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/vm/device_pager.c

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    1 /*-
    2  * Copyright (c) 1990 University of Utah.
    3  * Copyright (c) 1991, 1993
    4  *      The Regents of the University of California.  All rights reserved.
    5  *
    6  * This code is derived from software contributed to Berkeley by
    7  * the Systems Programming Group of the University of Utah Computer
    8  * Science Department.
    9  *
   10  * Redistribution and use in source and binary forms, with or without
   11  * modification, are permitted provided that the following conditions
   12  * are met:
   13  * 1. Redistributions of source code must retain the above copyright
   14  *    notice, this list of conditions and the following disclaimer.
   15  * 2. Redistributions in binary form must reproduce the above copyright
   16  *    notice, this list of conditions and the following disclaimer in the
   17  *    documentation and/or other materials provided with the distribution.
   18  * 4. Neither the name of the University nor the names of its contributors
   19  *    may be used to endorse or promote products derived from this software
   20  *    without specific prior written permission.
   21  *
   22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
   23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
   26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   32  * SUCH DAMAGE.
   33  *
   34  *      @(#)device_pager.c      8.1 (Berkeley) 6/11/93
   35  */
   36 
   37 #include <sys/cdefs.h>
   38 __FBSDID("$FreeBSD: src/sys/vm/device_pager.c,v 1.78 2005/06/10 17:27:54 alc Exp $");
   39 
   40 #include <sys/param.h>
   41 #include <sys/systm.h>
   42 #include <sys/conf.h>
   43 #include <sys/lock.h>
   44 #include <sys/proc.h>
   45 #include <sys/mutex.h>
   46 #include <sys/mman.h>
   47 #include <sys/sx.h>
   48 
   49 #include <vm/vm.h>
   50 #include <vm/vm_object.h>
   51 #include <vm/vm_page.h>
   52 #include <vm/vm_pager.h>
   53 #include <vm/uma.h>
   54 
   55 static void dev_pager_init(void);
   56 static vm_object_t dev_pager_alloc(void *, vm_ooffset_t, vm_prot_t,
   57                 vm_ooffset_t);
   58 static void dev_pager_dealloc(vm_object_t);
   59 static int dev_pager_getpages(vm_object_t, vm_page_t *, int, int);
   60 static void dev_pager_putpages(vm_object_t, vm_page_t *, int, 
   61                 boolean_t, int *);
   62 static boolean_t dev_pager_haspage(vm_object_t, vm_pindex_t, int *,
   63                 int *);
   64 
   65 /* list of device pager objects */
   66 static struct pagerlst dev_pager_object_list;
   67 /* protect against object creation */
   68 static struct sx dev_pager_sx;
   69 /* protect list manipulation */
   70 static struct mtx dev_pager_mtx;
   71 
   72 
   73 static uma_zone_t fakepg_zone;
   74 
   75 static vm_page_t dev_pager_getfake(vm_paddr_t);
   76 static void dev_pager_putfake(vm_page_t);
   77 static void dev_pager_updatefake(vm_page_t, vm_paddr_t);
   78 
   79 struct pagerops devicepagerops = {
   80         .pgo_init =     dev_pager_init,
   81         .pgo_alloc =    dev_pager_alloc,
   82         .pgo_dealloc =  dev_pager_dealloc,
   83         .pgo_getpages = dev_pager_getpages,
   84         .pgo_putpages = dev_pager_putpages,
   85         .pgo_haspage =  dev_pager_haspage,
   86 };
   87 
   88 static void
   89 dev_pager_init()
   90 {
   91         TAILQ_INIT(&dev_pager_object_list);
   92         sx_init(&dev_pager_sx, "dev_pager create");
   93         mtx_init(&dev_pager_mtx, "dev_pager list", NULL, MTX_DEF);
   94         fakepg_zone = uma_zcreate("DP fakepg", sizeof(struct vm_page),
   95             NULL, NULL, NULL, NULL, UMA_ALIGN_PTR,
   96             UMA_ZONE_NOFREE|UMA_ZONE_VM); 
   97 }
   98 
   99 /*
  100  * MPSAFE
  101  */
  102 static vm_object_t
  103 dev_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot, vm_ooffset_t foff)
  104 {
  105         struct cdev *dev;
  106         vm_object_t object;
  107         vm_pindex_t pindex;
  108         unsigned int npages;
  109         vm_paddr_t paddr;
  110         vm_offset_t off;
  111         struct cdevsw *csw;
  112 
  113         /*
  114          * Offset should be page aligned.
