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.\" $FreeBSD$ 30.\" 31.Dd November 24, 1997 32.Dt VOP_LOOKUP 9 33.Os 34.Sh NAME 35.Nm VOP_LOOKUP 36.Nd lookup a component of a pathname 37.Sh SYNOPSIS 38.In sys/param.h 39.In sys/vnode.h 40.In sys/namei.h 41.Ft int 42.Fn VOP_LOOKUP "struct vnode *dvp" "struct vnode **vpp" "struct componentname *cnp" 43.Sh DESCRIPTION 44This entry point looks up a single pathname component in a given directory. 45.Pp 46Its arguments are: 47.Bl -tag -width vpp 48.It Fa dvp 49The locked vnode of the directory to search. 50.It Fa vpp 51The address of a variable where the resulting locked vnode should be stored. 52.It Fa cnp 53The pathname component to be searched for. 54.El 55.Pp 56.Fa Cnp 57is a pointer to a componentname structure defined as follows: 58.Bd -literal 59struct componentname { 60 /* 61 * Arguments to lookup. 62 */ 63 u_long cn_nameiop; /* namei operation */ 64 u_long cn_flags; /* flags to namei */ 65 struct thread *cn_thread; /* thread requesting lookup */ 66 struct ucred *cn_cred; /* credentials */ 67 /* 68 * Shared between lookup and commit routines. 69 */ 70 char *cn_pnbuf; /* pathname buffer */ 71 char *cn_nameptr; /* pointer to looked up name */ 72 long cn_namelen; /* length of looked up component */ 73 u_long cn_hash; /* hash value of looked up name */ 74 long cn_consume; /* chars to consume in lookup() */ 75}; 76.Ed 77.Pp 78Convert a component of a pathname into a pointer to a locked vnode. 79This is a very central and rather complicated routine. 80If the file system is not maintained in a strict tree hierarchy, 81this can result in a deadlock situation. 82.Pp 83The 84.Fa cnp->cn_nameiop 85argument is 86.Dv LOOKUP , 87.Dv CREATE , 88.Dv RENAME , 89or 90.Dv DELETE 91depending on the intended use of the object. 92When 93.Dv CREATE , 94.Dv RENAME , 95or 96.Dv DELETE 97is specified, information usable in 98creating, renaming, or deleting a directory entry may be calculated. 99.Pp 100Overall outline of VOP_LOOKUP: 101.Bd -ragged -offset indent 102Check accessibility of directory. 103Look for name in cache, if found, then return name. 104Search for name in directory, goto to found or notfound as appropriate. 105.Ed 106.Pp 107notfound: 108.Bd -ragged -offset indent 109If creating or renaming and at end of pathname, 110return 111.Er EJUSTRETURN , 112leaving info on available slots else return 113.Er ENOENT . 114.Ed 115.Pp 116found: 117.Bd -ragged -offset indent 118If at end of path and deleting, return information to allow delete. 119If at end of path and renaming, lock target 120inode and return info to allow rename. 121If not at end, add name to cache; if at end and neither creating 122nor deleting, add name to cache. 123.Ed 124.Sh LOCKS 125The directory, 126.Fa dvp 127should be locked on entry. 128If an error (note: the return value 129.Er EJUSTRETURN 130is not considered an error) 131is detected, it will be returned locked. 132Otherwise, it will be unlocked unless both 133.Dv LOCKPARENT 134and 135.Dv ISLASTCN 136are specified in 137.Fa cnp->cn_flags . 138If an entry is found in the directory, it will be returned locked. 139.Sh RETURN VALUES 140Zero is returned with 141.Fa *vpp 142set to the locked vnode of the file if the component is found. 143If the component being searched for is ".", then the vnode just has 144an extra reference added to it with 145.Xr vref 9 . 146The caller must take care to release the locks appropriately in this 147case. 148.Pp 149If the component is not found and the operation is 150.Dv CREATE 151or 152.Dv RENAME , 153the flag 154.Dv ISLASTCN 155is specified and the operation would succeed, the special return value 156.Er EJUSTRETURN 157is returned. 158Otherwise, an appropriate error code is returned. 159.Sh ERRORS 160.Bl -tag -width Er 161.It Bq Er ENOTDIR 162The vnode 163.Fa dvp 164does not represent a directory. 165.It Bq Er ENOENT 166The component 167.Fa dvp 168was not found in this directory. 169.It Bq Er EACCES 170Access for the specified operation is denied. 171.It Bq Er EJUSTRETURN 172A 173.Dv CREATE 174or 175.Dv RENAME 176operation would be successful. 177.El 178.Sh SEE ALSO 179.Xr vnode 9 , 180.Xr VOP_ACCESS 9 , 181.Xr VOP_CREATE 9 , 182.Xr VOP_MKDIR 9 , 183.Xr VOP_MKNOD 9 , 184.Xr VOP_RENAME 9 , 185.Xr VOP_SYMLINK 9 186.Sh HISTORY 187The function 188.Nm 189appeared in 190.Bx 4.3 . 191.Sh AUTHORS 192This manual page was written by 193.An Doug Rabson , 194with some text from comments in 195.Pa ufs_lookup.c . 196