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Annotation of kernel/bsd/kern/kern_physio.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
        !             7:  * Reserved.  This file contains Original Code and/or Modifications of
        !             8:  * Original Code as defined in and that are subject to the Apple Public
        !             9:  * Source License Version 1.1 (the "License").  You may not use this file
        !            10:  * except in compliance with the License.  Please obtain a copy of the
        !            11:  * License at http://www.apple.com/publicsource and read it before using
        !            12:  * this file.
        !            13:  * 
        !            14:  * The Original Code and all software distributed under the License are
        !            15:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            16:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            17:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            18:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            19:  * License for the specific language governing rights and limitations
        !            20:  * under the License.
        !            21:  * 
        !            22:  * @APPLE_LICENSE_HEADER_END@
        !            23:  */
        !            24: 
        !            25: /*-
        !            26:  * Copyright (c) 1982, 1986, 1990, 1993
        !            27:  *     The Regents of the University of California.  All rights reserved.
        !            28:  * (c) UNIX System Laboratories, Inc.
        !            29:  * All or some portions of this file are derived from material licensed
        !            30:  * to the University of California by American Telephone and Telegraph
        !            31:  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
        !            32:  * the permission of UNIX System Laboratories, Inc.
        !            33:  *
        !            34:  * Redistribution and use in source and binary forms, with or without
        !            35:  * modification, are permitted provided that the following conditions
        !            36:  * are met:
        !            37:  * 1. Redistributions of source code must retain the above copyright
        !            38:  *    notice, this list of conditions and the following disclaimer.
        !            39:  * 2. Redistributions in binary form must reproduce the above copyright
        !            40:  *    notice, this list of conditions and the following disclaimer in the
        !            41:  *    documentation and/or other materials provided with the distribution.
        !            42:  * 3. All advertising materials mentioning features or use of this software
        !            43:  *    must display the following acknowledgement:
        !            44:  *     This product includes software developed by the University of
        !            45:  *     California, Berkeley and its contributors.
        !            46:  * 4. Neither the name of the University nor the names of its contributors
        !            47:  *    may be used to endorse or promote products derived from this software
        !            48:  *    without specific prior written permission.
        !            49:  *
        !            50:  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
        !            51:  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
        !            52:  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
        !            53:  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
        !            54:  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
        !            55:  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
        !            56:  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
        !            57:  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
        !            58:  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
        !            59:  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
        !            60:  * SUCH DAMAGE.
        !            61:  *
        !            62:  *     from: @(#)kern_physio.c 8.1 (Berkeley) 6/10/93
        !            63:  */
        !            64: /*
        !            65:  * HISTORY
        !            66:  * 27-July-97  Umesh Vaishampayan  ([email protected])
        !            67:  *     Allow physio() to kernel space.
        !            68:  */
        !            69: 
        !            70: #include <sys/param.h>
        !            71: #include <sys/systm.h>
        !            72: #include <sys/buf.h>
        !            73: #include <sys/conf.h>
        !            74: #include <sys/proc.h>
        !            75: 
        !            76: int
        !            77: physio(strategy, bp, dev, flags, minphys, uio, blocksize)
        !            78:        int (*strategy)(); 
        !            79:        struct buf *bp;
        !            80:        dev_t dev;
        !            81:        int flags;
        !            82:        u_int (*minphys)();
        !            83:        struct uio *uio;
        !            84:        int blocksize;
        !            85: {
        !            86:        struct iovec *iovp;
        !            87:        struct proc *p = current_proc();
        !            88:        int error, done, i, nobuf, s, todo;
        !            89: 
        !            90:        error = 0;
        !            91:        flags &= B_READ | B_WRITE;
        !            92: 
        !            93:        /*
        !            94:         * [check user read/write access to the data buffer]
        !            95:         *
        !            96:         * Check each iov one by one.  Note that we know if we're reading or
        !            97:         * writing, so we ignore the uio's rw parameter.  Also note that if
        !            98:         * we're doing a read, that's a *write* to user-space.
