Initial revision

1 files changed, 1053 insertions, 0 deletions

diff --git a/ufs/alloc.c b/ufs/alloc.c
new file mode 100644
index 00000000..161edcb8
--- /dev/null
+++ b/ufs/alloc.c
@@ -0,0 +1,1053 @@
+/* Disk allocation routines
+   Copyright (C) 1993, 1994 Free Software Foundation
+
+This file is part of the GNU Hurd.
+
+The GNU Hurd 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, or (at your option)
+any later version.
+
+The GNU Hurd 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 the GNU Hurd; see the file COPYING.  If not, write to
+the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+/* Modified from UCB by Michael I. Bushnell.  */
+
+/*
+ * Copyright (c) 1982, 1986, 1989 Regents of the University of California.
+ * All rights reserved.
+ *
+ * Redistribution is only permitted until one year after the first shipment
+ * of 4.4BSD by the Regents.  Otherwise, redistribution and use in source and
+ * binary forms are permitted provided that: (1) source distributions retain
+ * this entire copyright notice and comment, and (2) distributions including
+ * binaries display the following acknowledgement:  This product includes
+ * software developed by the University of California, Berkeley and its
+ * contributors'' in the documentation or other materials provided with the
+ * distribution and in all advertising materials mentioning features or use
+ * of this software.  Neither the name of the University nor the names of
+ * its contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ *	@(#)ufs_alloc.c	7.20 (Berkeley) 6/28/90
+ */
+
+#include "ufs.h"
+#include "fs.h"
+#include "dinode.h"
+
+#include <stdio.h>
+
+static u_long alloccg (int, daddr_t, int);
+static u_long ialloccg (int, daddr_t, int);
+static u_long hashalloc (int, long, int, u_long(*)(int, daddr_t, int));
+static daddr_t fragextend (int, long, int, int);
+static daddr_t alloccgblk (struct cg *, daddr_t);
+static daddr_t mapsearch (struct cg *, daddr_t, int);
+static ino_t dirpref ();
+
+/* These are in tables.c.  */
+extern int inside[], around[];     
+extern unsigned char	*fragtbl[];
+
+static spin_lock_t alloclock = SPIN_LOCK_INITIALIZER;
+
+/*
+ * Allocate a block in the file system.
+ * 
+ * The size of the requested block is given, which must be some
+ * multiple of fs_fsize and <= fs_bsize.
+ * A preference may be optionally specified. If a preference is given
+ * the following hierarchy is used to allocate a block:
+ *   1) allocate the requested block.
+ *   2) allocate a rotationally optimal block in the same cylinder.
+ *   3) allocate a block in the same cylinder group.
+ *   4) quadradically rehash into other cylinder groups, until an
+ *      available block is located.
+ * If no block preference is given the following heirarchy is used
+ * to allocate a block:
+ *   1) allocate a block in the cylinder group that contains the
+ *      inode for the file.
+ *   2) quadradically rehash into other cylinder groups, until an
+ *      available block is located.
+ */
+error_t
+alloc(struct node *np,
+      daddr_t lbn, 
+      daddr_t bpref,
+      int size,
+      daddr_t *bnp,
+      struct protid *cred)
+{
+  int cg;
+  daddr_t bno;
+
+  *bnp = 0;
+  assert ("Alloc of bad sized block" && (unsigned) size <= sblock->fs_bsize
+	  && !fragoff(size));
+
+  spin_lock (&alloclock);
+  
+  if (size == sblock->fs_bsize && sblock->fs_cstotal.cs_nbfree == 0)
+    goto nospace;
+  if (cred && !diskfs_isuid (0, cred) && freespace(sblock->fs_minfree) <= 0)
+    goto nospace;
+  
+  if (bpref >= sblock->fs_size)
+    bpref = 0;
+  if (bpref == 0)
+    cg = itog(np->dn->number);
+  else
+    cg = dtog(bpref);
+  bno = (daddr_t)hashalloc(cg, (long)bpref, size, alloccg);
+
+  spin_unlock (&alloclock);
+
+  if (bno > 0)
+    {
+      np->dn_stat.st_blocks += btodb(size);
+      np->dn_set_mtime = 1;
+      np->dn_set_ctime = 1;
+      *bnp = bno;
+      return 0;
+    }
+
+ nospace:
+  spin_unlock (&alloclock);
+  printf("file system full\n");
+  return (ENOSPC);
+}
+
+/*
+ * Reallocate a fragment to a bigger size
+ *
+ * The number and size of the old block is given, and a preference
+ * and new size is also specified. The allocator attempts to extend
+ * the original block. Failing that, the regular block allocator is
+ * invoked to get an appropriate block.
