text: /*
   * Copyright (c) 2000-2014 Apple 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@
   */
  /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
  /*
   * Copyright (c) 1989, 1991, 1993
   *	The Regents of the University of California.  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 the University of
   *	California, Berkeley and its contributors.
   * 4. Neither the name of the University nor the names of its contributors
   *    may be used to endorse or promote products derived from this software
   *    without specific prior written permission.
   *
   * THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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.
   *
   *	@(#)mount.h	8.21 (Berkeley) 5/20/95
   */
  /*
   * NOTICE: This file was modified by SPARTA, Inc. in 2005 to introduce
   * support for mandatory and extensible security protections.  This notice
   * is included in support of clause 2.2 (b) of the Apple Public License,
   * Version 2.0.
   */
  
  
  #ifndef _SYS_MOUNT_H_
  #define	_SYS_MOUNT_H_
  
  #include <sys/appleapiopts.h>
  #include <sys/cdefs.h>
  #include <sys/attr.h>		/* needed for vol_capabilities_attr_t */
  
  #include <sys/kernel_types.h>
  #include <uuid/uuid.h>
  
  #include <sys/_types/_fsid_t.h> /* file system id type */
  
  /*
   * file system statistics
   */
  
  #define	MFSNAMELEN	15	/* length of fs type name, not inc. null */
  #define	MFSTYPENAMELEN	16	/* length of fs type name including null */
  
  #if __DARWIN_64_BIT_INO_T
  #define	MNAMELEN	MAXPATHLEN	/* length of buffer for returned name */
  #else /* ! __DARWIN_64_BIT_INO_T */
  #define	MNAMELEN	90		/* length of buffer for returned name */
  #endif /* __DARWIN_64_BIT_INO_T */
  
  #define __DARWIN_STRUCT_STATFS64 { \
  	uint32_t	f_bsize;	/* fundamental file system block size */ \
  	int32_t		f_iosize;	/* optimal transfer block size */ \
  	uint64_t	f_blocks;	/* total data blocks in file system */ \
  	uint64_t	f_bfree;	/* free blocks in fs */ \
  	uint64_t	f_bavail;	/* free blocks avail to non-superuser */ \
  	uint64_t	f_files;	/* total file nodes in file system */ \
  	uint64_t	f_ffree;	/* free file nodes in fs */ \
  	fsid_t		f_fsid;		/* file system id */ \
  	uid_t		f_owner;	/* user that mounted the filesystem */ \
  	uint32_t	f_type;		/* type of filesystem */ \
  	uint32_t	f_flags;	/* copy of mount exported flags */ \
  	uint32_t	f_fssubtype;	/* fs sub-type (flavor) */ \
  	char		f_fstypename[MFSTYPENAMELEN];	/* fs type name */ \
  	char		f_mntonname[MAXPATHLEN];	/* directory on which mounted */ \
  	char		f_mntfromname[MAXPATHLEN];	/* mounted filesystem */ \
  	uint32_t	f_reserved[8];	/* For future use */ \
  }
  
  #if !__DARWIN_ONLY_64_BIT_INO_T
  
  struct statfs64 __DARWIN_STRUCT_STATFS64;
  
  #endif /* !__DARWIN_ONLY_64_BIT_INO_T */
  
  #if __DARWIN_64_BIT_INO_T
  
  struct statfs __DARWIN_STRUCT_STATFS64;
  
  #else /* !__DARWIN_64_BIT_INO_T */
  
  /*
   * LP64 - WARNING - must be kept in sync with struct user_statfs in mount_internal.h.
   */
  struct statfs {
  	short	f_otype;		/* TEMPORARY SHADOW COPY OF f_type */
  	short	f_oflags;		/* TEMPORARY SHADOW COPY OF f_flags */
  	long	f_bsize;		/* fundamental file system block size */
  	long	f_iosize;		/* optimal transfer block size */
  	long	f_blocks;		/* total data blocks in file system */
  	long	f_bfree;		/* free blocks in fs */
  	long	f_bavail;		/* free blocks avail to non-superuser */
  	long	f_files;		/* total file nodes in file system */
  	long	f_ffree;		/* free file nodes in fs */
  	fsid_t	f_fsid;			/* file system id */
  	uid_t	f_owner;		/* user that mounted the filesystem */
  	short	f_reserved1;	/* spare for later */
  	short	f_type;			/* type of filesystem */
  	long	f_flags;		/* copy of mount exported flags */
  	long    f_reserved2[2];	/* reserved for future use */
  	char	f_fstypename[MFSNAMELEN]; /* fs type name */
  	char	f_mntonname[MNAMELEN];	/* directory on which mounted */
  	char	f_mntfromname[MNAMELEN];/* mounted filesystem */
  	char	f_reserved3;	/* For alignment */
  	long	f_reserved4[4];	/* For future use */
  };
  
  #endif /* __DARWIN_64_BIT_INO_T */
  
  #pragma pack(4)
  
  struct vfsstatfs {
  	uint32_t	f_bsize;	/* fundamental file system block size */
  	size_t		f_iosize;	/* optimal transfer block size */
  	uint64_t	f_blocks;	/* total data blocks in file system */
  	uint64_t	f_bfree;	/* free blocks in fs */
  	uint64_t	f_bavail;	/* free blocks avail to non-superuser */
  	uint64_t	f_bused;	/* free blocks avail to non-superuser */
  	uint64_t	f_files;	/* total file nodes in file system */
  	uint64_t	f_ffree;	/* free file nodes in fs */
  	fsid_t		f_fsid;		/* file system id */
  	uid_t		f_owner;	/* user that mounted the filesystem */
  	uint64_t	f_flags;	/* copy of mount exported flags */ 
  	char		f_fstypename[MFSTYPENAMELEN];/* fs type name inclus */
  	char		f_mntonname[MAXPATHLEN];/* directory on which mounted */
  	char		f_mntfromname[MAXPATHLEN];/* mounted filesystem */
  	uint32_t	f_fssubtype;     /* fs sub-type (flavor) */
  	void		*f_reserved[2];		/* For future use == 0 */
  };
  
  #pragma pack()
  
  /*
   * Kernel level support for the VFS_GETATTR(), VFS_SETATTR() for use in
   * implementation of filesystem KEXTs, and by the vfs_getattr() and
   * vfs_setattr() KPIs.
   */
  
