Linux v2.6.16-rc1

[linux-2.6/next.git] / fs / jfs / jfs_txnmgr.c

/*
 *   Copyright (C) International Business Machines Corp., 2000-2005
 *   Portions Copyright (C) Christoph Hellwig, 2001-2002
 *
 *   This program is free software;  you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or 
 *   (at your option) any later version.
 * 
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program;  if not, write to the Free Software 
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

/*
 *      jfs_txnmgr.c: transaction manager
 *
 * notes:
 * transaction starts with txBegin() and ends with txCommit()
 * or txAbort().
 *
 * tlock is acquired at the time of update;
 * (obviate scan at commit time for xtree and dtree)
 * tlock and mp points to each other;
 * (no hashlist for mp -> tlock).
 *
 * special cases:
 * tlock on in-memory inode:
 * in-place tlock in the in-memory inode itself;
 * converted to page lock by iWrite() at commit time.
 *
 * tlock during write()/mmap() under anonymous transaction (tid = 0):
 * transferred (?) to transaction at commit time.
 *
 * use the page itself to update allocation maps
 * (obviate intermediate replication of allocation/deallocation data)
 * hold on to mp+lock thru update of maps
 */

#include <linux/fs.h>
#include <linux/vmalloc.h>
#include <linux/smp_lock.h>
#include <linux/completion.h>
#include <linux/suspend.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include "jfs_incore.h"
#include "jfs_inode.h"
#include "jfs_filsys.h"
#include "jfs_metapage.h"
#include "jfs_dinode.h"
#include "jfs_imap.h"
#include "jfs_dmap.h"
#include "jfs_superblock.h"
#include "jfs_debug.h"

/*
 *      transaction management structures
 */
static struct {
        int freetid;            /* index of a free tid structure */
        int freelock;           /* index first free lock word */
        wait_queue_head_t freewait;     /* eventlist of free tblock */
        wait_queue_head_t freelockwait; /* eventlist of free tlock */
        wait_queue_head_t lowlockwait;  /* eventlist of ample tlocks */
        int tlocksInUse;        /* Number of tlocks in use */
        spinlock_t LazyLock;    /* synchronize sync_queue & unlock_queue */
/*      struct tblock *sync_queue; * Transactions waiting for data sync */
        struct list_head unlock_queue;  /* Txns waiting to be released */
        struct list_head anon_list;     /* inodes having anonymous txns */
        struct list_head anon_list2;    /* inodes having anonymous txns
                                           that couldn't be sync'ed */
} TxAnchor;

int jfs_tlocks_low;             /* Indicates low number of available tlocks */

#ifdef CONFIG_JFS_STATISTICS
static struct {
        uint txBegin;
        uint txBegin_barrier;
        uint txBegin_lockslow;
        uint txBegin_freetid;
        uint txBeginAnon;
        uint txBeginAnon_barrier;
        uint txBeginAnon_lockslow;
        uint txLockAlloc;
        uint txLockAlloc_freelock;
} TxStat;
#endif

static int nTxBlock = -1;       /* number of transaction blocks */
module_param(nTxBlock, int, 0);
MODULE_PARM_DESC(nTxBlock,
                 "Number of transaction blocks (max:65536)");

static int nTxLock = -1;        /* number of transaction locks */
module_param(nTxLock, int, 0);
MODULE_PARM_DESC(nTxLock,
                 "Number of transaction locks (max:65536)");

struct tblock *TxBlock;         /* transaction block table */
static int TxLockLWM;           /* Low water mark for number of txLocks used */
static int TxLockHWM;           /* High water mark for number of txLocks used */
static int TxLockVHWM;          /* Very High water mark */
struct tlock *TxLock;           /* transaction lock table */

/*
 *      transaction management lock
 */
static DEFINE_SPINLOCK(jfsTxnLock);

#define TXN_LOCK()              spin_lock(&jfsTxnLock)
#define TXN_UNLOCK()            spin_unlock(&jfsTxnLock)

#define LAZY_LOCK_INIT()        spin_lock_init(&TxAnchor.LazyLock);
#define LAZY_LOCK(flags)        spin_lock_irqsave(&TxAnchor.LazyLock, flags)
#define LAZY_UNLOCK(flags) spin_unlock_irqrestore(&TxAnchor.LazyLock, flags)

DECLARE_WAIT_QUEUE_HEAD(jfs_sync_thread_wait);
DECLARE_WAIT_QUEUE_HEAD(jfs_commit_thread_wait);
static int jfs_commit_thread_waking;

/*
 * Retry logic exist outside these macros to protect from spurrious wakeups.
 */
static inline void TXN_SLEEP_DROP_LOCK(wait_queue_head_t * event)
{
        DECLARE_WAITQUEUE(wait, current);

        add_wait_queue(event, &wait);
        set_current_state(TASK_UNINTERRUPTIBLE);
        TXN_UNLOCK();
        schedule();
        current->state = TASK_RUNNING;
        remove_wait_queue(event, &wait);
}

#define TXN_SLEEP(event)\
{\
        TXN_SLEEP_DROP_LOCK(event);\
        TXN_LOCK();\
}

#define TXN_WAKEUP(event) wake_up_all(event)

/*
 *      statistics
 */
static struct {
        tid_t maxtid;           /* 4: biggest tid ever used */
        lid_t maxlid;           /* 4: biggest lid ever used */
        int ntid;               /* 4: # of transactions performed */
        int nlid;               /* 4: # of tlocks acquired */
        int waitlock;           /* 4: # of tlock wait */
} stattx;

/*
 * forward references
 */
static int diLog(struct jfs_log * log, struct tblock * tblk, struct lrd * lrd,
                struct tlock * tlck, struct commit * cd);
static int dataLog(struct jfs_log * log, struct tblock * tblk, struct lrd * lrd,
                struct tlock * tlck);
static void dtLog(struct jfs_log * log, struct tblock * tblk, struct lrd * lrd,
                struct tlock * tlck);
static void mapLog(struct jfs_log * log, struct tblock * tblk, struct lrd * lrd,
                struct tlock * tlck);
static void txAllocPMap(struct inode *ip, struct maplock * maplock,
                struct tblock * tblk);
static void txForce(struct tblock * tblk);
static int txLog(struct jfs_log * log, struct tblock * tblk,
                struct commit * cd);
static void txUpdateMap(struct tblock * tblk);
static void txRelease(struct tblock * tblk);
static void xtLog(struct jfs_log * log, struct tblock * tblk, struct lrd * lrd,
           struct tlock * tlck);
static void LogSyncRelease(struct metapage * mp);

/*
 *              transaction block/lock management
 *              ---------------------------------
 */

/*
 * Get a transaction lock from the free list.  If the number in use is
 * greater than the high water mark, wake up the sync daemon.  This should
 * free some anonymous transaction locks.  (TXN_LOCK must be held.)
 */
static lid_t txLockAlloc(void)
{
        lid_t lid;

        INCREMENT(TxStat.txLockAlloc);
        if (!TxAnchor.freelock) {
                INCREMENT(TxStat.txLockAlloc_freelock);
        }

        while (!(lid = TxAnchor.freelock))
                TXN_SLEEP(&TxAnchor.freelockwait);
        TxAnchor.freelock = TxLock[lid].next;
        HIGHWATERMARK(stattx.maxlid, lid);
        if ((++TxAnchor.tlocksInUse > TxLockHWM) && (jfs_tlocks_low == 0)) {
                jfs_info("txLockAlloc tlocks low");
                jfs_tlocks_low = 1;
                wake_up(&jfs_sync_thread_wait);
        }

        return lid;
}

static void txLockFree(lid_t lid)
{
        TxLock[lid].tid = 0;
        TxLock[lid].next = TxAnchor.freelock;
        TxAnchor.freelock = lid;
        TxAnchor.tlocksInUse--;
        if (jfs_tlocks_low && (TxAnchor.tlocksInUse < TxLockLWM)) {
                jfs_info("txLockFree jfs_tlocks_low no more");
                jfs_tlocks_low = 0;
                TXN_WAKEUP(&TxAnchor.lowlockwait);
        }
        TXN_WAKEUP(&TxAnchor.freelockwait);
}

/*
 * NAME:        txInit()
 *
 * FUNCTION:    initialize transaction management structures
 *
 * RETURN:
 *
 * serialization: single thread at jfs_init()
 */
int txInit(void)
{
        int k, size;
        struct sysinfo si;

        /* Set defaults for nTxLock and nTxBlock if unset */

        if (nTxLock == -1) {
                if (nTxBlock == -1) {
                        /* Base default on memory size */
                        si_meminfo(&si);
                        if (si.totalram > (256 * 1024)) /* 1 GB */
                                nTxLock = 64 * 1024;
                        else
                                nTxLock = si.totalram >> 2;
                } else if (nTxBlock > (8 * 1024))
                        nTxLock = 64 * 1024;
                else
                        nTxLock = nTxBlock << 3;
        }
        if (nTxBlock == -1)
                nTxBlock = nTxLock >> 3;

        /* Verify tunable parameters */
        if (nTxBlock < 16)
                nTxBlock = 16;  /* No one should set it this low */
        if (nTxBlock > 65536)
                nTxBlock = 65536;
        if (nTxLock < 256)
                nTxLock = 256;  /* No one should set it this low */
        if (nTxLock > 65536)
                nTxLock = 65536;

        printk(KERN_INFO "JFS: nTxBlock = %d, nTxLock = %d\n",
               nTxBlock, nTxLock);
        /*
         * initialize transaction block (tblock) table
         *
         * transaction id (tid) = tblock index
         * tid = 0 is reserved.
         */
        TxLockLWM = (nTxLock * 4) / 10;
        TxLockHWM = (nTxLock * 7) / 10;
        TxLockVHWM = (nTxLock * 8) / 10;

        size = sizeof(struct tblock) * nTxBlock;
        TxBlock = (struct tblock *) vmalloc(size);
        if (TxBlock == NULL)
                return -ENOMEM;

        for (k = 1; k < nTxBlock - 1; k++) {
                TxBlock[k].next = k + 1;
                init_waitqueue_head(&TxBlock[k].gcwait);
                init_waitqueue_head(&TxBlock[k].waitor);
        }
        TxBlock[k].next = 0;
        init_waitqueue_head(&TxBlock[k].gcwait);
        init_waitqueue_head(&TxBlock[k].waitor);

        TxAnchor.freetid = 1;
        init_waitqueue_head(&TxAnchor.freewait);

        stattx.maxtid = 1;      /* statistics */

        /*
         * initialize transaction lock (tlock) table
         *
         * transaction lock id = tlock index
         * tlock id = 0 is reserved.
         */
        size = sizeof(struct tlock) * nTxLock;
        TxLock = (struct tlock *) vmalloc(size);
        if (TxLock == NULL) {
                vfree(TxBlock);
                return -ENOMEM;
        }

        /* initialize tlock table */
        for (k = 1; k < nTxLock - 1; k++)
                TxLock[k].next = k + 1;
        TxLock[k].next = 0;
        init_waitqueue_head(&TxAnchor.freelockwait);
        init_waitqueue_head(&TxAnchor.lowlockwait);

        TxAnchor.freelock = 1;
        TxAnchor.tlocksInUse = 0;
        INIT_LIST_HEAD(&TxAnchor.anon_list);
        INIT_LIST_HEAD(&TxAnchor.anon_list2);

        LAZY_LOCK_INIT();
        INIT_LIST_HEAD(&TxAnchor.unlock_queue);

        stattx.maxlid = 1;      /* statistics */

        return 0;
}

/*
 * NAME:        txExit()
 *
 * FUNCTION:    clean up when module is unloaded
 */
void txExit(void)
{
        vfree(TxLock);
        TxLock = NULL;
        vfree(TxBlock);
        TxBlock = NULL;
}

/*
 * NAME:        txBegin()
 *
 * FUNCTION:    start a transaction.
 *
 * PARAMETER:   sb      - superblock
 *              flag    - force for nested tx;
 *
 * RETURN:      tid     - transaction id
 *
 * note: flag force allows to start tx for nested tx
 * to prevent deadlock on logsync barrier;
 */
tid_t txBegin(struct super_block *sb, int flag)
{
        tid_t t;
        struct tblock *tblk;
        struct jfs_log *log;

        jfs_info("txBegin: flag = 0x%x", flag);
        log = JFS_SBI(sb)->log;

        TXN_LOCK();