+ */
+error_t
+realloccg(struct node *np,
+	  daddr_t lbprev,
+	  volatile daddr_t bpref,
+	  int osize, 
+	  int nsize,
+	  daddr_t *pbn,
+	  struct protid *cred)
+{
+  volatile int cg, request;
+  daddr_t bprev, bno;
+  error_t error;
+  
+  *pbn = 0;
+  assert ("bad old size" && (unsigned) osize <= sblock->fs_bsize
+	  && !fragoff (osize));
+  assert ("bad new size" && (unsigned) nsize <= sblock->fs_bsize
+	  && !fragoff (nsize));
+
+  spin_lock (&alloclock);
+
+  if (cred && !diskfs_isuid (0, cred) && freespace(sblock->fs_minfree) <= 0)
+    {
+      spin_unlock (&alloclock);
+      goto nospace;
+    }
+
+  if (error = diskfs_catch_exception ())
+    return error;
+  bprev = dinodes[np->dn->number].di_db[lbprev];
+  diskfs_end_catch_exception ();
+  assert ("old block not allocated" && bprev);
+
+  /*
+   * Check for extension in the existing location.
+   */
+  cg = dtog(bprev);
+  if (bno = fragextend(cg, (long)bprev, osize, nsize))
+    {
+      spin_unlock (&alloclock);
+      assert ("fragextend behaved incorrectly" && bprev == bno);
+      np->dn_stat.st_blocks += btodb(nsize - osize);
+      np->dn_set_mtime = 1;
+      np->dn_set_ctime = 1;
+      *pbn = bno;
+      return (0);
+    }
+  /*
+   * Allocate a new disk location.
+   */
+  if (bpref >= sblock->fs_size)
+    bpref = 0;
+  switch ((int)sblock->fs_optim)
+    {
+    case FS_OPTSPACE:
+      /*
+       * Allocate an exact sized fragment. Although this makes 
+       * best use of space, we will waste time relocating it if 
+       * the file continues to grow. If the fragmentation is
+       * less than half of the minimum free reserve, we choose
+       * to begin optimizing for time.
+       */
+      request = nsize;
+      if (sblock->fs_minfree < 5 ||
+	  sblock->fs_cstotal.cs_nffree >
+	  sblock->fs_dsize * sblock->fs_minfree / (2 * 100))
+	break;
+      printf("optimization changed from SPACE to TIME\n");
+      sblock->fs_optim = FS_OPTTIME; 
+      break;
+    case FS_OPTTIME:
+      /*
+       * At this point we have discovered a file that is trying
+       * to grow a small fragment to a larger fragment. To save
+       * time, we allocate a full sized block, then free the 
+       * unused portion. If the file continues to grow, the 
+       * `fragextend' call above will be able to grow it in place
+       * without further copying. If aberrant programs cause
+       * disk fragmentation to grow within 2% of the free reserve,
+       * we choose to begin optimizing for space.
+       */
+      request = sblock->fs_bsize;
+      if (sblock->fs_cstotal.cs_nffree <
+	  sblock->fs_dsize * (sblock->fs_minfree - 2) / 100)
+	break;
+      printf("%s: optimization changed from TIME to SPACE\n",
+	     sblock->fs_fsmnt);
+      sblock->fs_optim = FS_OPTSPACE;
+      break;
+    default:
+      assert ("filesystem opitimazation bad value" && 0);
+    }
+  
+  bno = (daddr_t)hashalloc(cg, (long)bpref, request, 
+			   (u_long (*)())alloccg);
+
+  spin_unlock (&alloclock);
+
+  if (bno > 0) 
+    {
+      blkfree(bprev, (off_t)osize);
+      if (nsize < request)
+	blkfree(bno + numfrags(nsize), (off_t)(request - nsize));
+      np->dn_stat.st_blocks += btodb (nsize - osize);
+      np->dn_set_mtime = 1;
+      np->dn_set_ctime = 1;
+      *pbn = bno;
+      return (0);
+    }
+ nospace:
+  /*
+   * no space available
+   */
+  printf("file system full\n");
+  return (ENOSPC);
+}
+
+
+/* Implement the diskfs_alloc_node callback from the diskfs library.