  #define VFSATTR_INIT(s)			((s)->f_supported = (s)->f_active = 0LL)
  #define VFSATTR_SET_SUPPORTED(s, a)	((s)->f_supported |= VFSATTR_ ## a)
  #define VFSATTR_IS_SUPPORTED(s, a)	((s)->f_supported & VFSATTR_ ## a)
  #define VFSATTR_CLEAR_ACTIVE(s, a)	((s)->f_active &= ~VFSATTR_ ## a)
  #define VFSATTR_IS_ACTIVE(s, a)		((s)->f_active & VFSATTR_ ## a)
  #define VFSATTR_ALL_SUPPORTED(s)	(((s)->f_active & (s)->f_supported) == (s)->f_active)
  #define VFSATTR_WANTED(s, a)		((s)->f_active |= VFSATTR_ ## a)
  #define VFSATTR_RETURN(s, a, x)		do { (s)-> a = (x); VFSATTR_SET_SUPPORTED(s, a);} while(0)
  
  #define VFSATTR_f_objcount		(1LL<<  0)
  #define VFSATTR_f_filecount		(1LL<<  1)
  #define VFSATTR_f_dircount		(1LL<<  2)
  #define VFSATTR_f_maxobjcount		(1LL<<  3)
  #define VFSATTR_f_bsize			(1LL<< 4)
  #define VFSATTR_f_iosize		(1LL<<  5)
  #define VFSATTR_f_blocks		(1LL<<  6)
  #define VFSATTR_f_bfree			(1LL<<  7)
  #define VFSATTR_f_bavail		(1LL<<  8)
  #define VFSATTR_f_bused			(1LL<<  9)
  #define VFSATTR_f_files			(1LL<< 10)
  #define VFSATTR_f_ffree			(1LL<< 11)
  #define VFSATTR_f_fsid			(1LL<< 12)
  #define VFSATTR_f_owner			(1LL<< 13)
  #define VFSATTR_f_capabilities		(1LL<< 14)
  #define VFSATTR_f_attributes		(1LL<< 15)
  #define VFSATTR_f_create_time		(1LL<< 16)
  #define VFSATTR_f_modify_time		(1LL<< 17)
  #define VFSATTR_f_access_time		(1LL<< 18)
  #define VFSATTR_f_backup_time		(1LL<< 19)
  #define VFSATTR_f_fssubtype		(1LL<< 20)
  #define VFSATTR_f_vol_name		(1LL<< 21)
  #define VFSATTR_f_signature		(1LL<< 22)
  #define VFSATTR_f_carbon_fsid		(1LL<< 23)
  #define VFSATTR_f_uuid			(1LL<< 24)
  
  /*
   * Argument structure.
   */
  #pragma pack(4)
  /*
   * Note: the size of the vfs_attr structure can change.
   * A kext should only reference the fields that are
   * marked as active; it should not depend on the actual
   * size of the structure or attempt to copy it.
   */
  struct vfs_attr {
  	uint64_t	f_supported;
  	uint64_t	f_active;
  
  	uint64_t	f_objcount;	/* number of filesystem objects in volume */
  	uint64_t	f_filecount;	/* ... files */
  	uint64_t	f_dircount;	/* ... directories */
  	uint64_t	f_maxobjcount;	/* maximum number of filesystem objects */
  	
  	uint32_t	f_bsize;	/* block size for the below size values */
  	size_t		f_iosize;	/* optimal transfer block size */
  	uint64_t	f_blocks;	/* total data blocks in file system */
  	uint64_t	f_bfree;	/* free blocks in fs */
  	uint64_t	f_bavail;	/* free blocks avail to non-superuser */
  	uint64_t	f_bused;	/* blocks in use */
  	uint64_t	f_files;	/* total file nodes in file system */
  	uint64_t	f_ffree;	/* free file nodes in fs */
  	fsid_t		f_fsid;		/* file system id */
  	uid_t		f_owner;	/* user that mounted the filesystem */
  
   	vol_capabilities_attr_t f_capabilities;
  	vol_attributes_attr_t f_attributes;
  
  	struct timespec	f_create_time;	/* creation time */
  	struct timespec	f_modify_time;	/* last modification time */
  	struct timespec f_access_time;	/* time of last access */
  	struct timespec	f_backup_time;	/* last backup time */
  
  	uint32_t	f_fssubtype;	/* filesystem subtype */
  
  	char		*f_vol_name;	/* volume name */
  
  	uint16_t	f_signature;	/* used for ATTR_VOL_SIGNATURE, Carbon's FSVolumeInfo.signature */
  	uint16_t	f_carbon_fsid;	/* same as Carbon's FSVolumeInfo.filesystemID */
  	uuid_t		f_uuid;		/* file system UUID (version 3 or 5), available in 10.6 and later */
  };
  
  #pragma pack()
  
  
  /*
   * User specifiable flags.
   *
   * Unmount uses MNT_FORCE flag.
   */
  #define	MNT_RDONLY	0x00000001	/* read only filesystem */
  #define	MNT_SYNCHRONOUS	0x00000002	/* file system written synchronously */
  #define	MNT_NOEXEC	0x00000004	/* can't exec from filesystem */
  #define	MNT_NOSUID	0x00000008	/* don't honor setuid bits on fs */
  #define	MNT_NODEV	0x00000010	/* don't interpret special files */
  #define	MNT_UNION	0x00000020	/* union with underlying filesystem */
  #define	MNT_ASYNC	0x00000040	/* file system written asynchronously */
  #define	MNT_CPROTECT	0x00000080	/* file system supports content protection */
  
  /*
   * NFS export related mount flags.
   */
  #define	MNT_EXPORTED	0x00000100	/* file system is exported */
  
  /*
   * MAC labeled / "quarantined" flag
   */
  #define MNT_QUARANTINE	0x00000400	/* file system is quarantined */
  
  /*
   * Flags set by internal operations.
   */
  #define	MNT_LOCAL	0x00001000	/* filesystem is stored locally */
  #define	MNT_QUOTA	0x00002000	/* quotas are enabled on filesystem */
  #define	MNT_ROOTFS	0x00004000	/* identifies the root filesystem */
  #define	MNT_DOVOLFS	0x00008000	/* FS supports volfs (deprecated flag in Mac OS X 10.5) */
  
