)
                        error = VOP_BWRITE(bp->b_vp, bp);
                vput(pvp);
                if (error != 0)
                        return (error);
                ACQUIRE_LOCK(&lk);
                if (inodedep_lookup(fs, ip->i_number, 0, &inodedep) == 0)
                        break;
        }
        FREE_LOCK(&lk);
        return (0);
}

/*
 * Flush all the dirty bitmaps associated with the block device
 * before flushing the rest of the dirty blocks so as to reduce
 * the number of dependencies that will have to be rolled back.
 */
static int softdep_fsync_mountdev_bp(struct buf *bp, void *data);

void
softdep_fsync_mountdev(vp)
        struct vnode *vp;
{
        if (!vn_isdisk(vp, NULL))
                panic("softdep_fsync_mountdev: vnode not a disk");
        ACQUIRE_LOCK(&lk);
        RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, NULL, 
                softdep_fsync_mountdev_bp, NULL);
        drain_output(vp, 1);
        FREE_LOCK(&lk);
}

static int
softdep_fsync_mountdev_bp(struct buf *bp, void *data)
{
        struct worklist *wk;

        /* 
         * If it is already scheduled, skip to the next buffer.
         */
        if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT))
                return(0);
        if ((bp->b_flags & B_DELWRI) == 0) {
                FREE_LOCK(&lk);
                panic("softdep_fsync_mountdev: not dirty");
        }
        /*
         * We are only interested in bitmaps with outstanding
         * dependencies.
         */
        if ((wk = LIST_FIRST(&bp->b_dep)) == NULL ||
            wk->wk_type != D_BMSAFEMAP ||
            (bp->b_xflags & BX_BKGRDINPROG)) {
                BUF_UNLOCK(bp);
                return(0);
        }
        bremfree(bp);
        FREE_LOCK(&lk);
        (void) bawrite(bp);
        ACQUIRE_LOCK(&lk);
        return(0);
}

/*
 * This routine is called when we are trying to synchronously flush a
 * file. This routine must eliminate any filesystem metadata dependencies
 * so that the syncing routine can succeed by pushing the dirty blocks
 * associated with the file. If any I/O errors occur, they are returned.
 */
struct softdep_sync_metadata_info {
        struct vnode *vp;
        int waitfor;
};

static int softdep_sync_metadata_bp(struct buf *bp, void *data);

int
softdep_sync_metadata(struct vnode *vp, struct thread *td)
{
        struct softdep_sync_metadata_info info;
        int error, waitfor;

        /*
         * Check whether this vnode is involved in a filesystem
         * that is doing soft dependency processing.
         */
        if (!vn_isdisk(vp, NULL)) {
                if (!DOINGSOFTDEP(vp))
                        return (0);
        } else
                if (vp->v_rdev->si_mountpoint == NULL ||
                    (vp->v_rdev->si_mountpoint->mnt_flag & MNT_SOFTDEP) == 0)
                        return (0);
        /*
         * Ensure that any direct block dependencies have been cleared.
         */
        ACQUIRE_LOCK(&lk);
        if ((error = flush_inodedep_deps(VTOI(vp)->i_fs, VTOI(vp)->i_number))) {
                FREE_LOCK(&lk);
                return (error);
        }
        /*
         * For most files, the only metadata dependencies are the
         * cylinder group maps that allocate their inode or blocks.
         * The block allocation dependencies can be found by traversing
         * the dependency lists for any buffers that remain on their
         * dirty buffer list. The inode allocation dependency will
         * be resolved when the inode is updated with MNT_WAIT.
         * This work is done in two passes. The first pass grabs most
         * of the buffers and begins asynchronously writing them. The
         * only way to wait for these asynchronous writes is to sleep
         * on the filesystem vnode which may stay busy for a long time
         * if the filesystem is active. So, instead, we make a second
         * pass over the dependencies blocking on each write. In the
         * usual case we will be blocking against a write that we
         * initiated, so when it is done the dependency will have been
         * resolved. Thus the second pass is expected to end quickly.
         */
        waitfor = MNT_NOWAIT;
top:
        /*
         * We must wait for any I/O in progress to finish so that
         * all potential buffers on the dirty list will be visible.
         */
        drain_output(vp, 1);
        info.vp = vp;
        info.waitfor = waitfor;
        error = RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, NULL, 
                        softdep_sync_metadata_bp, &info);
        if (error < 0) {
                FREE_LOCK(&lk);
                return(-error); /* error code */
        }

