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/11.2/sys/kern/kern_physio.c 297633 2016-04-07 04:23:25Z trasz $");
   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/malloc.h>
   29 #include <sys/proc.h>
   30 #include <sys/racct.h>
   31 #include <sys/uio.h>
   32 #include <geom/geom.h>
   33 
   34 #include <vm/vm.h>
   35 #include <vm/vm_page.h>
   36 #include <vm/vm_extern.h>
   37 #include <vm/vm_map.h>
   38 
   39 int
   40 physio(struct cdev *dev, struct uio *uio, int ioflag)
   41 {
   42         struct cdevsw *csw;
   43         struct buf *pbuf;
   44         struct bio *bp;
   45         struct vm_page **pages;
   46         caddr_t sa;
   47         u_int iolen, poff;
   48         int error, i, npages, maxpages;
   49         vm_prot_t prot;
   50 
   51         csw = dev->si_devsw;
   52         /* check if character device is being destroyed */
   53         if (csw == NULL)
   54                 return (ENXIO);
   55 
   56         /* XXX: sanity check */
   57         if(dev->si_iosize_max < PAGE_SIZE) {
   58                 printf("WARNING: %s si_iosize_max=%d, using DFLTPHYS.\n",
   59                     devtoname(dev), dev->si_iosize_max);
   60                 dev->si_iosize_max = DFLTPHYS;
   61         }
   62 
   63         /*
   64          * If the driver does not want I/O to be split, that means that we
   65          * need to reject any requests that will not fit into one buffer.
   66          */
   67         if (dev->si_flags & SI_NOSPLIT &&
   68             (uio->uio_resid > dev->si_iosize_max || uio->uio_resid > MAXPHYS ||
   69             uio->uio_iovcnt > 1)) {
   70                 /*
   71                  * Tell the user why his I/O was rejected.
   72                  */
   73                 if (uio->uio_resid > dev->si_iosize_max)
   74                         uprintf("%s: request size=%zd > si_iosize_max=%d; "
   75                             "cannot split request\n", devtoname(dev),
   76                             uio->uio_resid, dev->si_iosize_max);
   77                 if (uio->uio_resid > MAXPHYS)
   78                         uprintf("%s: request size=%zd > MAXPHYS=%d; "
   79                             "cannot split request\n", devtoname(dev),
   80                             uio->uio_resid, MAXPHYS);
   81                 if (uio->uio_iovcnt > 1)
   82                         uprintf("%s: request vectors=%d > 1; "
   83                             "cannot split request\n", devtoname(dev),
   84                             uio->uio_iovcnt);
   85                 return (EFBIG);
   86         }
   87 
   88         /*
   89          * Keep the process UPAGES from being swapped.  Processes swapped
   90          * out while holding pbufs, used by swapper, may lead to deadlock.
   91          */
   92         PHOLD(curproc);
   93 
   94         bp = g_alloc_bio();
   95         if (uio->uio_segflg != UIO_USERSPACE) {
   96                 pbuf = NULL;
   97                 pages = NULL;
   98         } else if ((dev->si_flags & SI_UNMAPPED) && unmapped_buf_allowed) {
   99                 pbuf = NULL;
  100                 maxpages = btoc(MIN(uio->uio_resid, MAXPHYS)) + 1;
  101                 pages = malloc(sizeof(*pages) * maxpages, M_DEVBUF, M_WAITOK);
  102         } else {
  103                 pbuf = getpbuf(NULL);
  104                 sa = pbuf->b_data;
  105                 maxpages = btoc(MAXPHYS);
  106                 pages = pbuf->b_pages;
  107         }
  108         prot = VM_PROT_READ;
  109         if (uio->uio_rw == UIO_READ)
  110                 prot |= VM_PROT_WRITE;  /* Less backwards than it looks */
  111         error = 0;
  112         for (i = 0; i < uio->uio_iovcnt; i++) {
  113 #ifdef RACCT
  114                 if (racct_enable) {
  115                         PROC_LOCK(curproc);
  116                         if (uio->uio_rw == UIO_READ) {
  117                                 racct_add_force(curproc, RACCT_READBPS,
  118                                     uio->uio_iov[i].iov_len);
  119                                 racct_add_force(curproc, RACCT_READIOPS, 1);
  120                         } else {
  121                                 racct_add_force(curproc, RACCT_WRITEBPS,
  122                                     uio->uio_iov[i].iov_len);
  123                                 racct_add_force(curproc, RACCT_WRITEIOPS, 1);
  124                         }
  125                         PROC_UNLOCK(curproc);
  126                 }
  127 #endif /* RACCT */
  128 
  129                 while (uio->uio_iov[i].iov_len) {
  130                         g_reset_bio(bp);
  131                         if (uio->uio_rw == UIO_READ) {
  132                                 bp->bio_cmd = BIO_READ;
  133                                 curthread->td_ru.ru_inblock++;
  134                         } else {
  135                                 bp->bio_cmd = BIO_WRITE;
  136                                 curthread->td_ru.ru_oublock++;
  137                         }
  138                         bp->bio_offset = uio->uio_offset;
  139                         bp->bio_data = uio->uio_iov[i].iov_base;
  140                         bp->bio_length = uio->uio_iov[i].iov_len;
  141                         if (bp->bio_length > dev->si_iosize_max)
  142                                 bp->bio_length = dev->si_iosize_max;
  143                         if (bp->bio_length > MAXPHYS)
  144                                 bp->bio_length = MAXPHYS;
  145 
  146                         /*
  147                          * Make sure the pbuf can map the request.
