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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.