.\" -*- nroff -*-
.\"
.\" Copyright (c) 1996 Doug Rabson
.\"
.\" All rights reserved.
.\"
.\" This program is free software.
.\"
.\" 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 DEVELOPERS ``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 DEVELOPERS 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.
.\"
.\" $FreeBSD$
.\"
.Dd June 30, 1999
.Os
.Dt VNODE 9
.Sh NAME
.Nm vnode
.Nd internal representation of a file or directory
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Pp
.Bd -literal
/*
* Vnode types. VNON means no type.
*/
enum vtype { VNON, VREG, VDIR, VBLK, VCHR, VLNK, VSOCK, VFIFO, VBAD };
/*
* Vnode tag types.
* These are for the benefit of external programs only (e.g., pstat)
* and should NEVER be inspected by the kernel.
*/
enum vtagtype {
VT_NON, VT_UFS, VT_NFS, VT_UNUSED, VT_PC, VT_LFS, VT_LOFS, VT_FDESC,
VT_PORTAL, VT_NULL, VT_UMAP, VT_KERNFS, VT_PROCFS, VT_AFS, VT_ISOFS,
VT_UNION, VT_MSDOSFS, VT_DEVFS, VT_TFS, VT_VFS, VT_CODA, VT_NTFS,
VT_HPFS, VT_NWFS, VT_PSEUDOFS
};
/*
* Each underlying filesystem allocates its own private area and hangs
* it from v_data. If non-null, this area is freed in getnewvnode().
*/
TAILQ_HEAD(buflists, buf);
typedef int vop_t __P((void *));
struct namecache;
/*
* Reading or writing any of these items requires holding the appropriate lock.
* v_freelist is locked by the global vnode_free_list simple lock.
* v_mntvnodes is locked by the global mntvnodes simple lock.
* v_flag, v_usecount, v_holdcount and v_writecount are
* locked by the v_interlock simple lock.
* v_pollinfo is locked by the lock contained inside it.
*/
struct vnode {
u_long v_flag; /* vnode flags (see below) */
int v_usecount; /* reference count of users */
int v_writecount; /* reference count of writers */
int v_holdcnt; /* page & buffer references */
u_long v_id; /* capability identifier */
struct mount *v_mount; /* ptr to vfs we are in */
vop_t **v_op; /* vnode operations vector */
TAILQ_ENTRY(vnode) v_freelist; /* vnode freelist */
LIST_ENTRY(vnode) v_mntvnodes; /* vnodes for mount point */
struct buflists v_cleanblkhd; /* clean blocklist head */
struct buflists v_dirtyblkhd; /* dirty blocklist head */
LIST_ENTRY(vnode) v_synclist; /* vnodes with dirty buffers */
long v_numoutput; /* num of writes in progress */
enum vtype v_type; /* vnode type */
union {
struct mount *vu_mountedhere;/* ptr to mounted vfs (VDIR) */
struct socket *vu_socket; /* unix ipc (VSOCK) */
struct {
struct specinfo *vu_specinfo; /* device (VCHR, VBLK) */
SLIST_ENTRY(vnode) vu_specnext;
} vu_spec;
struct fifoinfo *vu_fifoinfo; /* fifo (VFIFO) */
} v_un;
struct nqlease *v_lease; /* Soft reference to lease */
daddr_t v_lastw; /* last write (write cluster) */
daddr_t v_cstart; /* start block of cluster */
daddr_t v_lasta; /* last allocation */
int v_clen; /* length of current cluster */
struct vm_object *v_object; /* Place to store VM object */
struct simplelock v_interlock; /* lock on usecount and flag */
struct lock *v_vnlock; /* used for non-locking fs's */
enum vtagtype v_tag; /* type of underlying data */
void *v_data; /* private data for fs */
LIST_HEAD(, namecache) v_cache_src; /* Cache entries from us */
TAILQ_HEAD(, namecache) v_cache_dst; /* Cache entries to us */
struct vnode *v_dd; /* .. vnode */
u_long v_ddid; /* .. capability identifier */
struct {
struct simplelock vpi_lock; /* lock to protect below */
struct selinfo vpi_selinfo; /* identity of poller(s) */
short vpi_events; /* what they are looking for */
short vpi_revents; /* what has happened */
} v_pollinfo;
};
#define v_mountedhere v_un.vu_mountedhere
#define v_socket v_un.vu_socket
#define v_rdev v_un.vu_spec.vu_specinfo
#define v_specnext v_un.vu_spec.vu_specnext
#define v_fifoinfo v_un.vu_fifoinfo
/*
* Vnode flags.
