4.3BSD - /usr/src/sys/vax/ufs_machdep.c

   1: /*
   2:  * Copyright (c) 1982, 1986 Regents of the University of California.
   3:  * All rights reserved.  The Berkeley software License Agreement
   4:  * specifies the terms and conditions for redistribution.
   5:  *
   6:  *	@(#)ufs_machdep.c	7.1 (Berkeley) 6/5/86
   7:  */
   8: 
   9: #include "pte.h"
  10: 
  11: #include "param.h"
  12: #include "systm.h"
  13: #include "dir.h"
  14: #include "user.h"
  15: #include "buf.h"
  16: #include "conf.h"
  17: #include "proc.h"
  18: #include "seg.h"
  19: #include "vm.h"
  20: 
  21: /*
  22:  * Machine dependent handling of the buffer cache.
  23:  */
  24: 
  25: /*
  26:  * Expand or contract the actual memory allocated to a buffer.
  27:  * If no memory is available, release buffer and take error exit
  28:  */
  29: allocbuf(tp, size)
  30:     register struct buf *tp;
  31:     int size;
  32: {
  33:     register struct buf *bp, *ep;
  34:     int sizealloc, take;
  35: 
  36:     sizealloc = roundup(size, CLBYTES);
  37:     /*
  38: 	 * Buffer size does not change
  39: 	 */
  40:     if (sizealloc == tp->b_bufsize)
  41:         goto out;
  42:     /*
  43: 	 * Buffer size is shrinking.
  44: 	 * Place excess space in a buffer header taken from the
  45: 	 * BQ_EMPTY buffer list and placed on the "most free" list.
  46: 	 * If no extra buffer headers are available, leave the
  47: 	 * extra space in the present buffer.
  48: 	 */
  49:     if (sizealloc < tp->b_bufsize) {
  50:         ep = bfreelist[BQ_EMPTY].av_forw;
  51:         if (ep == &bfreelist[BQ_EMPTY])
  52:             goto out;
  53:         notavail(ep);
  54:         pagemove(tp->b_un.b_addr + sizealloc, ep->b_un.b_addr,
  55:             (int)tp->b_bufsize - sizealloc);
  56:         ep->b_bufsize = tp->b_bufsize - sizealloc;
  57:         tp->b_bufsize = sizealloc;
  58:         ep->b_flags |= B_INVAL;
  59:         ep->b_bcount = 0;
  60:         brelse(ep);
  61:         goto out;
  62:     }
  63:     /*
  64: 	 * More buffer space is needed. Get it out of buffers on
  65: 	 * the "most free" list, placing the empty headers on the
  66: 	 * BQ_EMPTY buffer header list.
  67: 	 */
  68:     while (tp->b_bufsize < sizealloc) {
  69:         take = sizealloc - tp->b_bufsize;
  70:         bp = getnewbuf();
  71:         if (take >= bp->b_bufsize)
  72:             take = bp->b_bufsize;
  73:         pagemove(&bp->b_un.b_addr[bp->b_bufsize - take],
  74:             &tp->b_un.b_addr[tp->b_bufsize], take);
  75:         tp->b_bufsize += take;
  76:         bp->b_bufsize = bp->b_bufsize - take;
  77:         if (bp->b_bcount > bp->b_bufsize)
  78:             bp->b_bcount = bp->b_bufsize;
  79:         if (bp->b_bufsize <= 0) {
  80:             bremhash(bp);
  81:             binshash(bp, &bfreelist[BQ_EMPTY]);
  82:             bp->b_dev = (dev_t)NODEV;
  83:             bp->b_error = 0;
  84:             bp->b_flags |= B_INVAL;
  85:         }
  86:         brelse(bp);
  87:     }
  88: out:
  89:     tp->b_bcount = size;
  90:     return (1);
  91: }
  92: 
  93: /*
  94:  * Release space associated with a buffer.
  95:  */
  96: bfree(bp)
  97:     struct buf *bp;
  98: {
  99: 
 100:     bp->b_bcount = 0;
 101: }

Defined functions