        /*
         * The brief unlock is to allow any pent up dependency
         * processing to be done.  Then proceed with the second pass.
         */
        if (waitfor == MNT_NOWAIT) {
                waitfor = MNT_WAIT;
                FREE_LOCK(&lk);
                ACQUIRE_LOCK(&lk);
                goto top;
        }

        /*
         * If we have managed to get rid of all the dirty buffers,
         * then we are done. For certain directories and block
         * devices, we may need to do further work.
         *
         * We must wait for any I/O in progress to finish so that
         * all potential buffers on the dirty list will be visible.
         */
        drain_output(vp, 1);
        if (RB_EMPTY(&vp->v_rbdirty_tree)) {
                FREE_LOCK(&lk);
                return (0);
        }

        FREE_LOCK(&lk);
        /*
         * If we are trying to sync a block device, some of its buffers may
         * contain metadata that cannot be written until the contents of some
         * partially written files have been written to disk. The only easy
         * way to accomplish this is to sync the entire filesystem (luckily
         * this happens rarely).
         */
        if (vn_isdisk(vp, NULL) && 
            vp->v_rdev &&
            vp->v_rdev->si_mountpoint && !VOP_ISLOCKED(vp, NULL) &&
            (error = VFS_SYNC(vp->v_rdev->si_mountpoint, MNT_WAIT, td)) != 0)
                return (error);
        return (0);
}

static int
softdep_sync_metadata_bp(struct buf *bp, void *data)
{
        struct softdep_sync_metadata_info *info = data;
        struct pagedep *pagedep;
        struct allocdirect *adp;
        struct allocindir *aip;
        struct worklist *wk;
        struct buf *nbp;
        int error;
        int i;

        if (getdirtybuf(&bp, MNT_WAIT) == 0)
                return (0);

        /*
         * As we hold the buffer locked, none of its dependencies
         * will disappear.
         */
        LIST_FOREACH(wk, &bp->b_dep, wk_list) {
                switch (wk->wk_type) {

                case D_ALLOCDIRECT:
                        adp = WK_ALLOCDIRECT(wk);
                        if (adp->ad_state & DEPCOMPLETE)
                                break;
                        nbp = adp->ad_buf;
                        if (getdirtybuf(&nbp, info->waitfor) == 0)
                                break;
                        FREE_LOCK(&lk);
                        if (info->waitfor == MNT_NOWAIT) {
                                bawrite(nbp);
                        } else if ((error = VOP_BWRITE(nbp->b_vp, nbp)) != 0) {
                                bawrite(bp);
                                ACQUIRE_LOCK(&lk);
                                return (-error);
                        }
                        ACQUIRE_LOCK(&lk);
                        break;

                case D_ALLOCINDIR:
                        aip = WK_ALLOCINDIR(wk);
                        if (aip->ai_state & DEPCOMPLETE)
                                break;
                        nbp = aip->ai_buf;
                        if (getdirtybuf(&nbp, info->waitfor) == 0)
                                break;
                        FREE_LOCK(&lk);
                        if (info->waitfor == MNT_NOWAIT) {
                                bawrite(nbp);
                        } else if ((error = VOP_BWRITE(nbp->b_vp, nbp)) != 0) {
                                bawrite(bp);
                                ACQUIRE_LOCK(&lk);
                                return (-error);
                        }
                        ACQUIRE_LOCK(&lk);
                        break;

                case D_INDIRDEP:
                restart:

                        LIST_FOREACH(aip, &WK_INDIRDEP(wk)->ir_deplisthd, ai_next) {
                                if (aip->ai_state & DEPCOMPLETE)
                                        continue;
                                nbp = aip->ai_buf;
                                if (getdirtybuf(&nbp, MNT_WAIT) == 0)
                                        goto restart;
                                FREE_LOCK(&lk);
                                if ((error = VOP_BWRITE(nbp->b_vp, nbp)) != 0) {
                                        bawrite(bp);
                                        ACQUIRE_LOCK(&lk);
                                        return (-error);
                                }
                                ACQUIRE_LOCK(&lk);
                                goto restart;
                        }
                        break;

                case D_INODEDEP:
                        if ((error = flush_inodedep_deps(WK_INODEDEP(wk)->id_fs,
                            WK_INODEDEP(wk)->id_ino)) != 0) {
                                FREE_LOCK(&lk);
                                bawrite(bp);
                                ACQUIRE_LOCK(&lk);
                                return (-error);
                        }
                        break;

                case D_PAGEDEP:
                        /*
                         * We are trying to sync a directory that may
                         * have dependencies on both its own metadata
                         * and/or dependencies on the inodes of any
                         * recently allocated files. We walk its diradd
                         * lists pushing out the associated inode.
                         */
                        pagedep = WK_PAGEDEP(wk);
                        for (i = 0; i < DAHASHSZ; i++) {
                                if (LIST_FIRST(&pagedep->pd_diraddhd[i]) == 0)
                                        continue;
                                if ((error =
                                    flush_pagedep_deps(info->vp,
                                                pagedep->pd_mnt,
                                                &pagedep->pd_diraddhd[i]))) {
                                        FREE_LOCK(&lk);
                                        bawrite(bp);
                                        ACQUIRE_LOCK(&lk);
                                        return (-error);
                                }
                        }
                        break;

                case D_MKDIR:
                        /*
                         * This case should never happen if the vnode has
                         * been properly sync'ed. However, if this function
                         * is used at a place where the vnode has not yet
                         * been sync'ed, this dependency can show up. So,
                         * rather than panic, just flush it.
                         */
                        nbp = WK_MKDIR(wk)->md_buf;
                        if (getdirtybuf(&nbp, info->waitfor) == 0)
                                break;
                        FREE_LOCK(&lk);
                        if (info->waitfor == MNT_NOWAIT) {
                                bawrite(nbp);
                        } else if ((error = VOP_BWRITE(nbp->b_vp, nbp)) != 0) {
                                bawrite(bp);
                                ACQUIRE_LOCK(&lk);
                                return (-error);
                        }
                        ACQUIRE_LOCK(&lk);
                        break;

                case D_BMSAFEMAP:
                        /*
                         * This case should never happen if the vnode has
                         * been properly sync'ed. However, if this function
                         * is used at a place where the vnode has not yet
                         * been sync'ed, this dependency can show up. So,
                         * rather than panic, just flush it.
                         */
                        nbp = WK_BMSAFEMAP(wk)->sm_buf;
                        if (getdirtybuf(&nbp, info->waitfor) == 0)
                                break;
                        FREE_LOCK(&lk);
                        if (info->waitfor == MNT_NOWAIT) {
                                bawrite(nbp);
                        } else if ((error = VOP_BWRITE(nbp->b_vp, nbp)) != 0) {
                                bawrite(bp);
                                ACQUIRE_LOCK(&lk);
                                return (-error);
                        }
                        ACQUIRE_LOCK(&lk);
                        break;

                default:
                        FREE_LOCK(&lk);
                        panic("softdep_sync_metadata: Unknown type %s",
                            TYPENAME(wk->wk_type));
                        /* NOTREACHED */
                }
        }
        FREE_LOCK(&lk);
        bawrite(bp);
        ACQUIRE_LOCK(&lk);
        return(0);
}

/*
 * Flush the dependencies associated with an inodedep.
 * Called with splbio blocked.
 */
static int
flush_inodedep_deps(fs, ino)
        struct fs *fs;
        ino_t ino;
{
        struct inodedep *inodedep;
        struct allocdirect *adp;
        int error, waitfor;
        struct buf *bp;