+   See <hurd/diskfs.h> for the interface description. */
+error_t
+diskfs_alloc_node(struct node *dir,
+		  mode_t mode,
+		  struct node **npp)
+{
+  int ino;
+  struct node *np;
+  int cg;
+  error_t error;
+  int ipref;
+
+  if (S_ISDIR (mode))
+    ipref = dirpref ();
+  else
+    ipref = dir->dn->number;
+  
+  *npp = 0;
+
+  if (sblock->fs_cstotal.cs_nifree == 0)
+    goto noinodes;
+  if (ipref >= sblock->fs_ncg * sblock->fs_ipg)
+    ipref = 0;
+  cg = itog(ipref);
+  spin_lock (&alloclock);
+  ino = (int)hashalloc(cg, (long)ipref, mode, ialloccg);
+  spin_unlock (&alloclock);
+  if (ino == 0)
+    goto noinodes;
+  if (error = iget(ino, &np))
+    return error;
+  *npp = np;
+  assert ("duplicate allocation" && !np->dn_stat.st_mode);
+  if (np->dn_stat.st_blocks)
+    {
+      printf("free inode %d had %d blocks\n", ino, np->dn_stat.st_blocks);
+      np->dn_stat.st_blocks = 0;
+      np->dn_set_ctime = 1;
+    }
+  /*
+   * Set up a new generation number for this inode.
+   */
+  spin_lock (&gennumberlock);
+  if (++nextgennumber < (u_long)diskfs_mtime->seconds)
+    nextgennumber = diskfs_mtime->seconds;
+  np->dn_stat.st_gen = nextgennumber;
+  spin_unlock (&gennumberlock);
+  return (0);
+ noinodes:
+  printf("out of inodes\n");
+  return (ENOSPC);
+}
+
+/*
+ * Find a cylinder to place a directory.
+ *
+ * The policy implemented by this algorithm is to select from
+ * among those cylinder groups with above the average number of
+ * free inodes, the one with the smallest number of directories.
+ */
+static ino_t
+dirpref()
+{
+  int cg, minndir, mincg, avgifree;
+  
+  spin_lock (&alloclock);
+  avgifree = sblock->fs_cstotal.cs_nifree / sblock->fs_ncg;
+  minndir = sblock->fs_ipg;
+  mincg = 0;
+  for (cg = 0; cg < sblock->fs_ncg; cg++)
+    if (csum[cg].cs_ndir < minndir && csum[cg].cs_nifree >= avgifree)
+      {
+	mincg = cg;
+	minndir = csum[cg].cs_ndir;
+      }
+  spin_unlock (&alloclock);
+  return ((int)(sblock->fs_ipg * mincg));
+}
+
+/*
+ * Select the desired position for the next block in a file.  The file is
+ * logically divided into sections. The first section is composed of the
+ * direct blocks. Each additional section contains fs_maxbpg blocks.
+ * 
+ * If no blocks have been allocated in the first section, the policy is to
+ * request a block in the same cylinder group as the inode that describes
+ * the file. If no blocks have been allocated in any other section, the
+ * policy is to place the section in a cylinder group with a greater than
+ * average number of free blocks.  An appropriate cylinder group is found
+ * by using a rotor that sweeps the cylinder groups. When a new group of
+ * blocks is needed, the sweep begins in the cylinder group following the
+ * cylinder group from which the previous allocation was made. The sweep
+ * continues until a cylinder group with greater than the average number
+ * of free blocks is found. If the allocation is for the first block in an
+ * indirect block, the information on the previous allocation is unavailable;
+ * here a best guess is made based upon the logical block number being
+ * allocated.
+ * 
+ * If a section is already partially allocated, the policy is to
+ * contiguously allocate fs_maxcontig blocks.  The end of one of these
+ * contiguous blocks and the beginning of the next is physically separated
+ * so that the disk head will be in transit between them for at least
+ * fs_rotdelay milliseconds.  This is to allow time for the processor to
+ * schedule another I/O transfer.
+ */
+daddr_t
+blkpref(struct node *np,
+	daddr_t lbn,
+	int indx,
+	daddr_t *bap)
+{
+  int cg;
+  int avgbfree, startcg;
+  daddr_t nextblk;
+  
+  spin_lock (&alloclock);
+  if (indx % sblock->fs_maxbpg == 0 || bap[indx - 1] == 0) 
+    {
+      if (lbn < NDADDR) 
+	{
+	  spin_unlock (&alloclock);
+	  cg = itog(np->dn->number);
+	  return (sblock->fs_fpg * cg + sblock->fs_frag);
+	}
+      /*
+       * Find a cylinder with greater than average number of
+       * unused data blocks.