  
  #define MNT_DONTBROWSE	0x00100000	/* file system is not appropriate path to user data */
  #define MNT_IGNORE_OWNERSHIP 0x00200000 /* VFS will ignore ownership information on filesystem objects */
  #define MNT_AUTOMOUNTED 0x00400000	/* filesystem was mounted by automounter */
  #define MNT_JOURNALED   0x00800000  	/* filesystem is journaled */
  #define MNT_NOUSERXATTR	0x01000000	/* Don't allow user extended attributes */
  #define MNT_DEFWRITE	0x02000000	/* filesystem should defer writes */
  #define MNT_MULTILABEL	0x04000000	/* MAC support for individual labels */
  #define MNT_NOATIME	0x10000000	/* disable update of file access time */
  
  /* backwards compatibility only */
  #define MNT_UNKNOWNPERMISSIONS MNT_IGNORE_OWNERSHIP
  
  
  /*
   * XXX I think that this could now become (~(MNT_CMDFLAGS))
   * but the 'mount' program may need changing to handle this.
   */
  #define	MNT_VISFLAGMASK	(MNT_RDONLY	| MNT_SYNCHRONOUS | MNT_NOEXEC	| \
  			MNT_NOSUID	| MNT_NODEV	| MNT_UNION	| \
  			MNT_ASYNC	| MNT_EXPORTED	| MNT_QUARANTINE | \
  			MNT_LOCAL	| MNT_QUOTA | \
  			MNT_ROOTFS	| MNT_DOVOLFS	| MNT_DONTBROWSE | \
  			MNT_IGNORE_OWNERSHIP | MNT_AUTOMOUNTED | MNT_JOURNALED | \
  			MNT_NOUSERXATTR | MNT_DEFWRITE	| MNT_MULTILABEL | \
  			MNT_NOATIME | MNT_CPROTECT)
  /*
   * External filesystem command modifier flags.
   * Unmount can use the MNT_FORCE flag.
   * XXX These are not STATES and really should be somewhere else.
   * External filesystem control flags.
   */
  #define	MNT_UPDATE	0x00010000	/* not a real mount, just an update */
  #define	MNT_NOBLOCK	0x00020000	/* don't block unmount if not responding */
  #define	MNT_RELOAD	0x00040000	/* reload filesystem data */
  #define	MNT_FORCE	0x00080000	/* force unmount or readonly change */
  #define MNT_CMDFLAGS	(MNT_UPDATE|MNT_NOBLOCK|MNT_RELOAD|MNT_FORCE)
  
  
  
  /*
   * Sysctl CTL_VFS definitions.
   *
   * Second level identifier specifies which filesystem. Second level
   * identifier VFS_GENERIC returns information about all filesystems.
   */
  #define	VFS_GENERIC		0	/* generic filesystem information */
  #define VFS_NUMMNTOPS		1	/* int: total num of vfs mount/unmount operations */
  /*
   * Third level identifiers for VFS_GENERIC are given below; third
   * level identifiers for specific filesystems are given in their
   * mount specific header files.
   */
  #define VFS_MAXTYPENUM	1	/* int: highest defined filesystem type */
  #define VFS_CONF	2	/* struct: vfsconf for filesystem given
  				   as next argument */
  
  /*
   * Flags for various system call interfaces.
   *
   * waitfor flags to vfs_sync() and getfsstat()
   */
  #define MNT_WAIT	1	/* synchronized I/O file integrity completion */
  #define MNT_NOWAIT	2	/* start all I/O, but do not wait for it */
  #define	MNT_DWAIT	4	/* synchronized I/O data integrity completion */
  
  
  
  /* Reserved fields preserve binary compatibility */
  struct vfsconf {
  	uint32_t vfc_reserved1;		/* opaque */
  	char	vfc_name[MFSNAMELEN];	/* filesystem type name */
  	int	vfc_typenum;		/* historic filesystem type number */
  	int	vfc_refcount;		/* number mounted of this type */
  	int	vfc_flags;		/* permanent flags */
  	uint32_t vfc_reserved2;		/* opaque */
  	uint32_t vfc_reserved3;		/* opaque */
  };
  
  struct vfsidctl {
  	int		vc_vers;	/* should be VFSIDCTL_VERS1 (below) */
  	fsid_t		vc_fsid;	/* fsid to operate on. */
  	void		*vc_ptr;	/* pointer to data structure. */
  	size_t		vc_len;		/* sizeof said structure. */
  	u_int32_t	vc_spare[12];	/* spare (must be zero). */
  };
  
  
  /* vfsidctl API version. */
  #define VFS_CTL_VERS1	0x01
  
  struct user_vfsidctl {
         int				vc_vers;        /* should be VFSIDCTL_VERS1 (below) */
         fsid_t			vc_fsid;		/* fsid to operate on. */
         user_addr_t 		vc_ptr __attribute((aligned(8)));	/* pointer to data structure. */
         user_size_t 		vc_len;			/* sizeof said structure. */
         u_int32_t		vc_spare[12];   /* spare (must be zero). */
  };
  
  struct user32_vfsidctl {
         int				vc_vers;        /* should be VFSIDCTL_VERS1 (below) */
         fsid_t			vc_fsid;		/* fsid to operate on. */
         user32_addr_t 	vc_ptr;			/* pointer to data structure. */
         user32_size_t 	vc_len;			/* sizeof said structure. */
         u_int32_t		vc_spare[12];   /* spare (must be zero). */
  };
  
  union union_vfsidctl { /* the fields vc_vers and vc_fsid are compatible */
  		struct user32_vfsidctl vc32;
  		struct user_vfsidctl vc64;
  };
  
