text: /*
   * Copyright (c) 2004-2006 The DragonFly Project.  All rights reserved.
   * 
   * This code is derived from software contributed to The DragonFly Project
   * by Matthew Dillon <dillon@backplane.com>
   * 
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   * 3. Neither the name of The DragonFly Project nor the names of its
   *    contributors may be used to endorse or promote products derived
   *    from this software without specific, prior written permission.
   * 
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
   * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
   * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
   * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   *
   * $DragonFly: src/sys/kern/vfs_journal.c,v 1.33 2007/05/09 00:53:34 dillon Exp $
   */
  /*
   * The journaling protocol is intended to evolve into a two-way stream
   * whereby transaction IDs can be acknowledged by the journaling target
   * when the data has been committed to hard storage.  Both implicit and
   * explicit acknowledgement schemes will be supported, depending on the
   * sophistication of the journaling stream, plus resynchronization and
   * restart when a journaling stream is interrupted.  This information will
   * also be made available to journaling-aware filesystems to allow better
   * management of their own physical storage synchronization mechanisms as
   * well as to allow such filesystems to take direct advantage of the kernel's
   * journaling layer so they don't have to roll their own.
   *
   * In addition, the worker thread will have access to much larger 
   * spooling areas then the memory buffer is able to provide by e.g. 
   * reserving swap space, in order to absorb potentially long interruptions
   * of off-site journaling streams, and to prevent 'slow' off-site linkages
   * from radically slowing down local filesystem operations.  
   *
   * Because of the non-trivial algorithms the journaling system will be
   * required to support, use of a worker thread is mandatory.  Efficiencies
   * are maintained by utilitizing the memory FIFO to batch transactions when
   * possible, reducing the number of gratuitous thread switches and taking
   * advantage of cpu caches through the use of shorter batched code paths
   * rather then trying to do everything in the context of the process
   * originating the filesystem op.  In the future the memory FIFO can be
   * made per-cpu to remove BGL or other locking requirements.
   */
  #include <sys/param.h>
  #include <sys/systm.h>
  #include <sys/buf.h>
  #include <sys/conf.h>
  #include <sys/kernel.h>
  #include <sys/queue.h>
  #include <sys/lock.h>
  #include <sys/malloc.h>
  #include <sys/mount.h>
  #include <sys/unistd.h>
  #include <sys/vnode.h>
  #include <sys/poll.h>
  #include <sys/mountctl.h>
  #include <sys/journal.h>
  #include <sys/file.h>
  #include <sys/proc.h>
  #include <sys/xio.h>
  #include <sys/socket.h>
  #include <sys/socketvar.h>
  
  #include <machine/limits.h>
  
  #include <vm/vm.h>
  #include <vm/vm_object.h>
  #include <vm/vm_page.h>
  #include <vm/vm_pager.h>
  #include <vm/vnode_pager.h>
  
  #include <sys/file2.h>
  #include <sys/thread2.h>
  #include <sys/mplock2.h>
  #include <sys/spinlock2.h>
  
  static void journal_wthread(void *info);
  static void journal_rthread(void *info);
  
  static void *journal_reserve(struct journal *jo,
                          struct journal_rawrecbeg **rawpp,
                          int16_t streamid, int bytes);
  static void *journal_extend(struct journal *jo,
                          struct journal_rawrecbeg **rawpp,
                          int truncbytes, int bytes, int *newstreamrecp);
  static void journal_abort(struct journal *jo,
                          struct journal_rawrecbeg **rawpp);
  static void journal_commit(struct journal *jo,
                          struct journal_rawrecbeg **rawpp,
                          int bytes, int closeout);
  static void jrecord_data(struct jrecord *jrec,
  			void *buf, int bytes, int dtype);
  
  
  MALLOC_DEFINE(M_JOURNAL, "journal", "Journaling structures");
  MALLOC_DEFINE(M_JFIFO, "journal-fifo", "Journal FIFO");
  
  void
  journal_create_threads(struct journal *jo)
  {
  	jo->flags &= ~(MC_JOURNAL_STOP_REQ | MC_JOURNAL_STOP_IMM);
  	jo->flags |= MC_JOURNAL_WACTIVE;
  	lwkt_create(journal_wthread, jo, NULL, &jo->wthread,
  		    TDF_NOSTART, -1,
  		    "journal w:%.*s", JIDMAX, jo->id);
  	lwkt_setpri(&jo->wthread, TDPRI_KERN_DAEMON);
  	lwkt_schedule(&jo->wthread);
  
  	if (jo->flags & MC_JOURNAL_WANT_FULLDUPLEX) {
  	    jo->flags |= MC_JOURNAL_RACTIVE;
  	    lwkt_create(journal_rthread, jo, NULL, &jo->rthread,
  			TDF_NOSTART, -1,
  			"journal r:%.*s", JIDMAX, jo->id);
  	    lwkt_setpri(&jo->rthread, TDPRI_KERN_DAEMON);
  	    lwkt_schedule(&jo->rthread);
  	}
  }
  
  void
  journal_destroy_threads(struct journal *jo, int flags)
  {
      int wcount;
  
      jo->flags |= MC_JOURNAL_STOP_REQ | (flags & MC_JOURNAL_STOP_IMM);
      wakeup(&jo->fifo);
      wcount = 0;
      while (jo->flags & (MC_JOURNAL_WACTIVE | MC_JOURNAL_RACTIVE)) {
  	tsleep(jo, 0, "jwait", hz);
  	if (++wcount % 10 == 0) {
  	    kprintf("Warning: journal %s waiting for descriptors to close\n",
  		jo->id);
  	}
      }
  
      /*
       * XXX SMP - threads should move to cpu requesting the restart or
       * termination before finishing up to properly interlock.
       */
      tsleep(jo, 0, "jwait", hz);
      lwkt_free_thread(&jo->wthread);
      if (jo->flags & MC_JOURNAL_WANT_FULLDUPLEX)
  	lwkt_free_thread(&jo->rthread);
  }
  
  /*
   * The per-journal worker thread is responsible for writing out the
   * journal's FIFO to the target stream.
   */
  static void
  journal_wthread(void *info)
  {
      struct journal *jo = info;
      struct journal_rawrecbeg *rawp;
      int error;
      size_t avail;
      size_t bytes;
      size_t res;
  
      /* not MPSAFE yet */
      get_mplock();
  
      for (;;) {
  	/*
  	 * Calculate the number of bytes available to write.  This buffer
  	 * area may contain reserved records so we can't just write it out
  	 * without further checks.
  	 */
  	bytes = jo->fifo.windex - jo->fifo.rindex;
  
  	/*
  	 * sleep if no bytes are available or if an incomplete record is
  	 * encountered (it needs to be filled in before we can write it
  	 * out), and skip any pad records that we encounter.
  	 */
  	if (bytes == 0) {
  	    if (jo->flags & MC_JOURNAL_STOP_REQ)
  		break;
  	    tsleep(&jo->fifo, 0, "jfifo", hz);
  	    continue;
  	}
  
