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 1.7 1998/09/28 23:36:35 eivind Exp $ 30.\" 31.Dd June 30, 1999 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, VT_TFS, VT_VFS, VT_CODA, VT_NTFS 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 */ 62TAILQ_HEAD(buflists, buf); 63 64typedef int vop_t __P((void *)); 65struct namecache; 66 67/* 68 * Reading or writing any of these items requires holding the appropriate lock. 69 * v_freelist is locked by the global vnode_free_list simple lock. 70 * v_mntvnodes is locked by the global mntvnodes simple lock. 71 * v_flag, v_usecount, v_holdcount and v_writecount are 72 * locked by the v_interlock simple lock. 73 * v_pollinfo is locked by the lock contained inside it. 74 */ 75struct vnode { 76 u_long v_flag; /* vnode flags (see below) */ 77 int v_usecount; /* reference count of users */ 78 int v_writecount; /* reference count of writers */ 79 int v_holdcnt; /* page & buffer references */ 80 daddr_t v_lastr; /* last read (read-ahead) */ 81 u_long v_id; /* capability identifier */ 82 struct mount *v_mount; /* ptr to vfs we are in */ 83 vop_t **v_op; /* vnode operations vector */ 84 TAILQ_ENTRY(vnode) v_freelist; /* vnode freelist */ 85 LIST_ENTRY(vnode) v_mntvnodes; /* vnodes for mount point */ 86 struct buflists v_cleanblkhd; /* clean blocklist head */ 87 struct buflists v_dirtyblkhd; /* dirty blocklist head */ 88 LIST_ENTRY(vnode) v_synclist; /* vnodes with dirty buffers */ 89 long v_numoutput; /* num of writes in progress */ 90 enum vtype v_type; /* vnode type */ 91 union { 92 struct mount *vu_mountedhere;/* ptr to mounted vfs (VDIR) */ 93 struct socket *vu_socket; /* unix ipc (VSOCK) */ 94 struct specinfo *vu_specinfo; /* device (VCHR, VBLK) */ 95 struct fifoinfo *vu_fifoinfo; /* fifo (VFIFO) */ 96 } v_un; 97 struct nqlease *v_lease; /* Soft reference to lease */ 98 daddr_t v_lastw; /* last write (write cluster) */ 99 daddr_t v_cstart; /* start block of cluster */ 100 daddr_t v_lasta; /* last allocation */ 101 int v_clen; /* length of current cluster */ 102 int v_maxio; /* maximum I/O cluster size */ 103 struct vm_object *v_object; /* Place to store VM object */ 104 struct simplelock v_interlock; /* lock on usecount and flag */ 105 struct lock *v_vnlock; /* used for non-locking fs's */ 106 enum vtagtype v_tag; /* type of underlying data */ 107 void *v_data; /* private data for fs */ 108 LIST_HEAD(, namecache) v_cache_src; /* Cache entries from us */ 109 TAILQ_HEAD(, namecache) v_cache_dst; /* Cache entries to us */ 110 struct vnode *v_dd; /* .. vnode */ 111 u_long v_ddid; /* .. capability identifier */ 112 struct { 113 struct simplelock vpi_lock; /* lock to protect below */ 114 struct selinfo vpi_selinfo; /* identity of poller(s) */ 115 short vpi_events; /* what they are looking for */ 116 short vpi_revents; /* what has happened */ 117 } v_pollinfo; 118}; 119#define v_mountedhere v_un.vu_mountedhere 120#define v_socket v_un.vu_socket 121#define v_specinfo v_un.vu_specinfo 122#define v_fifoinfo v_un.vu_fifoinfo 123 124/* 125 * Vnode flags. 