        INCREMENT(TxStat.txBegin);

      retry:
        if (!(flag & COMMIT_FORCE)) {
                /*
                 * synchronize with logsync barrier
                 */
                if (test_bit(log_SYNCBARRIER, &log->flag) ||
                    test_bit(log_QUIESCE, &log->flag)) {
                        INCREMENT(TxStat.txBegin_barrier);
                        TXN_SLEEP(&log->syncwait);
                        goto retry;
                }
        }
        if (flag == 0) {
                /*
                 * Don't begin transaction if we're getting starved for tlocks
                 * unless COMMIT_FORCE or COMMIT_INODE (which may ultimately
                 * free tlocks)
                 */
                if (TxAnchor.tlocksInUse > TxLockVHWM) {
                        INCREMENT(TxStat.txBegin_lockslow);
                        TXN_SLEEP(&TxAnchor.lowlockwait);
                        goto retry;
                }
        }

        /*
         * allocate transaction id/block
         */
        if ((t = TxAnchor.freetid) == 0) {
                jfs_info("txBegin: waiting for free tid");
                INCREMENT(TxStat.txBegin_freetid);
                TXN_SLEEP(&TxAnchor.freewait);
                goto retry;
        }

        tblk = tid_to_tblock(t);

        if ((tblk->next == 0) && !(flag & COMMIT_FORCE)) {
                /* Don't let a non-forced transaction take the last tblk */
                jfs_info("txBegin: waiting for free tid");
                INCREMENT(TxStat.txBegin_freetid);
                TXN_SLEEP(&TxAnchor.freewait);
                goto retry;
        }

        TxAnchor.freetid = tblk->next;

        /*
         * initialize transaction
         */

        /*
         * We can't zero the whole thing or we screw up another thread being
         * awakened after sleeping on tblk->waitor
         *
         * memset(tblk, 0, sizeof(struct tblock));
         */
        tblk->next = tblk->last = tblk->xflag = tblk->flag = tblk->lsn = 0;

        tblk->sb = sb;
        ++log->logtid;
        tblk->logtid = log->logtid;

        ++log->active;

        HIGHWATERMARK(stattx.maxtid, t);        /* statistics */
        INCREMENT(stattx.ntid); /* statistics */

        TXN_UNLOCK();

        jfs_info("txBegin: returning tid = %d", t);

        return t;
}

/*
 * NAME:        txBeginAnon()
 *
 * FUNCTION:    start an anonymous transaction.
 *              Blocks if logsync or available tlocks are low to prevent
 *              anonymous tlocks from depleting supply.
 *
 * PARAMETER:   sb      - superblock
 *
 * RETURN:      none
 */
void txBeginAnon(struct super_block *sb)
{
        struct jfs_log *log;

        log = JFS_SBI(sb)->log;

        TXN_LOCK();
        INCREMENT(TxStat.txBeginAnon);

      retry:
        /*
         * synchronize with logsync barrier
         */
        if (test_bit(log_SYNCBARRIER, &log->flag) ||
            test_bit(log_QUIESCE, &log->flag)) {
                INCREMENT(TxStat.txBeginAnon_barrier);
                TXN_SLEEP(&log->syncwait);
                goto retry;
        }

        /*
         * Don't begin transaction if we're getting starved for tlocks
         */
        if (TxAnchor.tlocksInUse > TxLockVHWM) {
                INCREMENT(TxStat.txBeginAnon_lockslow);
                TXN_SLEEP(&TxAnchor.lowlockwait);
                goto retry;
        }
        TXN_UNLOCK();
}

/*
 *      txEnd()
 *
 * function: free specified transaction block.
 *
 *      logsync barrier processing:
 *
 * serialization:
 */
void txEnd(tid_t tid)
{
        struct tblock *tblk = tid_to_tblock(tid);
        struct jfs_log *log;

        jfs_info("txEnd: tid = %d", tid);
        TXN_LOCK();

        /*
         * wakeup transactions waiting on the page locked
         * by the current transaction
         */
        TXN_WAKEUP(&tblk->waitor);

        log = JFS_SBI(tblk->sb)->log;

        /*
         * Lazy commit thread can't free this guy until we mark it UNLOCKED,
         * otherwise, we would be left with a transaction that may have been
         * reused.
         *
         * Lazy commit thread will turn off tblkGC_LAZY before calling this
         * routine.
         */
        if (tblk->flag & tblkGC_LAZY) {
                jfs_info("txEnd called w/lazy tid: %d, tblk = 0x%p", tid, tblk);
                TXN_UNLOCK();

                spin_lock_irq(&log->gclock);    // LOGGC_LOCK
                tblk->flag |= tblkGC_UNLOCKED;
                spin_unlock_irq(&log->gclock);  // LOGGC_UNLOCK
                return;
        }

        jfs_info("txEnd: tid: %d, tblk = 0x%p", tid, tblk);

        assert(tblk->next == 0);

        /*
         * insert tblock back on freelist
         */
        tblk->next = TxAnchor.freetid;
        TxAnchor.freetid = tid;

        /*
         * mark the tblock not active
         */
        if (--log->active == 0) {
                clear_bit(log_FLUSH, &log->flag);

                /*
                 * synchronize with logsync barrier
                 */
                if (test_bit(log_SYNCBARRIER, &log->flag)) {
                        TXN_UNLOCK();

                        /* write dirty metadata & forward log syncpt */
                        jfs_syncpt(log, 1);

                        jfs_info("log barrier off: 0x%x", log->lsn);

                        /* enable new transactions start */
                        clear_bit(log_SYNCBARRIER, &log->flag);

                        /* wakeup all waitors for logsync barrier */
                        TXN_WAKEUP(&log->syncwait);

                        goto wakeup;
                }
        }

        TXN_UNLOCK();
wakeup:
        /*
         * wakeup all waitors for a free tblock
         */
        TXN_WAKEUP(&TxAnchor.freewait);
}

/*
 *      txLock()
 *
 * function: acquire a transaction lock on the specified <mp>
 *
 * parameter:
 *
 * return:      transaction lock id
 *
 * serialization:
 */
struct tlock *txLock(tid_t tid, struct inode *ip, struct metapage * mp,
                     int type)
{
        struct jfs_inode_info *jfs_ip = JFS_IP(ip);
        int dir_xtree = 0;
        lid_t lid;
        tid_t xtid;
        struct tlock *tlck;
        struct xtlock *xtlck;
        struct linelock *linelock;
        xtpage_t *p;
        struct tblock *tblk;

        TXN_LOCK();

        if (S_ISDIR(ip->i_mode) && (type & tlckXTREE) &&
            !(mp->xflag & COMMIT_PAGE)) {
                /*
                 * Directory inode is special.  It can have both an xtree tlock
                 * and a dtree tlock associated with it.
                 */
                dir_xtree = 1;
                lid = jfs_ip->xtlid;
        } else
                lid = mp->lid;

        /* is page not locked by a transaction ? */
        if (lid == 0)
                goto allocateLock;

        jfs_info("txLock: tid:%d ip:0x%p mp:0x%p lid:%d", tid, ip, mp, lid);

        /* is page locked by the requester transaction ? */
        tlck = lid_to_tlock(lid);
        if ((xtid = tlck->tid) == tid) {
                TXN_UNLOCK();
                goto grantLock;
        }

        /*
         * is page locked by anonymous transaction/lock ?
         *
         * (page update without transaction (i.e., file write) is
         * locked under anonymous transaction tid = 0:
         * anonymous tlocks maintained on anonymous tlock list of
         * the inode of the page and available to all anonymous
         * transactions until txCommit() time at which point
         * they are transferred to the transaction tlock list of
         * the commiting transaction of the inode)
         */
        if (xtid == 0) {
                tlck->tid = tid;
                TXN_UNLOCK();
                tblk = tid_to_tblock(tid);
                /*
                 * The order of the tlocks in the transaction is important
                 * (during truncate, child xtree pages must be freed before
                 * parent's tlocks change the working map).
                 * Take tlock off anonymous list and add to tail of
                 * transaction list
                 *
                 * Note:  We really need to get rid of the tid & lid and
                 * use list_head's.  This code is getting UGLY!
                 */
                if (jfs_ip->atlhead == lid) {
                        if (jfs_ip->atltail == lid) {
                                /* only anonymous txn.
                                 * Remove from anon_list
                                 */
                                TXN_LOCK();
                                list_del_init(&jfs_ip->anon_inode_list);
                                TXN_UNLOCK();
                        }
                        jfs_ip->atlhead = tlck->next;
                } else {
                        lid_t last;
                        for (last = jfs_ip->atlhead;
                             lid_to_tlock(last)->next != lid;
                             last = lid_to_tlock(last)->next) {
                                assert(last);
                        }
                        lid_to_tlock(last)->next = tlck->next;
                        if (jfs_ip->atltail == lid)
                                jfs_ip->atltail = last;
                }

                /* insert the tlock at tail of transaction tlock list */

                if (tblk->next)
                        lid_to_tlock(tblk->last)->next = lid;
                else
                        tblk->next = lid;
                tlck->next = 0;
                tblk->last = lid;

                goto grantLock;
        }

        goto waitLock;

        /*
         * allocate a tlock
         */
      allocateLock:
        lid = txLockAlloc();
        tlck = lid_to_tlock(lid);

        /*
         * initialize tlock
         */
        tlck->tid = tid;

        TXN_UNLOCK();

        /* mark tlock for meta-data page */
        if (mp->xflag & COMMIT_PAGE) {

                tlck->flag = tlckPAGELOCK;

                /* mark the page dirty and nohomeok */
                metapage_nohomeok(mp);

                jfs_info("locking mp = 0x%p, nohomeok = %d tid = %d tlck = 0x%p",
                         mp, mp->nohomeok, tid, tlck);

                /* if anonymous transaction, and buffer is on the group
                 * commit synclist, mark inode to show this.  This will
                 * prevent the buffer from being marked nohomeok for too
                 * long a time.
                 */
                if ((tid == 0) && mp->lsn)
                        set_cflag(COMMIT_Synclist, ip);
        }
        /* mark tlock for in-memory inode */
        else
                tlck->flag = tlckINODELOCK;

        if (S_ISDIR(ip->i_mode))
                tlck->flag |= tlckDIRECTORY;

        tlck->type = 0;

        /* bind the tlock and the page */
        tlck->ip = ip;
        tlck->mp = mp;
        if (dir_xtree)
                jfs_ip->xtlid = lid;
        else
                mp->lid = lid;

        /*
         * enqueue transaction lock to transaction/inode
         */
        /* insert the tlock at tail of transaction tlock list */
        if (tid) {
                tblk = tid_to_tblock(tid);
                if (tblk->next)
                        lid_to_tlock(tblk->last)->next = lid;
                else
                        tblk->next = lid;
                tlck->next = 0;
                tblk->last = lid;
        }
        /* anonymous transaction:
         * insert the tlock at head of inode anonymous tlock list
         */
        else {
                tlck->next = jfs_ip->atlhead;
                jfs_ip->atlhead = lid;
                if (tlck->next == 0) {
                        /* This inode's first anonymous transaction */
                        jfs_ip->atltail = lid;
                        TXN_LOCK();
                        list_add_tail(&jfs_ip->anon_inode_list,
                                      &TxAnchor.anon_list);
                        TXN_UNLOCK();
                }
        }

        /* initialize type dependent area for linelock */
        linelock = (struct linelock *) & tlck->lock;
        linelock->next = 0;
        linelock->flag = tlckLINELOCK;
        linelock->maxcnt = TLOCKSHORT;
        linelock->index = 0;

        switch (type & tlckTYPE) {
        case tlckDTREE:
                linelock->l2linesize = L2DTSLOTSIZE;
                break;

        case tlckXTREE:
                linelock->l2linesize = L2XTSLOTSIZE;

                xtlck = (struct xtlock *) linelock;
                xtlck->header.offset = 0;
                xtlck->header.length = 2;

                if (type & tlckNEW) {
                        xtlck->lwm.offset = XTENTRYSTART;
                } else {
                        if (mp->xflag & COMMIT_PAGE)
                                p = (xtpage_t *) mp->data;
                        else
                                p = &jfs_ip->i_xtroot;
                        xtlck->lwm.offset =
                            le16_to_cpu(p->header.nextindex);
                }
                xtlck->lwm.length = 0;  /* ! */
                xtlck->twm.offset = 0;
                xtlck->hwm.offset = 0;

                xtlck->index = 2;
                break;

        case tlckINODE:
                linelock->l2linesize = L2INODESLOTSIZE;
                break;

        case tlckDATA:
                linelock->l2linesize = L2DATASLOTSIZE;
                break;

        default:
                jfs_err("UFO tlock:0x%p", tlck);
        }

        /*
         * update tlock vector
         */
      grantLock:
        tlck->type |= type;

        return tlck;