        /*
         * This work is done in two passes. The first pass grabs most
         * of the buffers and begins asynchronously writing them. The
         * only way to wait for these asynchronous writes is to sleep
         * on the filesystem vnode which may stay busy for a long time
         * if the filesystem is active. So, instead, we make a second
         * pass over the dependencies blocking on each write. In the
         * usual case we will be blocking against a write that we
         * initiated, so when it is done the dependency will have been
         * resolved. Thus the second pass is expected to end quickly.
         * We give a brief window at the top of the loop to allow
         * any pending I/O to complete.
         */
        for (waitfor = MNT_NOWAIT; ; ) {
                FREE_LOCK(&lk);
                ACQUIRE_LOCK(&lk);
                if (inodedep_lookup(fs, ino, 0, &inodedep) == 0)
                        return (0);
                TAILQ_FOREACH(adp, &inodedep->id_inoupdt, ad_next) {
                        if (adp->ad_state & DEPCOMPLETE)
                                continue;
                        bp = adp->ad_buf;
                        if (getdirtybuf(&bp, waitfor) == 0) {
                                if (waitfor == MNT_NOWAIT)
                                        continue;
                                break;
                        }
                        FREE_LOCK(&lk);
                        if (waitfor == MNT_NOWAIT) {
                                bawrite(bp);
                        } else if ((error = VOP_BWRITE(bp->b_vp, bp)) != 0) {
                                ACQUIRE_LOCK(&lk);
                                return (error);
                        }
                        ACQUIRE_LOCK(&lk);
                        break;
                }
                if (adp != NULL)
                        continue;
                TAILQ_FOREACH(adp, &inodedep->id_newinoupdt, ad_next) {
                        if (adp->ad_state & DEPCOMPLETE)
                                continue;
                        bp = adp->ad_buf;
                        if (getdirtybuf(&bp, waitfor) == 0) {
                                if (waitfor == MNT_NOWAIT)
                                        continue;
                                break;
                        }
                        FREE_LOCK(&lk);
                        if (waitfor == MNT_NOWAIT) {
                                bawrite(bp);
                        } else if ((error = VOP_BWRITE(bp->b_vp, bp)) != 0) {
                                ACQUIRE_LOCK(&lk);
                                return (error);
                        }
                        ACQUIRE_LOCK(&lk);
                        break;
                }
                if (adp != NULL)
                        continue;
                /*
                 * If pass2, we are done, otherwise do pass 2.
                 */
                if (waitfor == MNT_WAIT)
                        break;
                waitfor = MNT_WAIT;
        }
        /*
         * Try freeing inodedep in case all dependencies have been removed.
         */
        if (inodedep_lookup(fs, ino, 0, &inodedep) != 0)
                (void) free_inodedep(inodedep);
        return (0);
}

/*
 * Eliminate a pagedep dependency by flushing out all its diradd dependencies.
 * Called with splbio blocked.
 */
static int
flush_pagedep_deps(pvp, mp, diraddhdp)
        struct vnode *pvp;
        struct mount *mp;
        struct diraddhd *diraddhdp;
{
        struct thread *td = curthread;          /* XXX */
        struct inodedep *inodedep;
        struct ufsmount *ump;
        struct diradd *dap;
        struct vnode *vp;
        int gotit, error = 0;
        struct buf *bp;
        ino_t inum;

