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36 .Nd lookup a component of a pathname
42 .Fn VOP_LOOKUP "struct vnode *dvp" "struct vnode **vpp" "struct componentname *cnp"
44 This entry point looks up a single pathname component in a given directory.
49 The locked vnode of the directory to search.
51 The address of a variable where the resulting locked vnode should be stored.
53 The pathname component to be searched for.
57 is a pointer to a componentname structure defined as follows:
59 struct componentname {
61 * Arguments to lookup.
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 */
68 * Shared between lookup and commit routines.
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() */
78 Convert a component of a pathname into a pointer to a locked vnode.
79 This is a very central and rather complicated routine.
80 If the file system is not maintained in a strict tree hierarchy,
81 this can result in a deadlock situation.
91 depending on the intended use of the object.
97 is specified, information usable in
98 creating, renaming, or deleting a directory entry may be calculated.
100 Overall outline of VOP_LOOKUP:
101 .Bd -ragged -offset indent
102 Check accessibility of directory.
103 Look for name in cache, if found, then return name.
104 Search for name in directory, goto to found or notfound as appropriate.
108 .Bd -ragged -offset indent
109 If creating or renaming and at end of pathname,
112 leaving info on available slots else return
117 .Bd -ragged -offset indent
118 If at end of path and deleting, return information to allow delete.
119 If at end of path and renaming, lock target
120 inode and return info to allow rename.
121 If not at end, add name to cache; if at end and neither creating
122 nor deleting, add name to cache.
127 should be locked on entry.
128 If an error (note: the return value
130 is not considered an error)
131 is detected, it will be returned locked.
132 Otherwise, it will be unlocked unless both
138 If an entry is found in the directory, it will be returned locked.
140 Zero is returned with
142 set to the locked vnode of the file if the component is found.
143 If the component being searched for is ".", then the vnode just has
144 an extra reference added to it with
146 The caller must take care to release the locks appropriately in this
149 If the component is not found and the operation is
155 is specified and the operation would succeed, the special return value
158 Otherwise, an appropriate error code is returned.
164 does not represent a directory.
168 was not found in this directory.
170 Access for the specified operation is denied.
171 .It Bq Er EJUSTRETURN
176 operation would be successful.
192 This manual page was written by
194 with some text from comments in