+       */
+      if (indx == 0 || bap[indx - 1] == 0)
+	startcg = itog(np->dn->number) + lbn / sblock->fs_maxbpg;
+      else
+	startcg = dtog(bap[indx - 1]) + 1;
+      startcg %= sblock->fs_ncg;
+      avgbfree = sblock->fs_cstotal.cs_nbfree / sblock->fs_ncg;
+      for (cg = startcg; cg < sblock->fs_ncg; cg++)
+	if (csum[cg].cs_nbfree >= avgbfree) 
+	  {
+	    spin_unlock (&alloclock);
+	    sblock->fs_cgrotor = cg;
+	    return (sblock->fs_fpg * cg + sblock->fs_frag);
+	  }
+      for (cg = 0; cg <= startcg; cg++)
+	if (csum[cg].cs_nbfree >= avgbfree) 
+	  {
+	    spin_unlock (&alloclock);
+	    sblock->fs_cgrotor = cg;
+	    return (sblock->fs_fpg * cg + sblock->fs_frag);
+	  }
+      spin_unlock (&alloclock);
+      return 0;
+    }
+
+  spin_unlock (&alloclock);
+
+  /*
+   * One or more previous blocks have been laid out. If less
+   * than fs_maxcontig previous blocks are contiguous, the
+   * next block is requested contiguously, otherwise it is
+   * requested rotationally delayed by fs_rotdelay milliseconds.
+   */
+  nextblk = bap[indx - 1] + sblock->fs_frag;
+  if (indx > sblock->fs_maxcontig &&
+      bap[indx - sblock->fs_maxcontig] + blkstofrags(sblock->fs_maxcontig)
+      != nextblk)
+    return (nextblk);
+  if (sblock->fs_rotdelay != 0)
+    /*
+     * Here we convert ms of delay to frags as:
+     * (frags) = (ms) * (rev/sec) * (sect/rev) /
+     *	((sect/frag) * (ms/sec))
+     * then round up to the next block.
+     */
+    nextblk += roundup(sblock->fs_rotdelay * sblock->fs_rps 
+		       * sblock->fs_nsect / (NSPF * 1000), sblock->fs_frag);
+  return (nextblk);
+}
+
+/*
+ * Implement the cylinder overflow algorithm.
+ *
+ * The policy implemented by this algorithm is:
+ *   1) allocate the block in its requested cylinder group.
+ *   2) quadradically rehash on the cylinder group number.
+ *   3) brute force search for a free block.
+ */
+/*VARARGS5*/
+static u_long
+hashalloc(int cg,
+	  long pref,
+	  int size,		/* size for data blocks, mode for inodes */
+	  u_long (*allocator)(int, daddr_t, int))
+{
+  long result;
+  int i, icg = cg;
+  
+  /*
+   * 1: preferred cylinder group
+   */
+  result = (*allocator)(cg, pref, size);
+  if (result)
+    return (result);
+  /*
+   * 2: quadratic rehash
+   */
+  for (i = 1; i < sblock->fs_ncg; i *= 2) 
+    {
+      cg += i;
+      if (cg >= sblock->fs_ncg)
+	cg -= sblock->fs_ncg;
+      result = (*allocator)(cg, 0, size);
+      if (result)
+	return (result);
+    }
+  /*
+   * 3: brute force search
+   * Note that we start at i == 2, since 0 was checked initially,
+   * and 1 is always checked in the quadratic rehash.
+   */
+  cg = (icg + 2) % sblock->fs_ncg;
+  for (i = 2; i < sblock->fs_ncg; i++)
+    {
+      result = (*allocator)(cg, 0, size);
+      if (result)
+	return (result);
+      cg++;
+      if (cg == sblock->fs_ncg)
+	cg = 0;
+    }
+  return 0;
+}
+
+/*
+ * Determine whether a fragment can be extended.
+ *
+ * Check to see if the necessary fragments are available, and 
+ * if they are, allocate them.
+ */
+static daddr_t
+fragextend(int cg,
+	   long bprev,
+	   int osize, 
+	   int nsize)
+{
+  struct cg *cgp;
+  long bno;
+  int frags, bbase;
+  int i;
+  
+  if (csum[cg].cs_nffree < numfrags(nsize - osize))
+    return 0;
+  frags = numfrags(nsize);
+  bbase = fragnum(bprev);
+  if (bbase > fragnum((bprev + frags - 1)))
+    /* cannot extend across a block boundary */
+    return 0;
+
+  cgp = (struct cg *) (cgs + sblock->fs_bsize * cg);
+
+  if (diskfs_catch_exception ())
+    return 0;			/* bogus, but that's what BSD does... */
+  
+  if (!cg_chkmagic(cgp))
+    {
+      printf ("Cylinder group %d bad magic number: %ld/%ld\n",
+	      cg, cgp->cg_magic, ((struct ocg *)(cgp))->cg_magic);
+      diskfs_end_catch_exception ();
+      return 0;
+    }
+  cgp->cg_time = diskfs_mtime->seconds;
+  bno = dtogd(bprev);
+  for (i = numfrags(osize); i < frags; i++)
+    if (isclr(cg_blksfree(cgp), bno + i))
+      {
+	diskfs_end_catch_exception ();
+	return 0;
+      }
+
+  /*
+   * the current fragment can be extended
+   * deduct the count on fragment being extended into
+   * increase the count on the remaining fragment (if any)
+   * allocate the extended piece
+   */
+  for (i = frags; i < sblock->fs_frag - bbase; i++)
+    if (isclr(cg_blksfree(cgp), bno + i))
+      break;
+  cgp->cg_frsum[i - numfrags(osize)]--;
+  if (i != frags)
+    cgp->cg_frsum[i - frags]++;
+  for (i = numfrags(osize); i < frags; i++)
+    {
+      clrbit(cg_blksfree(cgp), bno + i);
+      cgp->cg_cs.cs_nffree--;
+      sblock->fs_cstotal.cs_nffree--;
+      csum[cg].cs_nffree--;
+    }
+  diskfs_end_catch_exception ();
+  return (bprev);
+}
+
+/*
+ * Determine whether a block can be allocated.
