/* dskenq.c - dskenq */ #include <conf.h> #include <kernel.h> #include <disk.h> /*------------------------------------------------------------------------ * dskenq -- enqueue a disk request and start I/O if disk not busy *------------------------------------------------------------------------ */ dskenq(drptr, dsptr) struct dreq *drptr; struct dsblk *dsptr; { struct dreq *p, *q; /* q follows p through requests */ DBADDR block; int st; if ( (q=dsptr->dreqlst) == DRNULL ) { dsptr->dreqlst = drptr; drptr->drnext = DRNULL; dskstrt(dsptr); return(DONQ); } block = drptr->drdba; for (p = q->drnext ; p != DRNULL ; q=p,p=p->drnext) { if (p->drdba==block && (st=dskqopt(p, q, drptr)!=SYSERR)) return(st); if ( (q->drdba <= block && block < p->drdba) || (q->drdba >= block && block > p->drdba) ) { drptr->drnext = p; q->drnext = drptr; return(DONQ); } } drptr->drnext = DRNULL; q->drnext = drptr; return(DONQ); }