usr/src/sys/kern/kern_physio.c

/*      kern_physio.c   6.5     85/03/12        */

#include "../machine/pte.h"

#include "param.h"
#include "systm.h"
#include "dir.h"
#include "user.h"
#include "buf.h"
#include "conf.h"
#include "proc.h"
#include "seg.h"
#include "vm.h"
#include "trace.h"
#include "map.h"
#include "uio.h"

/*
 * Swap IO headers -
 * They contain the necessary information for the swap I/O.
 * At any given time, a swap header can be in three
 * different lists. When free it is in the free list,
 * when allocated and the I/O queued, it is on the swap
 * device list, and finally, if the operation was a dirty
 * page push, when the I/O completes, it is inserted
 * in a list of cleaned pages to be processed by the pageout daemon.
 */
struct  buf *swbuf;

/*
 * swap I/O -
 *
 * If the flag indicates a dirty page push initiated
 * by the pageout daemon, we map the page into the i th
 * virtual page of process 2 (the daemon itself) where i is
 * the index of the swap header that has been allocated.
 * We simply initialize the header and queue the I/O but
 * do not wait for completion. When the I/O completes,
 * iodone() will link the header to a list of cleaned
 * pages to be processed by the pageout daemon.
 */
swap(p, dblkno, addr, nbytes, rdflg, flag, dev, pfcent)
        struct proc *p;
        swblk_t dblkno;
        caddr_t addr;
        int nbytes, rdflg, flag;
        dev_t dev;
        u_int pfcent;
{
        register struct buf *bp;
        register u_int c;
        int p2dp;
        register struct pte *dpte, *vpte;
        int s;
        extern swdone();

        s = spl6();
        while (bswlist.av_forw == NULL) {
                bswlist.b_flags |= B_WANTED;
                sleep((caddr_t)&bswlist, PSWP+1);
        }
        bp = bswlist.av_forw;
        bswlist.av_forw = bp->av_forw;
        splx(s);

        bp->b_flags = B_BUSY | B_PHYS | rdflg | flag;
        if ((bp->b_flags & (B_DIRTY|B_PGIN)) == 0)
                if (rdflg == B_READ)
                        sum.v_pswpin += btoc(nbytes);
                else
                        sum.v_pswpout += btoc(nbytes);
        bp->b_proc = p;
        if (flag & B_DIRTY) {
                p2dp = ((bp - swbuf) * CLSIZE) * KLMAX;
                dpte = dptopte(&proc[2], p2dp);
                vpte = vtopte(p, btop(addr));
                for (c = 0; c < nbytes; c += NBPG) {
                        if (vpte->pg_pfnum == 0 || vpte->pg_fod)
                                panic("swap bad pte");
                        *dpte++ = *vpte++;
                }
                bp->b_un.b_addr = (caddr_t)ctob(dptov(&proc[2], p2dp));
                bp->b_flags |= B_CALL;
                bp->b_iodone = swdone;
                bp->b_pfcent = pfcent;
        } else
                bp->b_un.b_addr = addr;
        while (nbytes > 0) {
                bp->b_bcount = nbytes;
                minphys(bp);
                c = bp->b_bcount;
                bp->b_blkno = dblkno;
                bp->b_dev = dev;
#ifdef TRACE
                trace(TR_SWAPIO, dev, bp->b_blkno);
#endif
                physstrat(bp, bdevsw[major(dev)].d_strategy, PSWP);
                if (flag & B_DIRTY) {
                        if (c < nbytes)
                                panic("big push");
                        return;
                }
                bp->b_un.b_addr += c;
                bp->b_flags &= ~B_DONE;
                if (bp->b_flags & B_ERROR) {
                        if ((flag & (B_UAREA|B_PAGET)) || rdflg == B_WRITE)
                                panic("hard IO err in swap");
                        swkill(p, "swap: read error from swap device");
                }
                nbytes -= c;
                dblkno += btodb(c);
        }
        s = spl6();
        bp->b_flags &= ~(B_BUSY|B_WANTED|B_PHYS|B_PAGET|B_UAREA|B_DIRTY);
        bp->av_forw = bswlist.av_forw;
        bswlist.av_forw = bp;
        if (bswlist.b_flags & B_WANTED) {
                bswlist.b_flags &= ~B_WANTED;
                wakeup((caddr_t)&bswlist);
                wakeup((caddr_t)&proc[2]);
        }
        splx(s);
}

