.\" 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: src/share/man/man9/vnode.9,v 1.10.2.5 2001/12/17 11:30:19 ru Exp $ .\" .Dd May 5, 2007 .Dt VNODE 9 .Os .Sh NAME .Nm vnode .Nd internal representation of a file, directory, or other VFS entity .Sh SYNOPSIS .In sys/param.h .In sys/vnode.h .Sh DESCRIPTION The vnode is the focus of all file activity in .Ux . The .Nm is described by .Vt "struct vnode" . 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 numerous reference counts, .Fa v_sysref , .Fa v_auxrefs , .Fa v_opencount , and .Fa v_writecount . .Pp .Fa v_sysref represents the number of primary references to the vnode. It is actually a structure which utilizes the SYSREF API and also manages allocation and deallocation of the vnode. Primary references keep a vnode ready for I/O and prevent it from being deactivated. Primary references are managed by .Xr vref 9 and .Xr vrele 9 . .Pp .Fa v_auxrefs represents the number of auxiliary references to a vnode. Auxiliary references prevent a vnode from being reclaimed (if not already being reclaimed), reused for other purposes, or otherwise destroyed, but do not activate or deactivate the vnode. Auxiliary references are managed by .Xr vhold 9 and .Xr vdrop 9 . .Pp .Fa v_opencount represents the number of discrete .Fn open calls made on the vnode (reading or writing). .Fa v_writecount represents the number of discrete .Fn open calls made on the vnode for the purpose of writing. This field will be a subset of .Fa v_opencount . These fields are managed primarily by calls to .Xr vn_open 9 and .Xr vn_close 9 . .Pp A deactivated vnode or a vnode in an unknown state accessed from an Auxiliary data structure can be reactivated, referenced, and locked using .Xr vget 9 and .Xr vput 9 . .Pp An actively referenced and possibly locked vnode must be passed to most kernel procedures taking a vnode as an argument. Most kernel procedures returning a vnode will return one that is actively referenced. .Pp Other commonly used members of the vnode structure are .Fa v_mount which points at the filesystem which owns the vnode, .Fa v_type which contains the type of object the vnode represents and .Fa v_data which is used by filesystems to store filesystem specific data with the vnode. The .Fa v_ops 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 ".Dv 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 IMPLEMENTATION NOTES .Dv VFIFO uses the .Vt struct fileops from .Pa /sys/kern/sys_pipe.c . .Dv VSOCK uses the .Vt 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 .Vt 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 manual page was written by .An Doug Rabson .