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 August 8, 2018 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. 54It is a pointer to a componentname structure defined as follows: 55.Bd -literal 56struct componentname { 57 /* 58 * Arguments to lookup. 59 */ 60 u_long cn_nameiop; /* namei operation */ 61 u_long cn_flags; /* flags to namei */ 62 struct thread *cn_thread; /* thread requesting lookup */ 63 struct ucred *cn_cred; /* credentials */ 64 int cn_lkflags; /* Lock flags LK_EXCLUSIVE or LK_SHARED */ 65 /* 66 * Shared between lookup and commit routines. 67 */ 68 char *cn_pnbuf; /* pathname buffer */ 69 char *cn_nameptr; /* pointer to looked up name */ 70 long cn_namelen; /* length of looked up component */ 71}; 72.Ed 73.Pp 74Convert a component of a pathname into a pointer to a locked vnode. 75This is a very central and rather complicated routine. 76If the file system is not maintained in a strict tree hierarchy, 77this can result in a deadlock situation. 78.Pp 79The 80.Fa cnp->cn_nameiop 81argument is 82.Dv LOOKUP , 83.Dv CREATE , 84.Dv RENAME , 85or 86.Dv DELETE 87depending on the intended use of the object. 88When 89.Dv CREATE , 90.Dv RENAME , 91or 92.Dv DELETE 93is specified, information usable in 94creating, renaming, or deleting a directory entry may be calculated. 95.Pp 96Overall outline of VOP_LOOKUP: 97.Bd -ragged -offset indent 98Check accessibility of directory. 99Look for name in cache, if found, then return name. 100Search for name in directory, goto to found or notfound as appropriate. 101.Ed 102.Pp 103notfound: 104.Bd -ragged -offset indent 105If creating or renaming and at end of pathname, 106return 107.Er EJUSTRETURN , 108leaving info on available slots else return 109.Er ENOENT . 110.Ed 111.Pp 112found: 113.Bd -ragged -offset indent 114If at end of path and deleting, return information to allow delete. 115If at end of path and renaming, lock target 116inode and return info to allow rename. 117If not at end, add name to cache; if at end and neither creating 118nor deleting, add name to cache. 119.Ed 120.Sh LOCKS 121The directory 122.Fa dvp 123should be locked on entry and exit, regardless of error condition. 124If an entry is found in the directory, it will be returned locked. 125.Sh RETURN VALUES 126Zero is returned with 127.Fa *vpp 128set to the locked vnode of the file if the component is found. 129If the component being searched for is ".", then the vnode just has 130an extra reference added to it with 131.Xr vref 9 . 132The caller must take care to release the locks appropriately in this 133case. 134.Pp 135If the component is not found and the operation is 136.Dv CREATE 137or 138.Dv RENAME , 139the flag 140.Dv ISLASTCN 141is specified and the operation would succeed, the special return value 142.Er EJUSTRETURN 143is returned. 144Otherwise, an appropriate error code is returned. 145.Sh ERRORS 146.Bl -tag -width Er 147.It Bq Er ENOTDIR 148The vnode 149.Fa dvp 150does not represent a directory. 151.It Bq Er ENOENT 152The component 153.Fa dvp 154was not found in this directory. 155.It Bq Er EACCES 156Access for the specified operation is denied. 157.It Bq Er EJUSTRETURN 158A 159.Dv CREATE 160or 161.Dv RENAME 162operation would be successful. 163.El 164.Sh SEE ALSO 165.Xr vnode 9 , 166.Xr VOP_ACCESS 9 , 167.Xr VOP_CREATE 9 , 168.Xr VOP_MKDIR 9 , 169.Xr VOP_MKNOD 9 , 170.Xr VOP_RENAME 9 , 171.Xr VOP_SYMLINK 9 172.Sh HISTORY 173The function 174.Nm 175appeared in 176.Bx 4.3 . 177.Sh AUTHORS 178This manual page was written by 179.An Doug Rabson , 180with some text from comments in 181.Pa ufs_lookup.c . 182