From: CSRG <csrg@ucbvax.Berkeley.EDU>
Date: Wed, 28 Sep 1983 10:55:25 +0000 (-0800)
Subject: BSD 4_2 development
X-Git-Tag: BSD-4_3^2~35
X-Git-Url: https://git.subgeniuskitty.com/unix-history/.git/commitdiff_plain/a1183b775d29c753730e2bb5414401d5a851fff5

BSD 4_2 development
Work on file usr/src/sys/sys/ufs_alloc.c

Synthesized-from: CSRG/cd1/4.2
---

diff --git a/usr/src/sys/sys/ufs_alloc.c b/usr/src/sys/sys/ufs_alloc.c
new file mode 100644
index 0000000000..f9527b7d47
--- /dev/null
+++ b/usr/src/sys/sys/ufs_alloc.c
@@ -0,0 +1,937 @@
+/*	ufs_alloc.c	6.2	83/09/28	*/
+
+#include "../h/param.h"
+#include "../h/systm.h"
+#include "../h/mount.h"
+#include "../h/fs.h"
+#include "../h/conf.h"
+#include "../h/buf.h"
+#include "../h/inode.h"
+#include "../h/dir.h"
+#include "../h/user.h"
+#include "../h/quota.h"
+#include "../h/kernel.h"
+
+extern u_long		hashalloc();
+extern ino_t		ialloccg();
+extern daddr_t		alloccg();
+extern daddr_t		alloccgblk();
+extern daddr_t		fragextend();
+extern daddr_t		blkpref();
+extern daddr_t		mapsearch();
+extern int		inside[], around[];
+extern unsigned char	*fragtbl[];
+
+/*
+ * 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.
+ */
+struct buf *
+alloc(ip, bpref, size)
+	register struct inode *ip;
+	daddr_t bpref;
+	int size;
+{
+	daddr_t bno;
+	register struct fs *fs;
+	register struct buf *bp;
+	int cg;
+	
+	fs = ip->i_fs;
+	if ((unsigned)size > fs->fs_bsize || fragoff(fs, size) != 0) {
+		printf("dev = 0x%x, bsize = %d, size = %d, fs = %s\n",
+		    ip->i_dev, fs->fs_bsize, size, fs->fs_fsmnt);
+		panic("alloc: bad size");
+	}
+	if (size == fs->fs_bsize && fs->fs_cstotal.cs_nbfree == 0)
+		goto nospace;
+	if (u.u_uid != 0 && freespace(fs, fs->fs_minfree) <= 0)
+		goto nospace;
+#ifdef QUOTA
+	u.u_error = chkdq(ip, (long)btodb(size), 0);
+	if (u.u_error)
+		return (NULL);
+#endif
+	if (bpref >= fs->fs_size)
+		bpref = 0;
+	if (bpref == 0)
+		cg = itog(fs, ip->i_number);
+	else
+		cg = dtog(fs, bpref);
+	bno = (daddr_t)hashalloc(ip, cg, (long)bpref, size,
+		(u_long (*)())alloccg);
+	if (bno <= 0)
+		goto nospace;
+	ip->i_blocks += btodb(size);
+	ip->i_flag |= IUPD|ICHG;
+	bp = getblk(ip->i_dev, fsbtodb(fs, bno), size);
+	clrbuf(bp);
+	return (bp);
+nospace:
+	fserr(fs, "file system full");
+	uprintf("\n%s: write failed, file system is full\n", fs->fs_fsmnt);
+	u.u_error = ENOSPC;
+	return (NULL);
+}
+
+/*
+ * 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.
