VOP_LINK(9)

NAME

     VOP_LINK -- create a new name for a file

SYNOPSIS

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

     int
     VOP_LINK(struct vnode *dvp, struct vnode *vp, struct componentname *cnp);

DESCRIPTION

     This links a new name in the specified directory to an existing file.

     Its arguments are:

     dvp       the vnode of the directory

     vp        the vnode of the file to be linked

     cnp       pathname information about the file

     The pathname info should not be released on exit because it is done by
     the caller.  The directory and file vnodes should not be released on
     exit.

LOCKS

     VOP_LINK() expects the directory and file vnodes to be locked on entry
     and will leave the vnodes locked on return.

RETURN VALUES

     Zero is returned if the file was linked successfully, otherwise an error
     is returned.

PSEUDOCODE

     int
     vop_link(struct vnode *dvp, struct vnode *vp, struct componentname *cnp)
     {
	 int error = 0;

	 if (vp->v_mount != dvp->v_mount)
	     return (EXDEV);

	 if (vp would have too many links)
	     return (EMLINK);

	 if (vp is immutable)
	     return (EPERM);

	 /*
	  * Increment link count of vp and write back the on-disc version of it.
	  */
	 ...;

	 if (!error) {
	     /*
	      * Add the new name to the directory.
	      */
	     ...;
	 }

	 return error;
     }

ERRORS

     [EMLINK]		The file has too many links.

     [EPERM]		The file is immutable.

     [EXDEV]		A hard link is not possible between different file
			systems.

SEE ALSO

     vn_lock(9), vnode(9)

AUTHORS

     This man page was originally written by Doug Rabson.