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NDINIT (9)
  • >> NDINIT (9) ( FreeBSD man: Ядро )

  • BSD mandoc
     

    NAME

    namei
    
     
    NDINIT
    
     
    NDFREE
    
     
    NDHASGIANT
    
     - pathname translation and lookup operations
    
     
    

    SYNOPSIS

       #include <sys/param.h>
       #include <sys/proc.h>
       #include <sys/namei.h>
    int namei (struct nameidata *ndp);
    void Fo NDINIT Fa struct nameidata *ndp u_long op u_long flags Fa enum uio_seg segflg const char *namep struct thread *td Fc Ft void NDFREE (struct nameidata *ndp const uint flags);
    int NDHASGIANT (struct nameidata *ndp);
     

    DESCRIPTION

    The facility allows the client to perform pathname translation and lookup operations. The 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. If the Giant lock is required, will acquire it if the caller indicates it is MPSAFE in which case the caller must later release Giant based on the results of NDHASGIANT (.);

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

    Fa ndp
    The Vt struct nameidata to initialize.
    Fa 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.
    Fa flags
    Operation flags. Several of these can be effective at the same time.
    Fa segflg
    UIO segment indicator. This indicates if the name of the object is in userspace (UIO_USERSPACE ) or in the kernel address space (UIO_SYSSPACE )
    Fa namep
    Pointer to the component's pathname buffer (the file or directory name that will be looked up).
    Fa td
    The thread context to use for operations and locks.

     

    NAMEI OPERATION FLAGS

    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_UNLOCK9 should be used to release the lock (or vput(9) which is equivalent to calling VOP_UNLOCK9 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_UNLOCK9 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).
    MPSAFE
    With this flag set, namei ();
    will conditionally acquire Giant if it is required by a traversed file system. MPSAFE callers should pass the results of NDHASGIANT ();
    to VFS_UNLOCK_GIANT in order to conditionally release Giant if necessary.
    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 details.
    SAVESTART
    Retain an additional reference to the parent directory; do not free the pathname buffer. See below for details.

     

    ALLOCATED ELEMENTS

    The Vt 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 otherwise.

    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 NDF_NO_VP_RELE , NDF_NO_VP_PUT or NDF_NO_VP_UNLOCK (with the obvious effects).

    ni_cnd.cn_pnbuf
    The pathname buffer contains the location of the file or directory that will be used by the 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 NDF_NO_FREE_PNBUF flag can be passed to the NDFREE ();
    function.

     

    FILES

    src/sys/kern/vfs_lookup.c

     

    SEE ALSO

    uio(9), uma(9), VFS(9), VFS_UNLOCK_GIANT9, vnode(9), vput(9), vref(9)  

    AUTHORS

    An -nosplit This manual page was written by An Eivind Eklund Aq [email protected] and later significantly revised by An Hiten M. Pandya Aq [email protected] .  

    BUGS

    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.

    Non-MPSAFE file systems exist, requiring callers to conditionally unlock Giant


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    NAMEI OPERATION FLAGS
    ALLOCATED ELEMENTS
    FILES
    SEE ALSO
    AUTHORS
    BUGS


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