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 17, 2017 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}; 75.Ed 76.Pp 77Convert a component of a pathname into a pointer to a locked vnode. 78This is a very central and rather complicated routine. 79If the file system is not maintained in a strict tree hierarchy, 80this can result in a deadlock situation. 81.Pp 82The 83.Fa cnp->cn_nameiop 84argument is 85.Dv LOOKUP , 86.Dv CREATE , 87.Dv RENAME , 88or 89.Dv DELETE 90depending on the intended use of the object. 91When 92.Dv CREATE , 93.Dv RENAME , 94or 95.Dv DELETE 96is specified, information usable in 97creating, renaming, or deleting a directory entry may be calculated. 98.Pp 99Overall outline of VOP_LOOKUP: 100.Bd -ragged -offset indent 101Check accessibility of directory. 102Look for name in cache, if found, then return name. 103Search for name in directory, goto to found or notfound as appropriate. 104.Ed 105.Pp 106notfound: 107.Bd -ragged -offset indent 108If creating or renaming and at end of pathname, 109return 110.Er EJUSTRETURN , 111leaving info on available slots else return 112.Er ENOENT . 113.Ed 114.Pp 115found: 116.Bd -ragged -offset indent 117If at end of path and deleting, return information to allow delete. 118If at end of path and renaming, lock target 119inode and return info to allow rename. 120If not at end, add name to cache; if at end and neither creating 121nor deleting, add name to cache. 122.Ed 123.Sh LOCKS 124The directory 125.Fa dvp 126should be locked on entry and exit, regardless of error condition. 127If an entry is found in the directory, it will be returned locked. 128.Sh RETURN VALUES 129Zero is returned with 130.Fa *vpp 131set to the locked vnode of the file if the component is found. 132If the component being searched for is ".", then the vnode just has 133an extra reference added to it with 134.Xr vref 9 . 135The caller must take care to release the locks appropriately in this 136case. 137.Pp 138If the component is not found and the operation is 139.Dv CREATE 140or 141.Dv RENAME , 142the flag 143.Dv ISLASTCN 144is specified and the operation would succeed, the special return value 145.Er EJUSTRETURN 146is returned. 147Otherwise, an appropriate error code is returned. 148.Sh ERRORS 149.Bl -tag -width Er 150.It Bq Er ENOTDIR 151The vnode 152.Fa dvp 153does not represent a directory. 154.It Bq Er ENOENT 155The component 156.Fa dvp 157was not found in this directory. 158.It Bq Er EACCES 159Access for the specified operation is denied. 160.It Bq Er EJUSTRETURN 161A 162.Dv CREATE 163or 164.Dv RENAME 165operation would be successful. 166.El 167.Sh SEE ALSO 168.Xr vnode 9 , 169.Xr VOP_ACCESS 9 , 170.Xr VOP_CREATE 9 , 171.Xr VOP_MKDIR 9 , 172.Xr VOP_MKNOD 9 , 173.Xr VOP_RENAME 9 , 174.Xr VOP_SYMLINK 9 175.Sh HISTORY 176The function 177.Nm 178appeared in 179.Bx 4.3 . 180.Sh AUTHORS 181This manual page was written by 182.An Doug Rabson , 183with some text from comments in 184.Pa ufs_lookup.c . 185