text: /*	$NetBSD: uvm_anon.h,v 1.10 1999/03/26 17:34:15 chs 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] */
  	simple_lock_data_t 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.
   */
  
  /*
   * prototypes
   */
  
  struct vm_anon *uvm_analloc __P((void));
  void uvm_anfree __P((struct vm_anon *));
  void uvm_anon_init __P((void));
  void uvm_anon_add __P((int));
  struct vm_page *uvm_anon_lockloanpg __P((struct vm_anon *));
  void uvm_anon_dropswap __P((struct vm_anon *));
  
  #endif /* _UVM_UVM_ANON_H_ */
  