+ */
+struct buf *
+realloccg(ip, bprev, bpref, osize, nsize)
+	register struct inode *ip;
+	daddr_t bprev, bpref;
+	int osize, nsize;
+{
+	daddr_t bno;
+	register struct fs *fs;
+	register struct buf *bp, *obp;
+	int cg;
+	
+	fs = ip->i_fs;
+	if ((unsigned)osize > fs->fs_bsize || fragoff(fs, osize) != 0 ||
+	    (unsigned)nsize > fs->fs_bsize || fragoff(fs, nsize) != 0) {
+		printf("dev = 0x%x, bsize = %d, osize = %d, nsize = %d, fs = %s\n",
+		    ip->i_dev, fs->fs_bsize, osize, nsize, fs->fs_fsmnt);
+		panic("realloccg: bad size");
+	}
+	if (u.u_uid != 0 && freespace(fs, fs->fs_minfree) <= 0)
+		goto nospace;
+	if (bprev == 0) {
+		printf("dev = 0x%x, bsize = %d, bprev = %d, fs = %s\n",
+		    ip->i_dev, fs->fs_bsize, bprev, fs->fs_fsmnt);
+		panic("realloccg: bad bprev");
+	}
+#ifdef QUOTA
+	u.u_error = chkdq(ip, (long)btodb(nsize - osize), 0);
+	if (u.u_error)
+		return (NULL);
+#endif
+	cg = dtog(fs, bprev);
+	bno = fragextend(ip, cg, (long)bprev, osize, nsize);
+	if (bno != 0) {
+		do {
+			bp = bread(ip->i_dev, fsbtodb(fs, bno), osize);
+			if (bp->b_flags & B_ERROR) {
+				brelse(bp);
+				return (NULL);
+			}
+		} while (brealloc(bp, nsize) == 0);
+		bp->b_flags |= B_DONE;
+		bzero(bp->b_un.b_addr + osize, (unsigned)nsize - osize);
+		ip->i_blocks += btodb(nsize - osize);
+		ip->i_flag |= IUPD|ICHG;
+		return (bp);
+	}
+	if (bpref >= fs->fs_size)
+		bpref = 0;
+	bno = (daddr_t)hashalloc(ip, cg, (long)bpref, nsize,
+		(u_long (*)())alloccg);
+	if (bno > 0) {
+		obp = bread(ip->i_dev, fsbtodb(fs, bprev), osize);
+		if (obp->b_flags & B_ERROR) {
+			brelse(obp);
+			return (NULL);
+		}
+		bp = getblk(ip->i_dev, fsbtodb(fs, bno), nsize);
+		bcopy(obp->b_un.b_addr, bp->b_un.b_addr, (u_int)osize);
+		bzero(bp->b_un.b_addr + osize, (unsigned)nsize - osize);
+		brelse(obp);
+		free(ip, bprev, (off_t)osize);
+		ip->i_blocks += btodb(nsize - osize);
+		ip->i_flag |= IUPD|ICHG;
+		return (bp);
+	}
+nospace:
+	/*
+	 * no space available
+	 */
+	fserr(fs, "file system full");
+	uprintf("\n%s: write failed, file system is full\n", fs->fs_fsmnt);
+	u.u_error = ENOSPC;
+	return (NULL);
+}
+
+/*
+ * Allocate an inode in the file system.
+ * 
+ * A preference may be optionally specified. If a preference is given
+ * the following hierarchy is used to allocate an inode:
+ *   1) allocate the requested inode.
+ *   2) allocate an inode in the same cylinder group.
+ *   3) quadradically rehash into other cylinder groups, until an
+ *      available inode is located.
+ * If no inode preference is given the following heirarchy is used
+ * to allocate an inode:
+ *   1) allocate an inode in cylinder group 0.
+ *   2) quadradically rehash into other cylinder groups, until an
+ *      available inode is located.
+ */
+struct inode *
+ialloc(pip, ipref, mode)
+	register struct inode *pip;
+	ino_t ipref;
+	int mode;
+{
+	ino_t ino;
+	register struct fs *fs;
+	register struct inode *ip;
+	int cg;
+	
+	fs = pip->i_fs;
+	if (fs->fs_cstotal.cs_nifree == 0)
+		goto noinodes;
+#ifdef QUOTA
+	u.u_error = chkiq(pip->i_dev, (struct inode *)NULL, u.u_uid, 0);
+	if (u.u_error)
+		return (NULL);
+#endif
+	if (ipref >= fs->fs_ncg * fs->fs_ipg)
+		ipref = 0;
+	cg = itog(fs, ipref);
+	ino = (ino_t)hashalloc(pip, cg, (long)ipref, mode, ialloccg);
+	if (ino == 0)
+		goto noinodes;
+	ip = iget(pip->i_dev, pip->i_fs, ino);
+	if (ip == NULL) {
+		ifree(pip, ino, 0);
+		return (NULL);
+	}
+	if (ip->i_mode) {
+		printf("mode = 0%o, inum = %d, fs = %s\n",
+		    ip->i_mode, ip->i_number, fs->fs_fsmnt);
+		panic("ialloc: dup alloc");
+	}
+	if (ip->i_blocks) {				/* XXX */
+		printf("free inode %s/%d had %d blocks\n",
+		    fs->fs_fsmnt, ino, ip->i_blocks);
+		ip->i_blocks = 0;
+	}
+	return (ip);
+noinodes:
+	fserr(fs, "out of inodes");
+	uprintf("\n%s: create/symlink failed, no inodes free\n", fs->fs_fsmnt);
+	u.u_error = ENOSPC;
+	return (NULL);
+}
+
+/*
+ * 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.