        !            99:         */
        !           100:        for (i = 0; i < uio->uio_iovcnt; i++) {
        !           101:                if(uio->uio_segflg != UIO_SYSSPACE) {
        !           102:                        if (!useracc(uio->uio_iov[i].iov_base,
        !           103:                                uio->uio_iov[i].iov_len,
        !           104:                                (flags == B_READ) ? B_WRITE : B_READ))
        !           105:                        return (EFAULT);
        !           106:                }
        !           107:        }
        !           108:        /* Make sure we have a buffer, creating one if necessary. */
        !           109:        if (nobuf = (bp == NULL)) {
        !           110: //             bp = getphysbuf();
        !           111:                panic("physio: null buf pointer\n");
        !           112:                }
        !           113: 
        !           114:        /* [raise the processor priority level to splbio;] */
        !           115:        s = splbio();
        !           116: 
        !           117:        /* [while the buffer is marked busy] */
        !           118:        while (bp->b_flags & B_BUSY) {
        !           119:                /* [mark the buffer wanted] */
        !           120:                bp->b_flags |= B_WANTED;
        !           121:                /* [wait until the buffer is available] */
        !           122:                tsleep((caddr_t)bp, PRIBIO+1, "physbuf", 0);
        !           123:        }
        !           124: 
        !           125:        /* Mark it busy, so nobody else will use it. */
        !           126:        bp->b_flags |= B_BUSY;
        !           127: 
        !           128:        /* [lower the priority level] */
        !           129:        splx(s);
        !           130: 
        !           131:        /* [set up the fixed part of the buffer for a transfer] */
        !           132:        bp->b_dev = dev;
        !           133:        bp->b_error = 0;
        !           134:        bp->b_proc = p;
        !           135: 
        !           136:        /*
        !           137:         * [while there are data to transfer and no I/O error]
        !           138:         * Note that I/O errors are handled with a 'goto' at the bottom
        !           139:         * of the 'while' loop.
        !           140:         */
        !           141:        for (i = 0; i < uio->uio_iovcnt; i++) {
        !           142:                iovp = &uio->uio_iov[i];
        !           143:                while (iovp->iov_len > 0) {
        !           144:                        /*
        !           145:                         * [mark the buffer busy for physical I/O]
        !           146:                         * (i.e. set B_PHYS (because it's an I/O to user
        !           147:                         * memory, and B_RAW, because B_RAW is to be
        !           148:                         * "Set by physio for raw transfers.", in addition
        !           149:                         * to the "busy" and read/write flag.)
        !           150:                         */
        !           151:                        s = splbio();
        !           152:                        bp->b_flags = B_BUSY | B_PHYS | B_RAW | flags;
        !           153:                        splx(s);
        !           154: 
        !           155:                        /* [set up the buffer for a maximum-sized transfer] */
        !           156:                        bp->b_blkno = uio->uio_offset / blocksize;
        !           157: #if hppa
        !           158:                        bp->b_offset = (((u_int64_t)bp->b_blkno) * (u_int64_t)blocksize);
        !           159: #endif /* hppa */
        !           160:                        bp->b_bcount = iovp->iov_len;
        !           161:                        bp->b_data = iovp->iov_base;
        !           162:                        
        !           163:                        /*
        !           164:                         * [call minphys to bound the tranfer size]
        !           165:                         * and remember the amount of data to transfer,
        !           166:                         * for later comparison.
        !           167:                         */
        !           168:                        (*minphys)(bp);
        !           169:                        todo = bp->b_bcount;
        !           170: 
        !           171:                        /*
        !           172:                         * [lock the part of the user address space involved
        !           173:                         *    in the transfer]
        !           174:                         * Beware vmapbuf(); it clobbers b_data and
        !           175:                         * saves it in b_saveaddr.  However, vunmapbuf()
        !           176:                         * restores it.
        !           177:                         */
        !           178: 
        !           179:                        if(uio->uio_segflg == UIO_SYSSPACE)
        !           180:                                bp->b_flags |= B_KERNSPACE;
        !           181:                        else
        !           182:                                vslock(bp->b_data, todo);
        !           183:                        
        !           184: #if 0
        !           185:                        vmapbuf(bp, todo);
        !           186: #endif /* 0 */
        !           187:                        /* [call strategy to start the transfer] */
        !           188:                        (*strategy)(bp);
        !           189: 
        !           190:                        /*
        !           191:                         * Note that the raise/wait/lower/get error
        !           192:                         * steps below would be done by biowait(), but
        !           193:                         * we want to unlock the address space before
        !           194:                         * we lower the priority.
