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 March 27, 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. 127If an error (note: the return value 128.Er EJUSTRETURN 129is not considered an error) 130is detected, it will be returned locked. 131Otherwise, it will be unlocked unless both 132.Dv LOCKPARENT 133and 134.Dv ISLASTCN 135are specified in 136.Fa cnp->cn_flags . 137If an entry is found in the directory, it will be returned locked. 138.Sh RETURN VALUES 139Zero is returned with 140.Fa *vpp 141set to the locked vnode of the file if the component is found. 142If the component being searched for is ".", then the vnode just has 143an extra reference added to it with 144.Xr vref 9 . 145The caller must take care to release the locks appropriately in this 146case. 147.Pp 148If the component is not found and the operation is 149.Dv CREATE 150or 151.Dv RENAME , 152the flag 153.Dv ISLASTCN 154is specified and the operation would succeed, the special return value 155.Er EJUSTRETURN 156is returned. 157Otherwise, an appropriate error code is returned. 158.Sh ERRORS 159.Bl -tag -width Er 160.It Bq Er ENOTDIR 161The vnode 162.Fa dvp 163does not represent a directory. 164.It Bq Er ENOENT 165The component 166.Fa dvp 167was not found in this directory. 168.It Bq Er EACCES 169Access for the specified operation is denied. 170.It Bq Er EJUSTRETURN 171A 172.Dv CREATE 173or 174.Dv RENAME 175operation would be successful. 176.El 177.Sh SEE ALSO 178.Xr vnode 9 , 179.Xr VOP_ACCESS 9 , 180.Xr VOP_CREATE 9 , 181.Xr VOP_MKDIR 9 , 182.Xr VOP_MKNOD 9 , 183.Xr VOP_RENAME 9 , 184.Xr VOP_SYMLINK 9 185.Sh HISTORY 186The function 187.Nm 188appeared in 189.Bx 4.3 . 190.Sh AUTHORS 191This manual page was written by 192.An Doug Rabson , 193with some text from comments in 194.Pa ufs_lookup.c . 195