+ *
+ * Check to see if a block of the apprpriate size is available,
+ * and if it is, allocate it.
+ */
+static u_long
+alloccg(int cg,
+	volatile daddr_t bpref,
+	int size)
+{
+  struct cg *cgp;
+  int i;
+  int bno, frags, allocsiz;
+  
+  if (csum[cg].cs_nbfree == 0 && size == sblock->fs_bsize)
+    return 0;
+  cgp = (struct cg *) (cgs + sblock->fs_bsize * cg);
+
+  if (diskfs_catch_exception ())
+    return 0;
+  
+  if (!cg_chkmagic(cgp) ||
+      (cgp->cg_cs.cs_nbfree == 0 && size == sblock->fs_bsize))
+    {
+      printf ("Cylinder group %d bad magic number: %ld/%ld\n",
+	      cg, cgp->cg_magic, ((struct ocg *)(cgp))->cg_magic);
+      diskfs_end_catch_exception ();
+      return 0;
+    }
+  cgp->cg_time = diskfs_mtime->seconds;
+  if (size == sblock->fs_bsize)
+    {
+      bno = alloccgblk(cgp, bpref);
+      diskfs_end_catch_exception ();
+      return (u_long) (bno);
+    }
+  /*
+   * check to see if any fragments are already available
+   * allocsiz is the size which will be allocated, hacking
+   * it down to a smaller size if necessary
+   */
+  frags = numfrags(size);
+  for (allocsiz = frags; allocsiz < sblock->fs_frag; allocsiz++)
+    if (cgp->cg_frsum[allocsiz] != 0)
+      break;
+  if (allocsiz == sblock->fs_frag)
+    {
+      /*
+       * no fragments were available, so a block will be 
+       * allocated, and hacked up
+       */
+      if (cgp->cg_cs.cs_nbfree == 0)
+	{
+	  diskfs_end_catch_exception ();
+	  return 0;
+	}
+
+      bno = alloccgblk(cgp, bpref);
+      bpref = dtogd(bno);
+      for (i = frags; i < sblock->fs_frag; i++)
+	setbit(cg_blksfree(cgp), bpref + i);
+      i = sblock->fs_frag - frags;
+      cgp->cg_cs.cs_nffree += i;
+      sblock->fs_cstotal.cs_nffree += i;
+      csum[cg].cs_nffree += i;
+      cgp->cg_frsum[i]++;
+      return (u_long)(bno);
+    }
+  bno = mapsearch(cgp, bpref, allocsiz);
+  if (bno < 0)
+    {
+      diskfs_end_catch_exception ();
+      return 0;
+    }
+
+  for (i = 0; i < frags; i++)
+    clrbit(cg_blksfree(cgp), bno + i);
+  cgp->cg_cs.cs_nffree -= frags;
+  sblock->fs_cstotal.cs_nffree -= frags;
+  csum[cg].cs_nffree -= frags;
+  cgp->cg_frsum[allocsiz]--;
+  if (frags != allocsiz)
+    cgp->cg_frsum[allocsiz - frags]++;
+  diskfs_end_catch_exception ();
+  return (u_long) (cg * sblock->fs_fpg + bno);
+}
+
+/*
+ * Allocate a block in a cylinder group.
+ *
+ * This algorithm implements the following policy:
+ *   1) allocate the requested block.
+ *   2) allocate a rotationally optimal block in the same cylinder.
+ *   3) allocate the next available block on the block rotor for the
+ *      specified cylinder group.
+ * Note that this routine only allocates fs_bsize blocks; these
+ * blocks may be fragmented by the routine that allocates them.
