From owner-freebsd-hackers Sun Aug 22 23:49:56 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from critter.freebsd.dk (critter.freebsd.dk [212.242.40.131]) by hub.freebsd.org (Postfix) with ESMTP id 30E4214A0B; Sun, 22 Aug 1999 23:49:49 -0700 (PDT) (envelope-from phk@critter.freebsd.dk) Received: from critter.freebsd.dk (localhost [127.0.0.1]) by critter.freebsd.dk (8.9.3/8.9.2) with ESMTP id IAA07326; Mon, 23 Aug 1999 08:47:35 +0200 (CEST) (envelope-from phk@critter.freebsd.dk) To: Greg Lehey Cc: Matthew Dillon , FreeBSD Hackers , FreeBSD Committers , Garrett Wollman Subject: Re: Mandatory locking? In-reply-to: Your message of "Mon, 23 Aug 1999 15:28:49 +0930." <19990823152849.H83273@freebie.lemis.com> Date: Mon, 23 Aug 1999 08:47:34 +0200 Message-ID: <7324.935390854@critter.freebsd.dk> From: Poul-Henning Kamp Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In message <19990823152849.H83273@freebie.lemis.com>, Greg Lehey writes: >> Why should it be made unavailable ? > >So that certain multiple accesses can be done atomically. You don't need that. You initialize a index to 0, and whenever the sector with that index is written, you increment it. At any one time you know that all parityblocks <= your index are valid. All you need to do to recover you index then is to have an ioctl which will read one sector at a time, mark the buffer dirty write it out again. I have seen sources for two well-respected RAID-5 products which do it this way. >I'm a little surprised that there's any objection to the concept of >mandatory locking. Too many of us have had wedged systems because of it I guess... -- Poul-Henning Kamp FreeBSD coreteam member phk@FreeBSD.ORG "Real hackers run -current on their laptop." FreeBSD -- It will take a long time before progress goes too far! To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message