This is xnu-8019. See this file in:
/*
 * Copyright (c) 2000-2004 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */
/*
 * Mach Operating System
 * Copyright (c) 1987 Carnegie-Mellon University
 * All rights reserved.  The CMU software License Agreement specifies
 * the terms and conditions for use and redistribution.
 */

#ifndef _VNODE_PAGER_
#define _VNODE_PAGER_   1

#include <mach/kern_return.h>
#include <sys/types.h>
#include <kern/queue.h>

#ifdef  KERNEL
#include <mach/boolean.h>
#include <mach/memory_object_types.h>
#include <mach/vm_types.h>
#include <vm/vm_protos.h>
#include <vm/vm_pager.h>

/*
 *  Vstructs are the internal (to us) description of a unit of backing store.
 *  The are the link between memory objects and the backing store they represent.
 *  For the vnode pager, backing store comes in two flavors: normal files and
 *  swap files.
 *
 *  For objects that page to and from normal files (e.g. objects that represent
 *  program text segments), we maintain some simple parameters that allow us to
 *  access the file's contents directly through the vnode interface.
 *
 *  Data for objects without associated vnodes is maintained in the swap files.
 *  Each object that uses one of these as backing store has a vstruct indicating
 *  the swap file of preference (vs_pf) and a mapping between contiguous object
 *  offsets and swap file offsets (vs_pmap).  Each entry in this mapping specifies
 *  the pager file to use, and the offset of the page in that pager file.  These
 *  mapping entries are of type pfMapEntry.
 */

/*
 * Pager file structure.  One per swap file.
 */
typedef struct pager_file {
	queue_chain_t   pf_chain;       /* link to other paging files */
	struct  vnode   *pf_vp;         /* vnode of paging file */
	u_int           pf_count;       /* Number of vstruct using this file */
	u_char          *pf_bmap;       /* Map of used blocks */
	long            pf_npgs;        /* Size of file in pages */
	long            pf_pfree;       /* Number of unused pages */
	long            pf_lowat;       /* Low water page */
	long            pf_hipage;      /* Highest page allocated */
	long            pf_hint;        /* Lowest page unallocated */
	char            *pf_name;       /* Filename of this file */
	boolean_t       pf_prefer;
	int             pf_index;       /* index into the pager_file array */
	void *          pf_lock;        /* Lock for alloc and dealloc */
} *pager_file_t;

#define PAGER_FILE_NULL (pager_file_t) 0

#define MAXPAGERFILES 16

#define MAX_BACKING_STORE 100

struct bs_map {
	struct vnode    *vp;
	void            *bs;
};
extern struct bs_map  bs_port_table[];



/*
 * Pager file data structures.
 */
#define INDEX_NULL      0
typedef struct {
	unsigned int index:8;   /* paging file this block is in */
	unsigned int offset:24; /* page number where block resides */
} pf_entry;

typedef enum {
	IS_INODE,               /* Local disk */
	IS_RNODE                /* NFS */
} vpager_fstype;

/*
 *  Basic vnode pager structure.  One per object, backing-store pair.
 */
typedef struct vstruct {
	boolean_t       is_device;      /* Must be first - see vm_pager.h */
	pager_file_t    vs_pf;          /* Pager file this uses */
	pf_entry        **vs_pmap;      /* Map of pages into paging file */
	unsigned int
	/* boolean_t */ vs_swapfile:1;  /* vnode is a swapfile */
	short           vs_count;       /* use count */
	int             vs_size;        /* size of this chunk in pages*/
	struct vnode    *vs_vp;         /* vnode to page to */
} *vnode_pager_t;

#define VNODE_PAGER_NULL        ((vnode_pager_t) 0)

#endif  /* KERNEL */

#endif  /* _VNODE_PAGER_ */