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/10.1/sys/kern/kern_physio.c 255032 2013-08-29 16:41:40Z ken $");
   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(struct cdev *dev, struct uio *uio, int ioflag)
   36 {
   37         struct buf *bp;
   38         struct cdevsw *csw;
   39         caddr_t sa;
   40         u_int iolen;
   41         int error, i, mapped;
   42 
   43         /* Keep the process UPAGES from being swapped. XXX: why ? */
   44         PHOLD(curproc);
   45 
   46         bp = getpbuf(NULL);
   47         sa = bp->b_data;
   48         error = 0;
   49 
   50         /* XXX: sanity check */
   51         if(dev->si_iosize_max < PAGE_SIZE) {
   52                 printf("WARNING: %s si_iosize_max=%d, using DFLTPHYS.\n",
   53                     devtoname(dev), dev->si_iosize_max);
   54                 dev->si_iosize_max = DFLTPHYS;
   55         }
   56 
   57         /*
   58          * If the driver does not want I/O to be split, that means that we
   59          * need to reject any requests that will not fit into one buffer.
   60          */
   61         if (dev->si_flags & SI_NOSPLIT &&
   62             (uio->uio_resid > dev->si_iosize_max || uio->uio_resid > MAXPHYS ||
   63             uio->uio_iovcnt > 1)) {
   64                 /*
   65                  * Tell the user why his I/O was rejected.
   66                  */
   67                 if (uio->uio_resid > dev->si_iosize_max)
   68                         uprintf("%s: request size=%zd > si_iosize_max=%d; "
   69                             "cannot split request\n", devtoname(dev),
   70                             uio->uio_resid, dev->si_iosize_max);
   71                 if (uio->uio_resid > MAXPHYS)
   72                         uprintf("%s: request size=%zd > MAXPHYS=%d; "
   73                             "cannot split request\n", devtoname(dev),
   74                             uio->uio_resid, MAXPHYS);
   75                 if (uio->uio_iovcnt > 1)
   76                         uprintf("%s: request vectors=%d > 1; "
   77                             "cannot split request\n", devtoname(dev),
   78                             uio->uio_iovcnt);
   79 
   80                 error = EFBIG;
   81                 goto doerror;
   82         }
   83 
   84         for (i = 0; i < uio->uio_iovcnt; i++) {
   85                 while (uio->uio_iov[i].iov_len) {
   86                         bp->b_flags = 0;
   87                         if (uio->uio_rw == UIO_READ) {
   88                                 bp->b_iocmd = BIO_READ;
   89                                 curthread->td_ru.ru_inblock++;
   90                         } else {
   91                                 bp->b_iocmd = BIO_WRITE;
   92                                 curthread->td_ru.ru_oublock++;
   93                         }
   94                         bp->b_iodone = bdone;
   95                         bp->b_data = uio->uio_iov[i].iov_base;
   96                         bp->b_bcount = uio->uio_iov[i].iov_len;
   97                         bp->b_offset = uio->uio_offset;
   98                         bp->b_iooffset = uio->uio_offset;
   99                         bp->b_saveaddr = sa;
  100 
  101                         /* Don't exceed drivers iosize limit */
  102                         if (bp->b_bcount > dev->si_iosize_max)
  103                                 bp->b_bcount = dev->si_iosize_max;
  104 
  105                         /* 
  106                          * Make sure the pbuf can map the request
  107                          * XXX: The pbuf has kvasize = MAXPHYS so a request
  108                          * XXX: larger than MAXPHYS - PAGE_SIZE must be
  109                          * XXX: page aligned or it will be fragmented.
  110                          */
  111                         iolen = ((vm_offset_t) bp->b_data) & PAGE_MASK;
  112                         if ((bp->b_bcount + iolen) > bp->b_kvasize) {
  113                                 /*
  114                                  * This device does not want I/O to be split.
  115                                  */
  116                                 if (dev->si_flags & SI_NOSPLIT) {
  117                                         uprintf("%s: request ptr %p is not "
  118                                             "on a page boundary; cannot split "
  119                                             "request\n", devtoname(dev),
  120                                             bp->b_data);
  121                                         error = EFBIG;
  122                                         goto doerror;
  123                                 }
  124                                 bp->b_bcount = bp->b_kvasize;
  125                                 if (iolen != 0)
  126                                         bp->b_bcount -= PAGE_SIZE;
  127                         }
  128                         bp->b_bufsize = bp->b_bcount;
  129 
  130                         bp->b_blkno = btodb(bp->b_offset);
  131 
  132                         csw = dev->si_devsw;
  133                         if (uio->uio_segflg == UIO_USERSPACE) {
  134                                 if (dev->si_flags & SI_UNMAPPED)
  135                                         mapped = 0;
  136                                 else
  137                                         mapped = 1;
  138                                 if (vmapbuf(bp, mapped) < 0) {
  139                                         error = EFAULT;
  140                                         goto doerror;
  141                                 }
  142                         }
  143 
  144                         dev_strategy_csw(dev, csw, bp);
  145                         if (uio->uio_rw == UIO_READ)
  146                                 bwait(bp, PRIBIO, "physrd");
  147                         else
  148                                 bwait(bp, PRIBIO, "physwr");
  149 
  150                         if (uio->uio_segflg == UIO_USERSPACE)
  151                                 vunmapbuf(bp);
  152                         iolen = bp->b_bcount - bp->b_resid;
  153                         if (iolen == 0 && !(bp->b_ioflags & BIO_ERROR))
  154                                 goto doerror;   /* EOF */
  155                         uio->uio_iov[i].iov_len -= iolen;
  156                         uio->uio_iov[i].iov_base =
  157                             (char *)uio->uio_iov[i].iov_base + iolen;
  158                         uio->uio_resid -= iolen;
  159                         uio->uio_offset += iolen;
  160                         if( bp->b_ioflags & BIO_ERROR) {
  161                                 error = bp->b_error;
  162                                 goto doerror;
  163                         }
  164                 }
  165         }
  166 doerror:
  167         relpbuf(bp, NULL);
  168         PRELE(curproc);
  169         return (error);
  170 }

Cache object: 7c254c612abd97ebbb123ef7ae7ecb6a


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