  	/*
  	 * Sleep if we can not go any further due to hitting an incomplete
  	 * record.  This case should occur rarely but may have to be better
  	 * optimized XXX.
  	 */
  	rawp = (void *)(jo->fifo.membase + (jo->fifo.rindex & jo->fifo.mask));
  	if (rawp->begmagic == JREC_INCOMPLETEMAGIC) {
  	    tsleep(&jo->fifo, 0, "jpad", hz);
  	    continue;
  	}
  
  	/*
  	 * Skip any pad records.  We do not write out pad records if we can
  	 * help it. 
  	 */
  	if (rawp->streamid == JREC_STREAMID_PAD) {
  	    if ((jo->flags & MC_JOURNAL_WANT_FULLDUPLEX) == 0) {
  		if (jo->fifo.rindex == jo->fifo.xindex) {
  		    jo->fifo.xindex += (rawp->recsize + 15) & ~15;
  		    jo->total_acked += (rawp->recsize + 15) & ~15;
  		}
  	    }
  	    jo->fifo.rindex += (rawp->recsize + 15) & ~15;
  	    jo->total_acked += bytes;
  	    KKASSERT(jo->fifo.windex - jo->fifo.rindex >= 0);
  	    continue;
  	}
  
  	/*
  	 * 'bytes' is the amount of data that can potentially be written out.  
  	 * Calculate 'res', the amount of data that can actually be written
  	 * out.  res is bounded either by hitting the end of the physical
  	 * memory buffer or by hitting an incomplete record.  Incomplete
  	 * records often occur due to the way the space reservation model
  	 * works.
  	 */
  	res = 0;
  	avail = jo->fifo.size - (jo->fifo.rindex & jo->fifo.mask);
  	while (res < bytes && rawp->begmagic == JREC_BEGMAGIC) {
  	    res += (rawp->recsize + 15) & ~15;
  	    if (res >= avail) {
  		KKASSERT(res == avail);
  		break;
  	    }
  	    rawp = (void *)((char *)rawp + ((rawp->recsize + 15) & ~15));
  	}
  
  	/*
  	 * Issue the write and deal with any errors or other conditions.
  	 * For now assume blocking I/O.  Since we are record-aware the
  	 * code cannot yet handle partial writes.
  	 *
  	 * We bump rindex prior to issuing the write to avoid racing
  	 * the acknowledgement coming back (which could prevent the ack
  	 * from bumping xindex).  Restarts are always based on xindex so
  	 * we do not try to undo the rindex if an error occurs.
  	 *
  	 * XXX EWOULDBLOCK/NBIO
  	 * XXX notification on failure
  	 * XXX permanent verses temporary failures
  	 * XXX two-way acknowledgement stream in the return direction / xindex
  	 */
  	bytes = res;
  	jo->fifo.rindex += bytes;
  	error = fp_write(jo->fp, 
  			jo->fifo.membase +
  			 ((jo->fifo.rindex - bytes) & jo->fifo.mask),
  			bytes, &res, UIO_SYSSPACE);
  	if (error) {
  	    kprintf("journal_thread(%s) write, error %d\n", jo->id, error);
  	    /* XXX */
  	} else {
  	    KKASSERT(res == bytes);
  	}
  
  	/*
  	 * Advance rindex.  If the journal stream is not full duplex we also
  	 * advance xindex, otherwise the rjournal thread is responsible for
  	 * advancing xindex.
  	 */
  	if ((jo->flags & MC_JOURNAL_WANT_FULLDUPLEX) == 0) {
  	    jo->fifo.xindex += bytes;
  	    jo->total_acked += bytes;
  	}
  	KKASSERT(jo->fifo.windex - jo->fifo.rindex >= 0);
  	if ((jo->flags & MC_JOURNAL_WANT_FULLDUPLEX) == 0) {
  	    if (jo->flags & MC_JOURNAL_WWAIT) {
  		jo->flags &= ~MC_JOURNAL_WWAIT;	/* XXX hysteresis */
  		wakeup(&jo->fifo.windex);
  	    }
  	}
      }
      fp_shutdown(jo->fp, SHUT_WR);
      jo->flags &= ~MC_JOURNAL_WACTIVE;
      wakeup(jo);
      wakeup(&jo->fifo.windex);
      rel_mplock();
  }
  
  /*
   * A second per-journal worker thread is created for two-way journaling
   * streams to deal with the return acknowledgement stream.
   */
  static void
  journal_rthread(void *info)
  {
      struct journal_rawrecbeg *rawp;
      struct journal_ackrecord ack;
      struct journal *jo = info;
      int64_t transid;
      int error;
      size_t count;
      size_t bytes;
  
      transid = 0;
      error = 0;
  
      /* not MPSAFE yet */
      get_mplock();
  
      for (;;) {
  	/*
  	 * We have been asked to stop
  	 */
  	if (jo->flags & MC_JOURNAL_STOP_REQ)
  		break;
  
  	/*
  	 * If we have no active transaction id, get one from the return
  	 * stream.
  	 */
  	if (transid == 0) {
  	    error = fp_read(jo->fp, &ack, sizeof(ack), &count, 
  			    1, UIO_SYSSPACE);
  #if 0
  	    kprintf("fp_read ack error %d count %d\n", error, count);
  #endif
  	    if (error || count != sizeof(ack))
  		break;
  	    if (error) {
  		kprintf("read error %d on receive stream\n", error);
  		break;
  	    }
  	    if (ack.rbeg.begmagic != JREC_BEGMAGIC ||
  		ack.rend.endmagic != JREC_ENDMAGIC
  	    ) {
  		kprintf("bad begmagic or endmagic on receive stream\n");
  		break;
  	    }
  	    transid = ack.rbeg.transid;
  	}
  
  	/*
  	 * Calculate the number of unacknowledged bytes.  If there are no
  	 * unacknowledged bytes then unsent data was acknowledged, report,
  	 * sleep a bit, and loop in that case.  This should not happen 
  	 * normally.  The ack record is thrown away.
  	 */
  	bytes = jo->fifo.rindex - jo->fifo.xindex;
  
  	if (bytes == 0) {
  	    kprintf("warning: unsent data acknowledged transid %08llx\n",
  		    (long long)transid);
  	    tsleep(&jo->fifo.xindex, 0, "jrseq", hz);
  	    transid = 0;
  	    continue;
  	}
  
  	/*
  	 * Since rindex has advanced, the record pointed to by xindex
  	 * must be a valid record.
  	 */
  	rawp = (void *)(jo->fifo.membase + (jo->fifo.xindex & jo->fifo.mask));
  	KKASSERT(rawp->begmagic == JREC_BEGMAGIC);
  	KKASSERT(rawp->recsize <= bytes);
  
