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Annotation of 43BSDTahoe/sys/tahoe/ufs_machdep.c, revision 1.1.1.1

1.1       root        1: /*
                      2:  * Copyright (c) 1983, 1988 Regents of the University of California.
                      3:  * All rights reserved.
                      4:  *
                      5:  * Redistribution and use in source and binary forms are permitted
                      6:  * provided that the above copyright notice and this paragraph are
                      7:  * duplicated in all such forms and that any documentation,
                      8:  * advertising materials, and other materials related to such
                      9:  * distribution and use acknowledge that the software was developed
                     10:  * by the University of California, Berkeley.  The name of the
                     11:  * University may not be used to endorse or promote products derived
                     12:  * from this software without specific prior written permission.
                     13:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
                     14:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
                     15:  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
                     16:  *
                     17:  *     @(#)ufs_machdep.c       7.2 (Berkeley) 6/29/88
                     18:  */
                     19: 
                     20: #include "param.h"
                     21: #include "systm.h"
                     22: #include "dir.h"
                     23: #include "user.h"
                     24: #include "buf.h"
                     25: #include "conf.h"
                     26: #include "proc.h"
                     27: #include "seg.h"
                     28: #include "vm.h"
                     29: 
                     30: #include "pte.h"
                     31: 
                     32: /*
                     33:  * Machine dependent handling of the buffer cache.
                     34:  */
                     35: 
                     36: /*
                     37:  * Expand or contract the actual memory allocated to a buffer.
                     38:  * If no memory is available, release buffer and take error exit
                     39:  */
                     40: allocbuf(tp, size)
                     41:        register struct buf *tp;
                     42:        int size;
                     43: {
                     44:        register struct buf *bp, *ep;
                     45:        int sizealloc, take;
                     46: 
                     47:        sizealloc = roundup(size, CLBYTES);
                     48:        /*
                     49:         * Buffer size does not change
                     50:         */
                     51:        if (sizealloc == tp->b_bufsize)
                     52:                goto out;
                     53:        /*
                     54:         * Buffer size is shrinking.
                     55:         * Place excess space in a buffer header taken from the
                     56:         * BQ_EMPTY buffer list and placed on the "most free" list.
                     57:         * If no extra buffer headers are available, leave the
                     58:         * extra space in the present buffer.
                     59:         */
                     60:        if (sizealloc < tp->b_bufsize) {
                     61:                ep = bfreelist[BQ_EMPTY].av_forw;
                     62:                if (ep == &bfreelist[BQ_EMPTY])
                     63:                        goto out;
                     64:                notavail(ep);
                     65:                pagemove(tp->b_un.b_addr + sizealloc, ep->b_un.b_addr,
                     66:                    (int)tp->b_bufsize - sizealloc);
                     67:                ep->b_bufsize = tp->b_bufsize - sizealloc;
                     68:                tp->b_bufsize = sizealloc;
                     69:                ep->b_flags |= B_INVAL;
                     70:                ep->b_bcount = 0;
                     71:                brelse(ep);
                     72:                goto out;
                     73:        }
                     74:        /*
                     75:         * More buffer space is needed. Get it out of buffers on
                     76:         * the "most free" list, placing the empty headers on the
                     77:         * BQ_EMPTY buffer header list.
                     78:         */
                     79:        while (tp->b_bufsize < sizealloc) {
                     80:                take = sizealloc - tp->b_bufsize;
                     81:                bp = getnewbuf();
                     82:                if (take >= bp->b_bufsize)
                     83:                        take = bp->b_bufsize;
                     84:                pagemove(&bp->b_un.b_addr[bp->b_bufsize - take],
                     85:                    &tp->b_un.b_addr[tp->b_bufsize], take);
                     86:                tp->b_bufsize += take;
                     87:                bp->b_bufsize = bp->b_bufsize - take;
                     88:                if (bp->b_bcount > bp->b_bufsize)
                     89:                        bp->b_bcount = bp->b_bufsize;
                     90:                if (bp->b_bufsize <= 0) {
                     91:                        bremhash(bp);
                     92:                        binshash(bp, &bfreelist[BQ_EMPTY]);
                     93:                        bp->b_dev = (dev_t)NODEV;
                     94:                        bp->b_error = 0;
                     95:                        bp->b_flags |= B_INVAL;
                     96:                }
                     97:                brelse(bp);
                     98:        }
                     99: out:
                    100:        tp->b_bcount = size;
                    101:        return (1);
                    102: }
                    103: 
                    104: /*
                    105:  * Release space associated with a buffer.
                    106:  */
                    107: bfree(bp)
                    108:        struct buf *bp;
                    109: {
                    110: 
                    111:        bp->b_bcount = 0;
                    112: }

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