2.9BSD - /usr/src/sys/dev/dsort.c

   1: /*
   2:  *	SCCS id	@(#)dsort.c	2.1 (Berkeley)	8/5/83
   3:  */
   4: 
   5: /*
   6:  * generalized seek sort for disk
   7:  */
   8: 
   9: #include "param.h"
  10: #include <sys/systm.h>
  11: #include <sys/buf.h>
  12: 
  13: disksort(dp, bp)
  14: register struct buf *dp, *bp;
  15: {
  16:     register struct buf *ap;
  17:     struct buf *tp;
  18: 
  19:     ap = dp->b_actf;
  20:     if(ap == NULL) {
  21:         dp->b_actf = bp;
  22:         dp->b_actl = bp;
  23:         bp->av_forw = NULL;
  24:         return;
  25:     }
  26:     tp = NULL;
  27:     for(; ap != NULL; ap = ap->av_forw) {
  28:         if ((bp->b_flags&B_READ) && (ap->b_flags&B_READ) == 0) {
  29:             if (tp == NULL)
  30:                 tp = ap;
  31:             break;
  32:         }
  33:         if ((bp->b_flags&B_READ) == 0 && (ap->b_flags&B_READ))
  34:             continue;
  35:         if(ap->b_cylin <= bp->b_cylin)
  36:             if(tp == NULL || ap->b_cylin >= tp->b_cylin)
  37:                 tp = ap;
  38:     }
  39:     if(tp == NULL)
  40:         tp = dp->b_actl;
  41:     bp->av_forw = tp->av_forw;
  42:     tp->av_forw = bp;
  43:     if(tp == dp->b_actl)
  44:         dp->b_actl = bp;
  45: }

Defined functions