  	/*
  	 * The target can acknowledge several records at once.
  	 */
  	if (rawp->transid < transid) {
  #if 1
  	    kprintf("ackskip %08llx/%08llx\n",
  		    (long long)rawp->transid,
  		    (long long)transid);
  #endif
  	    jo->fifo.xindex += (rawp->recsize + 15) & ~15;
  	    jo->total_acked += (rawp->recsize + 15) & ~15;
  	    if (jo->flags & MC_JOURNAL_WWAIT) {
  		jo->flags &= ~MC_JOURNAL_WWAIT;	/* XXX hysteresis */
  		wakeup(&jo->fifo.windex);
  	    }
  	    continue;
  	}
  	if (rawp->transid == transid) {
  #if 1
  	    kprintf("ackskip %08llx/%08llx\n",
  		    (long long)rawp->transid,
  		    (long long)transid);
  #endif
  	    jo->fifo.xindex += (rawp->recsize + 15) & ~15;
  	    jo->total_acked += (rawp->recsize + 15) & ~15;
  	    if (jo->flags & MC_JOURNAL_WWAIT) {
  		jo->flags &= ~MC_JOURNAL_WWAIT;	/* XXX hysteresis */
  		wakeup(&jo->fifo.windex);
  	    }
  	    transid = 0;
  	    continue;
  	}
  	kprintf("warning: unsent data(2) acknowledged transid %08llx\n",
  		(long long)transid);
  	transid = 0;
      }
      jo->flags &= ~MC_JOURNAL_RACTIVE;
      wakeup(jo);
      wakeup(&jo->fifo.windex);
      rel_mplock();
  }
  
  /*
   * This builds a pad record which the journaling thread will skip over.  Pad
   * records are required when we are unable to reserve sufficient stream space
   * due to insufficient space at the end of the physical memory fifo.
   *
   * Even though the record is not transmitted, a normal transid must be 
   * assigned to it so link recovery operations after a failure work properly.
   */
  static
  void
  journal_build_pad(struct journal_rawrecbeg *rawp, int recsize, int64_t transid)
  {
      struct journal_rawrecend *rendp;
      
      KKASSERT((recsize & 15) == 0 && recsize >= 16);
  
      rawp->streamid = JREC_STREAMID_PAD;
      rawp->recsize = recsize;	/* must be 16-byte aligned */
      rawp->transid = transid;
      /*
       * WARNING, rendp may overlap rawp->transid.  This is necessary to
       * allow PAD records to fit in 16 bytes.  Use cpu_ccfence() to
       * hopefully cause the compiler to not make any assumptions.
       */
      rendp = (void *)((char *)rawp + rawp->recsize - sizeof(*rendp));
      rendp->endmagic = JREC_ENDMAGIC;
      rendp->check = 0;
      rendp->recsize = rawp->recsize;
  
      /*
       * Set the begin magic last.  This is what will allow the journal
       * thread to write the record out.  Use a store fence to prevent
       * compiler and cpu reordering of the writes.
       */
      cpu_sfence();
      rawp->begmagic = JREC_BEGMAGIC;
  }
  
  /*
   * Wake up the worker thread if the FIFO is more then half full or if
   * someone is waiting for space to be freed up.  Otherwise let the 
   * heartbeat deal with it.  Being able to avoid waking up the worker
   * is the key to the journal's cpu performance.
   */
  static __inline
  void
  journal_commit_wakeup(struct journal *jo)
  {
      int avail;
  
      avail = jo->fifo.size - (jo->fifo.windex - jo->fifo.xindex);
      KKASSERT(avail >= 0);
      if ((avail < (jo->fifo.size >> 1)) || (jo->flags & MC_JOURNAL_WWAIT))
  	wakeup(&jo->fifo);
  }
  
  /*
   * Create a new BEGIN stream record with the specified streamid and the
   * specified amount of payload space.  *rawpp will be set to point to the
   * base of the new stream record and a pointer to the base of the payload
   * space will be returned.  *rawpp does not need to be pre-NULLd prior to
   * making this call.  The raw record header will be partially initialized.
   *
   * A stream can be extended, aborted, or committed by other API calls
   * below.  This may result in a sequence of potentially disconnected
   * stream records to be output to the journaling target.  The first record
   * (the one created by this function) will be marked JREC_STREAMCTL_BEGIN,
   * while the last record on commit or abort will be marked JREC_STREAMCTL_END
   * (and possibly also JREC_STREAMCTL_ABORTED).  The last record could wind
   * up being the same as the first, in which case the bits are all set in
   * the first record.
   *
   * The stream record is created in an incomplete state by setting the begin
   * magic to JREC_INCOMPLETEMAGIC.  This prevents the worker thread from
   * flushing the fifo past our record until we have finished populating it.
   * Other threads can reserve and operate on their own space without stalling
   * but the stream output will stall until we have completed operations.  The
   * memory FIFO is intended to be large enough to absorb such situations
   * without stalling out other threads.
   */
  static
  void *
  journal_reserve(struct journal *jo, struct journal_rawrecbeg **rawpp,
  		int16_t streamid, int bytes)
  {
      struct journal_rawrecbeg *rawp;
      int avail;
      int availtoend;
      int req;
  
      /*
       * Add header and trailer overheads to the passed payload.  Note that
       * the passed payload size need not be aligned in any way.
       */
      bytes += sizeof(struct journal_rawrecbeg);
      bytes += sizeof(struct journal_rawrecend);
  
      for (;;) {
  	/*
  	 * First, check boundary conditions.  If the request would wrap around
  	 * we have to skip past the ending block and return to the beginning
  	 * of the FIFO's buffer.  Calculate 'req' which is the actual number
  	 * of bytes being reserved, including wrap-around dead space.
  	 *
  	 * Neither 'bytes' or 'req' are aligned.
  	 *
  	 * Note that availtoend is not truncated to avail and so cannot be
  	 * used to determine whether the reservation is possible by itself.
  	 * Also, since all fifo ops are 16-byte aligned, we can check
  	 * the size before calculating the aligned size.
  	 */
  	availtoend = jo->fifo.size - (jo->fifo.windex & jo->fifo.mask);
  	KKASSERT((availtoend & 15) == 0);
  	if (bytes > availtoend) 
  	    req = bytes + availtoend;	/* add pad to end */
  	else
  	    req = bytes;
  
  	/*
  	 * Next calculate the total available space and see if it is
  	 * sufficient.  We cannot overwrite previously buffered data
  	 * past xindex because otherwise we would not be able to restart
  	 * a broken link at the target's last point of commit.
  	 */
  	avail = jo->fifo.size - (jo->fifo.windex - jo->fifo.xindex);
  	KKASSERT(avail >= 0 && (avail & 15) == 0);
  
  	if (avail < req) {
  	    /* XXX MC_JOURNAL_STOP_IMM */
  	    jo->flags |= MC_JOURNAL_WWAIT;
  	    ++jo->fifostalls;
  	    tsleep(&jo->fifo.windex, 0, "jwrite", 0);
  	    continue;
  	}
  