/*
 * Put a buffer on the clean list after I/O is done.
 * Called from biodone.
 */
swdone(bp)
        register struct buf *bp;
{
        register int s;

        if (bp->b_flags & B_ERROR)
                panic("IO err in push");
        s = spl6();
        bp->av_forw = bclnlist;
        cnt.v_pgout++;
        cnt.v_pgpgout += bp->b_bcount / NBPG;
        bclnlist = bp;
        if (bswlist.b_flags & B_WANTED)
                wakeup((caddr_t)&proc[2]);
        splx(s);
}

/*
 * If rout == 0 then killed on swap error, else
 * rout is the name of the routine where we ran out of
 * swap space.
 */
swkill(p, rout)
        struct proc *p;
        char *rout;
{

        printf("pid %d: %s", p->p_pid, rout);
        uprintf("sorry, pid %d was killed in %s", p->p_pid, rout);
        /*
         * To be sure no looping (e.g. in vmsched trying to
         * swap out) mark process locked in core (as though
         * done by user) after killing it so noone will try
         * to swap it out.
         */
        psignal(p, SIGKILL);
        p->p_flag |= SULOCK;
}

/*
 * Raw I/O. The arguments are
 *      The strategy routine for the device
 *      A buffer, which will always be a special buffer
 *        header owned exclusively by the device for this purpose
 *      The device number
 *      Read/write flag
 * Essentially all the work is computing physical addresses and
 * validating them.
 * If the user has the proper access privilidges, the process is
 * marked 'delayed unlock' and the pages involved in the I/O are
 * faulted and locked. After the completion of the I/O, the above pages
 * are unlocked.
 */
physio(strat, bp, dev, rw, mincnt, uio)
        int (*strat)();
        register struct buf *bp;
        dev_t dev;
        int rw;
        unsigned (*mincnt)();
        struct uio *uio;
{
        register struct iovec *iov;
        register int c;
        char *a;
        int s, error = 0;

nextiov:
        if (uio->uio_iovcnt == 0)
                return (0);
        iov = uio->uio_iov;
        if (useracc(iov->iov_base,(u_int)iov->iov_len,rw==B_READ?B_WRITE:B_READ) == NULL)
                return (EFAULT);
        s = spl6();
        while (bp->b_flags&B_BUSY) {
                bp->b_flags |= B_WANTED;
                sleep((caddr_t)bp, PRIBIO+1);
        }
        splx(s);
        bp->b_error = 0;
        bp->b_proc = u.u_procp;
        bp->b_un.b_addr = iov->iov_base;
        while (iov->iov_len > 0) {
                bp->b_flags = B_BUSY | B_PHYS | rw;
                bp->b_dev = dev;
                bp->b_blkno = btodb(uio->uio_offset);
                bp->b_bcount = iov->iov_len;
                (*mincnt)(bp);
                c = bp->b_bcount;
                u.u_procp->p_flag |= SPHYSIO;
                vslock(a = bp->b_un.b_addr, c);
                physstrat(bp, strat, PRIBIO);
                (void) spl6();
                vsunlock(a, c, rw);
                u.u_procp->p_flag &= ~SPHYSIO;
                if (bp->b_flags&B_WANTED)
                        wakeup((caddr_t)bp);
                splx(s);
                c -= bp->b_resid;
                bp->b_un.b_addr += c;
                iov->iov_len -= c;
                uio->uio_resid -= c;
                uio->uio_offset += c;
                /* temp kludge for tape drives */
                if (bp->b_resid || (bp->b_flags&B_ERROR))
                        break;
        }
        bp->b_flags &= ~(B_BUSY|B_WANTED|B_PHYS);
        error = geterror(bp);
        /* temp kludge for tape drives */
        if (bp->b_resid || error)
                return (error);
        uio->uio_iov++;
        uio->uio_iovcnt--;
        goto nextiov;
}

#define MAXPHYS (63 * 1024)

unsigned
minphys(bp)
        struct buf *bp;
{

        if (bp->b_bcount > MAXPHYS)
                bp->b_bcount = MAXPHYS;
}