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Annotation of 43BSDReno/sys/tahoe/ufs_machdep.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1983, 1988 Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution is only permitted until one year after the first shipment
        !             6:  * of 4.4BSD by the Regents.  Otherwise, redistribution and use in source and
        !             7:  * binary forms are permitted provided that: (1) source distributions retain
        !             8:  * this entire copyright notice and comment, and (2) distributions including
        !             9:  * binaries display the following acknowledgement:  This product includes
        !            10:  * software developed by the University of California, Berkeley and its
        !            11:  * contributors'' in the documentation or other materials provided with the
        !            12:  * distribution and in all advertising materials mentioning features or use
        !            13:  * of this software.  Neither the name of the University nor the names of
        !            14:  * its contributors may be used to endorse or promote products derived from
        !            15:  * this software without specific prior written permission.
        !            16:  * THIS SOFTWARE IS PROVIDED AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
        !            17:  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
        !            18:  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            19:  *
        !            20:  *     @(#)ufs_machdep.c       7.5 (Berkeley) 6/28/90
        !            21:  */
        !            22: 
        !            23: #include "param.h"
        !            24: #include "systm.h"
        !            25: #include "user.h"
        !            26: #include "buf.h"
        !            27: #include "conf.h"
        !            28: #include "proc.h"
        !            29: #include "seg.h"
        !            30: #include "vm.h"
        !            31: 
        !            32: #include "pte.h"
        !            33: 
        !            34: /*
        !            35:  * Machine dependent handling of the buffer cache.
        !            36:  */
        !            37: 
        !            38: /*
        !            39:  * Expand or contract the actual memory allocated to a buffer.
        !            40:  * If no memory is available, release buffer and take error exit
        !            41:  */
        !            42: allocbuf(tp, size)
        !            43:        register struct buf *tp;
        !            44:        int size;
        !            45: {
        !            46:        register struct buf *bp, *ep;
        !            47:        int sizealloc, take, s;
        !            48: 
        !            49:        sizealloc = roundup(size, CLBYTES);
        !            50:        /*
        !            51:         * Buffer size does not change
        !            52:         */
        !            53:        if (sizealloc == tp->b_bufsize)
        !            54:                goto out;
        !            55:        /*
        !            56:         * Buffer size is shrinking.
        !            57:         * Place excess space in a buffer header taken from the
        !            58:         * BQ_EMPTY buffer list and placed on the "most free" list.
        !            59:         * If no extra buffer headers are available, leave the
        !            60:         * extra space in the present buffer.
        !            61:         */
        !            62:        if (sizealloc < tp->b_bufsize) {
        !            63:                ep = bfreelist[BQ_EMPTY].av_forw;
        !            64:                if (ep == &bfreelist[BQ_EMPTY])
        !            65:                        goto out;
        !            66:                s = splbio();
        !            67:                bremfree(ep);
        !            68:                ep->b_flags |= B_BUSY;
        !            69:                splx(s);
        !            70:                pagemove(tp->b_un.b_addr + sizealloc, ep->b_un.b_addr,
        !            71:                    (int)tp->b_bufsize - sizealloc);
        !            72:                ep->b_bufsize = tp->b_bufsize - sizealloc;
        !            73:                tp->b_bufsize = sizealloc;
        !            74:                ep->b_flags |= B_INVAL;
        !            75:                ep->b_bcount = 0;
        !            76:                brelse(ep);
        !            77:                goto out;
        !            78:        }
        !            79:        /*
        !            80:         * More buffer space is needed. Get it out of buffers on
        !            81:         * the "most free" list, placing the empty headers on the
        !            82:         * BQ_EMPTY buffer header list.
        !            83:         */
        !            84:        while (tp->b_bufsize < sizealloc) {
        !            85:                take = sizealloc - tp->b_bufsize;
        !            86:                bp = getnewbuf();
        !            87:                if (take >= bp->b_bufsize)
        !            88:                        take = bp->b_bufsize;
        !            89:                pagemove(&bp->b_un.b_addr[bp->b_bufsize - take],
        !            90:                    &tp->b_un.b_addr[tp->b_bufsize], take);
        !            91:                tp->b_bufsize += take;
        !            92:                bp->b_bufsize = bp->b_bufsize - take;
        !            93:                if (bp->b_bcount > bp->b_bufsize)
        !            94:                        bp->b_bcount = bp->b_bufsize;
        !            95:                if (bp->b_bufsize <= 0) {
        !            96:                        bremhash(bp);
        !            97:                        binshash(bp, &bfreelist[BQ_EMPTY]);
        !            98:                        bp->b_dev = (dev_t)NODEV;
        !            99:                        bp->b_error = 0;
        !           100:                        bp->b_flags |= B_INVAL;
        !           101:                }
        !           102:                brelse(bp);
        !           103:        }
        !           104: out:
        !           105:        tp->b_bcount = size;
        !           106:        return (1);
        !           107: }
        !           108: 
        !           109: /*
        !           110:  * Release space associated with a buffer.
        !           111:  */
        !           112: bfree(bp)
        !           113:        struct buf *bp;
        !           114: {
        !           115: 
        !           116:        bp->b_bcount = 0;
        !           117: }

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