        /*
         * page is being locked by another transaction:
         */
      waitLock:
        /* Only locks on ipimap or ipaimap should reach here */
        /* assert(jfs_ip->fileset == AGGREGATE_I); */
        if (jfs_ip->fileset != AGGREGATE_I) {
                jfs_err("txLock: trying to lock locked page!");
                dump_mem("ip", ip, sizeof(struct inode));
                dump_mem("mp", mp, sizeof(struct metapage));
                dump_mem("Locker's tblk", tid_to_tblock(tid),
                         sizeof(struct tblock));
                dump_mem("Tlock", tlck, sizeof(struct tlock));
                BUG();
        }
        INCREMENT(stattx.waitlock);     /* statistics */
        TXN_UNLOCK();
        release_metapage(mp);
        TXN_LOCK();
        xtid = tlck->tid;       /* reaquire after dropping TXN_LOCK */

        jfs_info("txLock: in waitLock, tid = %d, xtid = %d, lid = %d",
                 tid, xtid, lid);

        /* Recheck everything since dropping TXN_LOCK */
        if (xtid && (tlck->mp == mp) && (mp->lid == lid))
                TXN_SLEEP_DROP_LOCK(&tid_to_tblock(xtid)->waitor);
        else
                TXN_UNLOCK();
        jfs_info("txLock: awakened     tid = %d, lid = %d", tid, lid);

        return NULL;
}

/*
 * NAME:        txRelease()
 *
 * FUNCTION:    Release buffers associated with transaction locks, but don't
 *              mark homeok yet.  The allows other transactions to modify
 *              buffers, but won't let them go to disk until commit record
 *              actually gets written.
 *
 * PARAMETER:
 *              tblk    -
 *
 * RETURN:      Errors from subroutines.
 */
static void txRelease(struct tblock * tblk)
{
        struct metapage *mp;
        lid_t lid;
        struct tlock *tlck;

        TXN_LOCK();

        for (lid = tblk->next; lid; lid = tlck->next) {
                tlck = lid_to_tlock(lid);
                if ((mp = tlck->mp) != NULL &&
                    (tlck->type & tlckBTROOT) == 0) {
                        assert(mp->xflag & COMMIT_PAGE);
                        mp->lid = 0;
                }
        }

        /*
         * wakeup transactions waiting on a page locked
         * by the current transaction
         */
        TXN_WAKEUP(&tblk->waitor);

        TXN_UNLOCK();
}

/*
 * NAME:        txUnlock()
 *
 * FUNCTION:    Initiates pageout of pages modified by tid in journalled
 *              objects and frees their lockwords.
 */
static void txUnlock(struct tblock * tblk)
{
        struct tlock *tlck;
        struct linelock *linelock;
        lid_t lid, next, llid, k;
        struct metapage *mp;
        struct jfs_log *log;
        int difft, diffp;
        unsigned long flags;

        jfs_info("txUnlock: tblk = 0x%p", tblk);
        log = JFS_SBI(tblk->sb)->log;

        /*
         * mark page under tlock homeok (its log has been written):
         */
        for (lid = tblk->next; lid; lid = next) {
                tlck = lid_to_tlock(lid);
                next = tlck->next;

                jfs_info("unlocking lid = %d, tlck = 0x%p", lid, tlck);

                /* unbind page from tlock */
                if ((mp = tlck->mp) != NULL &&
                    (tlck->type & tlckBTROOT) == 0) {
                        assert(mp->xflag & COMMIT_PAGE);

                        /* hold buffer
                         */
                        hold_metapage(mp);

                        assert(mp->nohomeok > 0);
                        _metapage_homeok(mp);

                        /* inherit younger/larger clsn */
                        LOGSYNC_LOCK(log, flags);
                        if (mp->clsn) {
                                logdiff(difft, tblk->clsn, log);
                                logdiff(diffp, mp->clsn, log);
                                if (difft > diffp)
                                        mp->clsn = tblk->clsn;
                        } else
                                mp->clsn = tblk->clsn;
                        LOGSYNC_UNLOCK(log, flags);

                        assert(!(tlck->flag & tlckFREEPAGE));

                        put_metapage(mp);
                }

                /* insert tlock, and linelock(s) of the tlock if any,
                 * at head of freelist
                 */
                TXN_LOCK();

                llid = ((struct linelock *) & tlck->lock)->next;
                while (llid) {
                        linelock = (struct linelock *) lid_to_tlock(llid);
                        k = linelock->next;
                        txLockFree(llid);
                        llid = k;
                }
                txLockFree(lid);

                TXN_UNLOCK();
        }
        tblk->next = tblk->last = 0;

        /*
         * remove tblock from logsynclist
         * (allocation map pages inherited lsn of tblk and
         * has been inserted in logsync list at txUpdateMap())
         */
        if (tblk->lsn) {
                LOGSYNC_LOCK(log, flags);
                log->count--;
                list_del(&tblk->synclist);
                LOGSYNC_UNLOCK(log, flags);
        }
}

/*
 *      txMaplock()
 *
 * function: allocate a transaction lock for freed page/entry;
 *      for freed page, maplock is used as xtlock/dtlock type;
 */
struct tlock *txMaplock(tid_t tid, struct inode *ip, int type)
{
        struct jfs_inode_info *jfs_ip = JFS_IP(ip);
        lid_t lid;
        struct tblock *tblk;
        struct tlock *tlck;
        struct maplock *maplock;

        TXN_LOCK();

        /*
         * allocate a tlock
         */
        lid = txLockAlloc();
        tlck = lid_to_tlock(lid);

        /*
         * initialize tlock
         */
        tlck->tid = tid;

        /* bind the tlock and the object */
        tlck->flag = tlckINODELOCK;
        if (S_ISDIR(ip->i_mode))
                tlck->flag |= tlckDIRECTORY;
        tlck->ip = ip;
        tlck->mp = NULL;

        tlck->type = type;

        /*
         * enqueue transaction lock to transaction/inode
         */
        /* insert the tlock at tail of transaction tlock list */
        if (tid) {
                tblk = tid_to_tblock(tid);
                if (tblk->next)
                        lid_to_tlock(tblk->last)->next = lid;
                else
                        tblk->next = lid;
                tlck->next = 0;
                tblk->last = lid;
        }
        /* anonymous transaction:
         * insert the tlock at head of inode anonymous tlock list
         */
        else {
                tlck->next = jfs_ip->atlhead;
                jfs_ip->atlhead = lid;
                if (tlck->next == 0) {
                        /* This inode's first anonymous transaction */
                        jfs_ip->atltail = lid;
                        list_add_tail(&jfs_ip->anon_inode_list,
                                      &TxAnchor.anon_list);
                }
        }

        TXN_UNLOCK();

        /* initialize type dependent area for maplock */
        maplock = (struct maplock *) & tlck->lock;
        maplock->next = 0;
        maplock->maxcnt = 0;
        maplock->index = 0;

        return tlck;
}

/*
 *      txLinelock()
 *
 * function: allocate a transaction lock for log vector list
 */
struct linelock *txLinelock(struct linelock * tlock)
{
        lid_t lid;
        struct tlock *tlck;
        struct linelock *linelock;

        TXN_LOCK();

        /* allocate a TxLock structure */
        lid = txLockAlloc();
        tlck = lid_to_tlock(lid);

        TXN_UNLOCK();

        /* initialize linelock */
        linelock = (struct linelock *) tlck;
        linelock->next = 0;
        linelock->flag = tlckLINELOCK;
        linelock->maxcnt = TLOCKLONG;
        linelock->index = 0;
        if (tlck->flag & tlckDIRECTORY)
                linelock->flag |= tlckDIRECTORY;

        /* append linelock after tlock */
        linelock->next = tlock->next;
        tlock->next = lid;

        return linelock;
}

/*
 *              transaction commit management
 *              -----------------------------
 */

/*
 * NAME:        txCommit()
 *
 * FUNCTION:    commit the changes to the objects specified in
 *              clist.  For journalled segments only the
 *              changes of the caller are committed, ie by tid.
 *              for non-journalled segments the data are flushed to
 *              disk and then the change to the disk inode and indirect
 *              blocks committed (so blocks newly allocated to the
 *              segment will be made a part of the segment atomically).
 *
 *              all of the segments specified in clist must be in
 *              one file system. no more than 6 segments are needed
 *              to handle all unix svcs.
 *
 *              if the i_nlink field (i.e. disk inode link count)
 *              is zero, and the type of inode is a regular file or
 *              directory, or symbolic link , the inode is truncated
 *              to zero length. the truncation is committed but the
 *              VM resources are unaffected until it is closed (see
 *              iput and iclose).
 *
 * PARAMETER:
 *
 * RETURN:
 *
 * serialization:
 *              on entry the inode lock on each segment is assumed
 *              to be held.
 *
 * i/o error:
 */
int txCommit(tid_t tid,         /* transaction identifier */
             int nip,           /* number of inodes to commit */
             struct inode **iplist,     /* list of inode to commit */
             int flag)
{
        int rc = 0;
        struct commit cd;
        struct jfs_log *log;
        struct tblock *tblk;
        struct lrd *lrd;
        int lsn;
        struct inode *ip;
        struct jfs_inode_info *jfs_ip;
        int k, n;
        ino_t top;
        struct super_block *sb;

        jfs_info("txCommit, tid = %d, flag = %d", tid, flag);
        /* is read-only file system ? */
        if (isReadOnly(iplist[0])) {
                rc = -EROFS;
                goto TheEnd;
        }

        sb = cd.sb = iplist[0]->i_sb;
        cd.tid = tid;

        if (tid == 0)
                tid = txBegin(sb, 0);
        tblk = tid_to_tblock(tid);

        /*
         * initialize commit structure
         */
        log = JFS_SBI(sb)->log;
        cd.log = log;

        /* initialize log record descriptor in commit */
        lrd = &cd.lrd;
        lrd->logtid = cpu_to_le32(tblk->logtid);
        lrd->backchain = 0;

        tblk->xflag |= flag;

        if ((flag & (COMMIT_FORCE | COMMIT_SYNC)) == 0)
                tblk->xflag |= COMMIT_LAZY;
        /*
         *      prepare non-journaled objects for commit
         *
         * flush data pages of non-journaled file
         * to prevent the file getting non-initialized disk blocks
         * in case of crash.
         * (new blocks - )
         */
        cd.iplist = iplist;
        cd.nip = nip;

        /*
         *      acquire transaction lock on (on-disk) inodes
         *
         * update on-disk inode from in-memory inode
         * acquiring transaction locks for AFTER records
         * on the on-disk inode of file object
         *
         * sort the inodes array by inode number in descending order
         * to prevent deadlock when acquiring transaction lock
         * of on-disk inodes on multiple on-disk inode pages by
         * multiple concurrent transactions
         */
        for (k = 0; k < cd.nip; k++) {
                top = (cd.iplist[k])->i_ino;
                for (n = k + 1; n < cd.nip; n++) {
                        ip = cd.iplist[n];
                        if (ip->i_ino > top) {
                                top = ip->i_ino;
                                cd.iplist[n] = cd.iplist[k];
                                cd.iplist[k] = ip;
                        }
                }

                ip = cd.iplist[k];
                jfs_ip = JFS_IP(ip);

                /*
                 * BUGBUG - This code has temporarily been removed.  The
                 * intent is to ensure that any file data is written before
                 * the metadata is committed to the journal.  This prevents
                 * uninitialized data from appearing in a file after the
                 * journal has been replayed.  (The uninitialized data
                 * could be sensitive data removed by another user.)
                 *
                 * The problem now is that we are holding the IWRITELOCK
                 * on the inode, and calling filemap_fdatawrite on an
                 * unmapped page will cause a deadlock in jfs_get_block.
                 *
                 * The long term solution is to pare down the use of
                 * IWRITELOCK.  We are currently holding it too long.
                 * We could also be smarter about which data pages need
                 * to be written before the transaction is committed and
                 * when we don't need to worry about it at all.
                 *
                 * if ((!S_ISDIR(ip->i_mode))
                 *    && (tblk->flag & COMMIT_DELETE) == 0)
                 *      filemap_write_and_wait(ip->i_mapping);
                 */

