xref: /freebsd/share/man/man9/namei.9 (revision 7f3dea244c40159a41ab22da77a434d7c5b5e85a)

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.\" $FreeBSD$
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.Dd September 26th, 1998
.Os
.Dt NAMEI 9
.Sh NAME
.Nm namei ,
.Nm NDINIT
.Nd convert pathname to a pointer to a locked vnode.
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/namei.h>
.Ft int
.Fn namei "struct nameidata *ndp"
.Ft void
.Fn NDINIT "struct nameidata *ndp" "int operation" "int operflags" "int segflag" "const char *path" "struct proc *proc"

.Sh DESCRIPTION

.Fn namei
is used to get from a pathname to a vnode for the object.
This is a necessity to start doing VFS operations.  The vnode
returned will have its reference count increased; when you're through
with it, you have to release it using either
.Xr vrele 9
or
.Xr vput 9 ,
depending on whether you specified the LOCKLEAF flag or not.
.Pp
To initialize the nameidata struct, you usually use
.Fn NDINIT .
It takes the following arguments:
.Pp
.Bl -tag -width nameidatap
.It Ar nameidatap
pointer to the struct nameidata to initialize
.It Ar operation
The operation to have
.Fn namei
do.  The relevant operations are
.Dv LOOKUP ,
.Dv CREATE ,
.Dv DELETE ,
and
.Dv RENAME .
The latter three are just setup for those
effects; just calling
.Fn namei
will not result in
.Fn VOP_RENAME
being called.
.It Ar operflags
Operation flags.  Several of these can be effective at the same time.
.It Ar segflag
Segment indicator.  This tells if the name of the object is in
userspace (UIO_USERSPACE) or in the kernel address space (UIO_SYSSPACE).
.It Ar path
Pointer to pathname buffer (the file or directory name that will be
looked up)
.It Ar proc
Which process context to use for the
.Fn namei
locks.
.El
.Sh NAMEI OPERATION FLAGS
.Fn namei
takes the following set of 'operation flags' that influence
how it operates:
.Bl -tag -width WANTPARENT
.It Dv LOCKLEAF
Lock vnode on return.  This is a full lock of the vnode; you'll have to use
.Xr VOP_UNLOCK 9
to release the lock (or use
.Xr vput 9
to release the lock and do a
.Xr vrele 9 ,
all in one).
.It Dv LOCKPARENT
Make
.Fn namei
also return the parent (directory) vnode (in ndp->dvp),
in locked state.  Remember to release it (using
.Xr vput 9
or
.Xr VOP_UNLOCK 9
and
.Xr vrele 9 .)
.It Dv WANTPARENT
Make
.Fn namei
also return the parent (directory) vnode, in unlocked
state.  Remember to release it (using
.Xr vrele 9 .)
.It Dv NOCACHE
Avoid
.Fn namei
creating this entry in the namecache if it is not
already present.  Normally
.Fn namei
will add entries to the name cache
if they're not already there.
.It Dv FOLLOW
With this flag,
.Fn namei
will follow the symbolic link if the last part
of the path supplied is a symbolic link (i.e., it will return a vnode
for whatever the link points at, instead for the link itself).
.It Dv NOOBJ
Do not call
.Fn vfs_object_create
for the returned vnode even if it is
just a VREG and we're able to (ie, it is locked).
.It Dv NOFOLLOW
Do not follow symbolic links (pseudo).  This flag does not seem to be
honoured by the actual code.
.El
.Sh BUGS
.Fn namei
calls
.Fn lookup
for each component in the pathname, instead of
handing the actual names onwards to the stacking layers.  This hinders
the implementation of stacking layers that do full namespace escapes.
.Sh SEE ALSO
.Xr VFS 9 ,
.Xr vnode 9 ,
src/sys/kern/vfs_lookup.c
.Sh AUTHORS
This man page was written by
.An Eivind Eklund .