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Annotation of 40BSD/sys/dev/sw.c, revision 1.1.1.1

1.1       root        1: /*     sw.c    4.2     11/9/80 */
                      2: 
                      3: #include "../h/param.h"
                      4: #include "../h/systm.h"
                      5: #include "../h/buf.h"
                      6: #include "../h/conf.h"
                      7: #include "../h/dir.h"
                      8: #include "../h/user.h"
                      9: #include "../h/inode.h"
                     10: #include "../h/map.h"
                     11: 
                     12: struct buf rswbuf;
                     13: /*
                     14:  * Indirect driver for multi-controller paging.
                     15:  */
                     16: swstrategy(bp)
                     17:        register struct buf *bp;
                     18: {
                     19:        int sz, off, seg;
                     20:        dev_t dev;
                     21: 
                     22:        sz = (bp->b_bcount+511)/512;
                     23:        off = bp->b_blkno % DMMAX;
                     24:        if (bp->b_blkno+sz > nswap || off+sz > DMMAX) {
                     25:                bp->b_flags |= B_ERROR;
                     26:                iodone(bp);
                     27:                return;
                     28:        }
                     29:        seg = bp->b_blkno / DMMAX;
                     30:        dev = swdevt[seg % nswdev].sw_dev;
                     31:        seg /= nswdev;
                     32:        bp->b_blkno = seg*DMMAX + off;
                     33:        bp->b_dev = dev;
                     34:        if (dev == 0)
                     35:                panic("swstrategy");
                     36:        (*bdevsw[major(dev)].d_strategy)(bp);
                     37: }
                     38: 
                     39: swread(dev)
                     40: {
                     41: 
                     42:        physio(swstrategy, &rswbuf, dev, B_READ, minphys);
                     43: }
                     44: 
                     45: swwrite(dev)
                     46: {
                     47: 
                     48:        physio(swstrategy, &rswbuf, dev, B_WRITE, minphys);
                     49: }
                     50: 
                     51: /*
                     52:  * System call swapon(name) enables swapping on device name,
                     53:  * which must be in the swdevsw.  Return EBUSY
                     54:  * if already swapping on this device.
                     55:  */
                     56: vswapon()
                     57: {
                     58:        register struct inode *ip;
                     59:        dev_t dev;
                     60:        register struct swdevt *sp;
                     61: 
                     62:        ip = namei(uchar, 0);
                     63:        if (ip == NULL)
                     64:                return;
                     65:        if ((ip->i_mode&IFMT) != IFBLK) {
                     66:                u.u_error = ENOTBLK;
                     67:                iput(ip);
                     68:                return;
                     69:        }
                     70:        dev = (dev_t)ip->i_un.i_rdev;
                     71:        iput(ip);
                     72:        if (major(dev) >= nblkdev) {
                     73:                u.u_error = ENXIO;
                     74:                return;
                     75:        }
                     76:        /*
                     77:         * Search starting at second table entry,
                     78:         * since first (primary swap area) is freed at boot.
                     79:         */
                     80:        for (sp = &swdevt[1]; sp->sw_dev; sp++)
                     81:                if (sp->sw_dev == dev) {
                     82:                        if (sp->sw_freed) {
                     83:                                u.u_error = EBUSY;
                     84:                                return;
                     85:                        }
                     86:                        swfree(sp - swdevt);
                     87:                        return;
                     88:                }
                     89:        u.u_error = ENODEV;
                     90: }
                     91: 
                     92: /*
                     93:  * Swfree(index) frees the index'th portion of the swap map.
                     94:  * Each of the nswdev devices provides 1/nswdev'th of the swap
                     95:  * space, which is laid out with blocks of DMMAX pages circularly
                     96:  * among the devices.
                     97:  */
                     98: swfree(index)
                     99:        int index;
                    100: {
                    101:        register swblk_t vsbase;
                    102:        register int blk;
                    103: 
                    104:        swdevt[index].sw_freed = 1;
                    105:        for (vsbase = index*DMMAX; vsbase < nswap; vsbase += nswdev*DMMAX) {
                    106:                blk = nswap - vsbase;
                    107:                if (blk > DMMAX)
                    108:                        blk = DMMAX;
                    109:                if (vsbase == 0) {
                    110:                        /*
                    111:                         * Can't free a block starting at 0 in the swapmap
                    112:                         * but need some space for argmap so use this
                    113:                         * hunk which needs special treatment anyways.
                    114:                         */
                    115:                        argdev = swdevt[0].sw_dev;
                    116:                        mfree(argmap, blk-CLSIZE, vsbase+CLSIZE);
                    117:                } else
                    118:                        mfree(swapmap, blk, vsbase);
                    119:        }
                    120: }

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