                /*
                 * Mark inode as not dirty.  It will still be on the dirty
                 * inode list, but we'll know not to commit it again unless
                 * it gets marked dirty again
                 */
                clear_cflag(COMMIT_Dirty, ip);

                /* inherit anonymous tlock(s) of inode */
                if (jfs_ip->atlhead) {
                        lid_to_tlock(jfs_ip->atltail)->next = tblk->next;
                        tblk->next = jfs_ip->atlhead;
                        if (!tblk->last)
                                tblk->last = jfs_ip->atltail;
                        jfs_ip->atlhead = jfs_ip->atltail = 0;
                        TXN_LOCK();
                        list_del_init(&jfs_ip->anon_inode_list);
                        TXN_UNLOCK();
                }

                /*
                 * acquire transaction lock on on-disk inode page
                 * (become first tlock of the tblk's tlock list)
                 */
                if (((rc = diWrite(tid, ip))))
                        goto out;
        }

        /*
         *      write log records from transaction locks
         *
         * txUpdateMap() resets XAD_NEW in XAD.
         */
        if ((rc = txLog(log, tblk, &cd)))
                goto TheEnd;

        /*
         * Ensure that inode isn't reused before
         * lazy commit thread finishes processing
         */
        if (tblk->xflag & COMMIT_DELETE) {
                atomic_inc(&tblk->u.ip->i_count);
                /*
                 * Avoid a rare deadlock
                 *
                 * If the inode is locked, we may be blocked in
                 * jfs_commit_inode.  If so, we don't want the
                 * lazy_commit thread doing the last iput() on the inode
                 * since that may block on the locked inode.  Instead,
                 * commit the transaction synchronously, so the last iput
                 * will be done by the calling thread (or later)
                 */
                if (tblk->u.ip->i_state & I_LOCK)
                        tblk->xflag &= ~COMMIT_LAZY;
        }

        ASSERT((!(tblk->xflag & COMMIT_DELETE)) ||
               ((tblk->u.ip->i_nlink == 0) &&
                !test_cflag(COMMIT_Nolink, tblk->u.ip)));

        /*
         *      write COMMIT log record
         */
        lrd->type = cpu_to_le16(LOG_COMMIT);
        lrd->length = 0;
        lsn = lmLog(log, tblk, lrd, NULL);

        lmGroupCommit(log, tblk);

        /*
         *      - transaction is now committed -
         */

        /*
         * force pages in careful update
         * (imap addressing structure update)
         */
        if (flag & COMMIT_FORCE)
                txForce(tblk);

        /*
         *      update allocation map.
         *
         * update inode allocation map and inode:
         * free pager lock on memory object of inode if any.
         * update  block allocation map.
         *
         * txUpdateMap() resets XAD_NEW in XAD.
         */
        if (tblk->xflag & COMMIT_FORCE)
                txUpdateMap(tblk);

        /*
         *      free transaction locks and pageout/free pages
         */
        txRelease(tblk);

        if ((tblk->flag & tblkGC_LAZY) == 0)
                txUnlock(tblk);


        /*
         *      reset in-memory object state
         */
        for (k = 0; k < cd.nip; k++) {
                ip = cd.iplist[k];
                jfs_ip = JFS_IP(ip);

                /*
                 * reset in-memory inode state
                 */
                jfs_ip->bxflag = 0;
                jfs_ip->blid = 0;
        }

      out:
        if (rc != 0)
                txAbort(tid, 1);

      TheEnd:
        jfs_info("txCommit: tid = %d, returning %d", tid, rc);
        return rc;
}

/*
 * NAME:        txLog()
 *
 * FUNCTION:    Writes AFTER log records for all lines modified
 *              by tid for segments specified by inodes in comdata.
 *              Code assumes only WRITELOCKS are recorded in lockwords.
 *
 * PARAMETERS:
 *
 * RETURN :
 */
static int txLog(struct jfs_log * log, struct tblock * tblk, struct commit * cd)
{
        int rc = 0;
        struct inode *ip;
        lid_t lid;
        struct tlock *tlck;
        struct lrd *lrd = &cd->lrd;

        /*
         * write log record(s) for each tlock of transaction,
         */
        for (lid = tblk->next; lid; lid = tlck->next) {
                tlck = lid_to_tlock(lid);

                tlck->flag |= tlckLOG;

                /* initialize lrd common */
                ip = tlck->ip;
                lrd->aggregate = cpu_to_le32(JFS_SBI(ip->i_sb)->aggregate);
                lrd->log.redopage.fileset = cpu_to_le32(JFS_IP(ip)->fileset);
                lrd->log.redopage.inode = cpu_to_le32(ip->i_ino);

                /* write log record of page from the tlock */
                switch (tlck->type & tlckTYPE) {
                case tlckXTREE:
                        xtLog(log, tblk, lrd, tlck);
                        break;

                case tlckDTREE:
                        dtLog(log, tblk, lrd, tlck);
                        break;

                case tlckINODE:
                        diLog(log, tblk, lrd, tlck, cd);
                        break;

                case tlckMAP:
                        mapLog(log, tblk, lrd, tlck);
                        break;

                case tlckDATA:
                        dataLog(log, tblk, lrd, tlck);
                        break;

                default:
                        jfs_err("UFO tlock:0x%p", tlck);
                }
        }

        return rc;
}

/*
 *      diLog()
 *
 * function:    log inode tlock and format maplock to update bmap;
 */
static int diLog(struct jfs_log * log, struct tblock * tblk, struct lrd * lrd,
          struct tlock * tlck, struct commit * cd)
{
        int rc = 0;
        struct metapage *mp;
        pxd_t *pxd;
        struct pxd_lock *pxdlock;

        mp = tlck->mp;

        /* initialize as REDOPAGE record format */
        lrd->log.redopage.type = cpu_to_le16(LOG_INODE);
        lrd->log.redopage.l2linesize = cpu_to_le16(L2INODESLOTSIZE);

        pxd = &lrd->log.redopage.pxd;

        /*
         *      inode after image
         */
        if (tlck->type & tlckENTRY) {
                /* log after-image for logredo(): */
                lrd->type = cpu_to_le16(LOG_REDOPAGE);
                PXDaddress(pxd, mp->index);
                PXDlength(pxd,
                          mp->logical_size >> tblk->sb->s_blocksize_bits);
                lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, tlck));

                /* mark page as homeward bound */
                tlck->flag |= tlckWRITEPAGE;
        } else if (tlck->type & tlckFREE) {
                /*
                 *      free inode extent
                 *
                 * (pages of the freed inode extent have been invalidated and
                 * a maplock for free of the extent has been formatted at
                 * txLock() time);
                 *
                 * the tlock had been acquired on the inode allocation map page
                 * (iag) that specifies the freed extent, even though the map
                 * page is not itself logged, to prevent pageout of the map
                 * page before the log;
                 */

                /* log LOG_NOREDOINOEXT of the freed inode extent for
                 * logredo() to start NoRedoPage filters, and to update
                 * imap and bmap for free of the extent;
                 */
                lrd->type = cpu_to_le16(LOG_NOREDOINOEXT);
                /*
                 * For the LOG_NOREDOINOEXT record, we need
                 * to pass the IAG number and inode extent
                 * index (within that IAG) from which the
                 * the extent being released.  These have been
                 * passed to us in the iplist[1] and iplist[2].
                 */
                lrd->log.noredoinoext.iagnum =
                    cpu_to_le32((u32) (size_t) cd->iplist[1]);
                lrd->log.noredoinoext.inoext_idx =
                    cpu_to_le32((u32) (size_t) cd->iplist[2]);

                pxdlock = (struct pxd_lock *) & tlck->lock;
                *pxd = pxdlock->pxd;
                lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, NULL));

                /* update bmap */
                tlck->flag |= tlckUPDATEMAP;

                /* mark page as homeward bound */
                tlck->flag |= tlckWRITEPAGE;
        } else
                jfs_err("diLog: UFO type tlck:0x%p", tlck);
#ifdef  _JFS_WIP
        /*
         *      alloc/free external EA extent
         *
         * a maplock for txUpdateMap() to update bPWMAP for alloc/free
         * of the extent has been formatted at txLock() time;
         */
        else {
                assert(tlck->type & tlckEA);

                /* log LOG_UPDATEMAP for logredo() to update bmap for
                 * alloc of new (and free of old) external EA extent;
                 */
                lrd->type = cpu_to_le16(LOG_UPDATEMAP);
                pxdlock = (struct pxd_lock *) & tlck->lock;
                nlock = pxdlock->index;
                for (i = 0; i < nlock; i++, pxdlock++) {
                        if (pxdlock->flag & mlckALLOCPXD)
                                lrd->log.updatemap.type =
                                    cpu_to_le16(LOG_ALLOCPXD);
                        else
                                lrd->log.updatemap.type =
                                    cpu_to_le16(LOG_FREEPXD);
                        lrd->log.updatemap.nxd = cpu_to_le16(1);
                        lrd->log.updatemap.pxd = pxdlock->pxd;
                        lrd->backchain =
                            cpu_to_le32(lmLog(log, tblk, lrd, NULL));
                }

                /* update bmap */
                tlck->flag |= tlckUPDATEMAP;
        }
#endif                          /* _JFS_WIP */

        return rc;
}

/*
 *      dataLog()
 *
 * function:    log data tlock
 */
static int dataLog(struct jfs_log * log, struct tblock * tblk, struct lrd * lrd,
            struct tlock * tlck)
{
        struct metapage *mp;
        pxd_t *pxd;

        mp = tlck->mp;

        /* initialize as REDOPAGE record format */
        lrd->log.redopage.type = cpu_to_le16(LOG_DATA);
        lrd->log.redopage.l2linesize = cpu_to_le16(L2DATASLOTSIZE);

        pxd = &lrd->log.redopage.pxd;

        /* log after-image for logredo(): */
        lrd->type = cpu_to_le16(LOG_REDOPAGE);

        if (jfs_dirtable_inline(tlck->ip)) {
                /*
                 * The table has been truncated, we've must have deleted
                 * the last entry, so don't bother logging this
                 */
                mp->lid = 0;
                grab_metapage(mp);
                metapage_homeok(mp);
                discard_metapage(mp);
                tlck->mp = NULL;
                return 0;
        }

        PXDaddress(pxd, mp->index);
        PXDlength(pxd, mp->logical_size >> tblk->sb->s_blocksize_bits);

        lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, tlck));

        /* mark page as homeward bound */
        tlck->flag |= tlckWRITEPAGE;

        return 0;
}

/*
 *      dtLog()
 *
 * function:    log dtree tlock and format maplock to update bmap;
 */
static void dtLog(struct jfs_log * log, struct tblock * tblk, struct lrd * lrd,
           struct tlock * tlck)
{
        struct metapage *mp;
        struct pxd_lock *pxdlock;
        pxd_t *pxd;

        mp = tlck->mp;

        /* initialize as REDOPAGE/NOREDOPAGE record format */
        lrd->log.redopage.type = cpu_to_le16(LOG_DTREE);
        lrd->log.redopage.l2linesize = cpu_to_le16(L2DTSLOTSIZE);

        pxd = &lrd->log.redopage.pxd;

        if (tlck->type & tlckBTROOT)
                lrd->log.redopage.type |= cpu_to_le16(LOG_BTROOT);

        /*
         *      page extension via relocation: entry insertion;
         *      page extension in-place: entry insertion;
         *      new right page from page split, reinitialized in-line
         *      root from root page split: entry insertion;
         */
        if (tlck->type & (tlckNEW | tlckEXTEND)) {
                /* log after-image of the new page for logredo():
                 * mark log (LOG_NEW) for logredo() to initialize
                 * freelist and update bmap for alloc of the new page;
                 */
                lrd->type = cpu_to_le16(LOG_REDOPAGE);
                if (tlck->type & tlckEXTEND)
                        lrd->log.redopage.type |= cpu_to_le16(LOG_EXTEND);
                else
                        lrd->log.redopage.type |= cpu_to_le16(LOG_NEW);
                PXDaddress(pxd, mp->index);
                PXDlength(pxd,
                          mp->logical_size >> tblk->sb->s_blocksize_bits);
                lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, tlck));

                /* format a maplock for txUpdateMap() to update bPMAP for
                 * alloc of the new page;
                 */
                if (tlck->type & tlckBTROOT)
                        return;
                tlck->flag |= tlckUPDATEMAP;
                pxdlock = (struct pxd_lock *) & tlck->lock;
                pxdlock->flag = mlckALLOCPXD;
                pxdlock->pxd = *pxd;

                pxdlock->index = 1;