  115          */
  116         if (foff & PAGE_MASK)
  117                 return (NULL);
  118 
  119         size = round_page(size);
  120         pindex = OFF_TO_IDX(foff + size);
  121 
  122         /*
  123          * Make sure this device can be mapped.
  124          */
  125         dev = handle;
  126         csw = dev_refthread(dev);
  127         if (csw == NULL)
  128                 return (NULL);
  129         mtx_lock(&Giant);
  130 
  131         /*
  132          * Check that the specified range of the device allows the desired
  133          * protection.
  134          *
  135          * XXX assumes VM_PROT_* == PROT_*
  136          */
  137         npages = OFF_TO_IDX(size);
  138         for (off = foff; npages--; off += PAGE_SIZE)
  139                 if ((*csw->d_mmap)(dev, off, &paddr, (int)prot) != 0) {
  140                         mtx_unlock(&Giant);
  141                         dev_relthread(dev);
  142                         return (NULL);
  143                 }
  144 
  145         /*
  146          * Lock to prevent object creation race condition.
  147          */
  148         sx_xlock(&dev_pager_sx);
  149 
  150         /*
  151          * Look up pager, creating as necessary.
  152          */
  153         object = vm_pager_object_lookup(&dev_pager_object_list, handle);
  154         if (object == NULL) {
  155                 /*
  156                  * Allocate object and associate it with the pager.
  157                  */
  158                 object = vm_object_allocate(OBJT_DEVICE, pindex);
  159                 object->handle = handle;
  160                 TAILQ_INIT(&object->un_pager.devp.devp_pglist);
  161                 mtx_lock(&dev_pager_mtx);
  162                 TAILQ_INSERT_TAIL(&dev_pager_object_list, object, pager_object_list);
  163                 mtx_unlock(&dev_pager_mtx);
  164         } else {
  165                 /*
  166                  * Gain a reference to the object.
  167                  */
  168                 vm_object_reference(object);
  169                 if (pindex > object->size)
  170                         object->size = pindex;
  171         }
  172 
  173         sx_xunlock(&dev_pager_sx);
  174         mtx_unlock(&Giant);
  175         dev_relthread(dev);
  176         return (object);
  177 }
  178 
  179 static void
  180 dev_pager_dealloc(object)
  181         vm_object_t object;
  182 {
  183         vm_page_t m;
  184 
  185         mtx_lock(&dev_pager_mtx);
  186         TAILQ_REMOVE(&dev_pager_object_list, object, pager_object_list);
  187         mtx_unlock(&dev_pager_mtx);
  188         /*
  189          * Free up our fake pages.
  190          */
  191         while ((m = TAILQ_FIRST(&object->un_pager.devp.devp_pglist)) != 0) {
  192                 TAILQ_REMOVE(&object->un_pager.devp.devp_pglist, m, pageq);
  193                 dev_pager_putfake(m);
  194         }
  195 }
  196 
  197 static int
  198 dev_pager_getpages(object, m, count, reqpage)
  199         vm_object_t object;
  200         vm_page_t *m;
  201         int count;
  202         int reqpage;
  203 {
  204         vm_pindex_t offset;
  205         vm_paddr_t paddr;
  206         vm_page_t page;
  207         struct cdev *dev;
  208         int i, ret;
  209         int prot;
  210         struct cdevsw *csw;
  211 
  212         VM_OBJECT_LOCK_ASSERT(object, MA_OWNED);
  213         dev = object->handle;
  214         offset = m[reqpage]->pindex;
  215         VM_OBJECT_UNLOCK(object);
  216         csw = dev_refthread(dev);
  217         if (csw == NULL)
  218                 panic("dev_pager_getpage: no cdevsw");
  219         mtx_lock(&Giant);
  220         prot = PROT_READ;       /* XXX should pass in? */
  221 
  222         ret = (*csw->d_mmap)(dev, (vm_offset_t)offset << PAGE_SHIFT, &paddr, prot);
  223         KASSERT(ret == 0, ("dev_pager_getpage: map function returns error"));
  224         mtx_unlock(&Giant);
  225         dev_relthread(dev);
  226 
  227         if ((m[reqpage]->flags & PG_FICTITIOUS) != 0) {
  228                 /*
  229                  * If the passed in reqpage page is a fake page, update it with
  230                  * the new physical address.
