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     vn_fullpath - convert a vnode reference to a full pathname, given a
     process context


     #include <sys/param.h>
     #include <sys/vnode.h>

     vn_fullpath(struct thread *td, struct vnode *vp, char **retbuf,
             char **freebuf);


     The vn_fullpath() function makes a “best effort” attempt to generate a
     string pathname for the passed (locked) vnode; the resulting path, if
     any, will be relative to the root directory of the process associated
     with the passed thread pointer.  The vn_fullpath() function is
     implemented by inspecting the VFS name cache, and attempting to
     reconstruct a path from the process root to the object.

     This process is necessarily unreliable for several reasons: intermediate
     entries in the path may not be found in the cache; files may have more
     than one name (hard links), not all file systems use the name cache
     (specifically, most synthetic file systems do not); a single name may be
     used for more than one file (in the context of file systems covering
     other file systems); a file may have no name (if deleted but still open
     or referenced).  However, the resulting string may still be more useable
     to a user than a vnode pointer value, or a device number and inode
     number.  Code consuming the results of this function should anticipate
     (and properly handle) failure.

     Its arguments are:

     td       The thread performing the call; this pointer will be
              dereferenced to find the process and its file descriptor
              structure, in order to identify the root vnode to use.

     vp       The vnode to search for; must be locked by the caller.

     retbuf   Pointer to a char * that vn_fullpath() may (on success) point at
              a newly allocated buffer containing the resulting pathname.

     freebuf  Pointer to a char * that vn_fullpath() may (on success) point at
              a buffer to be freed, when the caller is done with retbuf.

     Typical consumers will declare two character pointers: fullpath and
     freepath; they will set freepath to NULL, and fullpath to a name to use
     in the event that the call to vn_fullpath() fails.  After done with the
     value of fullpath, the caller will check if freepath is non-NULL, and if
     so, invoke free(9) with a pool type of M_TEMP.


     If the vnode is successfully converted to a pathname, 0 is returned;
     otherwise, an error number is returned.




     This manual page was written by Robert Watson 〈〉.