        ump = VFSTOUFS(mp);
        while ((dap = LIST_FIRST(diraddhdp)) != NULL) {
                /*
                 * Flush ourselves if this directory entry
                 * has a MKDIR_PARENT dependency.
                 */
                if (dap->da_state & MKDIR_PARENT) {
                        FREE_LOCK(&lk);
                        if ((error = UFS_UPDATE(pvp, 1)) != 0)
                                break;
                        ACQUIRE_LOCK(&lk);
                        /*
                         * If that cleared dependencies, go on to next.
                         */
                        if (dap != LIST_FIRST(diraddhdp))
                                continue;
                        if (dap->da_state & MKDIR_PARENT) {
                                FREE_LOCK(&lk);
                                panic("flush_pagedep_deps: MKDIR_PARENT");
                        }
                }
                /*
                 * A newly allocated directory must have its "." and
                 * ".." entries written out before its name can be
                 * committed in its parent. We do not want or need
                 * the full semantics of a synchronous VOP_FSYNC as
                 * that may end up here again, once for each directory
                 * level in the filesystem. Instead, we push the blocks
                 * and wait for them to clear. We have to fsync twice
                 * because the first call may choose to defer blocks
                 * that still have dependencies, but deferral will
                 * happen at most once.
                 */
                inum = dap->da_newinum;
                if (dap->da_state & MKDIR_BODY) {
                        FREE_LOCK(&lk);
                        if ((error = VFS_VGET(mp, inum, &vp)) != 0)
                                break;
                        if ((error=VOP_FSYNC(vp, MNT_NOWAIT, td)) ||
                            (error=VOP_FSYNC(vp, MNT_NOWAIT, td))) {
                                vput(vp);
                                break;
                        }
                        drain_output(vp, 0);
                        vput(vp);
                        ACQUIRE_LOCK(&lk);
                        /*
                         * If that cleared dependencies, go on to next.
                         */
                        if (dap != LIST_FIRST(diraddhdp))
                                continue;
                        if (dap->da_state & MKDIR_BODY) {
                                FREE_LOCK(&lk);
                                panic("flush_pagedep_deps: MKDIR_BODY");
                        }
                }
                /*
                 * Flush the inode on which the directory entry depends.
                 * Having accounted for MKDIR_PARENT and MKDIR_BODY above,
                 * the only remaining dependency is that the updated inode
                 * count must get pushed to disk. The inode has already
                 * been pushed into its inode buffer (via VOP_UPDATE) at
                 * the time of the reference count change. So we need only
                 * locate that buffer, ensure that there will be no rollback
                 * caused by a bitmap dependency, then write the inode buffer.
                 */
                if (inodedep_lookup(ump->um_fs, inum, 0, &inodedep) == 0) {
                        FREE_LOCK(&lk);
                        panic("flush_pagedep_deps: lost inode");
                }
                /*
                 * If the inode still has bitmap dependencies,
                 * push them to disk.
                 */
                if ((inodedep->id_state & DEPCOMPLETE) == 0) {
                        gotit = getdirtybuf(&inodedep->id_buf, MNT_WAIT);
                        FREE_LOCK(&lk);
                        if (gotit &&
                            (error = VOP_BWRITE(inodedep->id_buf->b_vp,
                             inodedep->id_buf)) != 0)
                                break;
                        ACQUIRE_LOCK(&lk);
                        if (dap != LIST_FIRST(diraddhdp))
                                continue;
                }
                /*
                 * If the inode is still sitting in a buffer waiting
                 * to be written, push it to disk.
                 */
                FREE_LOCK(&lk);
                if ((error = bread(ump->um_devvp,
                    fsbtodb(ump->um_fs, ino_to_fsba(ump->um_fs, inum)),
                    (int)ump->um_fs->fs_bsize, &bp)) != 0)
                        break;
                if ((error = VOP_BWRITE(bp->b_vp, bp)) != 0)
                        break;
                ACQUIRE_LOCK(&lk);
                /*
                 * If we have failed to get rid of all the dependencies
                 * then something is seriously wrong.
                 */
                if (dap == LIST_FIRST(diraddhdp)) {
                        FREE_LOCK(&lk);
                        panic("flush_pagedep_deps: flush failed");
                }
        }
        if (error)
                ACQUIRE_LOCK(&lk);
        return (error);
}

/*
 * A large burst of file addition or deletion activity can drive the
 * memory load excessively high. First attempt to slow things down
 * using the techniques below. If that fails, this routine requests
 * the offending operations to fall back to running synchronously
 * until the memory load returns to a reasonable level.
 */
int
softdep_slowdown(vp)
        struct vnode *vp;
{
        int max_softdeps_hard;

        max_softdeps_hard = max_softdeps * 11 / 10;
        if (num_dirrem < max_softdeps_hard / 2 &&
            num_inodedep < max_softdeps_hard)
                return (0);
        stat_sync_limit_hit += 1;
        return (1);
}

/*
 * If memory utilization has gotten too high, deliberately slow things
 * down and speed up the I/O processing.
 */
static int
request_cleanup(resource, islocked)
        int resource;
        int islocked;
{
        struct thread *td = curthread;          /* XXX */

