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 1.46.2.4 2003/11/14 09:51:47 simokawa Exp $
   20  * $DragonFly: src/sys/kern/kern_physio.c,v 1.27 2008/08/22 08:47:56 swildner Exp $
   21  */
   22 
   23 #include <sys/param.h>
   24 #include <sys/systm.h>
   25 #include <sys/buf.h>
   26 #include <sys/conf.h>
   27 #include <sys/proc.h>
   28 #include <sys/uio.h>
   29 #include <sys/device.h>
   30 #include <sys/thread2.h>
   31 
   32 #include <vm/vm.h>
   33 #include <vm/vm_extern.h>
   34 
   35 static int
   36 physio(cdev_t dev, struct uio *uio, int ioflag)
   37 {
   38         int i;
   39         int error;
   40         int saflags;
   41         int iolen;
   42         int bcount;
   43         int bounceit;
   44         caddr_t ubase;
   45         struct buf *bp;
   46 
   47         bp = getpbuf_kva(NULL);
   48         saflags = bp->b_flags;
   49         error = 0;
   50 
   51         /* XXX: sanity check */
   52         if (dev->si_iosize_max < PAGE_SIZE) {
   53                 kprintf("WARNING: %s si_iosize_max=%d, using MAXPHYS.\n",
   54                     devtoname(dev), dev->si_iosize_max);
   55                 dev->si_iosize_max = MAXPHYS;
   56         }
   57 
   58         /* Must be a real uio */
   59         KKASSERT(uio->uio_segflg != UIO_NOCOPY);
   60 
   61         for (i = 0; i < uio->uio_iovcnt; i++) {
   62                 while (uio->uio_iov[i].iov_len) {
   63                         if (uio->uio_rw == UIO_READ)
   64                                 bp->b_cmd = BUF_CMD_READ;
   65                         else 
   66                                 bp->b_cmd = BUF_CMD_WRITE;
   67                         bp->b_flags = saflags;
   68                         bcount = uio->uio_iov[i].iov_len;
   69 
   70                         reinitbufbio(bp);       /* clear translation cache */
   71                         bp->b_bio1.bio_offset = uio->uio_offset;
   72                         bp->b_bio1.bio_done = biodone_sync;
   73                         bp->b_bio1.bio_flags |= BIO_SYNC;
   74 
   75                         /* 
   76                          * Setup for mapping the request into kernel memory.
   77                          *
   78                          * We can only write as much as fits in a pbuf,
   79                          * which is MAXPHYS, and no larger then the device's
   80                          * ability.
   81                          *
   82                          * If not using bounce pages the base address of the
   83                          * user mapping into the pbuf may be offset, further
   84                          * reducing how much will actually fit in the pbuf.
   85                          */
   86                         if (bcount > dev->si_iosize_max)
   87                                 bcount = dev->si_iosize_max;
   88 
   89                         ubase = uio->uio_iov[i].iov_base;
   90                         bounceit = (int)(((vm_offset_t)ubase) & 15);
   91                         iolen = ((vm_offset_t)ubase) & PAGE_MASK;
   92                         if (bounceit) {
   93                                 if (bcount > bp->b_kvasize)
   94                                         bcount = bp->b_kvasize;
   95                         } else {
   96                                 if ((bcount + iolen) > bp->b_kvasize) {
   97                                         bcount = bp->b_kvasize;
   98                                         if (iolen != 0)
   99                                                 bcount -= PAGE_SIZE;
  100                                 }
  101                         }
  102 
  103                         /*
  104                          * If we have to use a bounce buffer allocate kernel
  105                          * memory and copyin/copyout.  Otherwise map the
  106                          * user buffer directly into kernel memory without
  107                          * copying.
  108                          */
  109                         if (uio->uio_segflg == UIO_USERSPACE) {
  110                                 if (bounceit) {
  111                                         bp->b_data = bp->b_kvabase;
  112                                         bp->b_bcount = bcount;
  113                                         vm_hold_load_pages(bp, (vm_offset_t)bp->b_data, (vm_offset_t)bp->b_data + bcount);
  114                                         if (uio->uio_rw == UIO_WRITE) {
  115                                                 error = copyin(ubase, bp->b_data, bcount);
  116                                                 if (error) {
  117                                                         vm_hold_free_pages(bp, (vm_offset_t)bp->b_data, (vm_offset_t)bp->b_data + bcount);
  118                                                         goto doerror;
  119                                                 }
  120                                         }
  121                                 } else if (vmapbuf(bp, ubase, bcount) < 0) {
  122                                         error = EFAULT;
  123                                         goto doerror;
  124                                 }
  125                         } else {
  126                                 bp->b_data = uio->uio_iov[i].iov_base;
  127                                 bp->b_bcount = bcount;
  128                         }
  129                         dev_dstrategy(dev, &bp->b_bio1);
  130                         biowait(&bp->b_bio1, "physstr");
  131 
  132                         iolen = bp->b_bcount - bp->b_resid;
  133                         if (uio->uio_segflg == UIO_USERSPACE) {
  134                                 if (bounceit) {
  135                                         if (uio->uio_rw == UIO_READ && iolen) {
  136                                                 error = copyout(bp->b_data, ubase, iolen);
  137                                                 if (error) {
  138                                                         bp->b_flags |= B_ERROR;
  139                                                         bp->b_error = error;
  140                                                 }
  141                                         }
  142                                         vm_hold_free_pages(bp, (vm_offset_t)bp->b_data, (vm_offset_t)bp->b_data + bcount);
  143                                 } else {
  144                                         vunmapbuf(bp);
  145                                 }
  146                         }
  147                         if (iolen == 0 && !(bp->b_flags & B_ERROR))
  148                                 goto doerror;   /* EOF */
  149                         uio->uio_iov[i].iov_len -= iolen;
  150                         uio->uio_iov[i].iov_base = (char *)uio->uio_iov[i].iov_base + iolen;
  151                         uio->uio_resid -= iolen;
  152                         uio->uio_offset += iolen;
  153                         if (bp->b_flags & B_ERROR) {
  154                                 error = bp->b_error;
  155                                 goto doerror;
  156                         }
  157                 }
  158         }
  159 doerror:
  160         relpbuf(bp, NULL);
  161         return (error);
  162 }
  163 
  164 int
  165 physread(struct dev_read_args *ap)
  166 {
  167         return(physio(ap->a_head.a_dev, ap->a_uio, ap->a_ioflag));
  168 }
  169 
  170 int
  171 physwrite(struct dev_write_args *ap)
  172 {
  173         return(physio(ap->a_head.a_dev, ap->a_uio, ap->a_ioflag));
  174 }
  175 

Cache object: 2a6a3069472624288a11ef0f3af27552


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