FreeBSD/Linux Kernel Cross Reference
sys/vm/default_pager.c

     /*
      * Copyright (c) 1995, David Greenman
      * All rights reserved.
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
      * 1. Redistributions of source code must retain the above copyright
      *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 3. All advertising materials mentioning features or use of this software
     *    must display the following acknowledgement:
     *      This product includes software developed by David Greenman.
     * 4. The name of the author may not be used to endorse or promote products
     *    derived from this software without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * $FreeBSD$
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/malloc.h>
    #include <sys/vmmeter.h>
    
    #include <vm/vm.h>
    #include <vm/vm_prot.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pager.h>
    #include <vm/default_pager.h>
    #include <vm/swap_pager.h>
    
    static vm_object_t default_pager_alloc __P((void *, vm_ooffset_t, vm_prot_t,
                    vm_ooffset_t));
    static void default_pager_dealloc __P((vm_object_t));
    static int default_pager_getpages __P((vm_object_t, vm_page_t *, int, int));
    static int default_pager_putpages __P((vm_object_t, vm_page_t *, int, 
                    boolean_t, int *));
    static boolean_t default_pager_haspage __P((vm_object_t, vm_pindex_t, int *, 
                    int *));
    /*
     * pagerops for OBJT_DEFAULT - "default pager".
     */
    struct pagerops defaultpagerops = {
            NULL,
            default_pager_alloc,
            default_pager_dealloc,
            default_pager_getpages,
            default_pager_putpages,
            default_pager_haspage,
            NULL
    };
    
    /*
     * no_pager_alloc just returns an initialized object.
     */
    static vm_object_t
    default_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
                        vm_ooffset_t offset)
    {
            if (handle != NULL)
                    panic("default_pager_alloc: handle specified");
    
            return vm_object_allocate(OBJT_DEFAULT, OFF_TO_IDX(round_page(offset + size)));
    }
    
    static void
    default_pager_dealloc(object)
            vm_object_t object;
    {
            /*
             * OBJT_DEFAULT objects have no special resources allocated to them.
             */
    }
    
    /*
     * The default pager has no backing store, so we always return
     * failure.
     */
    static int
    default_pager_getpages(object, m, count, reqpage)
            vm_object_t object;
            vm_page_t *m;
            int count;
            int reqpage;
   {
           return VM_PAGER_FAIL;
   }
   
   static int
   default_pager_putpages(object, m, c, sync, rtvals)
           vm_object_t object;
           vm_page_t *m;
           int c;
           boolean_t sync;
           int *rtvals;
   {
           int i;
   
           /*
            * Try to convert the object type into a OBJT_SWAP.
            * If the swp structure allocation fails, convert it
            * back to OBJT_DEFAULT and return failure. Otherwise
            * pass this putpages to the swap pager.
            */
           object->type = OBJT_SWAP;
   
           if (swap_pager_swp_alloc(object, M_KERNEL) != 0) {
                   object->type = OBJT_DEFAULT;
                   for (i = 0; i < c; i++)
                           rtvals[i] = VM_PAGER_FAIL;
                   return VM_PAGER_FAIL;
           }
   
           return swap_pager_putpages(object, m, c, sync, rtvals);
   }
   
   static boolean_t
   default_pager_haspage(object, pindex, before, after)
           vm_object_t object;
           vm_pindex_t pindex;
           int *before;
           int *after;
   {
           return FALSE;
   }
   
   void
   default_pager_convert_to_swap(object)
           vm_object_t object;
   {
           object->type = OBJT_SWAP;
           if (swap_pager_swp_alloc(object, M_KERNEL) != 0) {
                   object->type = OBJT_DEFAULT;
           }
   }
   
   void
   default_pager_convert_to_swapq(object)
           vm_object_t object;
   {
           if (object &&
                   (object->type == OBJT_DEFAULT) &&
                   (object != kernel_object && object != kmem_object) &&
                   (object->size > ((cnt.v_page_count - cnt.v_wire_count) / 4)))
                   default_pager_convert_to_swap(object);
   }
   

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