From owner-freebsd-current@FreeBSD.ORG  Tue Jun 13 19:55:23 2006
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
X-Original-To: current@freebsd.org
Delivered-To: freebsd-current@FreeBSD.ORG
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id C872316A41B;
	Tue, 13 Jun 2006 19:55:23 +0000 (UTC)
	(envelope-from mi+mx@aldan.algebra.com)
Received: from aldan.algebra.com (aldan.algebra.com [216.254.65.224])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 0CC9E43D48;
	Tue, 13 Jun 2006 19:55:22 +0000 (GMT)
	(envelope-from mi+mx@aldan.algebra.com)
Received: from corbulon.video-collage.com
	(static-151-204-231-237.bos.east.verizon.net [151.204.231.237])
	by aldan.algebra.com (8.13.6/8.13.6) with ESMTP id k5DJtKZY018488
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK);
	Tue, 13 Jun 2006 15:55:21 -0400 (EDT)
	(envelope-from mi+mx@aldan.algebra.com)
Received: from [172.21.130.86] (mx-broadway [38.98.68.18])
	by corbulon.video-collage.com (8.13.6/8.13.6) with ESMTP id
	k5DJtEnV054105
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO);
	Tue, 13 Jun 2006 15:55:15 -0400 (EDT)
	(envelope-from mi+mx@aldan.algebra.com)
From: Mikhail Teterin <mi+mx@aldan.algebra.com>
Organization: Virtual Estates, Inc.
To: current@freebsd.org
Date: Tue, 13 Jun 2006 15:55:08 -0400
User-Agent: KMail/1.9.1
MIME-Version: 1.0
Content-Type: text/plain;
  charset="us-ascii"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline
Message-Id: <200606131555.09143.mi+mx@aldan.algebra.com>
X-Virus-Scanned: ClamAV 0.88/1536/Mon Jun 12 17:07:37 2006 on
	corbulon.video-collage.com
X-Virus-Status: Clean
X-Scanned-By: MIMEDefang 2.43
X-Mailman-Approved-At: Tue, 13 Jun 2006 20:50:50 +0000
Cc: jmg@freebsd.org
Subject: EVFILT_VNODE vs. fstat()
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Tue, 13 Jun 2006 19:55:23 -0000

Hello!

I have a program, that waits for the input file to be written to (using 
EVFILT_VNODE, fflags = NOTE_EXTEND) to process it.

When kevent() returns upon the file's extension, the program calls fstat() to 
learn the new size of the file.

Every once in a while, the fstat still reports the old size and my program 
goes into kevent() once again.

Is this discrepancy "normal"? Thanks!

	-mi

P.S. I would love to avoid having to call fstat() at all, but -- unlike 
EVFILT_READ -- the EVFILT_VNODE/NOTE_EXTEND does not place any additional 
results into the event's data :-( Using EVFILT_READ is not straigtforward 
either, because I mmap input, instead of read-ing it...