+ */
+ino_t
+dirpref(fs)
+	register struct fs *fs;
+{
+	int cg, minndir, mincg, avgifree;
+
+	avgifree = fs->fs_cstotal.cs_nifree / fs->fs_ncg;
+	minndir = fs->fs_ipg;
+	mincg = 0;
+	for (cg = 0; cg < fs->fs_ncg; cg++)
+		if (fs->fs_cs(fs, cg).cs_ndir < minndir &&
+		    fs->fs_cs(fs, cg).cs_nifree >= avgifree) {
+			mincg = cg;
+			minndir = fs->fs_cs(fs, cg).cs_ndir;
+		}
+	return ((ino_t)(fs->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 maintaining a rotor that sweeps the cylinder groups. When a new
+ * group of blocks is needed, the rotor is advanced until a cylinder group
+ * with greater than the average number of free blocks is found.
+ * 
+ * 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(ip, lbn, indx, bap)
+	struct inode *ip;
+	daddr_t lbn;
+	int indx;
+	daddr_t *bap;
+{
+	register struct fs *fs;
+	int cg, avgbfree;
+	daddr_t nextblk;
+
+	fs = ip->i_fs;
+	if (indx % fs->fs_maxbpg == 0 || bap[indx - 1] == 0) {
+		if (lbn < NDADDR) {
+			cg = itog(fs, ip->i_number);
+			return (fs->fs_fpg * cg + fs->fs_frag);
+		}
+		/*
+		 * Find a cylinder with greater than average number of
+		 * unused data blocks.
+		 */
+		avgbfree = fs->fs_cstotal.cs_nbfree / fs->fs_ncg;
+		for (cg = fs->fs_cgrotor + 1; cg < fs->fs_ncg; cg++)
+			if (fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
+				fs->fs_cgrotor = cg;
+				return (fs->fs_fpg * cg + fs->fs_frag);
+			}
+		for (cg = 0; cg <= fs->fs_cgrotor; cg++)
+			if (fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
+				fs->fs_cgrotor = cg;
+				return (fs->fs_fpg * cg + fs->fs_frag);
+			}
+		return (NULL);
+	}
+	/*
+	 * 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] + fs->fs_frag;
+	if (indx > fs->fs_maxcontig &&
+	    bap[indx - fs->fs_maxcontig] + blkstofrags(fs, fs->fs_maxcontig)
+	    != nextblk)
+		return (nextblk);
+	if (fs->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(fs->fs_rotdelay * fs->fs_rps * fs->fs_nsect /
+		    (NSPF(fs) * 1000), fs->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*/
+u_long
+hashalloc(ip, cg, pref, size, allocator)
+	struct inode *ip;
+	int cg;
+	long pref;
+	int size;	/* size for data blocks, mode for inodes */
+	u_long (*allocator)();
+{
+	register struct fs *fs;
+	long result;
+	int i, icg = cg;
+
+	fs = ip->i_fs;
+	/*
+	 * 1: preferred cylinder group
+	 */
+	result = (*allocator)(ip, cg, pref, size);
+	if (result)
+		return (result);
+	/*
+	 * 2: quadratic rehash
+	 */
+	for (i = 1; i < fs->fs_ncg; i *= 2) {
+		cg += i;
+		if (cg >= fs->fs_ncg)
+			cg -= fs->fs_ncg;
+		result = (*allocator)(ip, 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) % fs->fs_ncg;
+	for (i = 2; i < fs->fs_ncg; i++) {
+		result = (*allocator)(ip, cg, 0, size);
+		if (result)
+			return (result);
+		cg++;
+		if (cg == fs->fs_ncg)
+			cg = 0;
+	}
+	return (NULL);
+}
+
+/*
+ * Determine whether a fragment can be extended.
+ *
+ * Check to see if the necessary fragments are available, and 
+ * if they are, allocate them.