                /* mark page as homeward bound */
                tlck->flag |= tlckWRITEPAGE;
                return;
        }

        /*
         *      entry insertion/deletion,
         *      sibling page link update (old right page before split);
         */
        if (tlck->type & (tlckENTRY | tlckRELINK)) {
                /* log after-image for logredo(): */
                lrd->type = cpu_to_le16(LOG_REDOPAGE);
                PXDaddress(pxd, mp->index);
                PXDlength(pxd,
                          mp->logical_size >> tblk->sb->s_blocksize_bits);
                lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, tlck));

                /* mark page as homeward bound */
                tlck->flag |= tlckWRITEPAGE;
                return;
        }

        /*
         *      page deletion: page has been invalidated
         *      page relocation: source extent
         *
         *      a maplock for free of the page has been formatted
         *      at txLock() time);
         */
        if (tlck->type & (tlckFREE | tlckRELOCATE)) {
                /* log LOG_NOREDOPAGE of the deleted page for logredo()
                 * to start NoRedoPage filter and to update bmap for free
                 * of the deletd page
                 */
                lrd->type = cpu_to_le16(LOG_NOREDOPAGE);
                pxdlock = (struct pxd_lock *) & tlck->lock;
                *pxd = pxdlock->pxd;
                lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, NULL));

                /* a maplock for txUpdateMap() for free of the page
                 * has been formatted at txLock() time;
                 */
                tlck->flag |= tlckUPDATEMAP;
        }
        return;
}

/*
 *      xtLog()
 *
 * function:    log xtree tlock and format maplock to update bmap;
 */
static void xtLog(struct jfs_log * log, struct tblock * tblk, struct lrd * lrd,
           struct tlock * tlck)
{
        struct inode *ip;
        struct metapage *mp;
        xtpage_t *p;
        struct xtlock *xtlck;
        struct maplock *maplock;
        struct xdlistlock *xadlock;
        struct pxd_lock *pxdlock;
        pxd_t *page_pxd;
        int next, lwm, hwm;

        ip = tlck->ip;
        mp = tlck->mp;

        /* initialize as REDOPAGE/NOREDOPAGE record format */
        lrd->log.redopage.type = cpu_to_le16(LOG_XTREE);
        lrd->log.redopage.l2linesize = cpu_to_le16(L2XTSLOTSIZE);

        page_pxd = &lrd->log.redopage.pxd;

        if (tlck->type & tlckBTROOT) {
                lrd->log.redopage.type |= cpu_to_le16(LOG_BTROOT);
                p = &JFS_IP(ip)->i_xtroot;
                if (S_ISDIR(ip->i_mode))
                        lrd->log.redopage.type |=
                            cpu_to_le16(LOG_DIR_XTREE);
        } else
                p = (xtpage_t *) mp->data;
        next = le16_to_cpu(p->header.nextindex);

        xtlck = (struct xtlock *) & tlck->lock;

        maplock = (struct maplock *) & tlck->lock;
        xadlock = (struct xdlistlock *) maplock;

        /*
         *      entry insertion/extension;
         *      sibling page link update (old right page before split);
         */
        if (tlck->type & (tlckNEW | tlckGROW | tlckRELINK)) {
                /* log after-image for logredo():
                 * logredo() will update bmap for alloc of new/extended
                 * extents (XAD_NEW|XAD_EXTEND) of XAD[lwm:next) from
                 * after-image of XADlist;
                 * logredo() resets (XAD_NEW|XAD_EXTEND) flag when
                 * applying the after-image to the meta-data page.
                 */
                lrd->type = cpu_to_le16(LOG_REDOPAGE);
                PXDaddress(page_pxd, mp->index);
                PXDlength(page_pxd,
                          mp->logical_size >> tblk->sb->s_blocksize_bits);
                lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, tlck));

                /* format a maplock for txUpdateMap() to update bPMAP
                 * for alloc of new/extended extents of XAD[lwm:next)
                 * from the page itself;
                 * txUpdateMap() resets (XAD_NEW|XAD_EXTEND) flag.
                 */
                lwm = xtlck->lwm.offset;
                if (lwm == 0)
                        lwm = XTPAGEMAXSLOT;

                if (lwm == next)
                        goto out;
                if (lwm > next) {
                        jfs_err("xtLog: lwm > next\n");
                        goto out;
                }
                tlck->flag |= tlckUPDATEMAP;
                xadlock->flag = mlckALLOCXADLIST;
                xadlock->count = next - lwm;
                if ((xadlock->count <= 4) && (tblk->xflag & COMMIT_LAZY)) {
                        int i;
                        pxd_t *pxd;
                        /*
                         * Lazy commit may allow xtree to be modified before
                         * txUpdateMap runs.  Copy xad into linelock to
                         * preserve correct data.
                         *
                         * We can fit twice as may pxd's as xads in the lock
                         */
                        xadlock->flag = mlckALLOCPXDLIST;
                        pxd = xadlock->xdlist = &xtlck->pxdlock;
                        for (i = 0; i < xadlock->count; i++) {
                                PXDaddress(pxd, addressXAD(&p->xad[lwm + i]));
                                PXDlength(pxd, lengthXAD(&p->xad[lwm + i]));
                                p->xad[lwm + i].flag &=
                                    ~(XAD_NEW | XAD_EXTENDED);
                                pxd++;
                        }
                } else {
                        /*
                         * xdlist will point to into inode's xtree, ensure
                         * that transaction is not committed lazily.
                         */
                        xadlock->flag = mlckALLOCXADLIST;
                        xadlock->xdlist = &p->xad[lwm];
                        tblk->xflag &= ~COMMIT_LAZY;
                }
                jfs_info("xtLog: alloc ip:0x%p mp:0x%p tlck:0x%p lwm:%d "
                         "count:%d", tlck->ip, mp, tlck, lwm, xadlock->count);

                maplock->index = 1;

              out:
                /* mark page as homeward bound */
                tlck->flag |= tlckWRITEPAGE;

                return;
        }

        /*
         *      page deletion: file deletion/truncation (ref. xtTruncate())
         *
         * (page will be invalidated after log is written and bmap
         * is updated from the page);
         */
        if (tlck->type & tlckFREE) {
                /* LOG_NOREDOPAGE log for NoRedoPage filter:
                 * if page free from file delete, NoRedoFile filter from
                 * inode image of zero link count will subsume NoRedoPage
                 * filters for each page;
                 * if page free from file truncattion, write NoRedoPage
                 * filter;
                 *
                 * upadte of block allocation map for the page itself:
                 * if page free from deletion and truncation, LOG_UPDATEMAP
                 * log for the page itself is generated from processing
                 * its parent page xad entries;
                 */
                /* if page free from file truncation, log LOG_NOREDOPAGE
                 * of the deleted page for logredo() to start NoRedoPage
                 * filter for the page;
                 */
                if (tblk->xflag & COMMIT_TRUNCATE) {
                        /* write NOREDOPAGE for the page */
                        lrd->type = cpu_to_le16(LOG_NOREDOPAGE);
                        PXDaddress(page_pxd, mp->index);
                        PXDlength(page_pxd,
                                  mp->logical_size >> tblk->sb->
                                  s_blocksize_bits);
                        lrd->backchain =
                            cpu_to_le32(lmLog(log, tblk, lrd, NULL));

                        if (tlck->type & tlckBTROOT) {
                                /* Empty xtree must be logged */
                                lrd->type = cpu_to_le16(LOG_REDOPAGE);
                                lrd->backchain =
                                    cpu_to_le32(lmLog(log, tblk, lrd, tlck));
                        }
                }

                /* init LOG_UPDATEMAP of the freed extents
                 * XAD[XTENTRYSTART:hwm) from the deleted page itself
                 * for logredo() to update bmap;
                 */
                lrd->type = cpu_to_le16(LOG_UPDATEMAP);
                lrd->log.updatemap.type = cpu_to_le16(LOG_FREEXADLIST);
                xtlck = (struct xtlock *) & tlck->lock;
                hwm = xtlck->hwm.offset;
                lrd->log.updatemap.nxd =
                    cpu_to_le16(hwm - XTENTRYSTART + 1);
                /* reformat linelock for lmLog() */
                xtlck->header.offset = XTENTRYSTART;
                xtlck->header.length = hwm - XTENTRYSTART + 1;
                xtlck->index = 1;
                lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, tlck));

                /* format a maplock for txUpdateMap() to update bmap
                 * to free extents of XAD[XTENTRYSTART:hwm) from the
                 * deleted page itself;
                 */
                tlck->flag |= tlckUPDATEMAP;
                xadlock->count = hwm - XTENTRYSTART + 1;
                if ((xadlock->count <= 4) && (tblk->xflag & COMMIT_LAZY)) {
                        int i;
                        pxd_t *pxd;
                        /*
                         * Lazy commit may allow xtree to be modified before
                         * txUpdateMap runs.  Copy xad into linelock to
                         * preserve correct data.
                         *
                         * We can fit twice as may pxd's as xads in the lock
                         */
                        xadlock->flag = mlckFREEPXDLIST;
                        pxd = xadlock->xdlist = &xtlck->pxdlock;
                        for (i = 0; i < xadlock->count; i++) {
                                PXDaddress(pxd,
                                        addressXAD(&p->xad[XTENTRYSTART + i]));
                                PXDlength(pxd,
                                        lengthXAD(&p->xad[XTENTRYSTART + i]));
                                pxd++;
                        }
                } else {
                        /*
                         * xdlist will point to into inode's xtree, ensure
                         * that transaction is not committed lazily.
                         */
                        xadlock->flag = mlckFREEXADLIST;
                        xadlock->xdlist = &p->xad[XTENTRYSTART];
                        tblk->xflag &= ~COMMIT_LAZY;
                }
                jfs_info("xtLog: free ip:0x%p mp:0x%p count:%d lwm:2",
                         tlck->ip, mp, xadlock->count);

                maplock->index = 1;

                /* mark page as invalid */
                if (((tblk->xflag & COMMIT_PWMAP) || S_ISDIR(ip->i_mode))
                    && !(tlck->type & tlckBTROOT))
                        tlck->flag |= tlckFREEPAGE;
                /*
                   else (tblk->xflag & COMMIT_PMAP)
                   ? release the page;
                 */
                return;
        }

        /*
         *      page/entry truncation: file truncation (ref. xtTruncate())
         *
         *     |----------+------+------+---------------|
         *                |      |      |
         *                |      |     hwm - hwm before truncation
         *                |     next - truncation point
         *               lwm - lwm before truncation
         * header ?
         */
        if (tlck->type & tlckTRUNCATE) {
                pxd_t pxd;      /* truncated extent of xad */
                int twm;

                /*
                 * For truncation the entire linelock may be used, so it would
                 * be difficult to store xad list in linelock itself.
                 * Therefore, we'll just force transaction to be committed
                 * synchronously, so that xtree pages won't be changed before
                 * txUpdateMap runs.
                 */
                tblk->xflag &= ~COMMIT_LAZY;
                lwm = xtlck->lwm.offset;
                if (lwm == 0)
                        lwm = XTPAGEMAXSLOT;
                hwm = xtlck->hwm.offset;
                twm = xtlck->twm.offset;

                /*
                 *      write log records
                 */
                /* log after-image for logredo():
                 *
                 * logredo() will update bmap for alloc of new/extended
                 * extents (XAD_NEW|XAD_EXTEND) of XAD[lwm:next) from
                 * after-image of XADlist;
                 * logredo() resets (XAD_NEW|XAD_EXTEND) flag when
                 * applying the after-image to the meta-data page.
                 */
                lrd->type = cpu_to_le16(LOG_REDOPAGE);
                PXDaddress(page_pxd, mp->index);
                PXDlength(page_pxd,
                          mp->logical_size >> tblk->sb->s_blocksize_bits);
                lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, tlck));

                /*
                 * truncate entry XAD[twm == next - 1]:
                 */
                if (twm == next - 1) {
                        /* init LOG_UPDATEMAP for logredo() to update bmap for
                         * free of truncated delta extent of the truncated
                         * entry XAD[next - 1]:
                         * (xtlck->pxdlock = truncated delta extent);
                         */
                        pxdlock = (struct pxd_lock *) & xtlck->pxdlock;
                        /* assert(pxdlock->type & tlckTRUNCATE); */
                        lrd->type = cpu_to_le16(LOG_UPDATEMAP);
                        lrd->log.updatemap.type = cpu_to_le16(LOG_FREEPXD);
                        lrd->log.updatemap.nxd = cpu_to_le16(1);
                        lrd->log.updatemap.pxd = pxdlock->pxd;
                        pxd = pxdlock->pxd;     /* save to format maplock */
                        lrd->backchain =
                            cpu_to_le32(lmLog(log, tblk, lrd, NULL));
                }