+ */
+static daddr_t
+alloccgblk(struct cg *cgp,
+	   volatile daddr_t bpref)
+{
+  daddr_t bno;
+  int cylno, pos, delta;
+  short *cylbp;
+  int i;
+  daddr_t ret;
+  
+  if (diskfs_catch_exception ())
+    return 0;
+  
+  if (bpref == 0) 
+    {
+      bpref = cgp->cg_rotor;
+      goto norot;
+    }
+  bpref = blknum(bpref);
+  bpref = dtogd(bpref);
+  /*
+   * if the requested block is available, use it
+   */
+  if (isblock(cg_blksfree(cgp), fragstoblks(bpref)))
+    {
+      bno = bpref;
+      goto gotit;
+    }
+  /*
+   * check for a block available on the same cylinder
+   */
+  cylno = cbtocylno(bpref);
+  if (cg_blktot(cgp)[cylno] == 0)
+    goto norot;
+  if (sblock->fs_cpc == 0)
+    {
+      /*
+       * block layout info is not available, so just have
+       * to take any block in this cylinder.
+       */
+      bpref = howmany(sblock->fs_spc * cylno, NSPF);
+      goto norot;
+    }
+  /*
+   * check the summary information to see if a block is 
+   * available in the requested cylinder starting at the
+   * requested rotational position and proceeding around.
+   */
+  cylbp = cg_blks(cgp, cylno);
+  pos = cbtorpos(bpref);
+  for (i = pos; i < sblock->fs_nrpos; i++)
+    if (cylbp[i] > 0)
+      break;
+  if (i == sblock->fs_nrpos)
+    for (i = 0; i < pos; i++)
+      if (cylbp[i] > 0)
+	break;
+  if (cylbp[i] > 0)
+    {
+      /*
+       * found a rotational position, now find the actual
+       * block. A panic if none is actually there.
+       */
+      pos = cylno % sblock->fs_cpc;
+      bno = (cylno - pos) * sblock->fs_spc / NSPB;
+      assert ("postbl table bad" &&fs_postbl(pos)[i] != -1);
+      for (i = fs_postbl(pos)[i];; )
+	{
+	  if (isblock(cg_blksfree(cgp), bno + i))
+	    {
+	      bno = blkstofrags(bno + i);
+	      goto gotit;
+	    }
+	  delta = fs_rotbl[i];
+	  if (delta <= 0 ||
+	      delta + i > fragstoblks(sblock->fs_fpg))
+	    break;
+	  i += delta;
+	}
+      assert ("Inconsistent rotbl table" && 0);
+    }
+ norot:
+  /*
+   * no blocks in the requested cylinder, so take next
+   * available one in this cylinder group.
+   */
+  bno = mapsearch(cgp, bpref, (int)sblock->fs_frag);
+  if (bno < 0)
+    {
+      diskfs_end_catch_exception ();
+      return 0;
+    }
+  cgp->cg_rotor = bno;
+ gotit:
+  clrblock(cg_blksfree(cgp), (long)fragstoblks(bno));
+  cgp->cg_cs.cs_nbfree--;
+  sblock->fs_cstotal.cs_nbfree--;
+  csum[cgp->cg_cgx].cs_nbfree--;
+  cylno = cbtocylno(bno);
+  cg_blks(cgp, cylno)[cbtorpos(bno)]--;
+  cg_blktot(cgp)[cylno]--;
+  ret = cgp->cg_cgx * sblock->fs_fpg + bno;
+  diskfs_end_catch_exception ();
+  return ret;
+}
+
+/*
+ * Determine whether an inode can be allocated.
+ *
+ * Check to see if an inode is available, and if it is,
+ * allocate it using the following policy:
+ *   1) allocate the requested inode.
+ *   2) allocate the next available inode after the requested
+ *      inode in the specified cylinder group.