+ */
+daddr_t
+fragextend(ip, cg, bprev, osize, nsize)
+	struct inode *ip;
+	int cg;
+	long bprev;
+	int osize, nsize;
+{
+	register struct fs *fs;
+	register struct buf *bp;
+	register struct cg *cgp;
+	long bno;
+	int frags, bbase;
+	int i;
+
+	fs = ip->i_fs;
+	if (fs->fs_cs(fs, cg).cs_nffree < nsize - osize)
+		return (NULL);
+	frags = numfrags(fs, nsize);
+	bbase = fragoff(fs, bprev);
+	if (bbase > (bprev + frags - 1) % fs->fs_frag) {
+		/* cannot extend across a block boundry */
+		return (NULL);
+	}
+	bp = bread(ip->i_dev, fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize);
+	cgp = bp->b_un.b_cg;
+	if (bp->b_flags & B_ERROR || cgp->cg_magic != CG_MAGIC) {
+		brelse(bp);
+		return (NULL);
+	}
+	cgp->cg_time = time.tv_sec;
+	bno = dtogd(fs, bprev);
+	for (i = numfrags(fs, osize); i < frags; i++)
+		if (isclr(cgp->cg_free, bno + i)) {
+			brelse(bp);
+			return (NULL);
+		}
+	/*
+	 * 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 < fs->fs_frag - bbase; i++)
+		if (isclr(cgp->cg_free, bno + i))
+			break;
+	cgp->cg_frsum[i - numfrags(fs, osize)]--;
+	if (i != frags)
+		cgp->cg_frsum[i - frags]++;
+	for (i = numfrags(fs, osize); i < frags; i++) {
+		clrbit(cgp->cg_free, bno + i);
+		cgp->cg_cs.cs_nffree--;
+		fs->fs_cstotal.cs_nffree--;
+		fs->fs_cs(fs, cg).cs_nffree--;
+	}
+	fs->fs_fmod++;
+	bdwrite(bp);
+	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.
+ */
+daddr_t
+alloccg(ip, cg, bpref, size)
+	struct inode *ip;
+	int cg;
+	daddr_t bpref;
+	int size;
+{
+	register struct fs *fs;
+	register struct buf *bp;
+	register struct cg *cgp;
+	int bno, frags;
+	int allocsiz;
+	register int i;
+
+	fs = ip->i_fs;
+	if (fs->fs_cs(fs, cg).cs_nbfree == 0 && size == fs->fs_bsize)
+		return (NULL);
+	bp = bread(ip->i_dev, fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize);
+	cgp = bp->b_un.b_cg;
+	if (bp->b_flags & B_ERROR || cgp->cg_magic != CG_MAGIC) {
+		brelse(bp);
+		return (NULL);
+	}
+	if (cgp->cg_cs.cs_nbfree == 0 && size == fs->fs_bsize)
+		return (NULL);
+	cgp->cg_time = time.tv_sec;
+	if (size == fs->fs_bsize) {
+		bno = alloccgblk(fs, cgp, bpref);
+		bdwrite(bp);
+		return (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(fs, size);
+	for (allocsiz = frags; allocsiz < fs->fs_frag; allocsiz++)
+		if (cgp->cg_frsum[allocsiz] != 0)
+			break;
+	if (allocsiz == fs->fs_frag) {
+		/*
+		 * no fragments were available, so a block will be 
+		 * allocated, and hacked up
+		 */
+		if (cgp->cg_cs.cs_nbfree == 0) {
+			brelse(bp);
+			return (NULL);
+		}
+		bno = alloccgblk(fs, cgp, bpref);
+		bpref = dtogd(fs, bno);
+		for (i = frags; i < fs->fs_frag; i++)
+			setbit(cgp->cg_free, bpref + i);
+		i = fs->fs_frag - frags;
+		cgp->cg_cs.cs_nffree += i;
+		fs->fs_cstotal.cs_nffree += i;
+		fs->fs_cs(fs, cg).cs_nffree += i;
+		fs->fs_fmod++;
+		cgp->cg_frsum[i]++;
+		bdwrite(bp);
+		return (bno);
+	}
+	bno = mapsearch(fs, cgp, bpref, allocsiz);
+	if (bno < 0)
+		return (NULL);
+	for (i = 0; i < frags; i++)
+		clrbit(cgp->cg_free, bno + i);
+	cgp->cg_cs.cs_nffree -= frags;
+	fs->fs_cstotal.cs_nffree -= frags;
+	fs->fs_cs(fs, cg).cs_nffree -= frags;
+	fs->fs_fmod++;
+	cgp->cg_frsum[allocsiz]--;
+	if (frags != allocsiz)
+		cgp->cg_frsum[allocsiz - frags]++;
+	bdwrite(bp);
+	return (cg * fs->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.