  	/*
  	 * Create a pad record for any dead space and create an incomplete
  	 * record for the live space, then return a pointer to the
  	 * contiguous buffer space that was requested.
  	 *
  	 * NOTE: The worker thread will not flush past an incomplete
  	 * record, so the reserved space can be filled in at-will.  The
  	 * journaling code must also be aware the reserved sections occuring
  	 * after this one will also not be written out even if completed
  	 * until this one is completed.
  	 *
  	 * The transaction id must accomodate real and potential pad creation.
  	 */
  	rawp = (void *)(jo->fifo.membase + (jo->fifo.windex & jo->fifo.mask));
  	if (req != bytes) {
  	    journal_build_pad(rawp, availtoend, jo->transid);
  	    ++jo->transid;
  	    rawp = (void *)jo->fifo.membase;
  	}
  	rawp->begmagic = JREC_INCOMPLETEMAGIC;	/* updated by abort/commit */
  	rawp->recsize = bytes;			/* (unaligned size) */
  	rawp->streamid = streamid | JREC_STREAMCTL_BEGIN;
  	rawp->transid = jo->transid;
  	jo->transid += 2;
  
  	/*
  	 * Issue a memory barrier to guarentee that the record data has been
  	 * properly initialized before we advance the write index and return
  	 * a pointer to the reserved record.  Otherwise the worker thread
  	 * could accidently run past us.
  	 *
  	 * Note that stream records are always 16-byte aligned.
  	 */
  	cpu_sfence();
  	jo->fifo.windex += (req + 15) & ~15;
  	*rawpp = rawp;
  	return(rawp + 1);
      }
      /* not reached */
      *rawpp = NULL;
      return(NULL);
  }
  
  /*
   * Attempt to extend the stream record by <bytes> worth of payload space.
   *
   * If it is possible to extend the existing stream record no truncation
   * occurs and the record is extended as specified.  A pointer to the 
   * truncation offset within the payload space is returned.
   *
   * If it is not possible to do this the existing stream record is truncated
   * and committed, and a new stream record of size <bytes> is created.  A
   * pointer to the base of the new stream record's payload space is returned.
   *
   * *rawpp is set to the new reservation in the case of a new record but
   * the caller cannot depend on a comparison with the old rawp to determine if
   * this case occurs because we could end up using the same memory FIFO
   * offset for the new stream record.  Use *newstreamrecp instead.
   */
  static void *
  journal_extend(struct journal *jo, struct journal_rawrecbeg **rawpp, 
  		int truncbytes, int bytes, int *newstreamrecp)
  {
      struct journal_rawrecbeg *rawp;
      int16_t streamid;
      int availtoend;
      int avail;
      int osize;
      int nsize;
      int wbase;
      void *rptr;
  
      *newstreamrecp = 0;
      rawp = *rawpp;
      osize = (rawp->recsize + 15) & ~15;
      nsize = (rawp->recsize + bytes + 15) & ~15;
      wbase = (char *)rawp - jo->fifo.membase;
  
      /*
       * If the aligned record size does not change we can trivially adjust
       * the record size.
       */
      if (nsize == osize) {
  	rawp->recsize += bytes;
  	return((char *)(rawp + 1) + truncbytes);
      }
  
      /*
       * If the fifo's write index hasn't been modified since we made the
       * reservation and we do not hit any boundary conditions, we can 
       * trivially make the record smaller or larger.
       */
      if ((jo->fifo.windex & jo->fifo.mask) == wbase + osize) {
  	availtoend = jo->fifo.size - wbase;
  	avail = jo->fifo.size - (jo->fifo.windex - jo->fifo.xindex) + osize;
  	KKASSERT((availtoend & 15) == 0);
  	KKASSERT((avail & 15) == 0);
  	if (nsize <= avail && nsize <= availtoend) {
  	    jo->fifo.windex += nsize - osize;
  	    rawp->recsize += bytes;
  	    return((char *)(rawp + 1) + truncbytes);
  	}
      }
  
      /*
       * It was not possible to extend the buffer.  Commit the current
       * buffer and create a new one.  We manually clear the BEGIN mark that
       * journal_reserve() creates (because this is a continuing record, not
       * the start of a new stream).
       */
      streamid = rawp->streamid & JREC_STREAMID_MASK;
      journal_commit(jo, rawpp, truncbytes, 0);
      rptr = journal_reserve(jo, rawpp, streamid, bytes);
      rawp = *rawpp;
      rawp->streamid &= ~JREC_STREAMCTL_BEGIN;
      *newstreamrecp = 1;
      return(rptr);
  }
  
  /*
   * Abort a journal record.  If the transaction record represents a stream
   * BEGIN and we can reverse the fifo's write index we can simply reverse
   * index the entire record, as if it were never reserved in the first place.
   *
   * Otherwise we set the JREC_STREAMCTL_ABORTED bit and commit the record
   * with the payload truncated to 0 bytes.
   */
  static void
  journal_abort(struct journal *jo, struct journal_rawrecbeg **rawpp)
  {
      struct journal_rawrecbeg *rawp;
      int osize;
  
      rawp = *rawpp;
      osize = (rawp->recsize + 15) & ~15;
  
      if ((rawp->streamid & JREC_STREAMCTL_BEGIN) &&
  	(jo->fifo.windex & jo->fifo.mask) == 
  	 (char *)rawp - jo->fifo.membase + osize)
      {
  	jo->fifo.windex -= osize;
  	*rawpp = NULL;
      } else {
  	rawp->streamid |= JREC_STREAMCTL_ABORTED;
  	journal_commit(jo, rawpp, 0, 1);
      }
  }
  
  /*
   * Commit a journal record and potentially truncate it to the specified
   * number of payload bytes.  If you do not want to truncate the record,
   * simply pass -1 for the bytes parameter.  Do not pass rawp->recsize, that
   * field includes header and trailer and will not be correct.  Note that
   * passing 0 will truncate the entire data payload of the record.
   *
   * The logical stream is terminated by this function.
   *
   * If truncation occurs, and it is not possible to physically optimize the
   * memory FIFO due to other threads having reserved space after ours,
   * the remaining reserved space will be covered by a pad record.
   */
  static void
  journal_commit(struct journal *jo, struct journal_rawrecbeg **rawpp,
  		int bytes, int closeout)
  {
      struct journal_rawrecbeg *rawp;
      struct journal_rawrecend *rendp;
      int osize;
      int nsize;
  
      rawp = *rawpp;
      *rawpp = NULL;
  
      KKASSERT((char *)rawp >= jo->fifo.membase &&
  	     (char *)rawp + rawp->recsize <= jo->fifo.membase + jo->fifo.size);
      KKASSERT(((intptr_t)rawp & 15) == 0);
  
