vdrop(9) [freebsd man page]

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

NAME

     vhold, vdrop, vdropl -- acquire/release a hold on a vnode

SYNOPSIS

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

     void
     vhold(struct vnode *vp);

     void
     vholdl(struct vnode *vp);

     void
     vdrop(struct vnode *vp);

     void
     vdropl(struct vnode *vp);

DESCRIPTION

     The vhold() and vholdl() functions increment the v_holdcnt of the given vnode.  If the vnode has already been added to the free list and is
     still referenced, it will be removed.

     The vdrop() and vdropl() functions decrement the v_holdcnt of the vnode.  If the holdcount is less than or equal to zero prior to calling
     vdrop() or vdropl(), the system will panic.  If the vnode is no longer referenced, it will be freed.

     vhold() and vdrop() lock the vnode interlock while vholdl() and vdropl() expect the interlock to already be held.

SEE ALSO

     vnode(9)

AUTHORS

     This manual page was written by Chad David <davidc@acns.ab.ca>.

BSD
								   April 1, 2007							       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