                /*
                 * free entries XAD[next:hwm]:
                 */
                if (hwm >= next) {
                        /* init LOG_UPDATEMAP of the freed extents
                         * XAD[next:hwm] from the deleted page itself
                         * for logredo() to update bmap;
                         */
                        lrd->type = cpu_to_le16(LOG_UPDATEMAP);
                        lrd->log.updatemap.type =
                            cpu_to_le16(LOG_FREEXADLIST);
                        xtlck = (struct xtlock *) & tlck->lock;
                        hwm = xtlck->hwm.offset;
                        lrd->log.updatemap.nxd =
                            cpu_to_le16(hwm - next + 1);
                        /* reformat linelock for lmLog() */
                        xtlck->header.offset = next;
                        xtlck->header.length = hwm - next + 1;
                        xtlck->index = 1;
                        lrd->backchain =
                            cpu_to_le32(lmLog(log, tblk, lrd, tlck));
                }

                /*
                 *      format maplock(s) for txUpdateMap() to update bmap
                 */
                maplock->index = 0;

                /*
                 * allocate entries XAD[lwm:next):
                 */
                if (lwm < next) {
                        /* format a maplock for txUpdateMap() to update bPMAP
                         * for alloc of new/extended extents of XAD[lwm:next)
                         * from the page itself;
                         * txUpdateMap() resets (XAD_NEW|XAD_EXTEND) flag.
                         */
                        tlck->flag |= tlckUPDATEMAP;
                        xadlock->flag = mlckALLOCXADLIST;
                        xadlock->count = next - lwm;
                        xadlock->xdlist = &p->xad[lwm];

                        jfs_info("xtLog: alloc ip:0x%p mp:0x%p count:%d "
                                 "lwm:%d next:%d",
                                 tlck->ip, mp, xadlock->count, lwm, next);
                        maplock->index++;
                        xadlock++;
                }

                /*
                 * truncate entry XAD[twm == next - 1]:
                 */
                if (twm == next - 1) {
                        struct pxd_lock *pxdlock;

                        /* format a maplock for txUpdateMap() to update bmap
                         * to free truncated delta extent of the truncated
                         * entry XAD[next - 1];
                         * (xtlck->pxdlock = truncated delta extent);
                         */
                        tlck->flag |= tlckUPDATEMAP;
                        pxdlock = (struct pxd_lock *) xadlock;
                        pxdlock->flag = mlckFREEPXD;
                        pxdlock->count = 1;
                        pxdlock->pxd = pxd;

                        jfs_info("xtLog: truncate ip:0x%p mp:0x%p count:%d "
                                 "hwm:%d", ip, mp, pxdlock->count, hwm);
                        maplock->index++;
                        xadlock++;
                }

                /*
                 * free entries XAD[next:hwm]:
                 */
                if (hwm >= next) {
                        /* format a maplock for txUpdateMap() to update bmap
                         * to free extents of XAD[next:hwm] from thedeleted
                         * page itself;
                         */
                        tlck->flag |= tlckUPDATEMAP;
                        xadlock->flag = mlckFREEXADLIST;
                        xadlock->count = hwm - next + 1;
                        xadlock->xdlist = &p->xad[next];

                        jfs_info("xtLog: free ip:0x%p mp:0x%p count:%d "
                                 "next:%d hwm:%d",
                                 tlck->ip, mp, xadlock->count, next, hwm);
                        maplock->index++;
                }

                /* mark page as homeward bound */
                tlck->flag |= tlckWRITEPAGE;
        }
        return;
}

/*
 *      mapLog()
 *
 * function:    log from maplock of freed data extents;
 */
static void mapLog(struct jfs_log * log, struct tblock * tblk, struct lrd * lrd,
                   struct tlock * tlck)
{
        struct pxd_lock *pxdlock;
        int i, nlock;
        pxd_t *pxd;

        /*
         *      page relocation: free the source page extent
         *
         * a maplock for txUpdateMap() for free of the page
         * has been formatted at txLock() time saving the src
         * relocated page address;
         */
        if (tlck->type & tlckRELOCATE) {
                /* log LOG_NOREDOPAGE of the old relocated page
                 * for logredo() to start NoRedoPage filter;
                 */
                lrd->type = cpu_to_le16(LOG_NOREDOPAGE);
                pxdlock = (struct pxd_lock *) & tlck->lock;
                pxd = &lrd->log.redopage.pxd;
                *pxd = pxdlock->pxd;
                lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, NULL));

                /* (N.B. currently, logredo() does NOT update bmap
                 * for free of the page itself for (LOG_XTREE|LOG_NOREDOPAGE);
                 * if page free from relocation, LOG_UPDATEMAP log is
                 * specifically generated now for logredo()
                 * to update bmap for free of src relocated page;
                 * (new flag LOG_RELOCATE may be introduced which will
                 * inform logredo() to start NORedoPage filter and also
                 * update block allocation map at the same time, thus
                 * avoiding an extra log write);
                 */
                lrd->type = cpu_to_le16(LOG_UPDATEMAP);
                lrd->log.updatemap.type = cpu_to_le16(LOG_FREEPXD);
                lrd->log.updatemap.nxd = cpu_to_le16(1);
                lrd->log.updatemap.pxd = pxdlock->pxd;
                lrd->backchain = cpu_to_le32(lmLog(log, tblk, lrd, NULL));

                /* a maplock for txUpdateMap() for free of the page
                 * has been formatted at txLock() time;
                 */
                tlck->flag |= tlckUPDATEMAP;
                return;
        }
        /*

         * Otherwise it's not a relocate request
         *
         */
        else {
                /* log LOG_UPDATEMAP for logredo() to update bmap for
                 * free of truncated/relocated delta extent of the data;
                 * e.g.: external EA extent, relocated/truncated extent
                 * from xtTailgate();
                 */
                lrd->type = cpu_to_le16(LOG_UPDATEMAP);
                pxdlock = (struct pxd_lock *) & tlck->lock;
                nlock = pxdlock->index;
                for (i = 0; i < nlock; i++, pxdlock++) {
                        if (pxdlock->flag & mlckALLOCPXD)
                                lrd->log.updatemap.type =
                                    cpu_to_le16(LOG_ALLOCPXD);
                        else
                                lrd->log.updatemap.type =
                                    cpu_to_le16(LOG_FREEPXD);
                        lrd->log.updatemap.nxd = cpu_to_le16(1);
                        lrd->log.updatemap.pxd = pxdlock->pxd;
                        lrd->backchain =
                            cpu_to_le32(lmLog(log, tblk, lrd, NULL));
                        jfs_info("mapLog: xaddr:0x%lx xlen:0x%x",
                                 (ulong) addressPXD(&pxdlock->pxd),
                                 lengthPXD(&pxdlock->pxd));
                }

                /* update bmap */
                tlck->flag |= tlckUPDATEMAP;
        }
}

/*
 *      txEA()
 *
 * function:    acquire maplock for EA/ACL extents or
 *              set COMMIT_INLINE flag;
 */
void txEA(tid_t tid, struct inode *ip, dxd_t * oldea, dxd_t * newea)
{
        struct tlock *tlck = NULL;
        struct pxd_lock *maplock = NULL, *pxdlock = NULL;

        /*
         * format maplock for alloc of new EA extent
         */
        if (newea) {
                /* Since the newea could be a completely zeroed entry we need to
                 * check for the two flags which indicate we should actually
                 * commit new EA data
                 */
                if (newea->flag & DXD_EXTENT) {
                        tlck = txMaplock(tid, ip, tlckMAP);
                        maplock = (struct pxd_lock *) & tlck->lock;
                        pxdlock = (struct pxd_lock *) maplock;
                        pxdlock->flag = mlckALLOCPXD;
                        PXDaddress(&pxdlock->pxd, addressDXD(newea));
                        PXDlength(&pxdlock->pxd, lengthDXD(newea));
                        pxdlock++;
                        maplock->index = 1;
                } else if (newea->flag & DXD_INLINE) {
                        tlck = NULL;

                        set_cflag(COMMIT_Inlineea, ip);
                }
        }

        /*
         * format maplock for free of old EA extent
         */
        if (!test_cflag(COMMIT_Nolink, ip) && oldea->flag & DXD_EXTENT) {
                if (tlck == NULL) {
                        tlck = txMaplock(tid, ip, tlckMAP);
                        maplock = (struct pxd_lock *) & tlck->lock;
                        pxdlock = (struct pxd_lock *) maplock;
                        maplock->index = 0;
                }
                pxdlock->flag = mlckFREEPXD;
                PXDaddress(&pxdlock->pxd, addressDXD(oldea));
                PXDlength(&pxdlock->pxd, lengthDXD(oldea));
                maplock->index++;
        }
}

/*
 *      txForce()
 *
 * function: synchronously write pages locked by transaction
 *              after txLog() but before txUpdateMap();
 */
static void txForce(struct tblock * tblk)
{
        struct tlock *tlck;
        lid_t lid, next;
        struct metapage *mp;

        /*
         * reverse the order of transaction tlocks in
         * careful update order of address index pages
         * (right to left, bottom up)
         */
        tlck = lid_to_tlock(tblk->next);
        lid = tlck->next;
        tlck->next = 0;
        while (lid) {
                tlck = lid_to_tlock(lid);
                next = tlck->next;
                tlck->next = tblk->next;
                tblk->next = lid;
                lid = next;
        }

        /*
         * synchronously write the page, and
         * hold the page for txUpdateMap();
         */
        for (lid = tblk->next; lid; lid = next) {
                tlck = lid_to_tlock(lid);
                next = tlck->next;

                if ((mp = tlck->mp) != NULL &&
                    (tlck->type & tlckBTROOT) == 0) {
                        assert(mp->xflag & COMMIT_PAGE);

                        if (tlck->flag & tlckWRITEPAGE) {
                                tlck->flag &= ~tlckWRITEPAGE;

                                /* do not release page to freelist */
                                force_metapage(mp);
#if 0
                                /*
                                 * The "right" thing to do here is to
                                 * synchronously write the metadata.
                                 * With the current implementation this
                                 * is hard since write_metapage requires
                                 * us to kunmap & remap the page.  If we
                                 * have tlocks pointing into the metadata
                                 * pages, we don't want to do this.  I think
                                 * we can get by with synchronously writing
                                 * the pages when they are released.
                                 */
                                assert(mp->nohomeok);
                                set_bit(META_dirty, &mp->flag);
                                set_bit(META_sync, &mp->flag);
#endif
                        }
                }
        }
}

/*
 *      txUpdateMap()
 *
 * function:    update persistent allocation map (and working map
 *              if appropriate);
 *
 * parameter:
 */
static void txUpdateMap(struct tblock * tblk)
{
        struct inode *ip;
        struct inode *ipimap;
        lid_t lid;
        struct tlock *tlck;
        struct maplock *maplock;
        struct pxd_lock pxdlock;
        int maptype;
        int k, nlock;
        struct metapage *mp = NULL;

        ipimap = JFS_SBI(tblk->sb)->ipimap;

        maptype = (tblk->xflag & COMMIT_PMAP) ? COMMIT_PMAP : COMMIT_PWMAP;


        /*
         *      update block allocation map
         *
         * update allocation state in pmap (and wmap) and
         * update lsn of the pmap page;
         */
        /*
         * scan each tlock/page of transaction for block allocation/free:
         *
         * for each tlock/page of transaction, update map.
         *  ? are there tlock for pmap and pwmap at the same time ?
         */
        for (lid = tblk->next; lid; lid = tlck->next) {
                tlck = lid_to_tlock(lid);

                if ((tlck->flag & tlckUPDATEMAP) == 0)
                        continue;

                if (tlck->flag & tlckFREEPAGE) {
                        /*
                         * Another thread may attempt to reuse freed space
                         * immediately, so we want to get rid of the metapage
                         * before anyone else has a chance to get it.
                         * Lock metapage, update maps, then invalidate
                         * the metapage.
                         */
                        mp = tlck->mp;
                        ASSERT(mp->xflag & COMMIT_PAGE);
                        grab_metapage(mp);
                }