  
  /*
   * New style VFS sysctls, do not reuse/conflict with the namespace for
   * private sysctls.
   */
  #define VFS_CTL_STATFS	0x00010001	/* statfs */
  #define VFS_CTL_UMOUNT	0x00010002	/* unmount */
  #define VFS_CTL_QUERY	0x00010003	/* anything wrong? (vfsquery) */
  #define VFS_CTL_NEWADDR	0x00010004	/* reconnect to new address */
  #define VFS_CTL_TIMEO	0x00010005	/* set timeout for vfs notification */
  #define VFS_CTL_NOLOCKS	0x00010006	/* disable file locking */
  #define VFS_CTL_SADDR	0x00010007	/* get server address */
  #define VFS_CTL_DISC    0x00010008	/* server disconnected */
  #define VFS_CTL_SERVERINFO  0x00010009  /* information about fs server */
  #define VFS_CTL_NSTATUS 0x0001000A	/* netfs mount status */
  
  struct vfsquery {
  	u_int32_t	vq_flags;
  	u_int32_t	vq_spare[31];
  };
  
  struct vfs_server {
       int32_t  vs_minutes;                       /* minutes until server goes down. */
       u_int8_t vs_server_name[MAXHOSTNAMELEN*3]; /* UTF8 server name to display (null terminated) */
  };
  
  /*
   * NetFS mount status - returned by VFS_CTL_NSTATUS
   */
  struct netfs_status {
  	u_int32_t	ns_status;		// Current status of mount (vfsquery flags)
  	char		ns_mountopts[512];	// Significant mount options
  	uint32_t	ns_waittime;		// Time waiting for reply (sec)
  	uint32_t	ns_threadcount;		// Number of threads blocked on network calls
  	uint64_t	ns_threadids[0];	// Thread IDs of those blocked threads
  };
  
  /* vfsquery flags */
  #define VQ_NOTRESP	0x0001	/* server down */
  #define VQ_NEEDAUTH	0x0002	/* server bad auth */
  #define VQ_LOWDISK	0x0004	/* we're low on space */
  #define VQ_MOUNT	0x0008	/* new filesystem arrived */
  #define VQ_UNMOUNT	0x0010	/* filesystem has left */
  #define VQ_DEAD		0x0020	/* filesystem is dead, needs force unmount */
  #define VQ_ASSIST	0x0040	/* filesystem needs assistance from external program */
  #define VQ_NOTRESPLOCK	0x0080	/* server lockd down */
  #define VQ_UPDATE	0x0100	/* filesystem information has changed */
  #define VQ_VERYLOWDISK	0x0200	/* file system has *very* little disk space left */
  #define VQ_SYNCEVENT	0x0400	/* a sync just happened (not set by kernel starting Mac OS X 10.9) */
  #define VQ_SERVEREVENT  0x0800  /* server issued notification/warning */
  #define VQ_FLAG1000	0x1000	/* placeholder */
  #define VQ_FLAG2000	0x2000	/* placeholder */
  #define VQ_FLAG4000	0x4000	/* placeholder */
  #define VQ_FLAG8000	0x8000	/* placeholder */
  
  
  
  /* Structure for setting device IO parameters per mount point */
  struct vfsioattr {
  	u_int32_t	io_maxreadcnt;		/* Max. byte count for read */
  	u_int32_t	io_maxwritecnt;		/* Max. byte count for write */
  	u_int32_t	io_segreadcnt;		/* Max. segment count for read */
  	u_int32_t	io_segwritecnt;		/* Max. segment count for write */
  	u_int32_t	io_maxsegreadsize;	/* Max. segment read size  */
  	u_int32_t	io_maxsegwritesize;	/* Max. segment write size */
  	u_int32_t	io_devblocksize;	/* the underlying device block size */
  	u_int32_t	io_flags;			/* flags for underlying device */
  	void *		io_reserved[2];		/* extended attribute information */
  };
  
  #define VFS_IOATTR_FLAGS_FUA	0x01	/* Write-through cache supported */
  #define VFS_IOATTR_FLAGS_UNMAP		0x02	/* Unmap (trim) supported */
  
  /*
   * Filesystem Registration information
   */
  #define VFS_TBLTHREADSAFE		0x0001	/* Only threadsafe filesystems are supported */
  #define VFS_TBLFSNODELOCK		0x0002	/* Only threadsafe filesystems are supported */
  #define VFS_TBLNOTYPENUM		0x0008
  #define VFS_TBLLOCALVOL			0x0010
  #define VFS_TBL64BITREADY		0x0020
  #define VFS_TBLNATIVEXATTR		0x0040
  #define VFS_TBLDIRLINKS			0x0080
  #define VFS_TBLUNMOUNT_PREFLIGHT	0x0100	/* does a preflight check before unmounting */
  #define VFS_TBLGENERICMNTARGS		0x0200  /* force generic mount args for local fs */
  #define VFS_TBLREADDIR_EXTENDED		0x0400  /* fs supports VNODE_READDIR_EXTENDED */
  #define	VFS_TBLNOMACLABEL		0x1000
  #define VFS_TBLVNOP_PAGEINV2		0x2000
  #define VFS_TBLVNOP_PAGEOUTV2		0x4000
  #define VFS_TBLVNOP_NOUPDATEID_RENAME	0x8000	/* vfs should not call vnode_update_ident on rename */
  #if CONFIG_SECLUDED_RENAME
  #define	VFS_TBLVNOP_SECLUDE_RENAME 	0x10000
  #endif
  
  
  struct vfs_fsentry {
  	struct vfsops * vfe_vfsops;	/* vfs operations */
  	int		vfe_vopcnt;	/* # of vnodeopv_desc being registered (reg, spec, fifo ...) */
  	struct vnodeopv_desc ** vfe_opvdescs; /* null terminated;  */
  	int			vfe_fstypenum;	/* historic filesystem type number */
  	char		vfe_fsname[MFSNAMELEN];	/* filesystem type name */
  	uint32_t	vfe_flags;		/* defines the FS capabilities */
      void *		vfe_reserv[2];	/* reserved for future use; set this to zero*/
   };
  
  
  
  struct vfsops {
  	/*!
  	 @function vfs_mount
  	 @abstract Perform filesystem-specific operations required for mounting.
  	 @discussion Typical operations include setting the mount-specific data with vfs_setfsprivate().
  	 Note that if a mount call fails, the filesystem must clean up any state it has constructed, because
  	 vfs-level mount code will not clean it up.  
  	 @param mp Mount structure for the newly mounted filesystem.
  	 @param devvp Device that the filesystem is mounted from.
  	 @param data Filesystem-specific data passed down from userspace.
  	 @param context Context to authenticate for mount.
  	 @return 0 for success, else an error code.  Once success is returned, the filesystem should be ready to go active;
  	 VFS will not ask again.
  	 */
  	int  (*vfs_mount)(struct mount *mp, vnode_t devvp, user_addr_t data, vfs_context_t context);
  	