        /*
         * We never hold up the filesystem syncer process.
         */
        if (td == filesys_syncer)
                return (0);
        /*
         * First check to see if the work list has gotten backlogged.
         * If it has, co-opt this process to help clean up two entries.
         * Because this process may hold inodes locked, we cannot
         * handle any remove requests that might block on a locked
         * inode as that could lead to deadlock.
         */
        if (num_on_worklist > max_softdeps / 10) {
                if (islocked)
                        FREE_LOCK(&lk);
                process_worklist_item(NULL, LK_NOWAIT);
                process_worklist_item(NULL, LK_NOWAIT);
                stat_worklist_push += 2;
                if (islocked)
                        ACQUIRE_LOCK(&lk);
                return(1);
        }

        /*
         * If we are resource constrained on inode dependencies, try
         * flushing some dirty inodes. Otherwise, we are constrained
         * by file deletions, so try accelerating flushes of directories
         * with removal dependencies. We would like to do the cleanup
         * here, but we probably hold an inode locked at this point and 
         * that might deadlock against one that we try to clean. So,
         * the best that we can do is request the syncer daemon to do
         * the cleanup for us.
         */
        switch (resource) {

        case FLUSH_INODES:
                stat_ino_limit_push += 1;
                req_clear_inodedeps += 1;
                stat_countp = &stat_ino_limit_hit;
                break;

        case FLUSH_REMOVE:
                stat_blk_limit_push += 1;
                req_clear_remove += 1;
                stat_countp = &stat_blk_limit_hit;
                break;

        default:
                if (islocked)
                        FREE_LOCK(&lk);
                panic("request_cleanup: unknown type");
        }
        /*
         * Hopefully the syncer daemon will catch up and awaken us.
         * We wait at most tickdelay before proceeding in any case.
         */
        if (islocked == 0)
                ACQUIRE_LOCK(&lk);
        crit_enter();
        proc_waiting += 1;
        if (!callout_active(&handle))
                callout_reset(&handle, tickdelay > 2 ? tickdelay : 2,
                              pause_timer, NULL);
        interlocked_sleep(&lk, SLEEP, (caddr_t)&proc_waiting, 0,
            "softupdate", 0);
        proc_waiting -= 1;
        crit_exit();
        if (islocked == 0)
                FREE_LOCK(&lk);
        return (1);
}

/*
 * Awaken processes pausing in request_cleanup and clear proc_waiting
 * to indicate that there is no longer a timer running.
 */
void
pause_timer(arg)
        void *arg;
{
        *stat_countp += 1;
        wakeup_one(&proc_waiting);
        if (proc_waiting > 0)
                callout_reset(&handle, tickdelay > 2 ? tickdelay : 2,
                              pause_timer, NULL);
        else
                callout_deactivate(&handle);
}

/*
 * Flush out a directory with at least one removal dependency in an effort to
 * reduce the number of dirrem, freefile, and freeblks dependency structures.
 */
static void
clear_remove(struct thread *td)
{
        struct pagedep_hashhead *pagedephd;
        struct pagedep *pagedep;
        static int next = 0;
        struct mount *mp;
        struct vnode *vp;
        int error, cnt;
        ino_t ino;

        ACQUIRE_LOCK(&lk);
        for (cnt = 0; cnt < pagedep_hash; cnt++) {
                pagedephd = &pagedep_hashtbl[next++];
                if (next >= pagedep_hash)
                        next = 0;
                LIST_FOREACH(pagedep, pagedephd, pd_hash) {
                        if (LIST_FIRST(&pagedep->pd_dirremhd) == NULL)
                                continue;
                        mp = pagedep->pd_mnt;
                        ino = pagedep->pd_ino;
                        FREE_LOCK(&lk);
                        if ((error = VFS_VGET(mp, ino, &vp)) != 0) {
                                softdep_error("clear_remove: vget", error);
                                return;
                        }
                        if ((error = VOP_FSYNC(vp, MNT_NOWAIT, td)))
                                softdep_error("clear_remove: fsync", error);
                        drain_output(vp, 0);
                        vput(vp);
                        return;
                }
        }
        FREE_LOCK(&lk);
}

