int
namei(
struct nameidata *ndp
)
int
lookup(
struct nameidata *ndp
)
int
relookup(
struct vnode *dvp
, struct vnode **vpp
, struct componentname *cnp
)
void
NDINIT(
struct nameidata *ndp
, u_long op
, u_long flags
, enum uio_seg segflg
, const char *namep
)
The arguments passed to the functions are encapsulated in the
nameidata
structure.
It has the following structure:
struct nameidata {
/*
* Arguments to namei/lookup.
*/
const char *ni_dirp; /* pathname pointer */
enum uio_seg ni_segflg; /* location of pathname */
/*
* Arguments to lookup.
*/
struct vnode *ni_startdir; /* starting directory */
struct vnode *ni_rootdir; /* logical root directory */
/*
* Results: returned from/manipulated by lookup
*/
struct vnode *ni_vp; /* vnode of result */
struct vnode *ni_dvp; /* vnode of intermediate dir */
/*
* Shared between namei and lookup/commit routines.
*/
size_t ni_pathlen; /* remaining chars in path */
const char *ni_next; /* next location in pathname */
u_long ni_loopcnt; /* count of symlinks encountered */
/*
* Lookup parameters
*/
struct componentname {
/*
* Arguments to lookup.
*/
u_long cn_nameiop; /* namei operation */
u_long cn_flags; /* flags to namei */
kauth_cred_t cn_cred; /* credentials */
/*
* Shared between lookup and commit routines.
*/
char *cn_pnbuf; /* pathname buffer */
const 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 */
long cn_consume; /* chars to consume in lookup() */
} ni_cnd;
};
The
namei
interface accesses vnode operations by passing arguments in the
partially initialised
componentname
structure
ni_cnd.
This structure describes the subset of information from the nameidata
structure that is passed through to the vnode operations.
See
vnodeops(9)
for more information.
The details of the componentname structure are not absolutely necessary
since the members are initialised by the helper macro
NDINIT().
It is useful to know the operations and flags as specified in
vnodeops(9).
The
namei
interface overloads
ni_cnd.cn_flags
with some additional flags.
These flags should be specific to the
namei
interface and ignored by vnode operations.
However, due to the historic close relationship between the
namei
interface and the vnode operations, these flags are sometimes used
(and set) by vnode operations, particularly
VOP_LOOKUP().
The additional flags are:
If the caller of
namei()
sets the SAVENAME flag, then it must free the buffer.
If
VOP_LOOKUP(
)
sets the flag, then the buffer must be freed by either the commit
routine or the
VOP_ABORT(
)
routine.
The SAVESTART flag is set only by the callers of
namei(
).
It implies SAVENAME plus the addition of saving the parent directory
that contains the name in
ni_startdir.
It allows repeated calls to
lookup(
)
for the name being sought.
The caller is responsible for releasing the buffer and for invoking
vrele(
)
on
ni_startdir.
All access to the namei interface must be in process context. Pathname lookups cannot be done in interrupt context.
ndp
)The vnode for the pathname is returned in ndp->ni_vp. The parent directory is returned locked in ndp->ni_dvp iff LOCKPARENT is specified.
If ndp->ni_cnd.cn_flags has the FOLLOW flag set then symbolic links are followed when they occur at the end of the name translation process. Symbolic links are always followed for all other pathname components other than the last.
ndp
)The pathname is specified by ndp->ni_dirp and is of length ndp->ni_pathlen. The starting directory is taken from ndp->ni_startdir. The pathname is descended until done, or a symbolic link is encountered.
The semantics of
lookup()
are altered by the operation specified by
ndp->ni_cnd.cn_nameiop.
When CREATE, RENAME, or DELETE is specified, information usable in
creating, renaming, or deleting a directory entry may be calculated.
If the target of the pathname exists and LOCKLEAF is set, the target is returned locked in ndp->ni_vp, otherwise it is returned unlocked.
dvp
, vpp
, cnp
)
dvp
and the pathname component by
cnp
.
The vnode of the pathname is returned in the address specified by
vpp
.
ndp
, op
, flags
, segflg
, namep
)
ndp
for use by the
namei
interface.
It saves having to deal with the componentname structure inside
ndp
.
The operation and flags are specified by
op
and
flags
respectively.
These are the values to which
ndp->ni_cnd.cn_nameiop
and
ndp->ni_cnd.cn_flags
are respectively set.
The segment flags which defines whether the pathname is in kernel
address space or user address space is specified by
segflag
.
The argument
namep
is a pointer to the pathname that
ndp->ni_dirp
is set to.
This routine stores the credentials of the calling thread
(curlwp)
in
ndp
.
In the rare case that another set of credentials is required for the
namei operation,
ndp->ni_cnd.cn_cred
must be set manually.
/usr/src
.
The name lookup subsystem is implemented within the file
sys/kern/vfs_lookup.c
.