  148                          * The pbuf has kvasize = MAXPHYS, so a request
  149                          * larger than MAXPHYS - PAGE_SIZE must be
  150                          * page aligned or it will be fragmented.
  151                          */
  152                         poff = (vm_offset_t)bp->bio_data & PAGE_MASK;
  153                         if (pbuf && bp->bio_length + poff > pbuf->b_kvasize) {
  154                                 if (dev->si_flags & SI_NOSPLIT) {
  155                                         uprintf("%s: request ptr %p is not "
  156                                             "on a page boundary; cannot split "
  157                                             "request\n", devtoname(dev),
  158                                             bp->bio_data);
  159                                         error = EFBIG;
  160                                         goto doerror;
  161                                 }
  162                                 bp->bio_length = pbuf->b_kvasize;
  163                                 if (poff != 0)
  164                                         bp->bio_length -= PAGE_SIZE;
  165                         }
  166 
  167                         bp->bio_bcount = bp->bio_length;
  168                         bp->bio_dev = dev;
  169 
  170                         if (pages) {
  171                                 if ((npages = vm_fault_quick_hold_pages(
  172                                     &curproc->p_vmspace->vm_map,
  173                                     (vm_offset_t)bp->bio_data, bp->bio_length,
  174                                     prot, pages, maxpages)) < 0) {
  175                                         error = EFAULT;
  176                                         goto doerror;
  177                                 }
  178                                 if (pbuf) {
  179                                         pmap_qenter((vm_offset_t)sa,
  180                                             pages, npages);
  181                                         bp->bio_data = sa + poff;
  182                                 } else {
  183                                         bp->bio_ma = pages;
  184                                         bp->bio_ma_n = npages;
  185                                         bp->bio_ma_offset = poff;
  186                                         bp->bio_data = unmapped_buf;
  187                                         bp->bio_flags |= BIO_UNMAPPED;
  188                                 }
  189                         }
  190 
  191                         csw->d_strategy(bp);
  192                         if (uio->uio_rw == UIO_READ)
  193                                 biowait(bp, "physrd");
  194                         else
  195                                 biowait(bp, "physwr");
  196 
  197                         if (pages) {
  198                                 if (pbuf)
  199                                         pmap_qremove((vm_offset_t)sa, npages);
  200                                 vm_page_unhold_pages(pages, npages);
  201                         }
  202 
  203                         iolen = bp->bio_length - bp->bio_resid;
  204                         if (iolen == 0 && !(bp->bio_flags & BIO_ERROR))
  205                                 goto doerror;   /* EOF */
  206                         uio->uio_iov[i].iov_len -= iolen;
  207                         uio->uio_iov[i].iov_base =
  208                             (char *)uio->uio_iov[i].iov_base + iolen;
  209                         uio->uio_resid -= iolen;
  210                         uio->uio_offset += iolen;
  211                         if (bp->bio_flags & BIO_ERROR) {
  212                                 error = bp->bio_error;
  213                                 goto doerror;
  214                         }
  215                 }
  216         }
  217 doerror:
  218         if (pbuf)
  219                 relpbuf(pbuf, NULL);
  220         else if (pages)
  221                 free(pages, M_DEVBUF);
  222         g_destroy_bio(bp);
  223         PRELE(curproc);
  224         return (error);
  225 }

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