      /*
       * Truncate the record if necessary.  If the FIFO write index as still
       * at the end of our record we can optimally backindex it.  Otherwise
       * we have to insert a pad record to cover the dead space.
       *
       * We calculate osize which is the 16-byte-aligned original recsize.
       * We calculate nsize which is the 16-byte-aligned new recsize.
       *
       * Due to alignment issues or in case the passed truncation bytes is
       * the same as the original payload, nsize may be equal to osize even
       * if the committed bytes is less then the originally reserved bytes.
       */
      if (bytes >= 0) {
  	KKASSERT(bytes >= 0 && bytes <= rawp->recsize - sizeof(struct journal_rawrecbeg) - sizeof(struct journal_rawrecend));
  	osize = (rawp->recsize + 15) & ~15;
  	rawp->recsize = bytes + sizeof(struct journal_rawrecbeg) +
  			sizeof(struct journal_rawrecend);
  	nsize = (rawp->recsize + 15) & ~15;
  	KKASSERT(nsize <= osize);
  	if (osize == nsize) {
  	    /* do nothing */
  	} else if ((jo->fifo.windex & jo->fifo.mask) == (char *)rawp - jo->fifo.membase + osize) {
  	    /* we are able to backindex the fifo */
  	    jo->fifo.windex -= osize - nsize;
  	} else {
  	    /* we cannot backindex the fifo, emplace a pad in the dead space */
  	    journal_build_pad((void *)((char *)rawp + nsize), osize - nsize,
  				rawp->transid + 1);
  	}
      }
  
      /*
       * Fill in the trailer.  Note that unlike pad records, the trailer will
       * never overlap the header.
       */
      rendp = (void *)((char *)rawp + 
  	    ((rawp->recsize + 15) & ~15) - sizeof(*rendp));
      rendp->endmagic = JREC_ENDMAGIC;
      rendp->recsize = rawp->recsize;
      rendp->check = 0;		/* XXX check word, disabled for now */
  
      /*
       * Fill in begmagic last.  This will allow the worker thread to proceed.
       * Use a memory barrier to guarentee write ordering.  Mark the stream
       * as terminated if closeout is set.  This is the typical case.
       */
      if (closeout)
  	rawp->streamid |= JREC_STREAMCTL_END;
      cpu_sfence();		/* memory and compiler barrier */
      rawp->begmagic = JREC_BEGMAGIC;
  
      journal_commit_wakeup(jo);
  }
  
  /************************************************************************
   *			TRANSACTION SUPPORT ROUTINES			*
   ************************************************************************
   *
   * JRECORD_*() - routines to create subrecord transactions and embed them
   *		 in the logical streams managed by the journal_*() routines.
   */
  
  /*
   * Initialize the passed jrecord structure and start a new stream transaction
   * by reserving an initial build space in the journal's memory FIFO.
   */
  void
  jrecord_init(struct journal *jo, struct jrecord *jrec, int16_t streamid)
  {
      bzero(jrec, sizeof(*jrec));
      jrec->jo = jo;
      jrec->streamid = streamid;
      jrec->stream_residual = JREC_DEFAULTSIZE;
      jrec->stream_reserved = jrec->stream_residual;
      jrec->stream_ptr = 
  	journal_reserve(jo, &jrec->rawp, streamid, jrec->stream_reserved);
  }
  
  /*
   * Push a recursive record type.  All pushes should have matching pops.
   * The old parent is returned and the newly pushed record becomes the
   * new parent.  Note that the old parent's pointer may already be invalid
   * or may become invalid if jrecord_write() had to build a new stream
   * record, so the caller should not mess with the returned pointer in
   * any way other then to save it.
   */
  struct journal_subrecord *
  jrecord_push(struct jrecord *jrec, int16_t rectype)
  {
      struct journal_subrecord *save;
  
      save = jrec->parent;
      jrec->parent = jrecord_write(jrec, rectype|JMASK_NESTED, 0);
      jrec->last = NULL;
      KKASSERT(jrec->parent != NULL);
      ++jrec->pushcount;
      ++jrec->pushptrgood;	/* cleared on flush */
      return(save);
  }
  
  /*
   * Pop a previously pushed sub-transaction.  We must set JMASK_LAST
   * on the last record written within the subtransaction.  If the last 
   * record written is not accessible or if the subtransaction is empty,
   * we must write out a pad record with JMASK_LAST set before popping.
   *
   * When popping a subtransaction the parent record's recsize field
   * will be properly set.  If the parent pointer is no longer valid
   * (which can occur if the data has already been flushed out to the
   * stream), the protocol spec allows us to leave it 0.
   *
   * The saved parent pointer which we restore may or may not be valid,
   * and if not valid may or may not be NULL, depending on the value
   * of pushptrgood.
   */
  void
  jrecord_pop(struct jrecord *jrec, struct journal_subrecord *save)
  {
      struct journal_subrecord *last;
  
      KKASSERT(jrec->pushcount > 0);
      KKASSERT(jrec->residual == 0);
  
      /*
       * Set JMASK_LAST on the last record we wrote at the current
       * level.  If last is NULL we either no longer have access to the
       * record or the subtransaction was empty and we must write out a pad
       * record.
       */
      if ((last = jrec->last) == NULL) {
  	jrecord_write(jrec, JLEAF_PAD|JMASK_LAST, 0);
  	last = jrec->last;	/* reload after possible flush */
      } else {
  	last->rectype |= JMASK_LAST;
      }
  
      /*
       * pushptrgood tells us how many levels of parent record pointers
       * are valid.  The jrec only stores the current parent record pointer
       * (and it is only valid if pushptrgood != 0).  The higher level parent
       * record pointers are saved by the routines calling jrecord_push() and
       * jrecord_pop().  These pointers may become stale and we determine
       * that fact by tracking the count of valid parent pointers with 
       * pushptrgood.  Pointers become invalid when their related stream
       * record gets pushed out.
       *
       * If no pointer is available (the data has already been pushed out),
       * then no fixup of e.g. the length field is possible for non-leaf
       * nodes.  The protocol allows for this situation by placing a larger
       * burden on the program scanning the stream on the other end.
       *
       * [parentA]
       *	  [node X]
       *    [parentB]
       *	     [node Y]
       *	     [node Z]
       *    (pop B)	see NOTE B
       * (pop A)		see NOTE A
       *
       * NOTE B:	This pop sets LAST in node Z if the node is still accessible,
       *		else a PAD record is appended and LAST is set in that.
       *
       *		This pop sets the record size in parentB if parentB is still
       *		accessible, else the record size is left 0 (the scanner must
       *		deal with that).
       *
       *		This pop sets the new 'last' record to parentB, the pointer
       *		to which may or may not still be accessible.
       *
       * NOTE A:	This pop sets LAST in parentB if the node is still accessible,
       *		else a PAD record is appended and LAST is set in that.
       *
       *		This pop sets the record size in parentA if parentA is still
       *		accessible, else the record size is left 0 (the scanner must
       *		deal with that).
       *
       *		This pop sets the new 'last' record to parentA, the pointer
       *		to which may or may not still be accessible.
       *
       * Also note that the last record in the stream transaction, which in
       * the above example is parentA, does not currently have the LAST bit
       * set.
       *
       * The current parent becomes the last record relative to the
       * saved parent passed into us.  It's validity is based on 
       * whether pushptrgood is non-zero prior to decrementing.  The saved
       * parent becomes the new parent, and its validity is based on whether
       * pushptrgood is non-zero after decrementing.
       *
       * The old jrec->parent may be NULL if it is no longer accessible.
       * If pushptrgood is non-zero, however, it is guarenteed to not
       * be NULL (since no flush occured).
       */
      jrec->last = jrec->parent;
      --jrec->pushcount;
      if (jrec->pushptrgood) {
  	KKASSERT(jrec->last != NULL && last != NULL);
  	if (--jrec->pushptrgood == 0) {
  	    jrec->parent = NULL;	/* 'save' contains garbage or NULL */
  	} else {
  	    KKASSERT(save != NULL);
  	    jrec->parent = save;	/* 'save' must not be NULL */
  	}
  
