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.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/systm.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/rwlock.h>
    #include <sys/sysctl.h>
    
    #include <vm/vm.h>
    #include <vm/vm_param.h>
    #include <vm/vm_object.h>
    #include <vm/vm_page.h>
    #include <vm/vm_pager.h>
    
    /* list of phys 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);
    }
    
    static vm_object_t
    phys_pager_alloc(void *handle, vm_ooffset_t size, vm_prot_t prot,
        vm_ooffset_t foff, struct ucred *cred)
    {
            vm_object_t object, object1;
            vm_pindex_t pindex;
    
            /*
             * Offset should be page aligned.
             */
            if (foff & PAGE_MASK)
                    return (NULL);
    
            pindex = OFF_TO_IDX(foff + PAGE_MASK + size);
    
            if (handle != NULL) {
                    mtx_lock(&phys_pager_mtx);
                    /*
                     * Look up pager, creating as necessary.
                     */
                    object1 = NULL;
                    object = vm_pager_object_lookup(&phys_pager_object_list, handle);
                    if (object == NULL) {
                            /*
                             * Allocate object and associate it with the pager.
                             */
                            mtx_unlock(&phys_pager_mtx);
                            object1 = vm_object_allocate(OBJT_PHYS, pindex);
                            mtx_lock(&phys_pager_mtx);
                            object = vm_pager_object_lookup(&phys_pager_object_list,
                                handle);
                            if (object != NULL) {
                                    /*
                                     * We raced with other thread while
                                     * allocating object.
                                     */
                                    if (pindex > object->size)
                                            object->size = pindex;
                            } else {
                                    object = object1;
                                    object1 = NULL;
                                   object->handle = handle;
                                   TAILQ_INSERT_TAIL(&phys_pager_object_list,
                                       object, pager_object_list);
                           }
                   } else {
                           if (pindex > object->size)
                                   object->size = pindex;
                   }
                   mtx_unlock(&phys_pager_mtx);
                   vm_object_deallocate(object1);
           } else {
                   object = vm_object_allocate(OBJT_PHYS, pindex);
           }
   
           return (object);
   }
   
   static void
   phys_pager_dealloc(vm_object_t object)
   {
   
           if (object->handle != NULL) {
                   VM_OBJECT_WUNLOCK(object);
                   mtx_lock(&phys_pager_mtx);
                   TAILQ_REMOVE(&phys_pager_object_list, object, pager_object_list);
                   mtx_unlock(&phys_pager_mtx);
                   VM_OBJECT_WLOCK(object);
           }
           object->handle = NULL;
           object->type = OBJT_DEAD;
   }
   
   /*
    * Fill as many pages as vm_fault has allocated for us.
    */
   static int
   phys_pager_getpages(vm_object_t object, vm_page_t *m, int count, int reqpage)
   {
           int i;
   
           VM_OBJECT_ASSERT_WLOCKED(object);
           for (i = 0; i < count; i++) {
                   if (m[i]->valid == 0) {
                           if ((m[i]->flags & PG_ZERO) == 0)
                                   pmap_zero_page(m[i]);
                           m[i]->valid = VM_PAGE_BITS_ALL;
                   }
                   KASSERT(m[i]->valid == VM_PAGE_BITS_ALL,
                       ("phys_pager_getpages: partially valid page %p", m[i]));
                   KASSERT(m[i]->dirty == 0,
                       ("phys_pager_getpages: dirty page %p", m[i]));
                   /* The requested page must remain busy, the others not. */
                   if (i == reqpage) {
                           vm_page_lock(m[i]);
                           vm_page_flash(m[i]);
                           vm_page_unlock(m[i]);
                   } else
                           vm_page_xunbusy(m[i]);
           }
           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 = {
           .pgo_init =     phys_pager_init,
           .pgo_alloc =    phys_pager_alloc,
           .pgo_dealloc =  phys_pager_dealloc,
           .pgo_getpages = phys_pager_getpages,
           .pgo_putpages = phys_pager_putpages,
           .pgo_haspage =  phys_pager_haspage,
   };

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