+ */
+static u_long
+ialloccg(int cg,
+	 volatile daddr_t ipref,
+	 int modein)
+{
+  struct cg *cgp;
+  int start, len, loc, map, i;
+  mode_t mode = (mode_t) modein;
+  
+  if (csum[cg].cs_nifree == 0)
+    return 0;
+
+  cgp = (struct cg *)(cgs + sblock->fs_bsize * cg);
+
+  if (diskfs_catch_exception ())
+    return 0;
+  
+  if (!cg_chkmagic(cgp) || cgp->cg_cs.cs_nifree == 0)
+    {
+      printf ("Cylinder group %d bad magic number: %ld/%ld\n",
+	      cg, cgp->cg_magic, ((struct ocg *)(cgp))->cg_magic);
+      diskfs_end_catch_exception ();
+      return 0;
+    }
+  cgp->cg_time = diskfs_mtime->seconds;
+  if (ipref)
+    {
+      ipref %= sblock->fs_ipg;
+      if (isclr(cg_inosused(cgp), ipref))
+	goto gotit;
+    }
+  start = cgp->cg_irotor / NBBY;
+  len = howmany(sblock->fs_ipg - cgp->cg_irotor, NBBY);
+  loc = skpc(0xff, len, (u_char *) &cg_inosused(cgp)[start]);
+  if (loc == 0)
+    {
+      len = start + 1;
+      start = 0;
+      loc = skpc(0xff, len, (u_char *) &cg_inosused(cgp)[0]);
+      assert ("inconsistent cg_inosused table" && loc);
+    }
+  i = start + len - loc;
+  map = cg_inosused(cgp)[i];
+  ipref = i * NBBY;
+  for (i = 1; i < (1 << NBBY); i <<= 1, ipref++)
+    {
+      if ((map & i) == 0)
+	{
+	  cgp->cg_irotor = ipref;
+	  goto gotit;
+	}
+    }
+  assert ("inconsistent cg_inosused table" && 0);
+ gotit:
+  setbit(cg_inosused(cgp), ipref);
+  cgp->cg_cs.cs_nifree--;
+  sblock->fs_cstotal.cs_nifree--;
+  csum[cg].cs_nifree--;
+  if ((mode & IFMT) == IFDIR)
+    {
+      cgp->cg_cs.cs_ndir++;
+      sblock->fs_cstotal.cs_ndir++;
+      csum[cg].cs_ndir++;
+    }
+  diskfs_end_catch_exception ();
+  return (u_long)(cg * sblock->fs_ipg + ipref);
+}
+
+/*
+ * Free a block or fragment.
+ *
+ * The specified block or fragment is placed back in the
+ * free map. If a fragment is deallocated, a possible 
+ * block reassembly is checked.
+ */
+void
+blkfree(volatile daddr_t bno,
+	int size)
+{
+  struct cg *cgp;
+  int cg, blk, frags, bbase;
+  int i;
+  
+  assert ("free of bad sized block" &&(unsigned) size <= sblock->fs_bsize
+	  && !fragoff (size));
+  cg = dtog(bno);
+  if ((unsigned)bno >= sblock->fs_size)
+    {
+      printf("bad block %ld\n", bno);
+      return;
+    }
+
+  cgp = (struct cg *)(cgs + sblock->fs_bsize * cg);
+
+  spin_lock (&alloclock);
+
+  if (diskfs_catch_exception ())
+    {
+      spin_unlock (&alloclock);
+      return;
+    }
+
+  if (!cg_chkmagic(cgp))
+    {
+      spin_unlock (&alloclock);
+      printf ("Cylinder group %d bad magic number: %ld/%ld\n",
+	      cg, cgp->cg_magic, ((struct ocg *)(cgp))->cg_magic);
+      diskfs_end_catch_exception ();
+      return;
+    }
+  cgp->cg_time = diskfs_mtime->seconds;
+  bno = dtogd(bno);
+  if (size == sblock->fs_bsize)
+    {
+      assert ("inconsistent cg_blskfree table"
+	      && !isblock (cg_blksfree (cgp), fragstoblks (bno)));
+      setblock(cg_blksfree(cgp), fragstoblks(bno));
+      cgp->cg_cs.cs_nbfree++;
+      sblock->fs_cstotal.cs_nbfree++;
+      csum[cg].cs_nbfree++;
+      i = cbtocylno(bno);
+      cg_blks(cgp, i)[cbtorpos(bno)]++;
+      cg_blktot(cgp)[i]++;
+    } 
+  else
+    {
+      bbase = bno - fragnum(bno);
+      /*
+       * decrement the counts associated with the old frags
+       */
+      blk = blkmap(cg_blksfree(cgp), bbase);
+      fragacct(blk, cgp->cg_frsum, -1);
+      /*
+       * deallocate the fragment
+       */
+      frags = numfrags(size);
+      for (i = 0; i < frags; i++)
+	{
+	  assert ("inconsistent cg_blksfree table"
+		  && !isset (cg_blksfree (cgp), bno + i));
+	  setbit(cg_blksfree(cgp), bno + i);
+	}
+      cgp->cg_cs.cs_nffree += i;
+      sblock->fs_cstotal.cs_nffree += i;
+      csum[cg].cs_nffree += i;
+      /*
+       * add back in counts associated with the new frags
+       */
+      blk = blkmap(cg_blksfree(cgp), bbase);
+      fragacct(blk, cgp->cg_frsum, 1);
+      /*
+       * if a complete block has been reassembled, account for it
+       */
+      if (isblock(cg_blksfree(cgp), (daddr_t)fragstoblks(bbase)))
+	{
+	  cgp->cg_cs.cs_nffree -= sblock->fs_frag;
+	  sblock->fs_cstotal.cs_nffree -= sblock->fs_frag;
+	  csum[cg].cs_nffree -= sblock->fs_frag;
+	  cgp->cg_cs.cs_nbfree++;
+	  sblock->fs_cstotal.cs_nbfree++;
+	  csum[cg].cs_nbfree++;
+	  i = cbtocylno(bbase);
+	  cg_blks(cgp, i)[cbtorpos(bbase)]++;
+	  cg_blktot(cgp)[i]++;
+	}
+    }
+  spin_unlock (&alloclock);
+  diskfs_end_catch_exception ();
+}
+
+/*
+ * Free an inode.