  	/*!
  	 @function vfs_start
  	 @abstract Mark a mount as ready to be used.
  	 @discussion After receiving this calldown, a filesystem will be hooked into the mount list and should expect 
  	 calls down from the VFS layer.  
  	 @param mp Mount structure being activated.
  	 @param flags Unused.
  	 @param context Context to authenticate for mount.
  	 @return Return value is ignored.
  	 */
  	int  (*vfs_start)(struct mount *mp, int flags, vfs_context_t context);
  	
  	/*!
  	 @function vfs_unmount
  	 @abstract Perform filesystem-specific cleanup as part of unmount.
  	 @discussion If the unmount downcall succeeds, VFS considers itself authorized to destroy all
  	 state related to the mount.
  	 @param mp Mount structure to unmount.
  	 @param mntflags MNT_FORCE indicates that we wish to unmount even if there are active vnodes.
  	 @param context Context to authenticate for unmount.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_unmount)(struct mount *mp, int mntflags, vfs_context_t context);
  	
  	/*!
  	 @function vfs_root
  	 @abstract Get the root vnode of a filesystem.
  	 @discussion Upon success, should return with an iocount held on the root vnode which the caller will
  	 drop with vnode_put().
  	 @param mp Mount for which to get the root.
  	 @param vpp Destination for root vnode.
  	 @param context Context to authenticate for getting the root.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_root)(struct mount *mp, struct vnode **vpp, vfs_context_t context);
  	
  	/*!
  	 @function vfs_quotactl
  	 @abstract Manipulate quotas for a volume.
  	 @param mp Mount for which to manipulate quotas.
  	 @param cmds Detailed in "quotactl" manual page. 	 
  	 @param uid Detailed in "quotactl" manual page.
  	 @param arg Detailed in "quotactl" manual page.
  	 @param context Context to authenticate for changing quotas.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_quotactl)(struct mount *mp, int cmds, uid_t uid, caddr_t arg, vfs_context_t context);
  
  	/*!
  	 @function vfs_getattr
  	 @abstract Get filesystem attributes.
  	 @discussion See VFSATTR_RETURN, VFSATTR_ACTIVE, VFSATTR_SET_SUPPORTED, VFSATTR_WANTED macros.
  	 @param mp Mount for which to get parameters.
  	 @param vfa Container for specifying which attributes are desired and which attributes the filesystem
  	 supports, as well as for returning results.
  	 @param ctx Context to authenticate for getting filesystem attributes.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_getattr)(struct mount *mp, struct vfs_attr *, vfs_context_t context);
  /*	int  (*vfs_statfs)(struct mount *mp, struct vfsstatfs *sbp, vfs_context_t context);*/
  
  	/*!
  	 @function vfs_sync
  	 @abstract Flush all filesystem data to backing store.
  	 @discussion vfs_sync will be called as part of the sync() system call and during unmount.
  	 @param mp Mountpoint to sync.
  	 @param waitfor MNT_WAIT: flush synchronously, waiting for all data to be written before returning. MNT_NOWAIT: start I/O but do not wait for it.
  	 @param ctx Context to authenticate for the sync.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_sync)(struct mount *mp, int waitfor, vfs_context_t context);
  	
  	/*!
  	 @function vfs_vget
  	 @abstract Get a vnode by file id (inode number).
  	 @discussion This routine is chiefly used to build paths to vnodes.  Result should be turned with an iocount that the 
  	 caller will drop with vnode_put().
  	 @param mp Mount against which to look up inode number.
  	 @param ino File ID for desired file, as found through a readdir.
  	 @param vpp Destination for vnode.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_vget)(struct mount *mp, ino64_t ino, struct vnode **vpp, vfs_context_t context);
  	
  	/*!
  	 @function vfs_fhtovp
  	 @abstract Get the vnode corresponding to a file handle.
  	 @discussion Filesystems can return handles to files which are independent of their (transient) vnode identities.
  	 vfs_thtovp converts that persistent handle back to a vnode.  The vnode should be returned with an iocount which 
  	 the caller will drop with vnode_put().
  	 @param mp Mount against which to look up file handle.
  	 @param fhlen Size of file handle structure, as returned by vfs_vptofh.
  	 @param fhp Pointer to handle.
  	 @param vpp Destination for vnode.
  	 @param ctx Context against which to authenticate the file-handle conversion.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_fhtovp)(struct mount *mp, int fhlen, unsigned char *fhp, struct vnode **vpp,
  	                   vfs_context_t context);
  
  	/*!
  	 @function vfs_vptofh
  	 @abstract Get a persistent handle corresponding to a vnode.
  	 @param mp Mount against which to convert the vnode to a handle.
  	 @param fhlen Size of buffer provided for handle; set to size of actual handle returned.
  	 @param fhp Pointer to buffer in which to place handle data.
  	 @param ctx Context against which to authenticate the file-handle request.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_vptofh)(struct vnode *vp, int *fhlen, unsigned char *fhp, vfs_context_t context);
  
  	/*!
  	 @function vfs_init
  	 @abstract Prepare a filesystem for having instances mounted.
  	 @discussion This routine is called once, before any particular instance of a filesystem
  	 is mounted; it allows the filesystem to initialize whatever global data structures
  	 are shared across all mounts.  If this returns successfully, a filesystem should be ready to have
  	 instances mounted.
  	 @param vfsconf Configuration information.  Currently, the only useful data are the filesystem name,
  	 typenum, and flags.  The flags field will be either 0 or MNT_LOCAL.  Many filesystems ignore this
  	 parameter.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_init)(struct vfsconf *);
  	
  	/*!
  	 @function vfs_sysctl
  	 @abstract Broad interface for querying and controlling filesystem.
  	 @discussion VFS defines VFS_CTL_QUERY as a generic status request which is answered
  	 with the VQ_* macros in a "struct vfsquery."
  	 A filesystem may also define implementation-specific commands.  See "man 3 sysctl" 
  	 for the meaning of sysctl parameters.
  	 @param context Context against which to authenticate command.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_sysctl)(int *, u_int, user_addr_t, size_t *, user_addr_t, size_t, vfs_context_t context);
  