  231                  */
  232                 VM_OBJECT_LOCK(object);
  233                 dev_pager_updatefake(m[reqpage], paddr);
  234                 if (count > 1) {
  235                         vm_page_lock_queues();
  236                         for (i = 0; i < count; i++) {
  237                                 if (i != reqpage)
  238                                         vm_page_free(m[i]);
  239                         }
  240                         vm_page_unlock_queues();
  241                 }
  242         } else {
  243                 /*
  244                  * Replace the passed in reqpage page with our own fake page and
  245                  * free up the all of the original pages.
  246                  */
  247                 page = dev_pager_getfake(paddr);
  248                 VM_OBJECT_LOCK(object);
  249                 TAILQ_INSERT_TAIL(&object->un_pager.devp.devp_pglist, page, pageq);
  250                 vm_page_lock_queues();
  251                 for (i = 0; i < count; i++)
  252                         vm_page_free(m[i]);
  253                 vm_page_unlock_queues();
  254                 vm_page_insert(page, object, offset);
  255                 m[reqpage] = page;
  256         }
  257 
  258         return (VM_PAGER_OK);
  259 }
  260 
  261 static void
  262 dev_pager_putpages(object, m, count, sync, rtvals)
  263         vm_object_t object;
  264         vm_page_t *m;
  265         int count;
  266         boolean_t sync;
  267         int *rtvals;
  268 {
  269         panic("dev_pager_putpage called");
  270 }
  271 
  272 static boolean_t
  273 dev_pager_haspage(object, pindex, before, after)
  274         vm_object_t object;
  275         vm_pindex_t pindex;
  276         int *before;
  277         int *after;
  278 {
  279         if (before != NULL)
  280                 *before = 0;
  281         if (after != NULL)
  282                 *after = 0;
  283         return (TRUE);
  284 }
  285 
  286 /*
  287  * Instantiate a fictitious page.  Unlike physical memory pages, only
  288  * the machine-independent fields must be initialized.
  289  */
  290 static vm_page_t
  291 dev_pager_getfake(paddr)
  292         vm_paddr_t paddr;
  293 {
  294         vm_page_t m;
  295 
  296         m = uma_zalloc(fakepg_zone, M_WAITOK);
  297 
  298         m->flags = PG_BUSY | PG_FICTITIOUS;
  299         m->valid = VM_PAGE_BITS_ALL;
  300         m->dirty = 0;
  301         m->busy = 0;
  302         m->queue = PQ_NONE;
  303         m->object = NULL;
  304 
  305         m->wire_count = 1;
  306         m->hold_count = 0;
  307         m->phys_addr = paddr;
  308 
  309         return (m);
  310 }
  311 
  312 static void
  313 dev_pager_putfake(m)
  314         vm_page_t m;
  315 {
  316         if (!(m->flags & PG_FICTITIOUS))
  317                 panic("dev_pager_putfake: bad page");
  318         uma_zfree(fakepg_zone, m);
  319 }
  320 
  321 static void
  322 dev_pager_updatefake(m, paddr)
  323         vm_page_t m;
  324         vm_paddr_t paddr;
  325 {
  326         if (!(m->flags & PG_FICTITIOUS))
  327                 panic("dev_pager_updatefake: bad page");
  328         m->phys_addr = paddr;
  329         m->valid = VM_PAGE_BITS_ALL;
  330 }

Cache object: 6929cbd2ae592a6434f7782748514631


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