From: "J. Bruce Fields" Subject: Re: starting 90-second grace period Date: Fri, 11 Dec 2009 14:50:47 -0500 Message-ID: <20091211195047.GA15758@fieldses.org> References: <1629BB1E-EB8B-478C-8170-60413A5140A2@netapp.com> <1260554515.15701.0.camel@localhost> <1260555643.15701.4.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Tharindu Rukshan Bamunuarachchi , Andy Adamson , linux-nfs@vger.kernel.org To: Trond Myklebust Return-path: Received: from fieldses.org ([174.143.236.118]:44611 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755596AbZLKTup (ORCPT ); Fri, 11 Dec 2009 14:50:45 -0500 In-Reply-To: <1260555643.15701.4.camel@localhost> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Fri, Dec 11, 2009 at 01:20:43PM -0500, Trond Myklebust wrote: > On Fri, 2009-12-11 at 23:39 +0530, Tharindu Rukshan Bamunuarachchi > wrote: > > then why is it 90 by default ... is it RFC/Protocol requirement ? > > The purpose of the grace period is to give the clients enough time to > notice that the server has rebooted, and to reclaim their existing locks > without danger of having somebody else steal the lock from them. > > It is not a protocol requirement, but it is definitely a strongly > recommended feaature if you don't want to see corruption in your > mailbox/database/logfile/... that relies on those locks. There are a few things we could do to lessen the pain of the grace period, though--such as ending it when we know it's done. (In the v4 case, that's just when we know there are no clients to recover state; in the v4.1 case, that's when all the RECLAIM_COMPLETE's are done.) I'm hoping to work on that for 2.6.34. --b.