  	/*
  	 * Set the record size in the old parent.  'last' still points to
  	 * the original last record in the subtransaction being popped,
  	 * jrec->last points to the old parent (which became the last
  	 * record relative to the new parent being popped into).
  	 */
  	jrec->last->recsize = (char *)last + last->recsize - (char *)jrec->last;
      } else {
  	jrec->parent = NULL;
  	KKASSERT(jrec->last == NULL);
      }
  }
  
  /*
   * Write out a leaf record, including associated data.
   */
  void
  jrecord_leaf(struct jrecord *jrec, int16_t rectype, void *ptr, int bytes)
  {
      jrecord_write(jrec, rectype, bytes);
      jrecord_data(jrec, ptr, bytes, JDATA_KERN);
  }
  
  void
  jrecord_leaf_uio(struct jrecord *jrec, int16_t rectype,
  		 struct uio *uio)
  {
      struct iovec *iov;
      int i;
  
      for (i = 0; i < uio->uio_iovcnt; ++i) {
  	iov = &uio->uio_iov[i];
  	if (iov->iov_len == 0)
  	    continue;
  	if (uio->uio_segflg == UIO_SYSSPACE) {
  	    jrecord_write(jrec, rectype, iov->iov_len);
  	    jrecord_data(jrec, iov->iov_base, iov->iov_len, JDATA_KERN);
  	} else { /* UIO_USERSPACE */
  	    jrecord_write(jrec, rectype, iov->iov_len);
  	    jrecord_data(jrec, iov->iov_base, iov->iov_len, JDATA_USER);
  	}
      }
  }
  
  void
  jrecord_leaf_xio(struct jrecord *jrec, int16_t rectype, xio_t xio)
  {
      int bytes = xio->xio_npages * PAGE_SIZE;
  
      jrecord_write(jrec, rectype, bytes);
      jrecord_data(jrec, xio, bytes, JDATA_XIO);
  }
  
  /*
   * Write a leaf record out and return a pointer to its base.  The leaf
   * record may contain potentially megabytes of data which is supplied
   * in jrecord_data() calls.  The exact amount must be specified in this
   * call.
   *
   * THE RETURNED SUBRECORD POINTER IS ONLY VALID IMMEDIATELY AFTER THE
   * CALL AND MAY BECOME INVALID AT ANY TIME.  ONLY THE PUSH/POP CODE SHOULD
   * USE THE RETURN VALUE.
   */
  struct journal_subrecord *
  jrecord_write(struct jrecord *jrec, int16_t rectype, int bytes)
  {
      struct journal_subrecord *last;
      int pusheditout;
  
      /*
       * Try to catch some obvious errors.  Nesting records must specify a
       * size of 0, and there should be no left-overs from previous operations
       * (such as incomplete data writeouts).
       */
      KKASSERT(bytes == 0 || (rectype & JMASK_NESTED) == 0);
      KKASSERT(jrec->residual == 0);
  
      /*
       * Check to see if the current stream record has enough room for
       * the new subrecord header.  If it doesn't we extend the current
       * stream record.
       *
       * This may have the side effect of pushing out the current stream record
       * and creating a new one.  We must adjust our stream tracking fields
       * accordingly.
       */
      if (jrec->stream_residual < sizeof(struct journal_subrecord)) {
  	jrec->stream_ptr = journal_extend(jrec->jo, &jrec->rawp,
  				jrec->stream_reserved - jrec->stream_residual,
  				JREC_DEFAULTSIZE, &pusheditout);
  	if (pusheditout) {
  	    /*
  	     * If a pushout occured, the pushed out stream record was
  	     * truncated as specified and the new record is exactly the
  	     * extension size specified.
  	     */
  	    jrec->stream_reserved = JREC_DEFAULTSIZE;
  	    jrec->stream_residual = JREC_DEFAULTSIZE;
  	    jrec->parent = NULL;	/* no longer accessible */
  	    jrec->pushptrgood = 0;	/* restored parents in pops no good */
  	} else {
  	    /*
  	     * If no pushout occured the stream record is NOT truncated and
  	     * IS extended.
  	     */
  	    jrec->stream_reserved += JREC_DEFAULTSIZE;
  	    jrec->stream_residual += JREC_DEFAULTSIZE;
  	}
      }
      last = (void *)jrec->stream_ptr;
      last->rectype = rectype;
      last->reserved = 0;
  
      /*
       * We may not know the record size for recursive records and the 
       * header may become unavailable due to limited FIFO space.  Write
       * -1 to indicate this special case.
       */
      if ((rectype & JMASK_NESTED) && bytes == 0)
  	last->recsize = -1;
      else
  	last->recsize = sizeof(struct journal_subrecord) + bytes;
      jrec->last = last;
      jrec->residual = bytes;		/* remaining data to be posted */
      jrec->residual_align = -bytes & 7;	/* post-data alignment required */
      jrec->stream_ptr += sizeof(*last);	/* current write pointer */
      jrec->stream_residual -= sizeof(*last); /* space remaining in stream */
      return(last);
  }
  
  /*
   * Write out the data associated with a leaf record.  Any number of calls
   * to this routine may be made as long as the byte count adds up to the
   * amount originally specified in jrecord_write().
   *
   * The act of writing out the leaf data may result in numerous stream records
   * being pushed out.   Callers should be aware that even the associated
   * subrecord header may become inaccessible due to stream record pushouts.
   */
  static void
  jrecord_data(struct jrecord *jrec, void *buf, int bytes, int dtype)
  {
      int pusheditout;
      int extsize;
      int xio_offset = 0;
  
      KKASSERT(bytes >= 0 && bytes <= jrec->residual);
  
      /*
       * Push out stream records as long as there is insufficient room to hold
       * the remaining data.
       */
      while (jrec->stream_residual < bytes) {
  	/*
  	 * Fill in any remaining space in the current stream record.
  	 */
  	switch (dtype) {
  	case JDATA_KERN:
  	    bcopy(buf, jrec->stream_ptr, jrec->stream_residual);
  	    break;
  	case JDATA_USER:
  	    copyin(buf, jrec->stream_ptr, jrec->stream_residual);
  	    break;
  	case JDATA_XIO:
  	    xio_copy_xtok((xio_t)buf, xio_offset, jrec->stream_ptr,
  			  jrec->stream_residual);
  	    xio_offset += jrec->stream_residual;
  	    break;
  	}
  	if (dtype != JDATA_XIO)
  	    buf = (char *)buf + jrec->stream_residual;
  	bytes -= jrec->stream_residual;
  	/*jrec->stream_ptr += jrec->stream_residual;*/
  	jrec->residual -= jrec->stream_residual;
  	jrec->stream_residual = 0;
  
