258 lines
8.6 KiB
Groff
258 lines
8.6 KiB
Groff
.\" -*- 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 file system */
|
|
#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 UNIX. 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 .
|