+ */
+daddr_t
+alloccgblk(fs, cgp, bpref)
+	register struct fs *fs;
+	register struct cg *cgp;
+	daddr_t bpref;
+{
+	daddr_t bno;
+	int cylno, pos, delta;
+	short *cylbp;
+	register int i;
+
+	if (bpref == 0) {
+		bpref = cgp->cg_rotor;
+		goto norot;
+	}
+	bpref &= ~(fs->fs_frag - 1);
+	bpref = dtogd(fs, bpref);
+	/*
+	 * if the requested block is available, use it
+	 */
+	if (isblock(fs, cgp->cg_free, fragstoblks(fs, bpref))) {
+		bno = bpref;
+		goto gotit;
+	}
+	/*
+	 * check for a block available on the same cylinder
+	 */
+	cylno = cbtocylno(fs, bpref);
+	if (cgp->cg_btot[cylno] == 0)
+		goto norot;
+	if (fs->fs_cpc == 0) {
+		/*
+		 * block layout info is not available, so just have
+		 * to take any block in this cylinder.
+		 */
+		bpref = howmany(fs->fs_spc * cylno, NSPF(fs));
+		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 = cgp->cg_b[cylno];
+	pos = cbtorpos(fs, bpref);
+	for (i = pos; i < NRPOS; i++)
+		if (cylbp[i] > 0)
+			break;
+	if (i == 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 % fs->fs_cpc;
+		bno = (cylno - pos) * fs->fs_spc / NSPB(fs);
+		if (fs->fs_postbl[pos][i] == -1) {
+			printf("pos = %d, i = %d, fs = %s\n",
+			    pos, i, fs->fs_fsmnt);
+			panic("alloccgblk: cyl groups corrupted");
+		}
+		for (i = fs->fs_postbl[pos][i];; ) {
+			if (isblock(fs, cgp->cg_free, bno + i)) {
+				bno = blkstofrags(fs, (bno + i));
+				goto gotit;
+			}
+			delta = fs->fs_rotbl[i];
+			if (delta <= 0 || delta > MAXBPC - i)
+				break;
+			i += delta;
+		}
+		printf("pos = %d, i = %d, fs = %s\n", pos, i, fs->fs_fsmnt);
+		panic("alloccgblk: can't find blk in cyl");
+	}
+norot:
+	/*
+	 * no blocks in the requested cylinder, so take next
+	 * available one in this cylinder group.
+	 */
+	bno = mapsearch(fs, cgp, bpref, (int)fs->fs_frag);
+	if (bno < 0)
+		return (NULL);
+	cgp->cg_rotor = bno;
+gotit:
+	clrblock(fs, cgp->cg_free, (long)fragstoblks(fs, bno));
+	cgp->cg_cs.cs_nbfree--;
+	fs->fs_cstotal.cs_nbfree--;
+	fs->fs_cs(fs, cgp->cg_cgx).cs_nbfree--;
+	cylno = cbtocylno(fs, bno);
+	cgp->cg_b[cylno][cbtorpos(fs, bno)]--;
+	cgp->cg_btot[cylno]--;
+	fs->fs_fmod++;
+	return (cgp->cg_cgx * fs->fs_fpg + bno);
+}
+	
+/*
+ * 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.
