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/10.2/sys/kern/kern_physio.c 282568 2015-05-06 21:06:32Z mav $");
   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/uio.h>
   31 #include <geom/geom.h>
   32 
   33 #include <vm/vm.h>
   34 #include <vm/vm_page.h>
   35 #include <vm/vm_extern.h>
   36 #include <vm/vm_map.h>
   37 
   38 int
   39 physio(struct cdev *dev, struct uio *uio, int ioflag)
   40 {
   41         struct buf *pbuf;
   42         struct bio *bp;
   43         struct vm_page **pages;
   44         caddr_t sa;
   45         u_int iolen, poff;
   46         int error, i, npages, maxpages;
   47         vm_prot_t prot;
   48 
   49         /* XXX: sanity check */
   50         if(dev->si_iosize_max < PAGE_SIZE) {
   51                 printf("WARNING: %s si_iosize_max=%d, using DFLTPHYS.\n",
   52                     devtoname(dev), dev->si_iosize_max);
   53                 dev->si_iosize_max = DFLTPHYS;
   54         }
   55 
   56         /*
   57          * If the driver does not want I/O to be split, that means that we
   58          * need to reject any requests that will not fit into one buffer.
   59          */
   60         if (dev->si_flags & SI_NOSPLIT &&
   61             (uio->uio_resid > dev->si_iosize_max || uio->uio_resid > MAXPHYS ||
   62             uio->uio_iovcnt > 1)) {
   63                 /*
   64                  * Tell the user why his I/O was rejected.
   65                  */
   66                 if (uio->uio_resid > dev->si_iosize_max)
   67                         uprintf("%s: request size=%zd > si_iosize_max=%d; "
   68                             "cannot split request\n", devtoname(dev),
   69                             uio->uio_resid, dev->si_iosize_max);
   70                 if (uio->uio_resid > MAXPHYS)
   71                         uprintf("%s: request size=%zd > MAXPHYS=%d; "
   72                             "cannot split request\n", devtoname(dev),
   73                             uio->uio_resid, MAXPHYS);
   74                 if (uio->uio_iovcnt > 1)
   75                         uprintf("%s: request vectors=%d > 1; "
   76                             "cannot split request\n", devtoname(dev),
   77                             uio->uio_iovcnt);
   78                 return (EFBIG);
   79         }
   80 
   81         /*
   82          * Keep the process UPAGES from being swapped.  Processes swapped
   83          * out while holding pbufs, used by swapper, may lead to deadlock.
   84          */
   85         PHOLD(curproc);
   86 
   87         bp = g_alloc_bio();
   88         if (uio->uio_segflg != UIO_USERSPACE) {
   89                 pbuf = NULL;
   90                 pages = NULL;
   91         } else if ((dev->si_flags & SI_UNMAPPED) && unmapped_buf_allowed) {
   92                 pbuf = NULL;
   93                 maxpages = btoc(MIN(uio->uio_resid, MAXPHYS)) + 1;
   94                 pages = malloc(sizeof(*pages) * maxpages, M_DEVBUF, M_WAITOK);
   95         } else {
   96                 pbuf = getpbuf(NULL);
   97                 sa = pbuf->b_data;
   98                 maxpages = btoc(MAXPHYS);
   99                 pages = pbuf->b_pages;
  100         }
  101         prot = VM_PROT_READ;
  102         if (uio->uio_rw == UIO_READ)
  103                 prot |= VM_PROT_WRITE;  /* Less backwards than it looks */
  104         error = 0;
  105         for (i = 0; i < uio->uio_iovcnt; i++) {
  106                 while (uio->uio_iov[i].iov_len) {
  107                         bzero(bp, sizeof(*bp));
  108                         if (uio->uio_rw == UIO_READ) {
  109                                 bp->bio_cmd = BIO_READ;
  110                                 curthread->td_ru.ru_inblock++;
  111                         } else {
  112                                 bp->bio_cmd = BIO_WRITE;
  113                                 curthread->td_ru.ru_oublock++;
  114                         }
  115                         bp->bio_offset = uio->uio_offset;
  116                         bp->bio_data = uio->uio_iov[i].iov_base;
  117                         bp->bio_length = uio->uio_iov[i].iov_len;
  118                         if (bp->bio_length > dev->si_iosize_max)
  119                                 bp->bio_length = dev->si_iosize_max;
  120                         if (bp->bio_length > MAXPHYS)
  121                                 bp->bio_length = MAXPHYS;
  122 
  123                         /*
  124                          * Make sure the pbuf can map the request.