                /*
                 * extent list:
                 * . in-line PXD list:
                 * . out-of-line XAD list:
                 */
                maplock = (struct maplock *) & tlck->lock;
                nlock = maplock->index;

                for (k = 0; k < nlock; k++, maplock++) {
                        /*
                         * allocate blocks in persistent map:
                         *
                         * blocks have been allocated from wmap at alloc time;
                         */
                        if (maplock->flag & mlckALLOC) {
                                txAllocPMap(ipimap, maplock, tblk);
                        }
                        /*
                         * free blocks in persistent and working map:
                         * blocks will be freed in pmap and then in wmap;
                         *
                         * ? tblock specifies the PMAP/PWMAP based upon
                         * transaction
                         *
                         * free blocks in persistent map:
                         * blocks will be freed from wmap at last reference
                         * release of the object for regular files;
                         *
                         * Alway free blocks from both persistent & working
                         * maps for directories
                         */
                        else {  /* (maplock->flag & mlckFREE) */

                                if (tlck->flag & tlckDIRECTORY)
                                        txFreeMap(ipimap, maplock,
                                                  tblk, COMMIT_PWMAP);
                                else
                                        txFreeMap(ipimap, maplock,
                                                  tblk, maptype);
                        }
                }
                if (tlck->flag & tlckFREEPAGE) {
                        if (!(tblk->flag & tblkGC_LAZY)) {
                                /* This is equivalent to txRelease */
                                ASSERT(mp->lid == lid);
                                tlck->mp->lid = 0;
                        }
                        assert(mp->nohomeok == 1);
                        metapage_homeok(mp);
                        discard_metapage(mp);
                        tlck->mp = NULL;
                }
        }
        /*
         *      update inode allocation map
         *
         * update allocation state in pmap and
         * update lsn of the pmap page;
         * update in-memory inode flag/state
         *
         * unlock mapper/write lock
         */
        if (tblk->xflag & COMMIT_CREATE) {
                diUpdatePMap(ipimap, tblk->ino, FALSE, tblk);
                /* update persistent block allocation map
                 * for the allocation of inode extent;
                 */
                pxdlock.flag = mlckALLOCPXD;
                pxdlock.pxd = tblk->u.ixpxd;
                pxdlock.index = 1;
                txAllocPMap(ipimap, (struct maplock *) & pxdlock, tblk);
        } else if (tblk->xflag & COMMIT_DELETE) {
                ip = tblk->u.ip;
                diUpdatePMap(ipimap, ip->i_ino, TRUE, tblk);
                iput(ip);
        }
}

/*
 *      txAllocPMap()
 *
 * function: allocate from persistent map;
 *
 * parameter:
 *      ipbmap  -
 *      malock -
 *              xad list:
 *              pxd:
 *
 *      maptype -
 *              allocate from persistent map;
 *              free from persistent map;
 *              (e.g., tmp file - free from working map at releae
 *               of last reference);
 *              free from persistent and working map;
 *
 *      lsn     - log sequence number;
 */
static void txAllocPMap(struct inode *ip, struct maplock * maplock,
                        struct tblock * tblk)
{
        struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
        struct xdlistlock *xadlistlock;
        xad_t *xad;
        s64 xaddr;
        int xlen;
        struct pxd_lock *pxdlock;
        struct xdlistlock *pxdlistlock;
        pxd_t *pxd;
        int n;

        /*
         * allocate from persistent map;
         */
        if (maplock->flag & mlckALLOCXADLIST) {
                xadlistlock = (struct xdlistlock *) maplock;
                xad = xadlistlock->xdlist;
                for (n = 0; n < xadlistlock->count; n++, xad++) {
                        if (xad->flag & (XAD_NEW | XAD_EXTENDED)) {
                                xaddr = addressXAD(xad);
                                xlen = lengthXAD(xad);
                                dbUpdatePMap(ipbmap, FALSE, xaddr,
                                             (s64) xlen, tblk);
                                xad->flag &= ~(XAD_NEW | XAD_EXTENDED);
                                jfs_info("allocPMap: xaddr:0x%lx xlen:%d",
                                         (ulong) xaddr, xlen);
                        }
                }
        } else if (maplock->flag & mlckALLOCPXD) {
                pxdlock = (struct pxd_lock *) maplock;
                xaddr = addressPXD(&pxdlock->pxd);
                xlen = lengthPXD(&pxdlock->pxd);
                dbUpdatePMap(ipbmap, FALSE, xaddr, (s64) xlen, tblk);
                jfs_info("allocPMap: xaddr:0x%lx xlen:%d", (ulong) xaddr, xlen);
        } else {                /* (maplock->flag & mlckALLOCPXDLIST) */

                pxdlistlock = (struct xdlistlock *) maplock;
                pxd = pxdlistlock->xdlist;
                for (n = 0; n < pxdlistlock->count; n++, pxd++) {
                        xaddr = addressPXD(pxd);
                        xlen = lengthPXD(pxd);
                        dbUpdatePMap(ipbmap, FALSE, xaddr, (s64) xlen,
                                     tblk);
                        jfs_info("allocPMap: xaddr:0x%lx xlen:%d",
                                 (ulong) xaddr, xlen);
                }
        }
}

/*
 *      txFreeMap()
 *
 * function:    free from persistent and/or working map;
 *
 * todo: optimization
 */
void txFreeMap(struct inode *ip,
               struct maplock * maplock, struct tblock * tblk, int maptype)
{
        struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
        struct xdlistlock *xadlistlock;
        xad_t *xad;
        s64 xaddr;
        int xlen;
        struct pxd_lock *pxdlock;
        struct xdlistlock *pxdlistlock;
        pxd_t *pxd;
        int n;

        jfs_info("txFreeMap: tblk:0x%p maplock:0x%p maptype:0x%x",
                 tblk, maplock, maptype);

        /*
         * free from persistent map;
         */
        if (maptype == COMMIT_PMAP || maptype == COMMIT_PWMAP) {
                if (maplock->flag & mlckFREEXADLIST) {
                        xadlistlock = (struct xdlistlock *) maplock;
                        xad = xadlistlock->xdlist;
                        for (n = 0; n < xadlistlock->count; n++, xad++) {
                                if (!(xad->flag & XAD_NEW)) {
                                        xaddr = addressXAD(xad);
                                        xlen = lengthXAD(xad);
                                        dbUpdatePMap(ipbmap, TRUE, xaddr,
                                                     (s64) xlen, tblk);
                                        jfs_info("freePMap: xaddr:0x%lx "
                                                 "xlen:%d",
                                                 (ulong) xaddr, xlen);
                                }
                        }
                } else if (maplock->flag & mlckFREEPXD) {
                        pxdlock = (struct pxd_lock *) maplock;
                        xaddr = addressPXD(&pxdlock->pxd);
                        xlen = lengthPXD(&pxdlock->pxd);
                        dbUpdatePMap(ipbmap, TRUE, xaddr, (s64) xlen,
                                     tblk);
                        jfs_info("freePMap: xaddr:0x%lx xlen:%d",
                                 (ulong) xaddr, xlen);
                } else {        /* (maplock->flag & mlckALLOCPXDLIST) */

                        pxdlistlock = (struct xdlistlock *) maplock;
                        pxd = pxdlistlock->xdlist;
                        for (n = 0; n < pxdlistlock->count; n++, pxd++) {
                                xaddr = addressPXD(pxd);
                                xlen = lengthPXD(pxd);
                                dbUpdatePMap(ipbmap, TRUE, xaddr,
                                             (s64) xlen, tblk);
                                jfs_info("freePMap: xaddr:0x%lx xlen:%d",
                                         (ulong) xaddr, xlen);
                        }
                }
        }

        /*
         * free from working map;
         */
        if (maptype == COMMIT_PWMAP || maptype == COMMIT_WMAP) {
                if (maplock->flag & mlckFREEXADLIST) {
                        xadlistlock = (struct xdlistlock *) maplock;
                        xad = xadlistlock->xdlist;
                        for (n = 0; n < xadlistlock->count; n++, xad++) {
                                xaddr = addressXAD(xad);
                                xlen = lengthXAD(xad);
                                dbFree(ip, xaddr, (s64) xlen);
                                xad->flag = 0;
                                jfs_info("freeWMap: xaddr:0x%lx xlen:%d",
                                         (ulong) xaddr, xlen);
                        }
                } else if (maplock->flag & mlckFREEPXD) {
                        pxdlock = (struct pxd_lock *) maplock;
                        xaddr = addressPXD(&pxdlock->pxd);
                        xlen = lengthPXD(&pxdlock->pxd);
                        dbFree(ip, xaddr, (s64) xlen);
                        jfs_info("freeWMap: xaddr:0x%lx xlen:%d",
                                 (ulong) xaddr, xlen);
                } else {        /* (maplock->flag & mlckFREEPXDLIST) */

                        pxdlistlock = (struct xdlistlock *) maplock;
                        pxd = pxdlistlock->xdlist;
                        for (n = 0; n < pxdlistlock->count; n++, pxd++) {
                                xaddr = addressPXD(pxd);
                                xlen = lengthPXD(pxd);
                                dbFree(ip, xaddr, (s64) xlen);
                                jfs_info("freeWMap: xaddr:0x%lx xlen:%d",
                                         (ulong) xaddr, xlen);
                        }
                }
        }
}

/*
 *      txFreelock()
 *
 * function:    remove tlock from inode anonymous locklist
 */
void txFreelock(struct inode *ip)
{
        struct jfs_inode_info *jfs_ip = JFS_IP(ip);
        struct tlock *xtlck, *tlck;
        lid_t xlid = 0, lid;

        if (!jfs_ip->atlhead)
                return;

        TXN_LOCK();
        xtlck = (struct tlock *) &jfs_ip->atlhead;

        while ((lid = xtlck->next) != 0) {
                tlck = lid_to_tlock(lid);
                if (tlck->flag & tlckFREELOCK) {
                        xtlck->next = tlck->next;
                        txLockFree(lid);
                } else {
                        xtlck = tlck;
                        xlid = lid;
                }
        }

        if (jfs_ip->atlhead)
                jfs_ip->atltail = xlid;
        else {
                jfs_ip->atltail = 0;
                /*
                 * If inode was on anon_list, remove it
                 */
                list_del_init(&jfs_ip->anon_inode_list);
        }
        TXN_UNLOCK();
}

/*
 *      txAbort()
 *
 * function: abort tx before commit;
 *
 * frees line-locks and segment locks for all
 * segments in comdata structure.
 * Optionally sets state of file-system to FM_DIRTY in super-block.
 * log age of page-frames in memory for which caller has
 * are reset to 0 (to avoid logwarap).
 */
void txAbort(tid_t tid, int dirty)
{
        lid_t lid, next;
        struct metapage *mp;
        struct tblock *tblk = tid_to_tblock(tid);
        struct tlock *tlck;

        /*
         * free tlocks of the transaction
         */
        for (lid = tblk->next; lid; lid = next) {
                tlck = lid_to_tlock(lid);
                next = tlck->next;
                mp = tlck->mp;
                JFS_IP(tlck->ip)->xtlid = 0;

                if (mp) {
                        mp->lid = 0;

                        /*
                         * reset lsn of page to avoid logwarap:
                         *
                         * (page may have been previously committed by another
                         * transaction(s) but has not been paged, i.e.,
                         * it may be on logsync list even though it has not
                         * been logged for the current tx.)
                         */
                        if (mp->xflag & COMMIT_PAGE && mp->lsn)
                                LogSyncRelease(mp);
                }
                /* insert tlock at head of freelist */
                TXN_LOCK();
                txLockFree(lid);
                TXN_UNLOCK();
        }

        /* caller will free the transaction block */

        tblk->next = tblk->last = 0;

