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NAME
     VOP_OPEN, VOP_CLOSE - open or close a file


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

     int
     VOP_OPEN(struct vnode *vp, int mode, struct ucred *cred,
             struct thread *td, int fdidx);

     int
     VOP_CLOSE(struct vnode *vp, int mode, struct ucred *cred,
             struct thread *td);


DESCRIPTION
     The VOP_OPEN() entry point is called before a file is accessed by a
     process and the VOP_CLOSE() entry point is called after a file is
     finished with by the process.

     The arguments are:

     vp    The vnode of the file.

     mode  The access mode required by the calling process.

     td    The thread which is accessing the file.

     Additionally, VOP_OPEN() can accept a file descriptor number in fdidx;
     this is useful for file systems which require such information, e.g.,
     fdescfs(5).

     The access mode is a set of flags, including FREAD, FWRITE, O_NONBLOCK,
     O_APPEND.


LOCKS
     VOP_OPEN() expects vp to be locked on entry and will leave it locked on
     return.

     VOP_CLOSE() expects at least a reference to be associated with the vnode
     and does not care whether the vnode is locked or not.  The lock and
     reference state is left unchanged on return.  Note that vn_close expects
     an unlocked, referenced vnode and will dereference the vnode prior to
     returning.


IMPLEMENTATION NOTES
     The fdidx argument to VOP_OPEN() is currently unused, use ‘-1’ for the
     meantime; however, this will change in future.


RETURN VALUES
     Zero is returned on success, otherwise an error code is returned.


PSEUDOCODE
     int
     vop_open(struct vnode *vp, int mode, struct ucred *cred, struct thread *td)
     {
         /*
          * Most file systems don’t do much here.
          */
         return 0;
     }


SEE ALSO
     vnode(9), VOP_LOOKUP(9)


AUTHORS
     This manual page was written by Doug Rabson.