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
Check Out this Related Man Page
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
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