+ *
+ * The specified inode is placed back in the free map.
+ */
+void
+diskfs_free_node(struct node *np, mode_t mode)
+{
+  struct cg *cgp;
+  int cg;
+  volatile int ino = np->dn->number;
+  
+  assert ("invalid inode number" && ino < sblock->fs_ipg * sblock->fs_ncg);
+
+  cg = itog(ino);
+  cgp = (struct cg *)(cgs + sblock->fs_bsize * cg);
+
+  spin_lock (&alloclock);
+  if (diskfs_catch_exception ())
+    {
+      spin_unlock (&alloclock);
+      return;
+    }
+  
+  if (!cg_chkmagic(cgp))
+    {
+      spin_unlock (&alloclock);
+      printf ("Cylinder group %d bad magic number: %ld/%ld\n",
+	      cg, cgp->cg_magic, ((struct ocg *)(cgp))->cg_magic);
+      diskfs_end_catch_exception ();
+      return;
+    }
+  cgp->cg_time = diskfs_mtime->seconds;
+  ino %= sblock->fs_ipg;
+  assert ("inconsistent cg_inosused table" && !isclr (cg_inosused (cgp), ino));
+  clrbit(cg_inosused(cgp), ino);
+  if (ino < cgp->cg_irotor)
+    cgp->cg_irotor = ino;
+  cgp->cg_cs.cs_nifree++;
+  sblock->fs_cstotal.cs_nifree++;
+  csum[cg].cs_nifree++;
+  if ((mode & IFMT) == IFDIR)
+    {
+      cgp->cg_cs.cs_ndir--;
+      sblock->fs_cstotal.cs_ndir--;
+      csum[cg].cs_ndir--;
+    }
+  spin_unlock (&alloclock);
+  diskfs_end_catch_exception ();
+}
+
+
+/*
+ * Find a block of the specified size in the specified cylinder group.
+ *
+ * It is a panic if a request is made to find a block if none are
+ * available.
+ */
+/* This routine expects to be called from inside a diskfs_catch_exception */
+static daddr_t
+mapsearch(struct cg *cgp,
+	  daddr_t bpref,
+	  int allocsiz)
+{
+  daddr_t bno;
+  int start, len, loc, i;
+  int blk, field, subfield, pos;
+  
+  /*
+   * find the fragment by searching through the free block
+   * map for an appropriate bit pattern
+   */
+  if (bpref)
+    start = dtogd(bpref) / NBBY;
+  else
+    start = cgp->cg_frotor / NBBY;
+  len = howmany(sblock->fs_fpg, NBBY) - start;
+  loc = scanc((unsigned)len, (u_char *)&cg_blksfree(cgp)[start],
+	      (u_char *)fragtbl[sblock->fs_frag],
+	      (u_char)(1 << (allocsiz - 1 + (sblock->fs_frag % NBBY))));
+  if (loc == 0)
+    {
+      len = start + 1;
+      start = 0;
+      loc = scanc((unsigned)len, (u_char *)&cg_blksfree(cgp)[0],
+		  (u_char *)fragtbl[sblock->fs_frag],
+		  (u_char)(1 << (allocsiz - 1 + (sblock->fs_frag % NBBY))));
+      assert ("incosistent cg_blksfree table" && loc);
+    }
+  bno = (start + len - loc) * NBBY;
+  cgp->cg_frotor = bno;
+  /*
+   * found the byte in the map
+   * sift through the bits to find the selected frag
+   */
+  for (i = bno + NBBY; bno < i; bno += sblock->fs_frag)
+    {
+      blk = blkmap(cg_blksfree(cgp), bno);
+      blk <<= 1;
+      field = around[allocsiz];
+      subfield = inside[allocsiz];
+      for (pos = 0; pos <= sblock->fs_frag - allocsiz; pos++)
+	{
+	  if ((blk & field) == subfield)
+	    return (bno + pos);
+	  field <<= 1;
+	  subfield <<= 1;
+	}
+    }
+  assert ("inconsistent cg_blksfree table" && 0);
+}
+
+