FreeBSD/Linux Kernel Cross Reference
sys/uvm/uvm_anon.h

     /*      $NetBSD: uvm_anon.h,v 1.16.2.1 2004/05/10 14:26:37 tron Exp $   */
     
     /*
      *
      * Copyright (c) 1997 Charles D. Cranor and Washington University.
      * 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 Charles D. Cranor and
     *      Washington University.
     * 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 ``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 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.
     */
    
    #ifndef _UVM_UVM_ANON_H_
    #define _UVM_UVM_ANON_H_
    
    /*
     * uvm_anon.h
     */
    
    /*
     * anonymous memory management
     *
     * anonymous virtual memory is short term virtual memory that goes away
     * when the processes referencing it go away.    an anonymous page of
     * virtual memory is described by the following data structure:
     */
    
    struct vm_anon {
            int an_ref;                     /* reference count [an_lock] */
            struct simplelock an_lock;      /* lock for an_ref */
            union {
                    struct vm_anon *an_nxt; /* if on free list [afreelock] */
                    struct vm_page *an_page;/* if in RAM [an_lock] */
            } u;
            int an_swslot;          /* drum swap slot # (if != 0)
                                       [an_lock.  also, it is ok to read
                                       an_swslot if we hold an_page PG_BUSY] */
    };
    
    /*
     * a pool of vm_anon data structures is allocated and put on a global
     * free list at boot time.  vm_anon's on the free list use "an_nxt" as
     * a pointer to the next item on the free list.  for active vm_anon's
     * the data can be in one of the following state: [1] in a vm_page
     * with no backing store allocated yet, [2] in a vm_page with backing
     * store allocated, or [3] paged out to backing store (no vm_page).
     *
     * for pageout in case [2]: if the page has been modified then we must
     * flush it out to backing store, otherwise we can just dump the
     * vm_page.
     */
    
    /*
     * anons are grouped together in anonymous memory maps, or amaps.
     * amaps are defined in uvm_amap.h.
     */
    
    /*
     * processes reference anonymous virtual memory maps with an anonymous
     * reference structure:
     */
    
    struct vm_aref {
            int ar_pageoff;                 /* page offset into amap we start */
            struct vm_amap *ar_amap;        /* pointer to amap */
    };
    
    /*
     * the offset field indicates which part of the amap we are referencing.
     * locked by vm_map lock.
     */
    
    #ifdef _KERNEL
    
    /*
     * prototypes
     */
   
   struct vm_anon *uvm_analloc(void);
   void uvm_anfree(struct vm_anon *);
   void uvm_anon_init(void);
   int uvm_anon_add(int);
   void uvm_anon_remove(int);
   struct vm_page *uvm_anon_lockloanpg(struct vm_anon *);
   void uvm_anon_dropswap(struct vm_anon *);
   boolean_t anon_swap_off(int, int);
   void uvm_anon_release(struct vm_anon *);
   #endif /* _KERNEL */
   
   #endif /* _UVM_UVM_ANON_H_ */

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