Copyright (c) 1996 Doug Rabson
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$Id: vnode.9,v 1.2 1997/03/22 22:47:31 mpp Exp $
.Dd July 24, 1996 .Os .Dt VNODE 9 .Sh NAME .Nm vnode .Nd internal representation of a file or directory .Sh SYNOPSIS .Fd #include <sys/param.h> .Fd #include <sys/vnode.h>
p d -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_MFS, 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 }; /* * Each underlying filesystem allocates its own private area and hangs * it from v_data. If non-null, this area is freed in getnewvnode(). */ LIST_HEAD(buflists, buf); typedef int vop_t __P((void *)); 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 */ daddr_t v_lastr; /* last read (read-ahead) */ 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 */ 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 specinfo *vu_specinfo; /* device (VCHR, VBLK) */ 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 */ int v_ralen; /* Read-ahead length */ int v_usage; /* Vnode usage counter */ daddr_t v_maxra; /* last readahead block */ void *v_object; /* Place to store VM object */ enum vtagtype v_tag; /* type of underlying data */ void *v_data; /* private data for fs */ }; #define v_mountedhere v_un.vu_mountedhere #define v_socket v_un.vu_socket #define v_specinfo v_un.vu_specinfo #define v_fifoinfo v_un.vu_fifoinfo /* * Vnode flags. */ #define VROOT 0x0001 /* root of its file system */ #define VTEXT 0x0002 /* vnode is a pure text prototype */ #define VSYSTEM 0x0004 /* vnode being used by kernel */ #define VOLOCK 0x0008 /* vnode is locked waiting for an object */ #define VOWANT 0x0010 /* a process is waiting for VOLOCK */ #define VXLOCK 0x0100 /* vnode is locked to change underlying type */ #define VXWANT 0x0200 /* process is waiting for vnode */ #define VBWAIT 0x0400 /* waiting for output to complete */ #define VALIASED 0x0800 /* vnode has an alias */ #define VDIROP 0x1000 /* LFS: vnode is involved in a directory op */ #define VVMIO 0x2000 /* VMIO flag */ #define VNINACT 0x4000 /* LFS: skip ufs_inactive() in lfs_vunref */ #define VAGE 0x8000 /* Insert vnode at head of free list */ .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.
p Each vnode has two reference counts, .Dv v_usecount 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 . When the .Dv v_usecount of a vnode reaches zero then the vnode may be reused for another file, possibly in another filesystem. The second 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.
p 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).
p 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 SEE ALSO .Xr VFS 9 .Sh AUTHORS This man page was written by Doug Rabson.