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: stable/3/sys/kern/kern_physio.c 50583 1999-08-29 16:33:42Z peter $
   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 <sys/uio.h>
   28 
   29 #include <vm/vm.h>
   30 #include <vm/vm_extern.h>
   31 
   32 static void     physwakeup __P((struct buf *bp));
   33 static struct buf * phygetvpbuf(dev_t dev, int resid);
   34 
   35 int
   36 physio(strategy, bp, dev, rw, minp, uio)
   37         d_strategy_t *strategy;
   38         struct buf *bp;
   39         dev_t dev;
   40         int rw;
   41         u_int (*minp) __P((struct buf *bp));
   42         struct uio *uio;
   43 {
   44         int i;
   45         int bufflags = rw?B_READ:0;
   46         int error;
   47         int spl;
   48         caddr_t sa;
   49         int bp_alloc = (bp == 0);
   50         struct buf *bpa;
   51 
   52 /*
   53  * keep the process from being swapped
   54  */
   55         curproc->p_flag |= P_PHYSIO;
   56 
   57         /* create and build a buffer header for a transfer */
   58         bpa = (struct buf *)phygetvpbuf(dev, uio->uio_resid);
   59         if (!bp_alloc) {
   60                 spl = splbio();
   61                 while (bp->b_flags & B_BUSY) {
   62                         bp->b_flags |= B_WANTED;
   63                         tsleep((caddr_t)bp, PRIBIO, "physbw", 0);
   64                 }
   65                 bp->b_flags |= B_BUSY;
   66                 splx(spl);
   67         } else {
   68                 bp = bpa;
   69         }
   70 
   71         /*
   72          * get a copy of the kva from the physical buffer
   73          */
   74         sa = bpa->b_data;
   75         bp->b_proc = curproc;
   76         error = bp->b_error = 0;
   77 
   78         for(i=0;i<uio->uio_iovcnt;i++) {
   79                 while( uio->uio_iov[i].iov_len) {
   80 
   81                         bp->b_dev = dev;
   82                         bp->b_bcount = uio->uio_iov[i].iov_len;
   83                         bp->b_flags = B_BUSY | B_PHYS | B_CALL | bufflags;
   84                         bp->b_iodone = physwakeup;
   85                         bp->b_data = uio->uio_iov[i].iov_base;
   86                         bp->b_bcount = minp( bp);
   87                         if( minp != minphys)
   88                                 bp->b_bcount = minphys( bp);
   89                         bp->b_bufsize = bp->b_bcount;
   90                         /*
   91                          * pass in the kva from the physical buffer
   92                          * for the temporary kernel mapping.
   93                          */
   94                         bp->b_saveaddr = sa;
   95                         bp->b_blkno = btodb(uio->uio_offset);
   96                         bp->b_offset = uio->uio_offset;
   97 
   98                         if (uio->uio_segflg == UIO_USERSPACE) {
   99                                 if (rw && !useracc(bp->b_data, bp->b_bufsize, B_WRITE)) {
  100                                         error = EFAULT;
  101                                         goto doerror;
  102                                 }
  103                                 if (!rw && !useracc(bp->b_data, bp->b_bufsize, B_READ)) {
  104                                         error = EFAULT;
  105                                         goto doerror;
  106                                 }
  107 
  108                                 /* bring buffer into kernel space */
  109                                 vmapbuf(bp);
  110                         }
  111 
  112                         /* perform transfer */
  113                         (*strategy)(bp);
  114 
  115                         spl = splbio();
  116                         while ((bp->b_flags & B_DONE) == 0)
  117                                 tsleep((caddr_t)bp, PRIBIO, "physstr", 0);
  118                         splx(spl);
  119 
  120                         /* release mapping into kernel space */
  121                         if (uio->uio_segflg == UIO_USERSPACE)
  122                                 vunmapbuf(bp);
  123 
  124                         /*
  125                          * update the uio data
  126                          */
  127                         {
  128                                 int iolen = bp->b_bcount - bp->b_resid;
  129 
  130                                 if (iolen == 0 && !(bp->b_flags & B_ERROR))
  131                                         goto doerror;   /* EOF */
  132                                 uio->uio_iov[i].iov_len -= iolen;
  133                                 uio->uio_iov[i].iov_base += iolen;
  134                                 uio->uio_resid -= iolen;
  135                                 uio->uio_offset += iolen;
  136                         }
  137 
  138                         /*
  139                          * check for an error
  140                          */
  141                         if( bp->b_flags & B_ERROR) {
  142                                 error = bp->b_error;
  143                                 goto doerror;
  144                         }
  145                 }
  146         }
  147 
  148 
  149 doerror:
  150         relpbuf(bpa);
  151         if (!bp_alloc) {
  152                 bp->b_flags &= ~(B_BUSY|B_PHYS);
  153                 if( bp->b_flags & B_WANTED) {
  154                         bp->b_flags &= ~B_WANTED;
  155                         wakeup((caddr_t)bp);
  156                 }
  157         }
  158 /*
  159  * allow the process to be swapped
  160  */
  161         curproc->p_flag &= ~P_PHYSIO;
  162 
  163         return (error);
  164 }
  165 
  166 u_int
  167 minphys(bp)
  168         struct buf *bp;
  169 {
  170         u_int maxphys = DFLTPHYS;
  171         struct cdevsw *bdsw;
  172 
  173         bdsw = cdevsw[major(bp->b_dev)];
  174 
  175         if (bdsw && bdsw->d_maxio) {
  176                 maxphys = bdsw->d_maxio;
  177         }
  178         if (bp->b_kvasize && (bp->b_kvasize < maxphys))
  179                 maxphys = bp->b_kvasize;
  180 
  181         if(((vm_offset_t) bp->b_data) & PAGE_MASK) {
  182                 maxphys -= PAGE_SIZE;
  183         }
  184 
  185         if( bp->b_bcount > maxphys) {
  186                 bp->b_bcount = maxphys;
  187         }
  188 
  189         return bp->b_bcount;
  190 }
  191 
  192 struct buf *
  193 phygetvpbuf(dev_t dev, int resid)
  194 {
  195         struct cdevsw *bdsw;
  196         int maxio;
  197 
  198         bdsw = cdevsw[major(dev)];
  199         if ((bdsw == NULL) || (bdsw->d_bmaj == -1))
  200                 return getpbuf();
  201 
  202         maxio = bdsw->d_maxio;
  203         if (resid > maxio)
  204                 resid = maxio;
  205 
  206         return getpbuf();
  207 }
  208 
  209 static void
  210 physwakeup(bp)
  211         struct buf *bp;
  212 {
  213         wakeup((caddr_t) bp);
  214         bp->b_flags &= ~B_CALL;
  215 }

Cache object: 95a45a639aa56b4ddfa9723e126523f4


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