+ */
+ino_t
+ialloccg(ip, cg, ipref, mode)
+	struct inode *ip;
+	int cg;
+	daddr_t ipref;
+	int mode;
+{
+	register struct fs *fs;
+	register struct buf *bp;
+	register struct cg *cgp;
+	int i;
+
+	fs = ip->i_fs;
+	if (fs->fs_cs(fs, cg).cs_nifree == 0)
+		return (NULL);
+	bp = bread(ip->i_dev, fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize);
+	cgp = bp->b_un.b_cg;
+	if (bp->b_flags & B_ERROR || cgp->cg_magic != CG_MAGIC) {
+		brelse(bp);
+		return (NULL);
+	}
+	if (cgp->cg_cs.cs_nifree == 0)
+		return (NULL);
+	cgp->cg_time = time.tv_sec;
+	if (ipref) {
+		ipref %= fs->fs_ipg;
+		if (isclr(cgp->cg_iused, ipref))
+			goto gotit;
+	} else
+		ipref = cgp->cg_irotor;
+	for (i = 0; i < fs->fs_ipg; i++) {
+		ipref++;
+		if (ipref >= fs->fs_ipg)
+			ipref = 0;
+		if (isclr(cgp->cg_iused, ipref)) {
+			cgp->cg_irotor = ipref;
+			goto gotit;
+		}
+	}
+	brelse(bp);
+	return (NULL);
+gotit:
+	setbit(cgp->cg_iused, ipref);
+	cgp->cg_cs.cs_nifree--;
+	fs->fs_cstotal.cs_nifree--;
+	fs->fs_cs(fs, cg).cs_nifree--;
+	fs->fs_fmod++;
+	if ((mode & IFMT) == IFDIR) {
+		cgp->cg_cs.cs_ndir++;
+		fs->fs_cstotal.cs_ndir++;
+		fs->fs_cs(fs, cg).cs_ndir++;
+	}
+	bdwrite(bp);
+	return (cg * fs->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.
+ */
+free(ip, bno, size)
+	register struct inode *ip;
+	daddr_t bno;
+	off_t size;
+{
+	register struct fs *fs;
+	register struct cg *cgp;
+	register struct buf *bp;
+	int cg, blk, frags, bbase;
+	register int i;
+
+	fs = ip->i_fs;
+	if ((unsigned)size > fs->fs_bsize || fragoff(fs, size) != 0) {
+		printf("dev = 0x%x, bsize = %d, size = %d, fs = %s\n",
+		    ip->i_dev, fs->fs_bsize, size, fs->fs_fsmnt);
+		panic("free: bad size");
+	}
+	cg = dtog(fs, bno);
+	if (badblock(fs, bno)) {
+		printf("bad block %d, ino %d\n", bno, ip->i_number);
+		return;
+	}
+	bp = bread(ip->i_dev, fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize);
+	cgp = bp->b_un.b_cg;
+	if (bp->b_flags & B_ERROR || cgp->cg_magic != CG_MAGIC) {
+		brelse(bp);
+		return;
+	}
+	cgp->cg_time = time.tv_sec;
+	bno = dtogd(fs, bno);
+	if (size == fs->fs_bsize) {
+		if (isblock(fs, cgp->cg_free, fragstoblks(fs, bno))) {
+			printf("dev = 0x%x, block = %d, fs = %s\n",
+			    ip->i_dev, bno, fs->fs_fsmnt);
+			panic("free: freeing free block");
+		}
+		setblock(fs, cgp->cg_free, fragstoblks(fs, bno));
+		cgp->cg_cs.cs_nbfree++;
+		fs->fs_cstotal.cs_nbfree++;
+		fs->fs_cs(fs, cg).cs_nbfree++;
+		i = cbtocylno(fs, bno);
+		cgp->cg_b[i][cbtorpos(fs, bno)]++;
+		cgp->cg_btot[i]++;
+	} else {
+		bbase = bno - (bno % fs->fs_frag);
+		/*
+		 * decrement the counts associated with the old frags
+		 */
+		blk = blkmap(fs, cgp->cg_free, bbase);
+		fragacct(fs, blk, cgp->cg_frsum, -1);
+		/*
+		 * deallocate the fragment
+		 */
+		frags = numfrags(fs, size);
+		for (i = 0; i < frags; i++) {
+			if (isset(cgp->cg_free, bno + i)) {
+				printf("dev = 0x%x, block = %d, fs = %s\n",
+				    ip->i_dev, bno + i, fs->fs_fsmnt);
+				panic("free: freeing free frag");
+			}
+			setbit(cgp->cg_free, bno + i);
+		}
+		cgp->cg_cs.cs_nffree += i;
+		fs->fs_cstotal.cs_nffree += i;
+		fs->fs_cs(fs, cg).cs_nffree += i;
+		/*
+		 * add back in counts associated with the new frags
+		 */
+		blk = blkmap(fs, cgp->cg_free, bbase);
+		fragacct(fs, blk, cgp->cg_frsum, 1);
+		/*
+		 * if a complete block has been reassembled, account for it
+		 */
+		if (isblock(fs, cgp->cg_free, fragstoblks(fs, bbase))) {
+			cgp->cg_cs.cs_nffree -= fs->fs_frag;
+			fs->fs_cstotal.cs_nffree -= fs->fs_frag;
+			fs->fs_cs(fs, cg).cs_nffree -= fs->fs_frag;
+			cgp->cg_cs.cs_nbfree++;
+			fs->fs_cstotal.cs_nbfree++;
+			fs->fs_cs(fs, cg).cs_nbfree++;
+			i = cbtocylno(fs, bbase);
+			cgp->cg_b[i][cbtorpos(fs, bbase)]++;
+			cgp->cg_btot[i]++;
+		}
+	}
+	fs->fs_fmod++;
+	bdwrite(bp);
+}
+
+/*
+ * Free an inode.
