/* $NetBSD: uvm_anon.h,v 1.32 2020/03/20 19:08:54 ad 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.
*
* 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.
*/
/*
* 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 {
krwlock_t *an_lock; /* Lock for an_ref */
uintptr_t an_ref; /* Reference count [an_lock] */
struct vm_page *an_page; /* If in RAM [an_lock] */
#if defined(VMSWAP) || 1 /* XXX libkvm */
/*
* Drum swap slot # (if != 0) [an_lock. also, it is ok to read
* an_swslot if we hold an_page PG_BUSY].
*/
int an_swslot;
#endif
};
/*
* 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.
*/
