BSD 4 development

[unix-history] / usr / src / sys / dev / dsort.c

/*      dsort.c 4.1     11/9/80 */

/*
* generalized seek sort for disk
*/

#include "../h/param.h"
#include "../h/systm.h"
#include "../h/buf.h"

#define b_cylin b_resid

disksort(dp, bp)
register struct buf *dp, *bp;
{
       register struct buf *ap;
       struct buf *tp;

       ap = dp->b_actf;
       if(ap == NULL) {
               dp->b_actf = bp;
               dp->b_actl = bp;
               bp->av_forw = NULL;
               return;
       }
       tp = NULL;
       for(; ap != NULL; ap = ap->av_forw) {
               if ((bp->b_flags&B_READ) && (ap->b_flags&B_READ) == 0) {
                       if (tp == NULL)
                               tp = ap;
                       break;
               }
               if ((bp->b_flags&B_READ) == 0 && (ap->b_flags&B_READ))
                       continue;
               if(ap->b_cylin <= bp->b_cylin)
                       if(tp == NULL || ap->b_cylin >= tp->b_cylin)
                               tp = ap;
       }
       if(tp == NULL)
               tp = dp->b_actl;
       bp->av_forw = tp->av_forw;
       tp->av_forw = bp;
       if(tp == dp->b_actl)
               dp->b_actl = bp;
}