VOP_LOOKUP
—
lookup a component of a pathname
#include
<sys/param.h>
#include
<sys/vnode.h>
#include
<sys/namei.h>
int
VOP_LOOKUP
(
struct
vnode *dvp,
struct vnode
**vpp,
struct
componentname *cnp);
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. It 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 */
int cn_lkflags; /* Lock flags LK_EXCLUSIVE or LK_SHARED */
/*
* 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 */
};
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:
Check accessibility of directory. Look for name in
cache, if found, then return name. Search for name in directory, goto to
found or notfound as appropriate.
notfound:
If creating or renaming and at end of pathname,
return EJUSTRETURN
, leaving info on
available slots else return
ENOENT
.
found:
If at end of path and deleting, return information
to allow delete. If at end of path and renaming, lock target inode and
return info to allow rename. If not at end, add name to cache; if at end
and neither creating nor deleting, add name to cache.
The directory
dvp should be locked on entry and
exit, regardless of error condition. If an entry is found in the directory, it
will be returned locked.
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.
- [
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
or
RENAME
operation would be
successful.
vnode(9),
VOP_ACCESS(9),
VOP_CREATE(9),
VOP_MKDIR(9),
VOP_MKNOD(9),
VOP_RENAME(9),
VOP_SYMLINK(9)
The function
VOP_LOOKUP
appeared in
4.3BSD.
This manual page was written by
Doug Rabson,
with some text from comments in
ufs_lookup.c.