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.