*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->FreeBSD man pages -> namei (9)              



NAME    [Toc]    [Back]

     namei, NDINIT, NDFREE -- pathname translation and lookup operations

SYNOPSIS    [Toc]    [Back]

     #include <sys/param.h>
     #include <sys/proc.h>
     #include <sys/namei.h>

     namei(struct nameidata *ndp);

     NDINIT(struct nameidata *ndp, u_long op, u_long flags,
	 enum uio_seg segflg, const char *namep, struct thread *td);

     NDFREE(struct nameidata *ndp, const uint flags);

DESCRIPTION    [Toc]    [Back]

     The namei facility allows the client to perform pathname translation and
     lookup operations.  The namei functions will increment the reference
     count for the vnode in question.  The reference count has to be decremented
 after use of the vnode, by using either vrele(9) or vput(9),
     depending on whether the LOCKLEAF flag was specified or not.

     The NDINIT() function is used to initialize namei components.  It takes
     the following arguments:

     ndp     The struct nameidata to initialize.

     op      The operation which namei() will perform.	The following operations
 are valid: LOOKUP, CREATE, DELETE, and RENAME.  The latter
	     three are just setup for those effects; just calling namei() will
	     not result in VOP_RENAME() being called.

     flags   Operation flags.  Several of these can be effective at the same

     segflg  UIO segment indicator.  This indicates if the name of the object
	     is in userspace (UIO_USERSPACE) or in the kernel address space

     namep   Pointer to the component's pathname buffer (the file or directory
	     name that will be looked up).

     td      The thread context to use for namei operations and locks.


     The namei() function takes the following set of ``operation flags'' that
     influence its operation:

     LOCKLEAF	 Lock vnode on return.	This is a full lock of the vnode; the
		 VOP_UNLOCK(9) should be used to release the lock (or vput(9)
		 which is equivalent to calling VOP_UNLOCK(9) followed by
		 vrele(9), all in one).

     LOCKPARENT  This flag lets the namei() function return the parent (directory)
 vnode, ni_dvp in locked state, unless it is identical
		 to ni_vp, in which case ni_dvp is not locked per se (but may
		 be locked due to LOCKLEAF).  If a lock is enforced, it should
		 be released using vput(9) or VOP_UNLOCK(9) and vrele(9).

     WANTPARENT  This flag allows the namei() function to return the parent
		 (directory) vnode in an unlocked state.  The parent vnode
		 must be released separately by using vrele(9).

     NOCACHE	 Avoid namei() creating this entry in the namecache if it is
		 not already present.  Normally, namei() will add entries to
		 the name cache if they are not already there.

     FOLLOW	 With this flag, 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).

     NOOBJ	 Do not call vfs_object_create() for the returned vnode, even
		 though it meets required criteria for VM support.

     NOFOLLOW	 Do not follow symbolic links (pseudo).  This flag is not
		 looked for by the actual code, which looks for FOLLOW.
		 NOFOLLOW is used to indicate to the source code reader that
		 symlinks are intentionally not followed.

     SAVENAME	 Do not free the pathname buffer at the end of the namei()
		 invocation; instead, free it later in NDFREE() so that the
		 caller may access the pathname buffer.  See below for

     SAVESTART	 Retain an additional reference to the parent directory; do
		 not free the pathname buffer.	See below for details.


     The nameidata structure is composed of the following fields:

     ni_startdir      In the normal case, this is either the current directory
		      or the root.  It is the current directory if the name
		      passed in does not start with `/' and we have not gone
		      through any symlinks with an absolute path, and the root

		      In this case, it is only used by lookup(), and should
		      not be considered valid after a call to namei().	If
		      SAVESTART is set, this is set to the same as ni_dvp,
		      with an extra vref(9).  To block NDFREE() from releasing
		      ni_startdir, the NDF_NO_STARTDIR_RELE can be set.

     ni_dvp	      Vnode pointer to directory of the object on which lookup
		      is performed.  This is available on successful return if
		      LOCKPARENT or WANTPARENT is set.	It is locked if
		      LOCKPARENT is set.  Freeing this in NDFREE() can be
		      inhibited by NDF_NO_DVP_RELE, NDF_NO_DVP_PUT, or
		      NDF_NO_DVP_UNLOCK (with the obvious effects).

     ni_vp	      Vnode pointer to the resulting object, NULL otherwise.
		      The v_usecount field of this vnode is incremented.  If
		      LOCKLEAF is set, it is also locked.

		      Freeing this in NDFREE() can be inhibited by
		      the obvious effects).

     ni_cnd.cn_pnbuf  The pathname buffer contains the location of the file or
		      directory that will be used by the namei operations.  It
		      is managed by the uma(9) zone allocation interface.  If
		      the SAVESTART or SAVENAME flag is set, then the pathname
		      buffer is available after calling the namei() function.

		      To only deallocate resources used by the pathname
		      buffer, ni_cnd.cn_pnbuf, then NDF_ONLY_PNBUF flag can be
		      passed to the NDFREE() function.	To keep the pathname
		      buffer intact, the ND_NO_FREE_PNBUF flag can be passed
		      to the NDFREE() function.

FILES    [Toc]    [Back]


SEE ALSO    [Toc]    [Back]

     uio(9), uma(9), VFS(9), vnode(9), vput(9), vref(9)

AUTHORS    [Toc]    [Back]

     This manual page was written by Eivind Eklund <eivind@FreeBSD.org> and
     later significantly revised by Hiten M. Pandya <hmp@FreeBSD.org>.

BUGS    [Toc]    [Back]

     The LOCKPARENT flag does not always result in the parent vnode being
     locked.  This results in complications when the LOCKPARENT is used.  In
     order to solve this for the cases where both LOCKPARENT and LOCKLEAF are
     used, it is necessary to resort to recursive locking.

FreeBSD 5.2.1			 May 27, 2003			 FreeBSD 5.2.1
[ Back ]
 Similar pages
Name OS Title
NDINIT NetBSD pathname lookup
NDINIT OpenBSD pathname lookup
relookup OpenBSD pathname lookup
lookup OpenBSD pathname lookup
lookup NetBSD pathname lookup
namei NetBSD pathname lookup
relookup NetBSD pathname lookup
namei OpenBSD pathname lookup
VOP_LOOKUP FreeBSD lookup a component of a pathname
xlate_pro_add_range IRIX add a translation range
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service