*/
#define VROOT 0x00001 /* root of its filesystem */
#define VTEXT 0x00002 /* vnode is a pure text prototype */
#define VSYSTEM 0x00004 /* vnode being used by kernel */
#define VISTTY 0x00008 /* vnode represents a tty */
#define VXLOCK 0x00100 /* vnode is locked to change underlying type */
#define VXWANT 0x00200 /* process is waiting for vnode */
#define VBWAIT 0x00400 /* waiting for output to complete */
#define VOBJBUF 0x02000 /* Allocate buffers in VM object */
#define VAGE 0x08000 /* Insert vnode at head of free list */
#define VOLOCK 0x10000 /* vnode is locked waiting for an object */
#define VOWANT 0x20000 /* a process is waiting for VOLOCK */
#define VDOOMED 0x40000 /* This vnode is being recycled */
#define VFREE 0x80000 /* This vnode is on the freelist */
#define VTBFREE 0x100000 /* This vnode is on the to-be-freelist */
#define VONWORKLST 0x200000 /* On syncer work-list */
#define VMOUNT 0x400000 /* Mount in progress */
.Ed
.Sh DESCRIPTION
The vnode is the focus of all file activity in
.Ux .
There is a
unique vnode allocated for each active file, each current directory,
each mounted-on file, text file, and the root.
.Pp
Each vnode has three reference counts,
.Dv v_usecount ,
.Dv v_holdcnt
and
.Dv v_writecount .
The first is the number of clients within the kernel which are
using this vnode. This count is maintained by
.Xr vref 9 ,
.Xr vrele 9
and
.Xr vput 9 .
The second is the number of clients within the kernel who veto
the recycling of this vnode. This count is
maintained by
.Xr vhold 9
and
.Xr vdrop 9 .
When both the
.Dv v_usecount
and the
.Dv v_holdcnt
of a vnode reaches zero then the vnode will be put on the freelist
and may be reused for another file, possibly in another filesystem.
The transition to and from the freelist is handled by
.Xr getnewvnode 9 ,
.Xr vfree 9
and
.Xr vbusy 9 .
The third is a count of the number of clients which are writing into
the file. It is maintained by the
.Xr open 2
and
.Xr close 2
system calls.
.Pp
Any call which returns a vnode (e.g.\&
.Xr VFS_GET 9 ,
.Xr VOP_LOOKUP 9
etc.)
will increase the
.Dv v_usecount
of the vnode by one. When the caller is finished with the vnode, it
should release this reference by calling
.Xr vrele 9
(or
.Xr vput 9
if the vnode is locked).
.Pp
Other commonly used members of the vnode structure are
.Dv v_id
which is used to maintain consistency in the name cache,
.Dv v_mount
which points at the filesystem which owns the vnode,
.Dv v_type
which contains the type of object the vnode represents and
.Dv v_data
which is used by filesystems to store filesystem specific data with
the vnode.
The
.Dv v_op
field is used by the
.Dv VOP_*
macros to call functions in the filesystem which implement the vnode's
functionality.
.Sh VNODE TYPES
.Bl -tag -width VSOCK
.It Dv VNON
No type.
.It Dv VREG
A regular file; may be with or without VM object backing. If you want
to make sure this get a backing object, call
.Xr vfs_object_create 9 .
.It Dv VDIR
A directory.
.It Dv VBLK
A block device; may be with or without VM object backing. If you want
to make sure this get a backing object, call
.Xr vfs_object_create 9 .
.It Dv VCHR
A character device.
.It Dv VLNK
A symbolic link.
.It Dv VSOCK
A socket. Advisory locking won't work on this.
.It Dv VFIFO
A FIFO (named pipe). Advisory locking won't work on this.
.It Dv VBAD
An old style bad sector map
.El
.Sh NOTES
VFIFO uses the "struct fileops" from
.Pa /sys/kern/sys_pipe.c .
VSOCK uses the "struct fileops" from
.Pa /sys/kern/sys_socket.c .
Everything else uses the one from
.Pa /sys/kern/vfs_vnops.c .
.Pp
The VFIFO/VSOCK code, which is why "struct fileops" is used at all, is
an artifact of an incomplete integration of the VFS code into the
kernel.
.Sh SEE ALSO
.Xr VFS 9
.Sh AUTHORS
This man page was written by
.An Doug Rabson .