        /*
         * mark filesystem dirty
         */
        if (dirty)
                jfs_error(tblk->sb, "txAbort");

        return;
}

/*
 *      txLazyCommit(void)
 *
 *      All transactions except those changing ipimap (COMMIT_FORCE) are
 *      processed by this routine.  This insures that the inode and block
 *      allocation maps are updated in order.  For synchronous transactions,
 *      let the user thread finish processing after txUpdateMap() is called.
 */
static void txLazyCommit(struct tblock * tblk)
{
        struct jfs_log *log;

        while (((tblk->flag & tblkGC_READY) == 0) &&
               ((tblk->flag & tblkGC_UNLOCKED) == 0)) {
                /* We must have gotten ahead of the user thread
                 */
                jfs_info("jfs_lazycommit: tblk 0x%p not unlocked", tblk);
                yield();
        }

        jfs_info("txLazyCommit: processing tblk 0x%p", tblk);

        txUpdateMap(tblk);

        log = (struct jfs_log *) JFS_SBI(tblk->sb)->log;

        spin_lock_irq(&log->gclock);    // LOGGC_LOCK

        tblk->flag |= tblkGC_COMMITTED;

        if (tblk->flag & tblkGC_READY)
                log->gcrtc--;

        wake_up_all(&tblk->gcwait);     // LOGGC_WAKEUP

        /*
         * Can't release log->gclock until we've tested tblk->flag
         */
        if (tblk->flag & tblkGC_LAZY) {
                spin_unlock_irq(&log->gclock);  // LOGGC_UNLOCK
                txUnlock(tblk);
                tblk->flag &= ~tblkGC_LAZY;
                txEnd(tblk - TxBlock);  /* Convert back to tid */
        } else
                spin_unlock_irq(&log->gclock);  // LOGGC_UNLOCK

        jfs_info("txLazyCommit: done: tblk = 0x%p", tblk);
}

/*
 *      jfs_lazycommit(void)
 *
 *      To be run as a kernel daemon.  If lbmIODone is called in an interrupt
 *      context, or where blocking is not wanted, this routine will process
 *      committed transactions from the unlock queue.
 */
int jfs_lazycommit(void *arg)
{
        int WorkDone;
        struct tblock *tblk;
        unsigned long flags;
        struct jfs_sb_info *sbi;

        daemonize("jfsCommit");

        complete(&jfsIOwait);

        do {
                LAZY_LOCK(flags);
                jfs_commit_thread_waking = 0;   /* OK to wake another thread */
                while (!list_empty(&TxAnchor.unlock_queue)) {
                        WorkDone = 0;
                        list_for_each_entry(tblk, &TxAnchor.unlock_queue,
                                            cqueue) {

                                sbi = JFS_SBI(tblk->sb);
                                /*
                                 * For each volume, the transactions must be
                                 * handled in order.  If another commit thread
                                 * is handling a tblk for this superblock,
                                 * skip it
                                 */
                                if (sbi->commit_state & IN_LAZYCOMMIT)
                                        continue;

                                sbi->commit_state |= IN_LAZYCOMMIT;
                                WorkDone = 1;

                                /*
                                 * Remove transaction from queue
                                 */
                                list_del(&tblk->cqueue);

                                LAZY_UNLOCK(flags);
                                txLazyCommit(tblk);
                                LAZY_LOCK(flags);

                                sbi->commit_state &= ~IN_LAZYCOMMIT;
                                /*
                                 * Don't continue in the for loop.  (We can't
                                 * anyway, it's unsafe!)  We want to go back to
                                 * the beginning of the list.
                                 */
                                break;
                        }

                        /* If there was nothing to do, don't continue */
                        if (!WorkDone)
                                break;
                }
                /* In case a wakeup came while all threads were active */
                jfs_commit_thread_waking = 0;

                if (freezing(current)) {
                        LAZY_UNLOCK(flags);
                        refrigerator();
                } else {
                        DECLARE_WAITQUEUE(wq, current);

                        add_wait_queue(&jfs_commit_thread_wait, &wq);
                        set_current_state(TASK_INTERRUPTIBLE);
                        LAZY_UNLOCK(flags);
                        schedule();
                        current->state = TASK_RUNNING;
                        remove_wait_queue(&jfs_commit_thread_wait, &wq);
                }
        } while (!jfs_stop_threads);

        if (!list_empty(&TxAnchor.unlock_queue))
                jfs_err("jfs_lazycommit being killed w/pending transactions!");
        else
                jfs_info("jfs_lazycommit being killed\n");
        complete_and_exit(&jfsIOwait, 0);
}

void txLazyUnlock(struct tblock * tblk)
{
        unsigned long flags;

        LAZY_LOCK(flags);

        list_add_tail(&tblk->cqueue, &TxAnchor.unlock_queue);
        /*
         * Don't wake up a commit thread if there is already one servicing
         * this superblock, or if the last one we woke up hasn't started yet.
         */
        if (!(JFS_SBI(tblk->sb)->commit_state & IN_LAZYCOMMIT) &&
            !jfs_commit_thread_waking) {
                jfs_commit_thread_waking = 1;
                wake_up(&jfs_commit_thread_wait);
        }
        LAZY_UNLOCK(flags);
}

static void LogSyncRelease(struct metapage * mp)
{
        struct jfs_log *log = mp->log;

        assert(mp->nohomeok);
        assert(log);
        metapage_homeok(mp);
}

/*
 *      txQuiesce
 *
 *      Block all new transactions and push anonymous transactions to
 *      completion
 *
 *      This does almost the same thing as jfs_sync below.  We don't
 *      worry about deadlocking when jfs_tlocks_low is set, since we would
 *      expect jfs_sync to get us out of that jam.
 */
void txQuiesce(struct super_block *sb)
{
        struct inode *ip;
        struct jfs_inode_info *jfs_ip;
        struct jfs_log *log = JFS_SBI(sb)->log;
        tid_t tid;

        set_bit(log_QUIESCE, &log->flag);

        TXN_LOCK();
restart:
        while (!list_empty(&TxAnchor.anon_list)) {
                jfs_ip = list_entry(TxAnchor.anon_list.next,
                                    struct jfs_inode_info,
                                    anon_inode_list);
                ip = &jfs_ip->vfs_inode;

                /*
                 * inode will be removed from anonymous list
                 * when it is committed
                 */
                TXN_UNLOCK();
                tid = txBegin(ip->i_sb, COMMIT_INODE | COMMIT_FORCE);
                down(&jfs_ip->commit_sem);
                txCommit(tid, 1, &ip, 0);
                txEnd(tid);
                up(&jfs_ip->commit_sem);
                /*
                 * Just to be safe.  I don't know how
                 * long we can run without blocking
                 */
                cond_resched();
                TXN_LOCK();
        }

        /*
         * If jfs_sync is running in parallel, there could be some inodes
         * on anon_list2.  Let's check.
         */
        if (!list_empty(&TxAnchor.anon_list2)) {
                list_splice(&TxAnchor.anon_list2, &TxAnchor.anon_list);
                INIT_LIST_HEAD(&TxAnchor.anon_list2);
                goto restart;
        }
        TXN_UNLOCK();

        /*
         * We may need to kick off the group commit
         */
        jfs_flush_journal(log, 0);
}

/*
 * txResume()
 *
 * Allows transactions to start again following txQuiesce
 */
void txResume(struct super_block *sb)
{
        struct jfs_log *log = JFS_SBI(sb)->log;

        clear_bit(log_QUIESCE, &log->flag);
        TXN_WAKEUP(&log->syncwait);
}

/*
 *      jfs_sync(void)
 *
 *      To be run as a kernel daemon.  This is awakened when tlocks run low.
 *      We write any inodes that have anonymous tlocks so they will become
 *      available.
 */
int jfs_sync(void *arg)
{
        struct inode *ip;
        struct jfs_inode_info *jfs_ip;
        int rc;
        tid_t tid;

        daemonize("jfsSync");

        complete(&jfsIOwait);

        do {
                /*
                 * write each inode on the anonymous inode list
                 */
                TXN_LOCK();
                while (jfs_tlocks_low && !list_empty(&TxAnchor.anon_list)) {
                        jfs_ip = list_entry(TxAnchor.anon_list.next,
                                            struct jfs_inode_info,
                                            anon_inode_list);
                        ip = &jfs_ip->vfs_inode;

                        if (! igrab(ip)) {
                                /*
                                 * Inode is being freed
                                 */
                                list_del_init(&jfs_ip->anon_inode_list);
                        } else if (! down_trylock(&jfs_ip->commit_sem)) {
                                /*
                                 * inode will be removed from anonymous list
                                 * when it is committed
                                 */
                                TXN_UNLOCK();
                                tid = txBegin(ip->i_sb, COMMIT_INODE);
                                rc = txCommit(tid, 1, &ip, 0);
                                txEnd(tid);
                                up(&jfs_ip->commit_sem);

                                iput(ip);
                                /*
                                 * Just to be safe.  I don't know how
                                 * long we can run without blocking
                                 */
                                cond_resched();
                                TXN_LOCK();
                        } else {
                                /* We can't get the commit semaphore.  It may
                                 * be held by a thread waiting for tlock's
                                 * so let's not block here.  Save it to
                                 * put back on the anon_list.
                                 */

                                /* Take off anon_list */
                                list_del(&jfs_ip->anon_inode_list);

                                /* Put on anon_list2 */
                                list_add(&jfs_ip->anon_inode_list,
                                         &TxAnchor.anon_list2);

                                TXN_UNLOCK();
                                iput(ip);
                                TXN_LOCK();
                        }
                }
                /* Add anon_list2 back to anon_list */
                list_splice_init(&TxAnchor.anon_list2, &TxAnchor.anon_list);

                if (freezing(current)) {
                        TXN_UNLOCK();
                        refrigerator();
                } else {
                        DECLARE_WAITQUEUE(wq, current);

                        add_wait_queue(&jfs_sync_thread_wait, &wq);
                        set_current_state(TASK_INTERRUPTIBLE);
                        TXN_UNLOCK();
                        schedule();
                        current->state = TASK_RUNNING;
                        remove_wait_queue(&jfs_sync_thread_wait, &wq);
                }
        } while (!jfs_stop_threads);

        jfs_info("jfs_sync being killed");
        complete_and_exit(&jfsIOwait, 0);
}

#if defined(CONFIG_PROC_FS) && defined(CONFIG_JFS_DEBUG)
int jfs_txanchor_read(char *buffer, char **start, off_t offset, int length,
                      int *eof, void *data)
{
        int len = 0;
        off_t begin;
        char *freewait;
        char *freelockwait;
        char *lowlockwait;

        freewait =
            waitqueue_active(&TxAnchor.freewait) ? "active" : "empty";
        freelockwait =
            waitqueue_active(&TxAnchor.freelockwait) ? "active" : "empty";
        lowlockwait =
            waitqueue_active(&TxAnchor.lowlockwait) ? "active" : "empty";

        len += sprintf(buffer,
                       "JFS TxAnchor\n"
                       "============\n"
                       "freetid = %d\n"
                       "freewait = %s\n"
                       "freelock = %d\n"
                       "freelockwait = %s\n"
                       "lowlockwait = %s\n"
                       "tlocksInUse = %d\n"
                       "jfs_tlocks_low = %d\n"
                       "unlock_queue is %sempty\n",
                       TxAnchor.freetid,
                       freewait,
                       TxAnchor.freelock,
                       freelockwait,
                       lowlockwait,
                       TxAnchor.tlocksInUse,
                       jfs_tlocks_low,
                       list_empty(&TxAnchor.unlock_queue) ? "" : "not ");

        begin = offset;
        *start = buffer + begin;
        len -= begin;

        if (len > length)
                len = length;
        else
                *eof = 1;

        if (len < 0)
                len = 0;

        return len;
}
#endif

#if defined(CONFIG_PROC_FS) && defined(CONFIG_JFS_STATISTICS)
int jfs_txstats_read(char *buffer, char **start, off_t offset, int length,
                     int *eof, void *data)
{
        int len = 0;
        off_t begin;

        len += sprintf(buffer,
                       "JFS TxStats\n"
                       "===========\n"
                       "calls to txBegin = %d\n"
                       "txBegin blocked by sync barrier = %d\n"
                       "txBegin blocked by tlocks low = %d\n"
                       "txBegin blocked by no free tid = %d\n"
                       "calls to txBeginAnon = %d\n"
                       "txBeginAnon blocked by sync barrier = %d\n"
                       "txBeginAnon blocked by tlocks low = %d\n"
                       "calls to txLockAlloc = %d\n"
                       "tLockAlloc blocked by no free lock = %d\n",
                       TxStat.txBegin,
                       TxStat.txBegin_barrier,
                       TxStat.txBegin_lockslow,
                       TxStat.txBegin_freetid,
                       TxStat.txBeginAnon,
                       TxStat.txBeginAnon_barrier,
                       TxStat.txBeginAnon_lockslow,
                       TxStat.txLockAlloc,
                       TxStat.txLockAlloc_freelock);

        begin = offset;
        *start = buffer + begin;
        len -= begin;

        if (len > length)
                len = length;
        else
                *eof = 1;

        if (len < 0)
                len = 0;

        return len;
}
#endif