svn commit: r213983 - head/share/man/man9

[Konstantin Belousov]

Author: kib
Date: Sun Oct 17 16:30:33 2010
New Revision: 213983
URL: http://svn.freebsd.org/changeset/base/213983

Log:
  Document vunref(9), add some important notes for vrele(9) and vput(9).
  Merge all three manpages to one, removing separate file for vput(9).
  
  MFC after:	1 week

Deleted:
  head/share/man/man9/vput.9
Modified:
  head/share/man/man9/Makefile
  head/share/man/man9/vrele.9

Modified: head/share/man/man9/Makefile
==============================================================================
--- head/share/man/man9/Makefile	Sun Oct 17 15:55:46 2010	(r213982)
+++ head/share/man/man9/Makefile	Sun Oct 17 16:30:33 2010	(r213983)
@@ -364,7 +364,6 @@ MAN=	accept_filter.9 \
 	VOP_STRATEGY.9 \
 	VOP_VPTOCNP.9 \
 	VOP_VPTOFH.9 \
-	vput.9 \
 	vref.9 \
 	vrefcnt.9 \
 	vrele.9 \
@@ -1366,6 +1365,8 @@ MLINKS+=VOP_RDWR.9 VOP_READ.9 \
 	VOP_RDWR.9 VOP_WRITE.9
 MLINKS+=VOP_REMOVE.9 VOP_RMDIR.9
 MLINKS+=vref.9 VREF.9
+MLINKS+=vrele.9 vput.9 \
+	vrele.9 vunref.9
 MLINKS+=vslock.9 vsunlock.9
 MLINKS+=zero_copy.9 zero_copy_sockets.9
 MLINKS+=zone.9 uma.9 \

Modified: head/share/man/man9/vrele.9
==============================================================================
--- head/share/man/man9/vrele.9	Sun Oct 17 15:55:46 2010	(r213982)
+++ head/share/man/man9/vrele.9	Sun Oct 17 16:30:33 2010	(r213983)
@@ -1,6 +1,7 @@
 .\" -*- nroff -*-
 .\"
 .\" Copyright (c) 1996 Doug Rabson
+.\" Copyright (c) 2010 Konstantin Belousov <kib at 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 .