NAME
VOP_LOOKUP
—
lookup a component of a
pathname
SYNOPSIS
#include
<sys/param.h>
#include <sys/vnode.h>
#include <sys/namei.h>
int
VOP_LOOKUP
(struct
vnode *dvp, struct vnode
**vpp, struct
componentname *cnp);
DESCRIPTION
This entry point looks up a single pathname component in a given directory.Its arguments are:
- dvp
- The locked vnode of the directory to search.
- vpp
- The address of a variable where the resulting locked vnode should be stored.
- cnp
- The pathname component to be searched for.
Cnp is a pointer to a componentname structure defined as follows:
struct componentname { /* * Arguments to lookup. */ u_long cn_nameiop; /* namei operation */ u_long cn_flags; /* flags to namei */ struct thread *cn_thread; /* thread requesting lookup */ struct ucred *cn_cred; /* credentials */ /* * Shared between lookup and commit routines. */ char *cn_pnbuf; /* pathname buffer */ char *cn_nameptr; /* pointer to looked up name */ long cn_namelen; /* length of looked up component */ u_long cn_hash; /* hash value of looked up name */ };
Convert a component of a pathname into a pointer to a locked vnode. This is a very central and rather complicated routine. If the file system is not maintained in a strict tree hierarchy, this can result in a deadlock situation.
The cnp->cn_nameiop argument is
LOOKUP
, CREATE
,
RENAME
, or DELETE
depending
on the intended use of the object. When CREATE
,
RENAME
, or DELETE
is
specified, information usable in creating, renaming, or deleting a directory
entry may be calculated.
Overall outline of VOP_LOOKUP:
notfound:
EJUSTRETURN
, leaving info on available slots
else return ENOENT
.found:
LOCKS
The directory, dvp should be locked on
entry. If an error (note: the return value
EJUSTRETURN
is not considered an error) is detected,
it will be returned locked. Otherwise, it will be unlocked unless both
LOCKPARENT
and ISLASTCN
are
specified in cnp->cn_flags. If an entry is found in
the directory, it will be returned locked.
RETURN VALUES
Zero is returned with *vpp set to the locked vnode of the file if the component is found. If the component being searched for is ".", then the vnode just has an extra reference added to it with vref(9). The caller must take care to release the locks appropriately in this case.
If the component is not found and the operation is
CREATE
or RENAME
, the flag
ISLASTCN
is specified and the operation would
succeed, the special return value EJUSTRETURN
is
returned. Otherwise, an appropriate error code is returned.
ERRORS
- [
ENOTDIR
] - The vnode dvp does not represent a directory.
- [
ENOENT
] - The component dvp was not found in this directory.
- [
EACCES
] - Access for the specified operation is denied.
- [
EJUSTRETURN
] - A
CREATE
orRENAME
operation would be successful.
SEE ALSO
vnode(9), VOP_ACCESS(9), VOP_CREATE(9), VOP_MKDIR(9), VOP_MKNOD(9), VOP_RENAME(9), VOP_SYMLINK(9)
HISTORY
The function VOP_LOOKUP
appeared in
4.3BSD.
AUTHORS
This manual page was written by Doug Rabson, with some text from comments in ufs_lookup.c.