  125                          * The pbuf has kvasize = MAXPHYS, so a request
  126                          * larger than MAXPHYS - PAGE_SIZE must be
  127                          * page aligned or it will be fragmented.
  128                          */
  129                         poff = (vm_offset_t)bp->bio_data & PAGE_MASK;
  130                         if (pbuf && bp->bio_length + poff > pbuf->b_kvasize) {
  131                                 if (dev->si_flags & SI_NOSPLIT) {
  132                                         uprintf("%s: request ptr %p is not "
  133                                             "on a page boundary; cannot split "
  134                                             "request\n", devtoname(dev),
  135                                             bp->bio_data);
  136                                         error = EFBIG;
  137                                         goto doerror;
  138                                 }
  139                                 bp->bio_length = pbuf->b_kvasize;
  140                                 if (poff != 0)
  141                                         bp->bio_length -= PAGE_SIZE;
  142                         }
  143 
  144                         bp->bio_bcount = bp->bio_length;
  145                         bp->bio_dev = dev;
  146 
  147                         if (pages) {
  148                                 if ((npages = vm_fault_quick_hold_pages(
  149                                     &curproc->p_vmspace->vm_map,
  150                                     (vm_offset_t)bp->bio_data, bp->bio_length,
  151                                     prot, pages, maxpages)) < 0) {
  152                                         error = EFAULT;
  153                                         goto doerror;
  154                                 }
  155                                 if (pbuf) {
  156                                         pmap_qenter((vm_offset_t)sa,
  157                                             pages, npages);
  158                                         bp->bio_data = sa + poff;
  159                                 } else {
  160                                         bp->bio_ma = pages;
  161                                         bp->bio_ma_n = npages;
  162                                         bp->bio_ma_offset = poff;
  163                                         bp->bio_data = unmapped_buf;
  164                                         bp->bio_flags |= BIO_UNMAPPED;
  165                                 }
  166                         }
  167 
  168                         dev->si_devsw->d_strategy(bp);
  169                         if (uio->uio_rw == UIO_READ)
  170                                 biowait(bp, "physrd");
  171                         else
  172                                 biowait(bp, "physwr");
  173 
  174                         if (pages) {
  175                                 if (pbuf)
  176                                         pmap_qremove((vm_offset_t)sa, npages);
  177                                 vm_page_unhold_pages(pages, npages);
  178                         }
  179 
  180                         iolen = bp->bio_length - bp->bio_resid;
  181                         if (iolen == 0 && !(bp->bio_flags & BIO_ERROR))
  182                                 goto doerror;   /* EOF */
  183                         uio->uio_iov[i].iov_len -= iolen;
  184                         uio->uio_iov[i].iov_base =
  185                             (char *)uio->uio_iov[i].iov_base + iolen;
  186                         uio->uio_resid -= iolen;
  187                         uio->uio_offset += iolen;
  188                         if (bp->bio_flags & BIO_ERROR) {
  189                                 error = bp->bio_error;
  190                                 goto doerror;
  191                         }
  192                 }
  193         }
  194 doerror:
  195         if (pbuf)
  196                 relpbuf(pbuf, NULL);
  197         else if (pages)
  198                 free(pages, M_DEVBUF);
  199         g_destroy_bio(bp);
  200         PRELE(curproc);
  201         return (error);
  202 }

Cache object: 9db6cf3dc786e668eb5993a7d00e6a75


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