fixes to interactions of new fs and buffer cache with partial blocks

[unix-history] / usr / src / sys / ufs / ffs / ffs_alloc.c

/*      ffs_alloc.c     2.7     82/06/14        */

#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"

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 &&
           fs->fs_cstotal.cs_nbfree * fs->fs_frag + fs->fs_cstotal.cs_nffree <
             fs->fs_dsize * fs->fs_minfree / 100)
               goto nospace;
       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, alloccg);
       if (bno <= 0)
               goto nospace;
       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 &&
           fs->fs_cstotal.cs_nbfree * fs->fs_frag + fs->fs_cstotal.cs_nffree <
             fs->fs_dsize * fs->fs_minfree / 100)
               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");
       }
       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;
               blkclr(bp->b_un.b_addr + osize, nsize - osize);
               return (bp);
       }
       if (bpref >= fs->fs_size)
               bpref = 0;
       bno = (daddr_t)hashalloc(ip, cg, (long)bpref, nsize, 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, osize);
               blkclr(bp->b_un.b_addr + osize, nsize - osize);
               brelse(obp);
               fre(ip, bprev, (off_t)osize);
               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;
       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(ip, 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");
       }
       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.
*/
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 (fs->fs_ipg * mincg);
}

/*
* Select a cylinder to place a large block of data.
*
* The policy implemented by this algorithm is to maintain a
* rotor that sweeps the cylinder groups. When a block is 
* needed, the rotor is advanced until a cylinder group with
* greater than the average number of free blocks is found.
*/
daddr_t
blkpref(fs)
       register struct fs *fs;
{
       int cg, avgbfree;

       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);
}

/*
* 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
        */
       cg = icg;
       for (i = 0; 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)), fs->fs_bsize);
       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;
       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)), fs->fs_bsize);
       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;
       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;
               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;
       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
        */
/*
* disallow sequential layout.
*
       if (isblock(fs, cgp->cg_free, bpref/fs->fs_frag)) {
               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;
       }
       /*
        * find a block that is rotationally optimal
        */
       cylbp = cgp->cg_b[cylno];
       if (fs->fs_rotdelay == 0) {
               pos = cbtorpos(fs, bpref);
       } else {
               /*
                * 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 rotational position
                */
               bpref += fs->fs_rotdelay * fs->fs_rps * fs->fs_nsect /
                   (NSPF(fs) * 1000);
               pos = cbtorpos(fs, bpref);
               pos = (pos + 1) % NRPOS;
       }
       /*
        * check the summary information to see if a block is 
        * available in the requested cylinder starting at the
        * optimal rotational position and proceeding around.
        */
       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 = (bno + i) * fs->fs_frag;
                               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, fs->fs_frag);
       if (bno < 0)
               return (NULL);
       cgp->cg_rotor = bno;
gotit:
       clrblock(fs, cgp->cg_free, bno/fs->fs_frag);
       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)), fs->fs_bsize);
       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;
       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.
*/
fre(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)), fs->fs_bsize);
       cgp = bp->b_un.b_cg;
       if (bp->b_flags & B_ERROR || cgp->cg_magic != CG_MAGIC) {
               brelse(bp);
               return;
       }
       cgp->cg_time = time;
       bno = dtogd(fs, bno);
       if (size == fs->fs_bsize) {
               if (isblock(fs, cgp->cg_free, bno/fs->fs_frag)) {
                       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, bno/fs->fs_frag);
               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, bbase / fs->fs_frag)) {
                       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)), fs->fs_bsize);
       cgp = bp->b_un.b_cg;
       if (bp->b_flags & B_ERROR || cgp->cg_magic != CG_MAGIC) {
               brelse(bp);
               return;
       }
       cgp->cg_time = time;
       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(len, &cgp->cg_free[start], fragtbl[fs->fs_frag],
               1 << (allocsiz - 1 + (fs->fs_frag % NBBY)));
       if (loc == 0) {
               len = start + 1;
               start = 0;
               loc = scanc(len, &cgp->cg_free[start], fragtbl[fs->fs_frag],
                       1 << (allocsiz - 1 + (fs->fs_frag % NBBY)));
               if (loc == 0) {
                       printf("start = %d, len = %d, fs = %s\n",
                           start, len, fs->fs_fsmnt);
                       panic("alloccg: map corrupted");
                       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);
}

/*
* Update the frsum fields to reflect addition or deletion 
* of some frags.
*/
fragacct(fs, fragmap, fraglist, cnt)
       struct fs *fs;
       int fragmap;
       long fraglist[];
       int cnt;
{
       int inblk;
       register int field, subfield;
       register int siz, pos;

       inblk = (int)(fragtbl[fs->fs_frag][fragmap]) << 1;
       fragmap <<= 1;
       for (siz = 1; siz < fs->fs_frag; siz++) {
               if ((inblk & (1 << (siz + (fs->fs_frag % NBBY)))) == 0)
                       continue;
               field = around[siz];
               subfield = inside[siz];
               for (pos = siz; pos <= fs->fs_frag; pos++) {
                       if ((fragmap & field) == subfield) {
                               fraglist[siz] += cnt;
                               pos += siz;
                               field <<= siz;
                               subfield <<= siz;
                       }
                       field <<= 1;
                       subfield <<= 1;
               }
       }
}