+ *
+ * The specified inode is placed back in the free map.
+ */
+ifree(ip, ino, mode)
+	struct inode *ip;
+	ino_t ino;
+	int mode;
+{
+	register struct fs *fs;
+	register struct cg *cgp;
+	register struct buf *bp;
+	int cg;
+
+	fs = ip->i_fs;
+	if ((unsigned)ino >= fs->fs_ipg*fs->fs_ncg) {
+		printf("dev = 0x%x, ino = %d, fs = %s\n",
+		    ip->i_dev, ino, fs->fs_fsmnt);
+		panic("ifree: range");
+	}
+	cg = itog(fs, ino);
+	bp = bread(ip->i_dev, fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize);
+	cgp = bp->b_un.b_cg;
+	if (bp->b_flags & B_ERROR || cgp->cg_magic != CG_MAGIC) {
+		brelse(bp);
+		return;
+	}
+	cgp->cg_time = time.tv_sec;
+	ino %= fs->fs_ipg;
+	if (isclr(cgp->cg_iused, ino)) {
+		printf("dev = 0x%x, ino = %d, fs = %s\n",
+		    ip->i_dev, ino, fs->fs_fsmnt);
+		panic("ifree: freeing free inode");
+	}
+	clrbit(cgp->cg_iused, ino);
+	cgp->cg_cs.cs_nifree++;
+	fs->fs_cstotal.cs_nifree++;
+	fs->fs_cs(fs, cg).cs_nifree++;
+	if ((mode & IFMT) == IFDIR) {
+		cgp->cg_cs.cs_ndir--;
+		fs->fs_cstotal.cs_ndir--;
+		fs->fs_cs(fs, cg).cs_ndir--;
+	}
+	fs->fs_fmod++;
+	bdwrite(bp);
+}
+
+/*
+ * 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.
+ */
+daddr_t
+mapsearch(fs, cgp, bpref, allocsiz)
+	register struct fs *fs;
+	register 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(fs, bpref) / NBBY;
+	else
+		start = cgp->cg_frotor / NBBY;
+	len = howmany(fs->fs_fpg, NBBY) - start;
+	loc = scanc((unsigned)len, (caddr_t)&cgp->cg_free[start],
+		(caddr_t)fragtbl[fs->fs_frag],
+		(int)(1 << (allocsiz - 1 + (fs->fs_frag % NBBY))));
+	if (loc == 0) {
+		len = start + 1;
+		start = 0;
+		loc = scanc((unsigned)len, (caddr_t)&cgp->cg_free[start],
+			(caddr_t)fragtbl[fs->fs_frag],
+			(int)(1 << (allocsiz - 1 + (fs->fs_frag % NBBY))));
+		if (loc == 0)
+			return (-1);
+	}
+	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 += fs->fs_frag) {
+		blk = blkmap(fs, cgp->cg_free, bno);
+		blk <<= 1;
+		field = around[allocsiz];
+		subfield = inside[allocsiz];
+		for (pos = 0; pos <= fs->fs_frag - allocsiz; pos++) {
+			if ((blk & field) == subfield)
+				return (bno + pos);
+			field <<= 1;
+			subfield <<= 1;
+		}
+	}
+	printf("bno = %d, fs = %s\n", bno, fs->fs_fsmnt);
+	panic("alloccg: block not in map");
+	return (-1);
+}
+
+/*
+ * Fserr prints the name of a file system with an error diagnostic.
+ * 
+ * The form of the error message is:
+ *	fs: error message
+ */
+fserr(fs, cp)
+	struct fs *fs;
+	char *cp;
+{
+
+	printf("%s: %s\n", fs->fs_fsmnt, cp);
+}