        !           195:                         *
        !           196:                         * [raise the priority level to splbio]
        !           197:                         */
        !           198:                        s = splbio();
        !           199: 
        !           200:                        /* [wait for the transfer to complete] */
        !           201:                        while ((bp->b_flags & B_DONE) == 0)
        !           202:                                tsleep((caddr_t) bp, PRIBIO + 1, "physio", 0);
        !           203: 
        !           204:                        /*
        !           205:                         * [unlock the part of the address space previously
        !           206:                         *    locked]
        !           207:                         */
        !           208: #if 0
        !           209:                        vunmapbuf(bp, todo);
        !           210: #endif /* 0 */
        !           211:                        if(uio->uio_segflg != UIO_SYSSPACE)
        !           212:                                vsunlock(bp->b_data, todo);
        !           213: 
        !           214:                        /* remember error value (save a splbio/splx pair) */
        !           215:                        if (bp->b_flags & B_ERROR)
        !           216:                                error = (bp->b_error ? bp->b_error : EIO);
        !           217: 
        !           218:                        /* [lower the priority level] */
        !           219:                        splx(s);
        !           220: 
        !           221:                        /*
        !           222:                         * [deduct the transfer size from the total number
        !           223:                         *    of data to transfer]
        !           224:                         */
        !           225:                        done = bp->b_bcount - bp->b_resid;
        !           226:                        iovp->iov_len -= done;
        !           227:                         iovp->iov_base += done;
        !           228:                         uio->uio_offset += done;
        !           229:                         uio->uio_resid -= done;
        !           230: 
        !           231:                        /*
        !           232:                         * Now, check for an error.
        !           233:                         * Also, handle weird end-of-disk semantics.
        !           234:                         */
        !           235:                        if (error || done < todo)
        !           236:                                goto done;
        !           237:                }
        !           238:        }
        !           239: 
        !           240: done:
        !           241:        /*
        !           242:         * [clean up the state of the buffer]
        !           243:         * Remember if somebody wants it, so we can wake them up below.
        !           244:         * Also, if we had to steal it, give it back.
        !           245:         */
        !           246:        s = splbio();
        !           247:        bp->b_flags &= ~(B_BUSY | B_PHYS | B_RAW);
        !           248: #if 0
        !           249:        if (nobuf)
        !           250:                putphysbuf(bp);
        !           251: 
        !           252:        else 
        !           253: #endif /* 0 */
        !           254:                {
        !           255:                /*
        !           256:                 * [if another process is waiting for the raw I/O buffer,
        !           257:                 *    wake up processes waiting to do physical I/O;
        !           258:                 */
        !           259:                if (bp->b_flags & B_WANTED) {
        !           260:                        bp->b_flags &= ~B_WANTED;
        !           261:                        wakeup(bp);
        !           262:                }
        !           263:        }
        !           264:        splx(s);
        !           265: 
        !           266:        return (error);
        !           267: }
        !           268: 
        !           269: /*
        !           270:  * Leffler, et al., says on p. 231:
        !           271:  * "The minphys() routine is called by physio() to adjust the
        !           272:  * size of each I/O transfer before the latter is passed to
        !           273:  * the strategy routine..." 
        !           274:  *
        !           275:  * so, just adjust the buffer's count accounting to MAXPHYS here,
        !           276:  * and return the new count;
        !           277:  */
        !           278: u_int
        !           279: minphys(bp)
        !           280:        struct buf *bp;
        !           281: {
        !           282: 
        !           283:        bp->b_bcount = min(MAXPHYS, bp->b_bcount);
        !           284:         return bp->b_bcount;
        !           285: }
        !           286: 
        !           287: /*
        !           288:  * Do a read on a device for a user process.
        !           289:  */
        !           290: rawread(dev, uio)
        !           291:        dev_t dev;
        !           292:        struct uio *uio;
        !           293: {
        !           294:        return (physio(cdevsw[major(dev)].d_strategy, (struct buf *)NULL,
        !           295:            dev, B_READ, minphys, uio));
        !           296: }
        !           297: 
        !           298: /*
        !           299:  * Do a write on a device for a user process.
        !           300:  */
        !           301: rawwrite(dev, uio)
        !           302:        dev_t dev;
        !           303:        struct uio *uio;
        !           304: {
        !           305:        return (physio(cdevsw[major(dev)].d_strategy, (struct buf *)NULL,
        !           306:            dev, B_WRITE, minphys, uio));
        !           307: }

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