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Annotation of XNU/bsd/kern/subr_disk.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * The contents of this file constitute Original Code as defined in and
        !             7:  * are subject to the Apple Public Source License Version 1.1 (the
        !             8:  * "License").  You may not use this file except in compliance with the
        !             9:  * License.  Please obtain a copy of the License at
        !            10:  * http://www.apple.com/publicsource and read it before using this file.
        !            11:  * 
        !            12:  * This Original Code and all software distributed under the License are
        !            13:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            14:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            15:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            16:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            17:  * License for the specific language governing rights and limitations
        !            18:  * under the License.
        !            19:  * 
        !            20:  * @APPLE_LICENSE_HEADER_END@
        !            21:  */
        !            22: /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
        !            23: /*
        !            24:  * Copyright (c) 1982, 1986, 1988, 1993
        !            25:  *     The Regents of the University of California.  All rights reserved.
        !            26:  * (c) UNIX System Laboratories, Inc.
        !            27:  * All or some portions of this file are derived from material licensed
        !            28:  * to the University of California by American Telephone and Telegraph
        !            29:  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
        !            30:  * the permission of UNIX System Laboratories, Inc.
        !            31:  *
        !            32:  * Redistribution and use in source and binary forms, with or without
        !            33:  * modification, are permitted provided that the following conditions
        !            34:  * are met:
        !            35:  * 1. Redistributions of source code must retain the above copyright
        !            36:  *    notice, this list of conditions and the following disclaimer.
        !            37:  * 2. Redistributions in binary form must reproduce the above copyright
        !            38:  *    notice, this list of conditions and the following disclaimer in the
        !            39:  *    documentation and/or other materials provided with the distribution.
        !            40:  * 3. All advertising materials mentioning features or use of this software
        !            41:  *    must display the following acknowledgement:
        !            42:  *     This product includes software developed by the University of
        !            43:  *     California, Berkeley and its contributors.
        !            44:  * 4. Neither the name of the University nor the names of its contributors
        !            45:  *    may be used to endorse or promote products derived from this software
        !            46:  *    without specific prior written permission.
        !            47:  *
        !            48:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            49:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            50:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            51:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            52:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            53:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            54:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            55:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            56:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            57:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            58:  * SUCH DAMAGE.
        !            59:  *
        !            60:  *     @(#)ufs_disksubr.c      8.5 (Berkeley) 1/21/94
        !            61:  */
        !            62: 
        !            63: #include <sys/param.h>
        !            64: #include <sys/systm.h>
        !            65: #include <sys/buf.h>
        !            66: #include <sys/disklabel.h>
        !            67: #include <sys/syslog.h>
        !            68: 
        !            69: /*
        !            70:  * Seek sort for disks.  We depend on the driver which calls us using b_resid
        !            71:  * as the current cylinder number.
        !            72:  *
        !            73:  * The argument ap structure holds a b_actf activity chain pointer on which we
        !            74:  * keep two queues, sorted in ascending cylinder order.  The first queue holds
        !            75:  * those requests which are positioned after the current cylinder (in the first
        !            76:  * request); the second holds requests which came in after their cylinder number
        !            77:  * was passed.  Thus we implement a one way scan, retracting after reaching the
        !            78:  * end of the drive to the first request on the second queue, at which time it
        !            79:  * becomes the first queue.
        !            80:  *
        !            81:  * A one-way scan is natural because of the way UNIX read-ahead blocks are
        !            82:  * allocated.
        !            83:  */
        !            84: 
        !            85: /*
        !            86:  * For portability with historic industry practice, the
        !            87:  * cylinder number has to be maintained in the `b_resid'
        !            88:  * field.
        !            89:  */
        !            90: #define        b_cylinder      b_resid
        !            91: 
        !            92: void
        !            93: disksort(ap, bp)
        !            94:        register struct buf *ap, *bp;
        !            95: {
        !            96:        register struct buf *bq;
        !            97: 
        !            98:        /* If the queue is empty, then it's easy. */
        !            99:        if (ap->b_actf == NULL) {
        !           100:                bp->b_actf = NULL;
        !           101:                ap->b_actf = bp;
        !           102:                return;
        !           103:        }
        !           104: 
        !           105:        /*
        !           106:         * If we lie after the first (currently active) request, then we
        !           107:         * must locate the second request list and add ourselves to it.
        !           108:         */
        !           109:        bq = ap->b_actf;
        !           110:        if (bp->b_cylinder < bq->b_cylinder) {
        !           111:                while (bq->b_actf) {
        !           112:                        /*
        !           113:                         * Check for an ``inversion'' in the normally ascending
        !           114:                         * cylinder numbers, indicating the start of the second
        !           115:                         * request list.
        !           116:                         */
        !           117:                        if (bq->b_actf->b_cylinder < bq->b_cylinder) {
        !           118:                                /*
        !           119:                                 * Search the second request list for the first
        !           120:                                 * request at a larger cylinder number.  We go
        !           121:                                 * before that; if there is no such request, we
        !           122:                                 * go at end.
        !           123:                                 */
        !           124:                                do {
        !           125:                                        if (bp->b_cylinder <
        !           126:                                            bq->b_actf->b_cylinder)
        !           127:                                                goto insert;
        !           128:                                        if (bp->b_cylinder ==
        !           129:                                            bq->b_actf->b_cylinder &&
        !           130:                                            bp->b_blkno < bq->b_actf->b_blkno)
        !           131:                                                goto insert;
        !           132:                                        bq = bq->b_actf;
        !           133:                                } while (bq->b_actf);
        !           134:                                goto insert;            /* after last */
        !           135:                        }
        !           136:                        bq = bq->b_actf;
        !           137:                }
        !           138:                /*
        !           139:                 * No inversions... we will go after the last, and
        !           140:                 * be the first request in the second request list.