  	/*!
  	 @function vfs_setattr
  	 @abstract Set filesystem attributes.
  	 @discussion The other side of the vfs_getattr coin.  Currently only called to set volume name.
  	 @param mp Mount on which to set attributes.
  	 @param vfa VFS attribute structure containing requested attributes to set and their values.  Currently
  	 will only be called with f_vol_name set.
  	 @param context Context against which to authenticate attribute change.
  	 @return 0 for success, else an error code.  
  	 */
  	int  (*vfs_setattr)(struct mount *mp, struct vfs_attr *, vfs_context_t context);
  	void *vfs_reserved[7];
  };
  
  
  /*
   * flags passed into vfs_iterate
   */
  
  /*
   * return values from callback
   */
  #define VFS_RETURNED		0	/* done with vnode, reference can be dropped */
  #define VFS_RETURNED_DONE	1	/* done with vnode, reference can be dropped, terminate iteration */
  #define VFS_CLAIMED		2	/* don't drop reference */
  #define VFS_CLAIMED_DONE	3	/* don't drop reference, terminate iteration */
  
  
  __BEGIN_DECLS
  /*
   * prototypes for exported VFS operations
   */
  
  /*!
    @function vfs_fsadd
    @abstract Register a filesystem with VFS.
    @discussion Typically called by a filesystem Kernel Extension when it is loaded.
    @param vfe Filesystem information: table of vfs operations, list of vnode operation tables, 
    filesystem type number (can be omitted with VFS_TBLNOTYPENUM flag), name, flags.
    @param handle Opaque handle which will be passed to vfs_fsremove.
    @return 0 for success, else an error code.  
    */
  int vfs_fsadd(struct vfs_fsentry *, vfstable_t *);
  
  /*!
    @function vfs_fsremove
    @abstract Unregister a filesystem with VFS.
    @discussion Typically called by a filesystem Kernel Extension when it is unloaded.
    @param handle Handle which was returned by vfs_fsadd.
    @return 0 for success, else an error code.  
    */
  int vfs_fsremove(vfstable_t);
  
  /*!
    @function vfs_iterate
    @abstract Iterate over all mountpoints with a callback.  Used, for example, by sync().
    @param flags Unused.
    @param callback Function which takes a mount and arbitrary passed-in "arg," and returns one of VFS_RETURNED_DONE or VFS_CLAIMED_DONE: end
    iteration and return success.  VFS_RETURNED or VFS_CLAIMED: continue iterating. Anything else: continue iterating. 
    @param arg Arbitrary data to pass to callback.
    @return 0 for success, else an error code.  
    */
  int	vfs_iterate(int, int (*)(struct mount *, void *), void *);
  
  /*!
    @function vfs_init_io_attributes
    @abstract Set I/O attributes on a mountpoint based on device properties.
    @param devvp Block device vnode from which a filesystem is being mounted.
    @param mp Mountpoint whose I/O parameters to initialize.
    @return 0 for success, else an error code.  
    */
  int	vfs_init_io_attributes(vnode_t, mount_t);
  
  /*!
    @function vfs_flags
    @abstract Retrieve mount flags.
    @discussion Results will be in the bitwise "OR" of MNT_VISFLAGMASK and MNT_CMDFLAGS.
    @param mp Mount whose flags to grab.  
    @return Flags.
    */
  uint64_t vfs_flags(mount_t);
  
  /*!
    @function vfs_setflags
    @abstract Set flags on a mount.
    @discussion Sets mount flags to the bitwise "OR" of their current value and the specified bits. Often 
    used by a filesystem as part of the mount process.
    @param mp Mount whose flags to set.
    @param flags Flags to activate.  Must be in the bitwise "OR" of MNT_VISFLAGMASK and MNT_CMDFLAGS.
    @return Flags.
    */
  void	vfs_setflags(mount_t, uint64_t);
  
  /*!
    @function vfs_clearflags
    @abstract Clear flags on a mount.
    @discussion Sets mount flags to the bitwise "AND" of their current value and the complement of the specified bits.
    @param mp Mount whose flags to set.
    @param flags Flags to deactivate.  Must be in the bitwise "OR" of MNT_VISFLAGMASK and MNT_CMDFLAGS.
    @return void.
    */
  void	vfs_clearflags(mount_t, uint64_t);
  
  /*!
    @function vfs_issynchronous
    @abstract Determine if writes to a filesystem occur synchronously.
    @param mp Mount to test.
    @return Nonzero if writes occur synchronously, else 0.
    */
  int	vfs_issynchronous(mount_t);
  
  /*!
    @function vfs_iswriteupgrade
    @abstract Determine if a filesystem is mounted read-only but a request has been made to upgrade
    to read-write.
    @param mp Mount to test.
    @return Nonzero if a request has been made to update from read-only to read-write, else 0.
    */
  int	vfs_iswriteupgrade(mount_t);
  
  /*!
    @function vfs_isupdate
    @abstract Determine if a mount update is in progress.
    @param mp Mount to test.
    @return Nonzero if a mount update is in progress, 0 otherwise.
    */
  int	vfs_isupdate(mount_t); 
  
  /*!
    @function vfs_isreload
    @abstract Determine if a reload of filesystem data is in progress.  This can only be the case
    for a read-only filesystem; all data is brought in from secondary storage.
    @param mp Mount to test.
    @return Nonzero if a request has been made to reload data, else 0.
    */
  int	vfs_isreload(mount_t);
  
  /*!
    @function vfs_isforce
    @abstract Determine if a forced unmount is in progress.
    @discussion A forced unmount invalidates open files.
    @param mp Mount to test.
    @return Nonzero if a request has been made to forcibly unmount, else 0.
    */
  int	vfs_isforce(mount_t);
  
  /*!
    @function vfs_isunmount
    @abstract Determine if an unmount is in progress.
    @discussion This is an unsynchronized snapshot of the mount state.  It should only be called
    if the mount is known to be valid, e.g. there are known to be live files on that volume.
    @param mp Mount to test.
    @return Nonzero if an unmount is in progress, else zero.
    */
  int 	vfs_isunmount(mount_t mp);
  
  /*!
    @function vfs_isrdonly
    @abstract Determine if a filesystem is mounted read-only.
    @param mp Mount to test.
    @return Nonzero if filesystem is mounted read-only, else 0.
    */
  int	vfs_isrdonly(mount_t);
  