/*
 * Clear out a block of dirty inodes in an effort to reduce
 * the number of inodedep dependency structures.
 */
struct clear_inodedeps_info {
        struct fs *fs;
        struct mount *mp;
};

static int
clear_inodedeps_mountlist_callback(struct mount *mp, void *data)
{
        struct clear_inodedeps_info *info = data;

        if ((mp->mnt_flag & MNT_SOFTDEP) && info->fs == VFSTOUFS(mp)->um_fs) {
                info->mp = mp;
                return(-1);
        }
        return(0);
}

static void
clear_inodedeps(struct thread *td)
{
        struct clear_inodedeps_info info;
        struct inodedep_hashhead *inodedephd;
        struct inodedep *inodedep;
        static int next = 0;
        struct vnode *vp;
        struct fs *fs;
        int error, cnt;
        ino_t firstino, lastino, ino;

        ACQUIRE_LOCK(&lk);
        /*
         * Pick a random inode dependency to be cleared.
         * We will then gather up all the inodes in its block 
         * that have dependencies and flush them out.
         */
        for (cnt = 0; cnt < inodedep_hash; cnt++) {
                inodedephd = &inodedep_hashtbl[next++];
                if (next >= inodedep_hash)
                        next = 0;
                if ((inodedep = LIST_FIRST(inodedephd)) != NULL)
                        break;
        }
        if (inodedep == NULL) {
                FREE_LOCK(&lk);
                return;
        }
        /*
         * Ugly code to find mount point given pointer to superblock.
         */
        fs = inodedep->id_fs;
        info.mp = NULL;
        info.fs = fs;
        mountlist_scan(clear_inodedeps_mountlist_callback, 
                        &info, MNTSCAN_FORWARD|MNTSCAN_NOBUSY);
        /*
         * Find the last inode in the block with dependencies.
         */
        firstino = inodedep->id_ino & ~(INOPB(fs) - 1);
        for (lastino = firstino + INOPB(fs) - 1; lastino > firstino; lastino--)
                if (inodedep_lookup(fs, lastino, 0, &inodedep) != 0)
                        break;
        /*
         * Asynchronously push all but the last inode with dependencies.
         * Synchronously push the last inode with dependencies to ensure
         * that the inode block gets written to free up the inodedeps.
         */
        for (ino = firstino; ino <= lastino; ino++) {
                if (inodedep_lookup(fs, ino, 0, &inodedep) == 0)
                        continue;
                FREE_LOCK(&lk);
                if ((error = VFS_VGET(info.mp, ino, &vp)) != 0) {
                        softdep_error("clear_inodedeps: vget", error);
                        return;
                }
                if (ino == lastino) {
                        if ((error = VOP_FSYNC(vp, MNT_WAIT, td)))
                                softdep_error("clear_inodedeps: fsync1", error);
                } else {
                        if ((error = VOP_FSYNC(vp, MNT_NOWAIT, td)))
                                softdep_error("clear_inodedeps: fsync2", error);
                        drain_output(vp, 0);
                }
                vput(vp);
                ACQUIRE_LOCK(&lk);
        }
        FREE_LOCK(&lk);
}

/*
 * Function to determine if the buffer has outstanding dependencies
 * that will cause a roll-back if the buffer is written. If wantcount
 * is set, return number of dependencies, otherwise just yes or no.
 */
static int
softdep_count_dependencies(bp, wantcount)
        struct buf *bp;
        int wantcount;
{
        struct worklist *wk;
        struct inodedep *inodedep;
        struct indirdep *indirdep;
        struct allocindir *aip;
        struct pagedep *pagedep;
        struct diradd *dap;
        int i, retval;

        retval = 0;
        ACQUIRE_LOCK(&lk);
        LIST_FOREACH(wk, &bp->b_dep, wk_list) {
                switch (wk->wk_type) {

                case D_INODEDEP:
                        inodedep = WK_INODEDEP(wk);
                        if ((inodedep->id_state & DEPCOMPLETE) == 0) {
                                /* bitmap allocation dependency */
                                retval += 1;
                                if (!wantcount)
                                        goto out;
                        }
                        if (TAILQ_FIRST(&inodedep->id_inoupdt)) {
                                /* direct block pointer dependency */
                                retval += 1;
                                if (!wantcount)
                                        goto out;
                        }
                        continue;

                case D_INDIRDEP:
                        indirdep = WK_INDIRDEP(wk);

