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 
   20 #include <sys/cdefs.h>
   21 __FBSDID("$FreeBSD: releng/5.2/sys/kern/kern_physio.c 122747 2003-11-15 09:28:09Z phk $");
   22 
   23 #include <sys/param.h>
   24 #include <sys/systm.h>
   25 #include <sys/bio.h>
   26 #include <sys/buf.h>
   27 #include <sys/conf.h>
   28 #include <sys/proc.h>
   29 #include <sys/uio.h>
   30 
   31 #include <vm/vm.h>
   32 #include <vm/vm_extern.h>
   33 
   34 int
   35 physio(dev_t dev, struct uio *uio, int ioflag)
   36 {
   37         int i;
   38         int error;
   39         int spl;
   40         caddr_t sa;
   41         u_int iolen;
   42         struct buf *bp;
   43 
   44         /* We cannot trust the device driver to hold Giant for us */
   45         mtx_lock(&Giant);
   46         /* Keep the process UPAGES from being swapped. XXX: why ? */
   47         PHOLD(curproc);
   48 
   49         bp = getpbuf(NULL);
   50         sa = bp->b_data;
   51         error = 0;
   52 
   53         /* XXX: sanity check */
   54         if(dev->si_iosize_max < PAGE_SIZE) {
   55                 printf("WARNING: %s si_iosize_max=%d, using DFLTPHYS.\n",
   56                     devtoname(dev), dev->si_iosize_max);
   57                 dev->si_iosize_max = DFLTPHYS;
   58         }
   59 
   60         for (i = 0; i < uio->uio_iovcnt; i++) {
   61                 while (uio->uio_iov[i].iov_len) {
   62                         bp->b_flags = 0;
   63                         if (uio->uio_rw == UIO_READ)
   64                                 bp->b_iocmd = BIO_READ;
   65                         else 
   66                                 bp->b_iocmd = BIO_WRITE;
   67                         bp->b_dev = dev;
   68                         bp->b_iodone = bdone;
   69                         bp->b_data = uio->uio_iov[i].iov_base;
   70                         bp->b_bcount = uio->uio_iov[i].iov_len;
   71                         bp->b_offset = uio->uio_offset;
   72                         bp->b_iooffset = uio->uio_offset;
   73                         bp->b_saveaddr = sa;
   74 
   75                         /* Don't exceed drivers iosize limit */
   76                         if (bp->b_bcount > dev->si_iosize_max)
   77                                 bp->b_bcount = dev->si_iosize_max;
   78 
   79                         /* 
   80                          * Make sure the pbuf can map the request
   81                          * XXX: The pbuf has kvasize = MAXPHYS so a request
   82                          * XXX: larger than MAXPHYS - PAGE_SIZE must be
   83                          * XXX: page aligned or it will be fragmented.
   84                          */
   85                         iolen = ((vm_offset_t) bp->b_data) & PAGE_MASK;
   86                         if ((bp->b_bcount + iolen) > bp->b_kvasize) {
   87                                 bp->b_bcount = bp->b_kvasize;
   88                                 if (iolen != 0)
   89                                         bp->b_bcount -= PAGE_SIZE;
   90                         }
   91                         bp->b_bufsize = bp->b_bcount;
   92 
   93                         bp->b_blkno = btodb(bp->b_offset);
   94 
   95                         if (uio->uio_segflg == UIO_USERSPACE)
   96                                 if (vmapbuf(bp) < 0) {
   97                                         error = EFAULT;
   98                                         goto doerror;
   99                                 }
  100 
  101                         DEV_STRATEGY(bp);
  102                         spl = splbio();
  103                         if (uio->uio_rw == UIO_READ)
  104                                 bwait(bp, PRIBIO, "physrd");
  105                         else
  106                                 bwait(bp, PRIBIO, "physwr");
  107                         splx(spl);
  108 
  109                         if (uio->uio_segflg == UIO_USERSPACE)
  110                                 vunmapbuf(bp);
  111                         iolen = bp->b_bcount - bp->b_resid;
  112                         if (iolen == 0 && !(bp->b_ioflags & BIO_ERROR))
  113                                 goto doerror;   /* EOF */
  114                         uio->uio_iov[i].iov_len -= iolen;
  115                         uio->uio_iov[i].iov_base =
  116                             (char *)uio->uio_iov[i].iov_base + iolen;
  117                         uio->uio_resid -= iolen;
  118                         uio->uio_offset += iolen;
  119                         if( bp->b_ioflags & BIO_ERROR) {
  120                                 error = bp->b_error;
  121                                 goto doerror;
  122                         }
  123                 }
  124         }
  125 doerror:
  126         relpbuf(bp, NULL);
  127         PRELE(curproc);
  128         mtx_unlock(&Giant);
  129         return (error);
  130 }

Cache object: d90227959b2622a915ca299a22eb82f1


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