The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_physio.c

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    1 /*
    2  * Copyright (c) 1994 John S. Dyson
    3  * All rights reserved.
    4  *
    5  * Redistribution and use in source and binary forms, with or without
    6  * modification, are permitted provided that the following conditions
    7  * are met:
    8  * 1. Redistributions of source code must retain the above copyright
    9  *    notice immediately at the beginning of the file, without modification,
   10  *    this list of conditions, and the following disclaimer.
   11  * 2. Redistributions in binary form must reproduce the above copyright
   12  *    notice, this list of conditions and the following disclaimer in the
   13  *    documentation and/or other materials provided with the distribution.
   14  * 3. Absolutely no warranty of function or purpose is made by the author
   15  *    John S. Dyson.
   16  * 4. Modifications may be freely made to this file if the above conditions
   17  *    are met.
   18  *
   19  * $FreeBSD: src/sys/kern/kern_physio.c,v 1.17.2.1 1999/09/05 08:15:00 peter Exp $
   20  */
   21 
   22 #include <sys/param.h>
   23 #include <sys/systm.h>
   24 #include <sys/buf.h>
   25 #include <sys/conf.h>
   26 #include <sys/proc.h>
   27 #include <vm/vm.h>
   28 #include <vm/vm_param.h>
   29 #include <vm/vm_extern.h>
   30 
   31 static void     physwakeup __P((struct buf *bp));
   32 
   33 int
   34 physio(strategy, bp, dev, rw, minp, uio)
   35         d_strategy_t *strategy;
   36         struct buf *bp;
   37         dev_t dev;
   38         int rw;
   39         u_int (*minp) __P((struct buf *bp));
   40         struct uio *uio;
   41 {
   42         int i;
   43         int bufflags = rw?B_READ:0;
   44         int error;
   45         int spl;
   46         caddr_t sa;
   47         int bp_alloc = (bp == 0);
   48         struct buf *bpa;
   49 
   50 /*
   51  * keep the process from being swapped
   52  */
   53         curproc->p_flag |= P_PHYSIO;
   54 
   55         /* create and build a buffer header for a transfer */
   56         bpa = (struct buf *)getpbuf();
   57         if (!bp_alloc) {
   58                 spl = splbio();
   59                 while (bp->b_flags & B_BUSY) {
   60                         bp->b_flags |= B_WANTED;
   61                         tsleep((caddr_t)bp, PRIBIO, "physbw", 0);
   62                 }
   63                 bp->b_flags |= B_BUSY;
   64                 splx(spl);
   65         } else {
   66                 bp = bpa;
   67         }
   68 
   69         /*
   70          * get a copy of the kva from the physical buffer
   71          */
   72         sa = bpa->b_data;
   73         bp->b_proc = curproc;
   74         bp->b_dev = dev;
   75         error = bp->b_error = 0;
   76 
   77         for(i=0;i<uio->uio_iovcnt;i++) {
   78                 while( uio->uio_iov[i].iov_len) {
   79 
   80                         bp->b_bcount = uio->uio_iov[i].iov_len;
   81                         bp->b_flags = B_BUSY | B_PHYS | B_CALL | bufflags;
   82                         bp->b_iodone = physwakeup;
   83                         bp->b_data = uio->uio_iov[i].iov_base;
   84                         bp->b_bcount = minp( bp);
   85                         if( minp != minphys)
   86                                 bp->b_bcount = minphys( bp);
   87                         bp->b_bufsize = bp->b_bcount;
   88                         /*
   89                          * pass in the kva from the physical buffer
   90                          * for the temporary kernel mapping.
   91                          */
   92                         bp->b_saveaddr = sa;
   93                         bp->b_blkno = btodb(uio->uio_offset);
   94 
   95 
   96                         if (uio->uio_segflg == UIO_USERSPACE) {
   97                                 if (rw && !useracc(bp->b_data, bp->b_bufsize, B_WRITE)) {
   98                                         error = EFAULT;
   99                                         goto doerror;
  100                                 }
  101                                 if (!rw && !useracc(bp->b_data, bp->b_bufsize, B_READ)) {
  102                                         error = EFAULT;
  103                                         goto doerror;
  104                                 }
  105 
  106                                 /* bring buffer into kernel space */
  107                                 vmapbuf(bp);
  108                         }
  109 
  110                         /* perform transfer */
  111                         (*strategy)(bp);
  112 
  113                         spl = splbio();
  114                         while ((bp->b_flags & B_DONE) == 0)
  115                                 tsleep((caddr_t)bp, PRIBIO, "physstr", 0);
  116                         splx(spl);
  117 
  118                         /* release mapping into kernel space */
  119                         if (uio->uio_segflg == UIO_USERSPACE)
  120                                 vunmapbuf(bp);
  121 
  122                         /*
  123                          * update the uio data
  124                          */
  125                         {
  126                                 int iolen = bp->b_bcount - bp->b_resid;
  127 
  128                                 if (iolen == 0 && !(bp->b_flags & B_ERROR))
  129                                         goto doerror;   /* EOF */
  130                                 uio->uio_iov[i].iov_len -= iolen;
  131                                 uio->uio_iov[i].iov_base += iolen;
  132                                 uio->uio_resid -= iolen;
  133                                 uio->uio_offset += iolen;
  134                         }
  135 
  136                         /*
  137                          * check for an error
  138                          */
  139                         if( bp->b_flags & B_ERROR) {
  140                                 error = bp->b_error;
  141                                 goto doerror;
  142                         }
  143                 }
  144         }
  145 
  146 
  147 doerror:
  148         relpbuf(bpa);
  149         if (!bp_alloc) {
  150                 bp->b_flags &= ~(B_BUSY|B_PHYS);
  151                 if( bp->b_flags & B_WANTED) {
  152                         bp->b_flags &= ~B_WANTED;
  153                         wakeup((caddr_t)bp);
  154                 }
  155         }
  156 /*
  157  * allow the process to be swapped
  158  */
  159         curproc->p_flag &= ~P_PHYSIO;
  160 
  161         return (error);
  162 }
  163 
  164 u_int
  165 minphys(struct buf *bp)
  166 {
  167         u_int maxphys = MAXPHYS;
  168 
  169         if( ((vm_offset_t) bp->b_data) & PAGE_MASK) {
  170                 maxphys = MAXPHYS - PAGE_SIZE;
  171         }
  172 
  173         if( bp->b_bcount > maxphys) {
  174                 bp->b_bcount = maxphys;
  175         }
  176         return bp->b_bcount;
  177 }
  178 
  179 int
  180 rawread(dev_t dev, struct uio *uio, int ioflag)
  181 {
  182         return (physio(cdevsw[major(dev)]->d_strategy, (struct buf *)NULL,
  183             dev, 1, minphys, uio));
  184 }
  185 
  186 int
  187 rawwrite(dev_t dev, struct uio *uio, int ioflag)
  188 {
  189         return (physio(cdevsw[major(dev)]->d_strategy, (struct buf *)NULL,
  190             dev, 0, minphys, uio));
  191 }
  192 
  193 static void
  194 physwakeup(bp)
  195         struct buf *bp;
  196 {
  197         wakeup((caddr_t) bp);
  198         bp->b_flags &= ~B_CALL;
  199 }

Cache object: ccf9d40cef1b232f3c82568dadb2762b


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