                        LIST_FOREACH(aip, &indirdep->ir_deplisthd, ai_next) {
                                /* indirect block pointer dependency */
                                retval += 1;
                                if (!wantcount)
                                        goto out;
                        }
                        continue;

                case D_PAGEDEP:
                        pagedep = WK_PAGEDEP(wk);
                        for (i = 0; i < DAHASHSZ; i++) {

                                LIST_FOREACH(dap, &pagedep->pd_diraddhd[i], da_pdlist) {
                                        /* directory entry dependency */
                                        retval += 1;
                                        if (!wantcount)
                                                goto out;
                                }
                        }
                        continue;

                case D_BMSAFEMAP:
                case D_ALLOCDIRECT:
                case D_ALLOCINDIR:
                case D_MKDIR:
                        /* never a dependency on these blocks */
                        continue;

                default:
                        FREE_LOCK(&lk);
                        panic("softdep_check_for_rollback: Unexpected type %s",
                            TYPENAME(wk->wk_type));
                        /* NOTREACHED */
                }
        }
out:
        FREE_LOCK(&lk);
        return retval;
}

/*
 * Acquire exclusive access to a buffer.
 * Must be called with splbio blocked.
 * Return 1 if buffer was acquired.
 */
static int
getdirtybuf(bpp, waitfor)
        struct buf **bpp;
        int waitfor;
{
        struct buf *bp;
        int error;

        for (;;) {
                if ((bp = *bpp) == NULL)
                        return (0);
                if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT) == 0) {
                        if ((bp->b_xflags & BX_BKGRDINPROG) == 0)
                                break;
                        BUF_UNLOCK(bp);
                        if (waitfor != MNT_WAIT)
                                return (0);
                        bp->b_xflags |= BX_BKGRDWAIT;
                        interlocked_sleep(&lk, SLEEP, &bp->b_xflags, 0,
                            "getbuf", 0);
                        continue;
                }
                if (waitfor != MNT_WAIT)
                        return (0);
                error = interlocked_sleep(&lk, LOCKBUF, bp,
                    LK_EXCLUSIVE | LK_SLEEPFAIL, 0, 0);
                if (error != ENOLCK) {
                        FREE_LOCK(&lk);
                        panic("getdirtybuf: inconsistent lock");
                }
        }
        if ((bp->b_flags & B_DELWRI) == 0) {
                BUF_UNLOCK(bp);
                return (0);
        }
        bremfree(bp);
        return (1);
}

/*
 * Wait for pending output on a vnode to complete.
 * Must be called with vnode locked.
 */
static void
drain_output(vp, islocked)
        struct vnode *vp;
        int islocked;
{

        if (!islocked)
                ACQUIRE_LOCK(&lk);
        while (vp->v_numoutput) {
                vp->v_flag |= VBWAIT;
                interlocked_sleep(&lk, SLEEP, (caddr_t)&vp->v_numoutput,
                    0, "drainvp", 0);
        }
        if (!islocked)
                FREE_LOCK(&lk);
}

/*
 * Called whenever a buffer that is being invalidated or reallocated
 * contains dependencies. This should only happen if an I/O error has
 * occurred. The routine is called with the buffer locked.
 */ 
static void
softdep_deallocate_dependencies(bp)
        struct buf *bp;
{

        if ((bp->b_flags & B_ERROR) == 0)
                panic("softdep_deallocate_dependencies: dangling deps");
        softdep_error(bp->b_vp->v_mount->mnt_stat.f_mntfromname, bp->b_error);
        panic("softdep_deallocate_dependencies: unrecovered I/O error");
}

/*
 * Function to handle asynchronous write errors in the filesystem.
 */
void
softdep_error(func, error)
        char *func;
        int error;
{

        /* XXX should do something better! */
        printf("%s: got error %d while accessing filesystem\n", func, error);
}