  /*!
    @function vfs_isrdwr
    @abstract Determine if a filesystem is mounted with writes enabled.
    @param mp Mount to test.
    @return Nonzero if filesystem is mounted read-write, else 0.
    */
  int	vfs_isrdwr(mount_t);
  
  /*!
    @function vfs_authopaque
    @abstract Determine if a filesystem's authorization decisions occur remotely.
    @param mp Mount to test.
    @return Nonzero if filesystem authorization is controlled remotely, else 0.
    */
  int	vfs_authopaque(mount_t);
  
  /*!
    @function vfs_authopaqueaccess
    @abstract Check if a filesystem is marked as having reliable remote VNOP_ACCESS support.
    @param mp Mount to test.
    @return Nonzero if VNOP_ACCESS is supported remotely, else 0.
    */
  int	vfs_authopaqueaccess(mount_t);
  
  /*!
    @function vfs_setauthopaque
    @abstract Mark a filesystem as having authorization decisions controlled remotely.
    @param mp Mount to mark.
    @return void.
    */
  void	vfs_setauthopaque(mount_t);
  
  /*!
    @function vfs_setauthopaqueaccess
    @abstract Mark a filesystem as having remote VNOP_ACCESS support.
    @param mp Mount to mark.
    @return void.
    */
  void	vfs_setauthopaqueaccess(mount_t);
  
  /*!
    @function vfs_clearauthopaque
    @abstract Mark a filesystem as not having remote authorization decisions.
    @param mp Mount to mark.
    @return void.
    */
  void	vfs_clearauthopaque(mount_t);
  
  /*!
    @function vfs_clearauthopaque
    @abstract Mark a filesystem as not having remote VNOP_ACCESS support.
    @param mp Mount to mark.
    @return void.
    */
  void	vfs_clearauthopaqueaccess(mount_t);
  
  /*!
    @function vfs_setextendedsecurity
    @abstract Mark a filesystem as supporting security controls beyond POSIX permissions.
    @discussion Specific controls include ACLs, file owner UUIDs, and group UUIDs.
    @param mp Mount to test.
    @return void.
    */
  void	vfs_setextendedsecurity(mount_t);
  
  /*!
    @function vfs_clearextendedsecurity
    @abstract Mark a filesystem as NOT supporting security controls beyond POSIX permissions.
    @discussion Specific controls include ACLs, file owner UUIDs, and group UUIDs.
    @param mp Mount to test.
    @return void.
    */
  void	vfs_clearextendedsecurity(mount_t);
  
  /*!
    @function vfs_setlocklocal
    @abstract Mark a filesystem as using VFS-level advisory locking support.
    @discussion Advisory locking operations will not call down to the filesystem if this flag is set.
    @param mp Mount to mark.
    @return void.
    */
  void	vfs_setlocklocal(mount_t);
  
  /*!
    @function vfs_authcache_ttl
    @abstract Determine the time-to-live of cached authorized credentials for files in this filesystem.
    @discussion If a filesystem is set to allow caching credentials, the VFS layer can authorize
    previously-authorized actions from the same vfs_context_t without calling down to the filesystem (though
    it will not deny based on the cache).
    @param mp Mount for which to check cache lifetime.
    @return  Cache lifetime in seconds.  CACHED_RIGHT_INFINITE_TTL indicates that credentials never expire.
    */
  int	vfs_authcache_ttl(mount_t);
  
  /*!
    @function vfs_setauthcache_ttl
    @abstract Enable credential caching and set  time-to-live of cached authorized credentials for files in this filesystem.
    @discussion If a filesystem is set to allow caching credentials, the VFS layer can authorize
    previously-authorized actions from the same vfs_context_t without calling down to the filesystem (though
    it will not deny based on the cache).
    @param mp Mount for which to set cache lifetime.
    @return void.
    */
  void	vfs_setauthcache_ttl(mount_t, int);
  
  /*!
    @function vfs_clearauthcache_ttl
    @abstract Remove time-to-live controls for cached credentials on a filesytem.  Filesystems with remote authorization
    decisions (opaque) will still have KAUTH_VNODE_SEARCH rights cached for a default of CACHED_LOOKUP_RIGHT_TTL seconds.
    @param mp Mount for which to clear cache lifetime.
    @return void.
    */
  void	vfs_clearauthcache_ttl(mount_t);
  
  /*
   * return value from vfs_cachedrights_ttl if
   * neither MNTK_AUTH_OPAQUE | MNTK_AUTH_CACHE_TTL
   * is set in mnt_kern_flag.. it indicates
   * that no TTL is being applied to the vnode rights cache
   */
  #define CACHED_RIGHT_INFINITE_TTL	~0
  
  /*!
    @function vfs_maxsymlen
    @abstract Get the maximum length of a symbolic link on a filesystem.
    @param mp Mount from which to get symlink length cap.
    @return Max symlink length.
    */
  uint32_t vfs_maxsymlen(mount_t);
  
  /*!
    @function vfs_setmaxsymlen
    @abstract Set the maximum length of a symbolic link on a filesystem.
    @param mp Mount on which to set symlink length cap.
    @param symlen Length to set.
    @return Max symlink length.
    */
  void	vfs_setmaxsymlen(mount_t, uint32_t);
  
  /*!
    @function vfs_fsprivate
    @abstract Get filesystem-private mount data.
    @discussion A filesystem generally has an internal mount structure which it attaches to the VFS-level mount structure
    as part of the mounting process.
    @param mp Mount for which to get private data.
    @return Private data.
    */
  void *	vfs_fsprivate(mount_t);
  
  /*!
    @function vfs_setfsprivate
    @abstract Set filesystem-private mount data.
    @discussion A filesystem generally has an internal mount structure which it attaches to the VFS-level mount structure
    as part of the mounting process.
    @param mp Mount for which to set private data.
    @return Void.
    */
  void	vfs_setfsprivate(mount_t, void *mntdata);
  
  /*!
    @function vfs_statfs
    @abstract Get information about filesystem status.
    @discussion Each filesystem has a struct vfsstatfs associated with it which is updated as events occur; this function
    returns a pointer to it.  Note that the data in the structure will continue to change over time and also that it may
    be quite stale of vfs_update_vfsstat has not been called recently.
    @param mp Mount for which to get vfsstatfs pointer.
    @return Pointer to vfsstatfs.
    */
  struct vfsstatfs *	vfs_statfs(mount_t);
  #define	VFS_USER_EVENT		0
  #define	VFS_KERNEL_EVENT	1
  