        !           141:                 */
        !           142:                goto insert;
        !           143:        }
        !           144:        /*
        !           145:         * Request is at/after the current request...
        !           146:         * sort in the first request list.
        !           147:         */
        !           148:        while (bq->b_actf) {
        !           149:                /*
        !           150:                 * We want to go after the current request if there is an
        !           151:                 * inversion after it (i.e. it is the end of the first
        !           152:                 * request list), or if the next request is a larger cylinder
        !           153:                 * than our request.
        !           154:                 */
        !           155:                if (bq->b_actf->b_cylinder < bq->b_cylinder ||
        !           156:                    bp->b_cylinder < bq->b_actf->b_cylinder ||
        !           157:                    (bp->b_cylinder == bq->b_actf->b_cylinder &&
        !           158:                    bp->b_blkno < bq->b_actf->b_blkno))
        !           159:                        goto insert;
        !           160:                bq = bq->b_actf;
        !           161:        }
        !           162:        /*
        !           163:         * Neither a second list nor a larger request... we go at the end of
        !           164:         * the first list, which is the same as the end of the whole schebang.
        !           165:         */
        !           166: insert:        bp->b_actf = bq->b_actf;
        !           167:        bq->b_actf = bp;
        !           168: }
        !           169: 
        !           170: /* encoding of disk minor numbers, should be elsewhere... */
        !           171: #define dkunit(dev)            (minor(dev) >> 3)
        !           172: #define dkpart(dev)            (minor(dev) & 07)
        !           173: #define dkminor(unit, part)    (((unit) << 3) | (part))
        !           174: 
        !           175: /*
        !           176:  * Compute checksum for disk label.
        !           177:  */
        !           178: u_int
        !           179: dkcksum(lp)
        !           180:        register struct disklabel *lp;
        !           181: {
        !           182:        register u_short *start, *end;
        !           183:        register u_short sum = 0;
        !           184: 
        !           185:        start = (u_short *)lp;
        !           186:        end = (u_short *)&lp->d_partitions[lp->d_npartitions];
        !           187:        while (start < end)
        !           188:                sum ^= *start++;
        !           189:        return (sum);
        !           190: }
        !           191: 
        !           192: /*
        !           193:  * Disk error is the preface to plaintive error messages
        !           194:  * about failing disk transfers.  It prints messages of the form
        !           195: 
        !           196: hp0g: hard error reading fsbn 12345 of 12344-12347 (hp0 bn %d cn %d tn %d sn %d)
        !           197: 
        !           198:  * if the offset of the error in the transfer and a disk label
        !           199:  * are both available.  blkdone should be -1 if the position of the error
        !           200:  * is unknown; the disklabel pointer may be null from drivers that have not
        !           201:  * been converted to use them.  The message is printed with printf
        !           202:  * if pri is LOG_PRINTF, otherwise it uses log at the specified priority.
        !           203:  * The message should be completed (with at least a newline) with printf
        !           204:  * or addlog, respectively.  There is no trailing space.
        !           205:  */
        !           206: void
        !           207: diskerr(bp, dname, what, pri, blkdone, lp)
        !           208:        register struct buf *bp;
        !           209:        char *dname, *what;
        !           210:        int pri, blkdone;
        !           211:        register struct disklabel *lp;
        !           212: {
        !           213:        int unit = dkunit(bp->b_dev), part = dkpart(bp->b_dev);
        !           214:        register void (*pr) __P((const char *, ...));
        !           215:        char partname = 'a' + part;
        !           216:        int sn;
        !           217: 
        !           218:        if (pri != LOG_PRINTF) {
        !           219:                log(pri, "");
        !           220:                pr = addlog;
        !           221:        } else
        !           222:                pr = printf;
        !           223:        (*pr)("%s%d%c: %s %sing fsbn ", dname, unit, partname, what,
        !           224:            bp->b_flags & B_READ ? "read" : "writ");
        !           225:        sn = bp->b_blkno;
        !           226:        if (bp->b_bcount <= DEV_BSIZE)
        !           227:                (*pr)("%d", sn);
        !           228:        else {
        !           229:                if (blkdone >= 0) {
        !           230:                        sn += blkdone;
        !           231:                        (*pr)("%d of ", sn);
        !           232:                }
        !           233:                (*pr)("%d-%d", bp->b_blkno,
        !           234:                    bp->b_blkno + (bp->b_bcount - 1) / DEV_BSIZE);
        !           235:        }
        !           236:        if (lp && (blkdone >= 0 || bp->b_bcount <= lp->d_secsize)) {
        !           237: #ifdef tahoe
        !           238:                sn *= DEV_BSIZE / lp->d_secsize;                /* XXX */
        !           239: #endif
        !           240:                sn += lp->d_partitions[part].p_offset;
        !           241:                (*pr)(" (%s%d bn %d; cn %d", dname, unit, sn,
        !           242:                    sn / lp->d_secpercyl);
        !           243:                sn %= lp->d_secpercyl;
        !           244:                (*pr)(" tn %d sn %d)", sn / lp->d_nsectors, sn % lp->d_nsectors);
        !           245:        }
        !           246: }

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