  	/*
  	 * Try to extend the current stream record, but no more then 1/4
  	 * the size of the FIFO.
  	 */
  	extsize = jrec->jo->fifo.size >> 2;
  	if (extsize > bytes)
  	    extsize = (bytes + 15) & ~15;
  
  	jrec->stream_ptr = journal_extend(jrec->jo, &jrec->rawp,
  				jrec->stream_reserved - jrec->stream_residual,
  				extsize, &pusheditout);
  	if (pusheditout) {
  	    jrec->stream_reserved = extsize;
  	    jrec->stream_residual = extsize;
  	    jrec->parent = NULL;	/* no longer accessible */
  	    jrec->last = NULL;		/* no longer accessible */
  	    jrec->pushptrgood = 0;	/* restored parents in pops no good */
  	} else {
  	    jrec->stream_reserved += extsize;
  	    jrec->stream_residual += extsize;
  	}
      }
  
      /*
       * Push out any remaining bytes into the current stream record.
       */
      if (bytes) {
  	switch (dtype) {
  	case JDATA_KERN:
  	    bcopy(buf, jrec->stream_ptr, bytes);
  	    break;
  	case JDATA_USER:
  	    copyin(buf, jrec->stream_ptr, bytes);
  	    break;
  	case JDATA_XIO:
  	    xio_copy_xtok((xio_t)buf, xio_offset, jrec->stream_ptr, bytes);
  	    break;
  	}
  	jrec->stream_ptr += bytes;
  	jrec->stream_residual -= bytes;
  	jrec->residual -= bytes;
      }
  
      /*
       * Handle data alignment requirements for the subrecord.  Because the
       * stream record's data space is more strictly aligned, it must already
       * have sufficient space to hold any subrecord alignment slop.
       */
      if (jrec->residual == 0 && jrec->residual_align) {
  	KKASSERT(jrec->residual_align <= jrec->stream_residual);
  	bzero(jrec->stream_ptr, jrec->residual_align);
  	jrec->stream_ptr += jrec->residual_align;
  	jrec->stream_residual -= jrec->residual_align;
  	jrec->residual_align = 0;
      }
  }
  
  /*
   * We are finished with the transaction.  This closes the transaction created
   * by jrecord_init().
   *
   * NOTE: If abortit is not set then we must be at the top level with no
   *	 residual subrecord data left to output.
   *
   *	 If abortit is set then we can be in any state, all pushes will be 
   *	 popped and it is ok for there to be residual data.  This works 
   *	 because the virtual stream itself is truncated.  Scanners must deal
   *	 with this situation.
   *
   * The stream record will be committed or aborted as specified and jrecord
   * resources will be cleaned up.
   */
  void
  jrecord_done(struct jrecord *jrec, int abortit)
  {
      KKASSERT(jrec->rawp != NULL);
  
      if (abortit) {
  	journal_abort(jrec->jo, &jrec->rawp);
      } else {
  	KKASSERT(jrec->pushcount == 0 && jrec->residual == 0);
  	journal_commit(jrec->jo, &jrec->rawp, 
  			jrec->stream_reserved - jrec->stream_residual, 1);
      }
  
      /*
       * jrec should not be used beyond this point without another init,
       * but clean up some fields to ensure that we panic if it is.
       *
       * Note that jrec->rawp is NULLd out by journal_abort/journal_commit.
       */
      jrec->jo = NULL;
      jrec->stream_ptr = NULL;
  }
  
  /************************************************************************
   *			LOW LEVEL RECORD SUPPORT ROUTINES		*
   ************************************************************************
   *
   * These routine create low level recursive and leaf subrecords representing
   * common filesystem structures.
   */
  
  /*
   * Write out a filename path relative to the base of the mount point.
   * rectype is typically JLEAF_PATH{1,2,3,4}.
   */
  void
  jrecord_write_path(struct jrecord *jrec, int16_t rectype, struct namecache *ncp)
  {
      char buf[64];	/* local buffer if it fits, else malloced */
      char *base;
      int pathlen;
      int index;
      struct namecache *scan;
  
      /*
       * Pass 1 - figure out the number of bytes required.  Include terminating
       * 	       \0 on last element and '/' separator on other elements.
       *
       * The namecache topology terminates at the root of the filesystem
       * (the normal lookup code would then continue by using the mount
       * structure to figure out what it was mounted on).
       */
  again:
      pathlen = 0;
      for (scan = ncp; scan; scan = scan->nc_parent) {
  	if (scan->nc_nlen > 0)
  	    pathlen += scan->nc_nlen + 1;
      }
  
      if (pathlen <= sizeof(buf))
  	base = buf;
      else
  	base = kmalloc(pathlen, M_TEMP, M_INTWAIT);
  
      /*
       * Pass 2 - generate the path buffer
       */
      index = pathlen;
      for (scan = ncp; scan; scan = scan->nc_parent) {
  	if (scan->nc_nlen == 0)
  	    continue;
  	if (scan->nc_nlen >= index) {
  	    if (base != buf)
  		kfree(base, M_TEMP);
  	    goto again;
  	}
  	if (index == pathlen)
  	    base[--index] = 0;
  	else
  	    base[--index] = '/';
  	index -= scan->nc_nlen;
  	bcopy(scan->nc_name, base + index, scan->nc_nlen);
      }
      jrecord_leaf(jrec, rectype, base + index, pathlen - index);
      if (base != buf)
  	kfree(base, M_TEMP);
  }
  
  /*
   * Write out a file attribute structure.  While somewhat inefficient, using
   * a recursive data structure is the most portable and extensible way.
   */
  void
  jrecord_write_vattr(struct jrecord *jrec, struct vattr *vat)
  {
      void *save;
  
      save = jrecord_push(jrec, JTYPE_VATTR);
      if (vat->va_type != VNON)
  	jrecord_leaf(jrec, JLEAF_VTYPE, &vat->va_type, sizeof(vat->va_type));
      if (vat->va_mode != (mode_t)VNOVAL)
  	jrecord_leaf(jrec, JLEAF_MODES, &vat->va_mode, sizeof(vat->va_mode));
      if (vat->va_nlink != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_NLINK, &vat->va_nlink, sizeof(vat->va_nlink));
      if (vat->va_uid != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_UID, &vat->va_uid, sizeof(vat->va_uid));
      if (vat->va_gid != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_GID, &vat->va_gid, sizeof(vat->va_gid));
      if (vat->va_fsid != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_FSID, &vat->va_fsid, sizeof(vat->va_fsid));
      if (vat->va_fileid != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_INUM, &vat->va_fileid, sizeof(vat->va_fileid));
      if (vat->va_size != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_SIZE, &vat->va_size, sizeof(vat->va_size));
      if (vat->va_atime.tv_sec != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_ATIME, &vat->va_atime, sizeof(vat->va_atime));
      if (vat->va_mtime.tv_sec != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_MTIME, &vat->va_mtime, sizeof(vat->va_mtime));
      if (vat->va_ctime.tv_sec != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_CTIME, &vat->va_ctime, sizeof(vat->va_ctime));
      if (vat->va_gen != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_GEN, &vat->va_gen, sizeof(vat->va_gen));
      if (vat->va_flags != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_FLAGS, &vat->va_flags, sizeof(vat->va_flags));
      if (vat->va_rmajor != VNOVAL) {
  	udev_t rdev = makeudev(vat->va_rmajor, vat->va_rminor);
  	jrecord_leaf(jrec, JLEAF_UDEV, &rdev, sizeof(rdev));
  	jrecord_leaf(jrec, JLEAF_UMAJOR, &vat->va_rmajor, sizeof(vat->va_rmajor));
  	jrecord_leaf(jrec, JLEAF_UMINOR, &vat->va_rminor, sizeof(vat->va_rminor));
      }
  #if 0
      if (vat->va_filerev != VNOVAL)
  	jrecord_leaf(jrec, JLEAF_FILEREV, &vat->va_filerev, sizeof(vat->va_filerev));
  #endif
      jrecord_pop(jrec, save);
  }
  