126 */ 127#define VROOT 0x00001 /* root of its file system */ 128#define VTEXT 0x00002 /* vnode is a pure text prototype */ 129#define VSYSTEM 0x00004 /* vnode being used by kernel */ 130#define VISTTY 0x00008 /* vnode represents a tty */ 131#define VXLOCK 0x00100 /* vnode is locked to change underlying type */ 132#define VXWANT 0x00200 /* process is waiting for vnode */ 133#define VBWAIT 0x00400 /* waiting for output to complete */ 134#define VALIASED 0x00800 /* vnode has an alias */ 135#define VDIROP 0x01000 /* LFS: vnode is involved in a directory op */ 136#define VOBJBUF 0x02000 /* Allocate buffers in VM object */ 137#define VNINACT 0x04000 /* LFS: skip ufs_inactive() in lfs_vunref */ 138#define VAGE 0x08000 /* Insert vnode at head of free list */ 139#define VOLOCK 0x10000 /* vnode is locked waiting for an object */ 140#define VOWANT 0x20000 /* a process is waiting for VOLOCK */ 141#define VDOOMED 0x40000 /* This vnode is being recycled */ 142#define VFREE 0x80000 /* This vnode is on the freelist */ 143#define VTBFREE 0x100000 /* This vnode is on the to-be-freelist */ 144#define VONWORKLST 0x200000 /* On syncer work-list */ 145#define VMOUNT 0x400000 /* Mount in progress */ 146 147.Ed 148.Sh DESCRIPTION 149The vnode is the focus of all file activity in UNIX. There is a 150unique vnode allocated for each active file, each current directory, 151each mounted-on file, text file, and the root. 152.Pp 153Each vnode has three reference counts, 154.Dv v_usecount , 155.Dv v_holdcnt 156and 157.Dv v_writecount . 158The first is the number of clients within the kernel which are 159using this vnode. This count is maintained by 160.Xr vref 9 , 161.Xr vrele 9 162and 163.Xr vput 9 . 164The second is the number of clients within the kernel who veto 165the recycling of this vnode. This count is 166maintained by 167.Xr vhold 9 168and 169.Xr vdrop 9 . 170When both the 171.Dv v_usecount 172and the 173.Dv v_holdcnt 174of a vnode reaches zero then the vnode will be put on the freelist 175and may be reused for another file, possibly in another filesystem. 176The transition to and from the freelist is handled by 177.Xr getnewvnode 9 , 178.Xr vfree 9 179and 180.Xr vbusy 9 . 181The third is a count of the number of clients which are writing into 182the file. It is maintained by the 183.Xr open 2 184and 185.Xr close 2 186system calls. 187.Pp 188Any call which returns a vnode (e.g. 189.Xr VFS_GET 9 , 190.Xr VOP_LOOKUP 9 191etc.) 192will increase the 193.Dv v_usecount 194of the vnode by one. When the caller is finished with the vnode, it 195should release this reference by calling 196.Xr vrele 9 197(or 198.Xr vput 9 199if the vnode is locked). 200.Pp 201Other commonly used members of the vnode structure are 202.Dv v_id 203which is used to maintain consistency in the name cache, 204.Dv v_mount 205which points at the filesystem which owns the vnode, 206.Dv v_type 207which contains the type of object the vnode represents and 208.Dv v_data 209which is used by filesystems to store filesystem specific data with 210the vnode. 211The 212.Dv v_op 213field is used by the 214.Dv VOP_* 215macros to call functions in the filesystem which implement the vnode's 216functionality. 217.Sh VNODE TYPES 218.Bl -tag -width VSOCK 219.It Dv VNON 220No type. 221.It Dv VREG 222A regular file; may be with or without VM object backing. If you want 223to make sure this get a backing object, call 224.Xr vfs_object_create 9 . 225.It Dv VDIR 226A directory. 227.It Dv VBLK 228A block device; may be with or without VM object backing. If you want 229to make sure this get a backing object, call 230.Xr vfs_object_create 9 . 231.It Dv VCHR 232A character device. 233.It Dv VLNK 234A symbolic link. 235.It Dv VSOCK 236A socket. Advisory locking won't work on this. 237.It Dv VFIFO 238A FIFO (named pipe). Advisory locking won't work on this. 239.It Dv VBAD 240An old style bad sector map 241.El 242 243.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 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