/*
* Check that a specified block number is in range.
*/
badblock(fs, bn)
       register struct fs *fs;
       daddr_t bn;
{

       if ((unsigned)bn >= fs->fs_size) {
               printf("bad block %d, ", bn);
               fserr(fs, "bad block");
               return (1);
       }
       return (0);
}

/*
* Getfs maps a device number into a pointer to the incore super block.
*
* The algorithm is a linear search through the mount table. A
* consistency check of the super block magic number is performed.
*
* panic: no fs -- the device is not mounted.
*      this "cannot happen"
*/
struct fs *
getfs(dev)
       dev_t dev;
{
       register struct mount *mp;
       register struct fs *fs;

       for (mp = &mount[0]; mp < &mount[NMOUNT]; mp++) {
               if (mp->m_bufp == NULL || mp->m_dev != dev)
                       continue;
               fs = mp->m_bufp->b_un.b_fs;
               if (fs->fs_magic != FS_MAGIC) {
                       printf("dev = 0x%x, fs = %s\n", dev, fs->fs_fsmnt);
                       panic("getfs: bad magic");
               }
               return (fs);
       }
       printf("dev = 0x%x\n", dev);
       panic("getfs: no fs");
       return (NULL);
}

/*
* 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);
}

/*
* Getfsx returns the index in the file system
* table of the specified device.  The swap device
* is also assigned a pseudo-index.  The index may
* be used as a compressed indication of the location
* of a block, recording
*      <getfsx(dev),blkno>
* rather than
*      <dev, blkno>
* provided the information need remain valid only
* as long as the file system is mounted.
*/
getfsx(dev)
       dev_t dev;
{
       register struct mount *mp;

       if (dev == swapdev)
               return (MSWAPX);
       for(mp = &mount[0]; mp < &mount[NMOUNT]; mp++)
               if (mp->m_dev == dev)
                       return (mp - &mount[0]);
       return (-1);
}

/*
* Update is the internal name of 'sync'.  It goes through the disk
* queues to initiate sandbagged IO; goes through the inodes to write
* modified nodes; and it goes through the mount table to initiate
* the writing of the modified super blocks.
*/
update(flag)
       int flag;
{
       register struct inode *ip;
       register struct mount *mp;
       register struct buf *bp;
       struct fs *fs;
       int i, blks;

       if (updlock)
               return;
       updlock++;
       /*
        * Write back modified superblocks.
        * Consistency check that the superblock
        * of each file system is still in the buffer cache.
        */
       for (mp = &mount[0]; mp < &mount[NMOUNT]; mp++) {
               if (mp->m_bufp == NULL)
                       continue;
               fs = mp->m_bufp->b_un.b_fs;
               if (fs->fs_fmod == 0)
                       continue;
               if (fs->fs_ronly != 0) {                /* ### */
                       printf("fs = %s\n", fs->fs_fsmnt);
                       panic("update: rofs mod");
               }
               fs->fs_fmod = 0;
               fs->fs_time = time;
               sbupdate(mp);
       }
       /*
        * Write back each (modified) inode.
        */
       for (ip = inode; ip < inodeNINODE; ip++) {
               if ((ip->i_flag & ILOCK) != 0 || ip->i_count == 0)
                       continue;
               ip->i_flag |= ILOCK;
               ip->i_count++;
               iupdat(ip, &time, &time, 0);
               iput(ip);
       }
       updlock = 0;
       /*
        * Force stale buffer cache information to be flushed,
        * for all devices.
        */
       bflush(NODEV);
}

/*
* block operations
*
* check if a block is available
*/
isblock(fs, cp, h)
       struct fs *fs;
       unsigned char *cp;
       int h;
{
       unsigned char mask;

       switch (fs->fs_frag) {
       case 8:
               return (cp[h] == 0xff);
       case 4:
               mask = 0x0f << ((h & 0x1) << 2);
               return ((cp[h >> 1] & mask) == mask);
       case 2:
               mask = 0x03 << ((h & 0x3) << 1);
               return ((cp[h >> 2] & mask) == mask);
       case 1:
               mask = 0x01 << (h & 0x7);
               return ((cp[h >> 3] & mask) == mask);
       default:
               panic("isblock");
               return (NULL);
       }
}

/*
* take a block out of the map
*/
clrblock(fs, cp, h)
       struct fs *fs;
       unsigned char *cp;
       int h;
{
       switch ((fs)->fs_frag) {
       case 8:
               cp[h] = 0;
               return;
       case 4:
               cp[h >> 1] &= ~(0x0f << ((h & 0x1) << 2));
               return;
       case 2:
               cp[h >> 2] &= ~(0x03 << ((h & 0x3) << 1));
               return;
       case 1:
               cp[h >> 3] &= ~(0x01 << (h & 0x7));
               return;
       default:
               panic("clrblock");
               return;
       }
}

/*
* put a block into the map
*/
setblock(fs, cp, h)
       struct fs *fs;
       unsigned char *cp;
       int h;
{
       switch (fs->fs_frag) {
       case 8:
               cp[h] = 0xff;
               return;
       case 4:
               cp[h >> 1] |= (0x0f << ((h & 0x1) << 2));
               return;
       case 2:
               cp[h >> 2] |= (0x03 << ((h & 0x3) << 1));
               return;
       case 1:
               cp[h >> 3] |= (0x01 << (h & 0x7));
               return;
       default:
               panic("setblock");
               return;
       }
}