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.\" $FreeBSD: src/share/man/man9/vnode.9,v 1.10.2.5 2001/12/17 11:30:19 ru Exp $ 30.\" $DragonFly: src/share/man/man9/vnode.9,v 1.2 2003/06/17 04:37:01 dillon Exp $ 31.\" 32.Dd June 30, 1999 33.Os 34.Dt VNODE 9 35.Sh NAME 36.Nm vnode 37.Nd internal representation of a file or directory 38.Sh SYNOPSIS 39.In sys/param.h 40.In sys/vnode.h 41.Pp 42.Bd -literal 43/* 44 * Vnode types. VNON means no type. 45 */ 46enum vtype { VNON, VREG, VDIR, VBLK, VCHR, VLNK, VSOCK, VFIFO, VBAD }; 47 48/* 49 * Vnode tag types. 50 * These are for the benefit of external programs only (e.g., pstat) 51 * and should NEVER be inspected by the kernel. 52 */ 53enum vtagtype { 54 VT_NON, VT_UFS, VT_NFS, VT_MFS, VT_PC, VT_LFS, VT_LOFS, VT_FDESC, 55 VT_PORTAL, VT_NULL, VT_UMAP, VT_KERNFS, VT_PROCFS, VT_AFS, VT_ISOFS, 56 VT_UNION, VT_MSDOSFS, VT_TFS, VT_VFS, VT_CODA, VT_NTFS 57}; 58 59/* 60 * Each underlying filesystem allocates its own private area and hangs 61 * it from v_data. If non-null, this area is freed in getnewvnode(). 62 */ 63TAILQ_HEAD(buflists, buf); 64 65typedef int vop_t __P((void *)); 66struct namecache; 67 68/* 69 * Reading or writing any of these items requires holding the appropriate lock. 70 * v_freelist is locked by the global vnode_free_list simple lock. 71 * v_mntvnodes is locked by the global mntvnodes simple lock. 72 * v_flag, v_usecount, v_holdcount and v_writecount are 73 * locked by the v_interlock simple lock. 74 * v_pollinfo is locked by the lock contained inside it. 75 */ 76struct vnode { 77 u_long v_flag; /* vnode flags (see below) */ 78 int v_usecount; /* reference count of users */ 79 int v_writecount; /* reference count of writers */ 80 int v_holdcnt; /* page & buffer references */ 81 daddr_t v_lastr; /* last read (read-ahead) */ 82 u_long v_id; /* capability identifier */ 83 struct mount *v_mount; /* ptr to vfs we are in */ 84 vop_t **v_op; /* vnode operations vector */ 85 TAILQ_ENTRY(vnode) v_freelist; /* vnode freelist */ 86 LIST_ENTRY(vnode) v_mntvnodes; /* vnodes for mount point */ 87 struct buflists v_cleanblkhd; /* clean blocklist head */ 88 struct buflists v_dirtyblkhd; /* dirty blocklist head */ 89 LIST_ENTRY(vnode) v_synclist; /* vnodes with dirty buffers */ 90 long v_numoutput; /* num of writes in progress */ 91 enum vtype v_type; /* vnode type */ 92 union { 93 struct mount *vu_mountedhere;/* ptr to mounted vfs (VDIR) */ 94 struct socket *vu_socket; /* unix ipc (VSOCK) */ 95 struct specinfo *vu_specinfo; /* device (VCHR, VBLK) */ 96 struct fifoinfo *vu_fifoinfo; /* fifo (VFIFO) */ 97 } v_un; 98 struct nqlease *v_lease; /* Soft reference to lease */ 99 daddr_t v_lastw; /* last write (write cluster) */ 100 daddr_t v_cstart; /* start block of cluster */ 101 daddr_t v_lasta; /* last allocation */ 102 int v_clen; /* length of current cluster */ 103 int v_maxio; /* maximum I/O cluster size */ 104 struct vm_object *v_object; /* Place to store VM object */ 105 struct simplelock v_interlock; /* lock on usecount and flag */ 106 struct lock *v_vnlock; /* used for non-locking fs's */ 107 enum vtagtype v_tag; /* type of underlying data */ 108 void *v_data; /* private data for fs */ 109 LIST_HEAD(, namecache) v_cache_src; /* Cache entries from us */ 110 TAILQ_HEAD(, namecache) v_cache_dst; /* Cache entries to us */ 111 struct vnode *v_dd; /* .. vnode */ 112 u_long v_ddid; /* .. capability identifier */ 113 struct { 114 struct simplelock vpi_lock; /* lock to protect below */ 115 struct selinfo vpi_selinfo; /* identity of poller(s) */ 116 short vpi_events; /* what they are looking for */ 117 short vpi_revents; /* what has happened */ 118 } v_pollinfo; 119}; 120#define v_mountedhere v_un.vu_mountedhere 121#define v_socket v_un.vu_socket 122#define v_specinfo v_un.vu_specinfo 123#define v_fifoinfo v_un.vu_fifoinfo 124 125/* 126 * Vnode flags. 