1 files changed, 47 insertions, 7 deletions
diff --git a/share/man/man9/vrele.9 b/share/man/man9/vrele.9
index be5d5f7..8d28d5e 100644
--- a/share/man/man9/vrele.9
+++ b/share/man/man9/vrele.9
@@ -1,6 +1,7 @@
 .\" -*- nroff -*-
 .\"
 .\" Copyright (c) 1996 Doug Rabson
+.\" Copyright (c) 2010 Konstantin Belousov <kib@FreeBSD.org>
 .\"
 .\" All rights reserved.
 .\"
@@ -28,17 +29,23 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd July 24, 1996
+.Dd October 17, 2010
 .Dt VRELE 9
 .Os
 .Sh NAME
-.Nm vrele
+.Nm vput ,
+.Nm vrele ,
+.Nm vunref
 .Nd decrement the use count for a vnode
 .Sh SYNOPSIS
 .In sys/param.h
 .In sys/vnode.h
 .Ft void
+.Fn vput "struct vnode *vp"
+.Ft void
 .Fn vrele "struct vnode *vp"
+.Ft void
+.Fn vunref "struct vnode *vp"
 .Sh DESCRIPTION
 Decrement the
 .Va v_usecount
@@ -48,18 +55,51 @@ field of a vnode.
 the vnode to decrement
 .El
 .Pp
-Any code in the system which is using a vnode should call
+The
 .Fn vrele
-when it is finished with the vnode.
+function takes an unlocked vnode and returns with the vnode unlocked.
+.Pp
+.The
+.Fn vput
+function should be given a locked vnode as argument, the vnode is unlocked
+after the function returned.
+The
+.Fn vput
+is operationally equivalent to calling
+.Xr VOP_UNLOCK 9
+followed by
+.Xr vrele 9 ,
+with less overhead.
+.Pp
+The
+.Fn vunref
+function takes a locked vnode as argument, and returns with the vnode locked.
+Nonetheless, the
+.Fn vunref
+might drop the vnode lock during the operation, so caller should not expect
+that non-doomed vnode is still non-doomed after the function returned.
+.Pp
+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
 .Va v_usecount
-field of the vnode reaches zero, then it will be placed on the free list.
+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
+.Va Giant
+mutex should be conditionally locked around the call.
+.Pp
+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
+.Xr vflush 9 .
 .Sh SEE ALSO
 .Xr vget 9 ,
 .Xr vnode 9 ,
-.Xr vput 9 ,
 .Xr vref 9 ,
 .Xr vrefcnt 9
 .Sh AUTHORS
 This manual page was written by
-.An Doug Rabson .
+.An Doug Rabson
+and
+.An Konstantin Belousov .