vref(9) [freebsd man page]

VREF(9) 						   BSD Kernel Developer's Manual						   VREF(9)

NAME

     vref -- increment the use count for a vnode

SYNOPSIS

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

     void
     vref(struct vnode *vp);

DESCRIPTION

     Increment the v_usecount field of a vnode.

     vp  the vnode to increment

     Each vnode maintains a reference count of how many parts of the system are using the vnode.  This allows the system to detect when a vnode is
     no longer being used and can be safely recycled for a different file.

     Any code in the system which is using a vnode (e.g. during the operation of some algorithm or to store in a data structure) should call
     vref().

SEE ALSO

     vget(9), vnode(9), vput(9), vrefcnt(9), vrele(9)

AUTHORS

     This manual page was written by Doug Rabson.

BSD
								   July 24, 1996							       BSD

VRELE(9)						   BSD Kernel Developer's Manual						  VRELE(9)

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 opera-
     tionally 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.

BSD
								 November 20, 2010							       BSD