127 */ 128#define VROOT 0x00001 /* root of its file system */ 129#define VTEXT 0x00002 /* vnode is a pure text prototype */ 130#define VSYSTEM 0x00004 /* vnode being used by kernel */ 131#define VISTTY 0x00008 /* vnode represents a tty */ 132#define VXLOCK 0x00100 /* vnode is locked to change underlying type */ 133#define VXWANT 0x00200 /* process is waiting for vnode */ 134#define VBWAIT 0x00400 /* waiting for output to complete */ 135#define VALIASED 0x00800 /* vnode has an alias */ 136#define VDIROP 0x01000 /* LFS: vnode is involved in a directory op */ 137#define VOBJBUF 0x02000 /* Allocate buffers in VM object */ 138#define VNINACT 0x04000 /* LFS: skip ufs_inactive() in lfs_vunref */ 139#define VAGE 0x08000 /* Insert vnode at head of free list */ 140#define VOLOCK 0x10000 /* vnode is locked waiting for an object */ 141#define VOWANT 0x20000 /* a process is waiting for VOLOCK */ 142#define VDOOMED 0x40000 /* This vnode is being recycled */ 143#define VFREE 0x80000 /* This vnode is on the freelist */ 144#define VTBFREE 0x100000 /* This vnode is on the to-be-freelist */ 145#define VONWORKLST 0x200000 /* On syncer work-list */ 146#define VMOUNT 0x400000 /* Mount in progress */ 147 148.Ed 149.Sh DESCRIPTION 150The vnode is the focus of all file activity in UNIX. There is a 151unique vnode allocated for each active file, each current directory, 152each mounted-on file, text file, and the root. 153.Pp 154Each vnode has three reference counts, 155.Dv v_usecount , 156.Dv v_holdcnt 157and 158.Dv v_writecount . 159The first is the number of clients within the kernel which are 160using this vnode. This count is maintained by 161.Xr vref 9 , 162.Xr vrele 9 163and 164.Xr vput 9 . 165The second is the number of clients within the kernel who veto 166the recycling of this vnode. This count is 167maintained by 168.Xr vhold 9 169and 170.Xr vdrop 9 . 171When both the 172.Dv v_usecount 173and the 174.Dv v_holdcnt 175of a vnode reaches zero then the vnode will be put on the freelist 176and may be reused for another file, possibly in another filesystem. 177The transition to and from the freelist is handled by 178.Xr getnewvnode 9 , 179.Xr vfree 9 180and 181.Xr vbusy 9 . 182The third is a count of the number of clients which are writing into 183the file. It is maintained by the 184.Xr open 2 185and 186.Xr close 2 187system calls. 188.Pp 189Any call which returns a vnode (e.g.\& 190.Xr VFS_GET 9 , 191.Xr VOP_LOOKUP 9 192etc.) 193will increase the 194.Dv v_usecount 195of the vnode by one. When the caller is finished with the vnode, it 196should release this reference by calling 197.Xr vrele 9 198(or 199.Xr vput 9 200if the vnode is locked). 201.Pp 202Other commonly used members of the vnode structure are 203.Dv v_id 204which is used to maintain consistency in the name cache, 205.Dv v_mount 206which points at the filesystem which owns the vnode, 207.Dv v_type 208which contains the type of object the vnode represents and 209.Dv v_data 210which is used by filesystems to store filesystem specific data with 211the vnode. 212The 213.Dv v_op 214field is used by the 215.Dv VOP_* 216macros to call functions in the filesystem which implement the vnode's 217functionality. 218.Sh VNODE TYPES 219.Bl -tag -width VSOCK 220.It Dv VNON 221No type. 222.It Dv VREG 223A regular file; may be with or without VM object backing. If you want 224to make sure this get a backing object, call 225.Xr vfs_object_create 9 . 226.It Dv VDIR 227A directory. 228.It Dv VBLK 229A block device; may be with or without VM object backing. If you want 230to make sure this get a backing object, call 231.Xr vfs_object_create 9 . 232.It Dv VCHR 233A character device. 234.It Dv VLNK 235A symbolic link. 236.It Dv VSOCK 237A socket. Advisory locking won't work on this. 238.It Dv VFIFO 239A FIFO (named pipe). Advisory locking won't work on this. 240.It Dv VBAD 241An old style bad sector map 242.El 243.Sh NOTES 244VFIFO uses the "struct fileops" from 245.Pa /sys/kern/sys_pipe.c . 246VSOCK uses the "struct fileops" from 247.Pa /sys/kern/sys_socket.c . 248Everything else uses the one from 249.Pa /sys/kern/vfs_vnops.c . 250.Pp 251The VFIFO/VSOCK code, which is why "struct fileops" is used at all, is 252an artifact of an incomplete integration of the VFS code into the 253kernel. 254.Sh SEE ALSO 255.Xr VFS 9 256.Sh AUTHORS 257This man page was written by 258.An Doug Rabson . 259