NAME

       vput, vrele, vunref — decrement the use count for a vnode

SYNOPSIS

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

       void
       vput(struct vnode *vp);

       void
       vrele(struct vnode *vp);

       void
       vunref(struct vnode *vp);

DESCRIPTION

       Decrement the v_usecount field of a vnode.

       vp  the vnode to decrement

       The vrele() function takes an unlocked vnode and returns with the vnode unlocked.

       The  vput() function should be given a locked vnode as argument, the vnode is unlocked after the function
       returned.  The vput() is operationally equivalent to calling VOP_UNLOCK(9)  followed  by  vrele(9),  with
       less overhead.

       The vunref() function takes a locked vnode as argument, and returns with the vnode locked.

       Any  code  in  the  system  which  signified its use of a vnode by usecount should call one of the listed
       function to decrement use counter.  If the v_usecount field of the non-doomed vnode reaches zero, then it
       will be inactivated and placed on the free list.  Since the functions might need to  call  VOPs  for  the
       vnode, the Giant mutex should be conditionally locked around the call.

       The  hold  count for the vnode is always greater or equal to the usecount.  Non-forced unmount fails when
       mount point owns a vnode that has non-zero usecount, see vflush(9).

SEE ALSO

       vget(9), vnode(9), vref(9), vrefcnt(9)

AUTHORS

       This manual page was written by Doug Rabson and
       Konstantin Belousov.

Debian                                          November 20, 2010                                       VRELE(9)