  /*
   * Write out the creds used to issue a file operation.  If a process is
   * available write out additional tracking information related to the 
   * process.
   *
   * XXX additional tracking info
   * XXX tty line info
   */
  void
  jrecord_write_cred(struct jrecord *jrec, struct thread *td, struct ucred *cred)
  {
      void *save;
      struct proc *p;
  
      save = jrecord_push(jrec, JTYPE_CRED);
      jrecord_leaf(jrec, JLEAF_UID, &cred->cr_uid, sizeof(cred->cr_uid));
      jrecord_leaf(jrec, JLEAF_GID, &cred->cr_gid, sizeof(cred->cr_gid));
      if (td && (p = td->td_proc) != NULL) {
  	jrecord_leaf(jrec, JLEAF_PID, &p->p_pid, sizeof(p->p_pid));
  	jrecord_leaf(jrec, JLEAF_COMM, p->p_comm, sizeof(p->p_comm));
      }
      jrecord_pop(jrec, save);
  }
  
  /*
   * Write out information required to identify a vnode
   *
   * XXX this needs work.  We should write out the inode number as well,
   * and in fact avoid writing out the file path for seqential writes
   * occuring within e.g. a certain period of time.
   */
  void
  jrecord_write_vnode_ref(struct jrecord *jrec, struct vnode *vp)
  {
      struct nchandle nch;
  
      nch.mount = vp->v_mount;
      spin_lock(&vp->v_spin);
      TAILQ_FOREACH(nch.ncp, &vp->v_namecache, nc_vnode) {
  	if ((nch.ncp->nc_flag & (NCF_UNRESOLVED|NCF_DESTROYED)) == 0)
  	    break;
      }
      if (nch.ncp) {
  	cache_hold(&nch);
  	spin_unlock(&vp->v_spin);
  	jrecord_write_path(jrec, JLEAF_PATH_REF, nch.ncp);
  	cache_drop(&nch);
      } else {
  	spin_unlock(&vp->v_spin);
      }
  }
  
  void
  jrecord_write_vnode_link(struct jrecord *jrec, struct vnode *vp, 
  			 struct namecache *notncp)
  {
      struct nchandle nch;
  
      nch.mount = vp->v_mount;
      spin_lock(&vp->v_spin);
      TAILQ_FOREACH(nch.ncp, &vp->v_namecache, nc_vnode) {
  	if (nch.ncp == notncp)
  	    continue;
  	if ((nch.ncp->nc_flag & (NCF_UNRESOLVED|NCF_DESTROYED)) == 0)
  	    break;
      }
      if (nch.ncp) {
  	cache_hold(&nch);
  	spin_unlock(&vp->v_spin);
  	jrecord_write_path(jrec, JLEAF_PATH_REF, nch.ncp);
  	cache_drop(&nch);
      } else {
  	spin_unlock(&vp->v_spin);
      }
  }
  
  /*
   * Write out the data represented by a pagelist
   */
  void
  jrecord_write_pagelist(struct jrecord *jrec, int16_t rectype,
  			struct vm_page **pglist, int *rtvals, int pgcount,
  			off_t offset)
  {
      struct xio xio;
      int error;
      int b;
      int i;
  
      i = 0;
      xio_init(&xio);
      while (i < pgcount) {
  	/*
  	 * Find the next valid section.  Skip any invalid elements
  	 */
  	if (rtvals[i] != VM_PAGER_OK) {
  	    ++i;
  	    offset += PAGE_SIZE;
  	    continue;
  	}
  
  	/*
  	 * Figure out how big the valid section is, capping I/O at what the
  	 * MSFBUF can represent.
  	 */
  	b = i;
  	while (i < pgcount && i - b != XIO_INTERNAL_PAGES && 
  	       rtvals[i] == VM_PAGER_OK
  	) {
  	    ++i;
  	}
  
  	/*
  	 * And write it out.
  	 */
  	if (i - b) {
  	    error = xio_init_pages(&xio, pglist + b, i - b, XIOF_READ);
  	    if (error == 0) {
  		jrecord_leaf(jrec, JLEAF_SEEKPOS, &offset, sizeof(offset));
  		jrecord_leaf_xio(jrec, rectype, &xio);
  	    } else {
  		kprintf("jrecord_write_pagelist: xio init failure\n");
  	    }
  	    xio_release(&xio);
  	    offset += (off_t)(i - b) << PAGE_SHIFT;
  	}
      }
  }
  
  /*
   * Write out the data represented by a UIO.
   */
  void
  jrecord_write_uio(struct jrecord *jrec, int16_t rectype, struct uio *uio)
  {
      if (uio->uio_segflg != UIO_NOCOPY) {
  	jrecord_leaf(jrec, JLEAF_SEEKPOS, &uio->uio_offset, 
  		     sizeof(uio->uio_offset));
  	jrecord_leaf_uio(jrec, rectype, uio);
      }
  }
  
  void
  jrecord_file_data(struct jrecord *jrec, struct vnode *vp, 
  		  off_t off, off_t bytes)
  {
      const int bufsize = 8192;
      char *buf;
      int error;
      int n;
  
      buf = kmalloc(bufsize, M_JOURNAL, M_WAITOK);
      jrecord_leaf(jrec, JLEAF_SEEKPOS, &off, sizeof(off));
      while (bytes) {
  	n = (bytes > bufsize) ? bufsize : (int)bytes;
  	error = vn_rdwr(UIO_READ, vp, buf, n, off, UIO_SYSSPACE, IO_NODELOCKED,
  			proc0.p_ucred, NULL);
  	if (error) {
  	    jrecord_leaf(jrec, JLEAF_ERROR, &error, sizeof(error));
  	    break;
  	}
  	jrecord_leaf(jrec, JLEAF_FILEDATA, buf, n);
  	bytes -= n;
  	off += n;
      }
      kfree(buf, M_JOURNAL);
  }
  
  