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

     /*
      * Copyright (c) 2000 Peter Wemm
      *
      * 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.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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: releng/5.1/sys/vm/phys_pager.c 108306 2002-12-27 06:09:56Z alc $
     */
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/linker_set.h>
    #include <sys/conf.h>
    #include <sys/kernel.h>
    #include <sys/lock.h>
    #include <sys/proc.h>
    #include <sys/mutex.h>
    #include <sys/mman.h>
    #include <sys/sysctl.h>
    
    #include <vm/vm.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pager.h>
    
    /* prevent concurrant creation races */
    static int phys_pager_alloc_lock;
    /* list of device pager objects */
    static struct pagerlst phys_pager_object_list;
    /* protect access to phys_pager_object_list */
    static struct mtx phys_pager_mtx;
    
    static void
    phys_pager_init(void)
    {
    
            TAILQ_INIT(&phys_pager_object_list);
            mtx_init(&phys_pager_mtx, "phys_pager list", NULL, MTX_DEF);
    }
    
    /*
     * MPSAFE
     */
    static vm_object_t
    phys_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
                     vm_ooffset_t foff)
    {
            vm_object_t object;
    
            /*
             * Offset should be page aligned.
             */
            if (foff & PAGE_MASK)
                    return (NULL);
    
            size = round_page(size);
    
            if (handle != NULL) {
                    mtx_lock(&Giant);
                    /*
                     * Lock to prevent object creation race condition.
                     */
                    while (phys_pager_alloc_lock) {
                            phys_pager_alloc_lock = -1;
                            tsleep(&phys_pager_alloc_lock, PVM, "swpalc", 0);
                    }
                    phys_pager_alloc_lock = 1;
    
                    /*
                     * Look up pager, creating as necessary.
                     */
                    object = vm_pager_object_lookup(&phys_pager_object_list, handle);
                    if (object == NULL) {
                            /*
                             * Allocate object and associate it with the pager.
                             */
                            object = vm_object_allocate(OBJT_PHYS,
                                    OFF_TO_IDX(foff + size));
                            object->handle = handle;
                            mtx_lock(&phys_pager_mtx);
                            TAILQ_INSERT_TAIL(&phys_pager_object_list, object,
                               pager_object_list);
                           mtx_unlock(&phys_pager_mtx);
                   } else {
                           /*
                            * Gain a reference to the object.
                            */
                           vm_object_reference(object);
                           if (OFF_TO_IDX(foff + size) > object->size)
                                   object->size = OFF_TO_IDX(foff + size);
                   }
                   if (phys_pager_alloc_lock == -1)
                           wakeup(&phys_pager_alloc_lock);
                   phys_pager_alloc_lock = 0;
                   mtx_unlock(&Giant);
           } else {
                   object = vm_object_allocate(OBJT_PHYS,
                           OFF_TO_IDX(foff + size));
           }
   
           return (object);
   }
   
   /*
    * MPSAFE
    */
   static void
   phys_pager_dealloc(vm_object_t object)
   {
   
           if (object->handle != NULL) {
                   mtx_lock(&phys_pager_mtx);
                   TAILQ_REMOVE(&phys_pager_object_list, object, pager_object_list);
                   mtx_unlock(&phys_pager_mtx);
           }
   }
   
   static int
   phys_pager_getpages(vm_object_t object, vm_page_t *m, int count, int reqpage)
   {
           int i, s;
   
           s = splvm();
           vm_page_lock_queues();
           /*
            * Fill as many pages as vm_fault has allocated for us.
            */
           for (i = 0; i < count; i++) {
                   if ((m[i]->flags & PG_ZERO) == 0) {
                           vm_page_unlock_queues();
                           pmap_zero_page(m[i]);
                           vm_page_lock_queues();
                   }
                   vm_page_flag_set(m[i], PG_ZERO);
                   /* Switch off pv_entries */
                   vm_page_unmanage(m[i]);
                   m[i]->valid = VM_PAGE_BITS_ALL;
                   m[i]->dirty = 0;
                   /* The requested page must remain busy, the others not. */
                   if (reqpage != i) {
                           vm_page_flag_clear(m[i], PG_BUSY);
                           m[i]->busy = 0;
                   }
           }
           vm_page_unlock_queues();
           splx(s);
   
           return (VM_PAGER_OK);
   }
   
   static void
   phys_pager_putpages(vm_object_t object, vm_page_t *m, int count, boolean_t sync,
                       int *rtvals)
   {
   
           panic("phys_pager_putpage called");
   }
   
   /*
    * Implement a pretty aggressive clustered getpages strategy.  Hint that
    * everything in an entire 4MB window should be prefaulted at once.
    *
    * XXX 4MB (1024 slots per page table page) is convenient for x86,
    * but may not be for other arches.
    */
   #ifndef PHYSCLUSTER
   #define PHYSCLUSTER 1024
   #endif
   static boolean_t
   phys_pager_haspage(vm_object_t object, vm_pindex_t pindex, int *before,
                      int *after)
   {
           vm_pindex_t base, end;
   
           base = pindex & (~(PHYSCLUSTER - 1));
           end = base + (PHYSCLUSTER - 1);
           if (before != NULL)
                   *before = pindex - base;
           if (after != NULL)
                   *after = end - pindex;
           return (TRUE);
   }
   
   struct pagerops physpagerops = {
           phys_pager_init,
           phys_pager_alloc,
           phys_pager_dealloc,
           phys_pager_getpages,
           phys_pager_putpages,
           phys_pager_haspage,
           NULL
   };

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