  /*!
    @function vfs_update_vfsstat
    @abstract Update cached filesystem status information in the VFS mount structure.
    @discussion Each filesystem has a struct vfsstatfs associated with it which is updated as events occur; this function
    updates it so that the structure pointer returned by vfs_statfs() returns a pointer to fairly recent data.
    @param mp Mount for which to update cached status information.
    @param ctx Context to authenticate against for call down to filesystem.
    @param eventtype VFS_USER_EVENT: need for update is driven by user-level request; perform additional authentication.
    VFS_KERNEL_EVENT: need for update is driven by in-kernel events.  Skip extra authentication.
    @return 0 for success, or an error code for authentication failure or problem with call to filesystem to 
    request information.
    */
  int	vfs_update_vfsstat(mount_t, vfs_context_t, int eventtype);
  
  /*!
    @function vfs_typenum
    @abstract Get (archaic) filesystem type number.
    @discussion Filesystem type numbers are an old construct; most filesystems just get a number assigned based on 
    the order in which they are registered with the system.
    @param mp Mount for which to get type number.
    @return Type number.
    */
  int	vfs_typenum(mount_t);
  
  /*!
    @function vfs_name
    @abstract Copy filesystem name into a buffer.
    @discussion Get filesystem name; this refers to the filesystem type of which a mount is an instantiation,
    rather than a name specific to the mountpoint.
    @param mp Mount for which to get name.
    @param buffer Destination for name; length should be at least MFSNAMELEN.
    @return void.
    */
  void	vfs_name(mount_t, char *);
  
  /*!
    @function vfs_devblocksize
    @abstract Get the block size of the device underlying a mount.
    @param mp Mount for which to get block size.
    @return Block size.
    */
  int	vfs_devblocksize(mount_t);
  
  /*!
    @function vfs_ioattr
    @abstract Get I/O attributes associated with a mounpoint.
    @param mp Mount for which to get attributes.  If NULL, system defaults are filled into ioattrp.
    @param ioattrp Destination for results.
    @return void.
    */
  void	vfs_ioattr(mount_t, struct vfsioattr *);
  
  /*!
    @function vfs_setioattr
    @abstract Set I/O attributes associated with a mounpoint.
    @param mp Mount for which to set attributes.  
    @param ioattrp Structure containing I/O parameters; all fields must be filled in.
    @return void.
    */
  void	vfs_setioattr(mount_t, struct vfsioattr *);
  
  /*!
    @function vfs_64bitready
    @abstract Check if the filesystem associated with a mountpoint is marked ready for interaction with 64-bit user processes.
    @param mp Mount to test.
    @return Nonzero if filesystem is ready for 64-bit; 0 otherwise.
    */
  int 	vfs_64bitready(mount_t);
  
  
  #define LK_NOWAIT 1
  /*!
    @function vfs_busy
    @abstract "Busy" a mountpoint.
    @discussion vfs_busy() will "busy" a mountpoint, preventing unmounts from taking off, by taking its reader-writer lock 
    in a shared manner.  If a mount is dead,
    it will fail; if an unmount is in progress, depending on flags, it will either fail immediately or block
    until the unmount completes (then failing if the unmount has succeeded, or potentially succeeding if unmounting failed).
    A successful vfs_busy() must be followed by a vfs_unbusy() to release the lock on the mount.
    @param mp Mount to busy.
    @param flags LK_NOWAIT: fail with ENOENT if an unmount is in progress.
    @return 0 for success, with a lock held; an error code otherwise, with no lock held.
    */
  int	vfs_busy(mount_t, int);
  
  /*!
    @function vfs_unbusy
    @abstract "Unbusy" a mountpoint by releasing its read-write lock.
    @discussion A successful vfs_busy() must be followed by a vfs_unbusy() to release the lock on the mount.
    @param mp Mount to unbusy.
    @return void.
    */
  void	vfs_unbusy(mount_t);
  
  /*!
    @function vfs_getnewfsid
    @abstract Generate a unique filesystem ID for a mount and store it in the mount structure.
    @discussion Filesystem IDs are returned as part of "struct statfs."  This function is typically
    called as part of file-system specific mount code (i.e. through VFS_MOUNT).
    @param mp Mount to set an ID for.
    @return void.
    */
  void	vfs_getnewfsid(struct mount *);
  
  /*!
    @function vfs_getvfs
    @abstract Given a filesystem ID, look up a mount structure.
    @param fsid Filesystem ID to look up.
    @return Mountpoint if found, else NULL.  Note unmounting mountpoints can be returned.
    */
  mount_t	vfs_getvfs(fsid_t *);
  
  /*!
    @function vfs_mountedon
    @abstract Check whether a given block device has a filesystem mounted on it.
    @discussion Note that this is NOT a check for a covered vnode (the directory upon which 
    a filesystem is mounted)--it is a test for whether a block device is being used as the source
    of a filesystem.  Note that a block device marked as being mounted on cannot be opened.
    @param vp The vnode to test.
    @return EBUSY if vnode is indeed the source of a filesystem; 0 if it is not.
    */
  int	vfs_mountedon(struct vnode *);
  
  /*!
    @function vfs_unmountbyfsid
    @abstract Find a filesystem by ID and unmount it.
    @param fsid ID of filesystem to unmount, as found through (for example) statfs.
    @param flags MNT_FORCE: forcibly invalidate files open on the mount (though in-flight I/O operations 
    will be allowed to complete).
    @param ctx Context against which to authenticate unmount operation.
    @return 0 for succcess, nonero for failure.
    */
  int	vfs_unmountbyfsid(fsid_t *, int, vfs_context_t);
  
  /*!
    @function vfs_event_signal
    @abstract Post a kqueue-style event on a filesystem (EVFILT_FS).
    @param fsid Unused.
    @param event Events to post.
    @param data Unused.
    @return void.
    */
  void	vfs_event_signal(fsid_t *, u_int32_t, intptr_t);
  /*!
    @function vfs_event_init
    @abstract This function should not be called by kexts.
    */
  void	vfs_event_init(void); /* XXX We should not export this */
  __END_DECLS
  
  
  #endif /* !_SYS_MOUNT_H_ */
  