1.\" -*- nroff -*- 2.\" 3.\" Copyright (c) 1996 Doug Rabson 4.\" 5.\" All rights reserved. 6.\" 7.\" This program is free software. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 19.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 22.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28.\" 29.\" $Id: vnode.9,v 1.4 1997/10/11 07:39:45 phk Exp $ 30.\" 31.Dd July 24, 1996 32.Os 33.Dt VNODE 9 34.Sh NAME 35.Nm vnode 36.Nd internal representation of a file or directory 37.Sh SYNOPSIS 38.Fd #include <sys/param.h> 39.Fd #include <sys/vnode.h> 40.Pp 41.Bd -literal 42/* 43 * Vnode types. VNON means no type. 44 */ 45enum vtype { VNON, VREG, VDIR, VBLK, VCHR, VLNK, VSOCK, VFIFO, VBAD }; 46 47/* 48 * Vnode tag types. 49 * These are for the benefit of external programs only (e.g., pstat) 50 * and should NEVER be inspected by the kernel. 51 */ 52enum vtagtype { 53 VT_NON, VT_UFS, VT_NFS, VT_MFS, VT_PC, VT_LFS, VT_LOFS, VT_FDESC, 54 VT_PORTAL, VT_NULL, VT_UMAP, VT_KERNFS, VT_PROCFS, VT_AFS, VT_ISOFS, 55 VT_UNION, VT_MSDOSFS, VT_DEVFS 56}; 57 58/* 59 * Each underlying filesystem allocates its own private area and hangs 60 * it from v_data. If non-null, this area is freed in getnewvnode(). 61 */ 62LIST_HEAD(buflists, buf); 63 64typedef int vop_t __P((void *)); 65 66struct vnode { 67 u_long v_flag; /* vnode flags (see below) */ 68 int v_usecount; /* reference count of users */ 69 int v_writecount; /* reference count of writers */ 70 int v_holdcnt; /* page & buffer references */ 71 daddr_t v_lastr; /* last read (read-ahead) */ 72 u_long v_id; /* capability identifier */ 73 struct mount *v_mount; /* ptr to vfs we are in */ 74 vop_t **v_op; /* vnode operations vector */ 75 TAILQ_ENTRY(vnode) v_freelist; /* vnode freelist */ 76 LIST_ENTRY(vnode) v_mntvnodes; /* vnodes for mount point */ 77 struct buflists v_cleanblkhd; /* clean blocklist head */ 78 struct buflists v_dirtyblkhd; /* dirty blocklist head */ 79 long v_numoutput; /* num of writes in progress */ 80 enum vtype v_type; /* vnode type */ 81 union { 82 struct mount *vu_mountedhere;/* ptr to mounted vfs (VDIR) */ 83 struct socket *vu_socket; /* unix ipc (VSOCK) */ 84 struct specinfo *vu_specinfo; /* device (VCHR, VBLK) */ 85 struct fifoinfo *vu_fifoinfo; /* fifo (VFIFO) */ 86 } v_un; 87 struct nqlease *v_lease; /* Soft reference to lease */ 88 daddr_t v_lastw; /* last write (write cluster) */ 89 daddr_t v_cstart; /* start block of cluster */ 90 daddr_t v_lasta; /* last allocation */ 91 int v_clen; /* length of current cluster */ 92 int v_ralen; /* Read-ahead length */ 93 int v_usage; /* Vnode usage counter */ 94 daddr_t v_maxra; /* last readahead block */ 95 void *v_object; /* Place to store VM object */ 96 enum vtagtype v_tag; /* type of underlying data */ 97 void *v_data; /* private data for fs */ 98}; 99#define v_mountedhere v_un.vu_mountedhere 100#define v_socket v_un.vu_socket 101#define v_specinfo v_un.vu_specinfo 102#define v_fifoinfo v_un.vu_fifoinfo 103 104/* 105 * Vnode flags. 106 */ 107#define VROOT 0x00001 /* root of its file system */ 108#define VTEXT 0x00002 /* vnode is a pure text prototype */ 109#define VSYSTEM 0x00004 /* vnode being used by kernel */ 110#define VOLOCK 0x00008 /* vnode is locked waiting for an object */ 111#define VOWANT 0x00010 /* a process is waiting for VOLOCK */ 112#define VXLOCK 0x00100 /* vnode is locked to change underlying type */ 113#define VXWANT 0x00200 /* process is waiting for vnode */ 114#define VBWAIT 0x00400 /* waiting for output to complete */ 115#define VALIASED 0x00800 /* vnode has an alias */ 116#define VDIROP 0x01000 /* LFS: vnode is involved in a directory op */ 117#define VVMIO 0x02000 /* VMIO flag */ 118#define VNINACT 0x04000 /* LFS: skip ufs_inactive() in lfs_vunref */ 119#define VAGE 0x08000 /* Insert vnode at head of free list */ 120#define VOLOCK 0x10000 /* vnode is locked waiting for an object */ 121#define VOWANT 0x20000 /* a process is waiting for VOLOCK */ 122#define VDOOMED 0x40000 /* This vnode is being recycled */ 123#define VFREE 0x80000 /* This vnode is on the freelist */ 124 125 126.Ed 127.Sh DESCRIPTION 128The vnode is the focus of all file activity in UNIX. There is a 129unique vnode allocated for each active file, each current directory, 130each mounted-on file, text file, and the root. 131.Pp 132Each vnode has three reference counts, 133.Dv v_usecount , 134.Dv v_holdcnt 135and 136.Dv v_writecount . 137The first is the number of clients within the kernel which are 138using this vnode. This count is maintained by 139.Xr vref 9 , 140.Xr vrele 9 141and 142.Xr vput 9 . 143The second is the number of clients within the kernel who veto 144the recycling of this vnode. This count is 145maintained by 146.Xr vhold 9 147and 148.Xr vdrop 9 . 149When both the 150.Dv v_usecount 151and the 152.Dv v_holdcnt 153of a vnode reaches zero then the vnode will be put on the freelist 154and may be reused for another file, possibly in another filesystem. 155The transition to and from the freelist is handled by 156.Xr getnetvnode 9 , 157.Xr vfree 9 158and 159.Xr vbusy 9 . 160The third is a count of the number of clients which are writing into 161the file. It is maintained by the 162.Xr open 2 163and 164.Xr close 2 165system calls. 166.Pp 167Any call which returns a vnode (e.g. 168.Xr VFS_GET 9 , 169.Xr VOP_LOOKUP 9 170etc.) 171will increase the 172.Dv v_usecount 173of the vnode by one. When the caller is finished with the vnode, it 174should release this reference by calling 175.Xr vrele 9 176(or 177.Xr vput 9 178if the vnode is locked). 179.Pp 180Other commonly used members of the vnode structure are 181.Dv v_id 182which is used to maintain consistency in the name cache, 183.Dv v_mount 184which points at the filesystem which owns the vnode, 185.Dv v_type 186which contains the type of object the vnode represents and 187.Dv v_data 188which is used by filesystems to store filesystem specific data with 189the vnode. 190The 191.Dv v_op 192field is used by the 193.Dv VOP_* 194macros to call functions in the filesystem which implement the vnode's 195functionality. 196.Sh SEE ALSO 197.Xr VFS 9 198.Sh AUTHORS 199This man page was written by Doug Rabson. 200 201