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.El 74.Pp 75Convert a component of a pathname into a pointer to a locked vnode. 76This is a very central and rather complicated routine. 77If the file system is not maintained in a strict tree hierarchy, 78this can result in a deadlock situation. 79.Pp 80The 81.Fa cnp->cn_nameiop 82argument is 83.Dv LOOKUP , 84.Dv CREATE , 85.Dv RENAME , 86or 87.Dv DELETE 88depending on the intended use of the object. 89When 90.Dv CREATE , 91.Dv RENAME , 92or 93.Dv DELETE 94is specified, information usable in 95creating, renaming, or deleting a directory entry may be calculated. 96.Pp 97Overall outline of VOP_LOOKUP: 98.Bd -ragged -offset indent 99Check accessibility of directory. 100Look for name in cache, if found, then return name. 101Search for name in directory, goto to found or notfound as appropriate. 102.Ed 103.Pp 104notfound: 105.Bd -ragged -offset indent 106If creating or renaming and at end of pathname, 107return 108.Er EJUSTRETURN , 109leaving info on available slots else return 110.Er ENOENT . 111.Ed 112.Pp 113found: 114.Bd -ragged -offset indent 115If at end of path and deleting, return information to allow delete. 116If at end of path and renaming, lock target 117inode and return info to allow rename. 118If not at end, add name to cache; if at end and neither creating 119nor deleting, add name to cache. 120.Ed 121.Sh LOCKS 122The directory 123.Fa dvp 124should be locked on entry and exit, regardless of error condition. 125If an entry is found in the directory, it will be returned locked. 126.Sh RETURN VALUES 127Zero is returned with 128.Fa *vpp 129set to the locked vnode of the file if the component is found. 130If the component being searched for is ".", then the vnode just has 131an extra reference added to it with 132.Xr vref 9 . 133The caller must take care to release the locks appropriately in this 134case. 135.Pp 136If the component is not found and the operation is 137.Dv CREATE 138or 139.Dv RENAME , 140the flag 141.Dv ISLASTCN 142is specified and the operation would succeed, the special return value 143.Er EJUSTRETURN 144is returned. 145Otherwise, an appropriate error code is returned. 146.Sh ERRORS 147.Bl -tag -width Er 148.It Bq Er ENOTDIR 149The vnode 150.Fa dvp 151does not represent a directory. 152.It Bq Er ENOENT 153The component 154.Fa dvp 155was not found in this directory. 156.It Bq Er EACCES 157Access for the specified operation is denied. 158.It Bq Er EJUSTRETURN 159A 160.Dv CREATE 161or 162.Dv RENAME 163operation would be successful. 164.El 165.Sh SEE ALSO 166.Xr vnode 9 , 167.Xr VOP_ACCESS 9 , 168.Xr VOP_CREATE 9 , 169.Xr VOP_MKDIR 9 , 170.Xr VOP_MKNOD 9 , 171.Xr VOP_RENAME 9 , 172.Xr VOP_SYMLINK 9 173.Sh HISTORY 174The function 175.Nm 176appeared in 177.Bx 4.3 . 178.Sh AUTHORS 179This manual page was written by 180.An Doug Rabson , 181with some text from comments in 182.Pa ufs_lookup.c . 183