From owner-freebsd-current@FreeBSD.ORG Sat Aug 23 11:32:46 2003 Return-Path: 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 DE84A16A4C0 for ; Sat, 23 Aug 2003 11:32:46 -0700 (PDT) Received: from beastie.mckusick.com (beastie.mckusick.com [209.31.233.184]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4641043FEA for ; Sat, 23 Aug 2003 11:32:46 -0700 (PDT) (envelope-from mckusick@beastie.mckusick.com) Received: from beastie.mckusick.com (localhost [127.0.0.1]) by beastie.mckusick.com (8.12.8/8.12.3) with ESMTP id h7NIWiol053778; Sat, 23 Aug 2003 11:32:44 -0700 (PDT) (envelope-from mckusick@beastie.mckusick.com) Message-Id: <200308231832.h7NIWiol053778@beastie.mckusick.com> To: "Poul-Henning Kamp" In-Reply-To: Your message of "Sat, 23 Aug 2003 11:01:28 +0200." <24772.1061629288@critter.freebsd.dk> Date: Sat, 23 Aug 2003 11:32:43 -0700 From: Kirk McKusick cc: "\[iso-8859-2\] Branko F. Gračnar" cc: freebsd-current@freebsd.org cc: Robert Watson cc: Paul Saab Subject: Re: mksnap_ffs, snapshot issues, again X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 23 Aug 2003 18:32:47 -0000 To: Kirk McKusick cc: "[iso-8859-2] Branko F. Gračnar" , Paul Saab , Robert Watson , freebsd-current@freebsd.org Subject: Re: mksnap_ffs, snapshot issues, again From: "Poul-Henning Kamp" In-Reply-To: Your message of "Sat, 23 Aug 2003 01:32:38 PDT." Date: Sat, 23 Aug 2003 11:01:28 +0200 X-ASK-Info: Whitelist match In message <200308230832.h7N8Wcol050681@beastie.mckusick.com>, Kirk McKusick writes: >But, to get to the problem that you are having with accessing your >filesystem. The problem is that although the filesystem is only >locked briefly, the snapshot file is locked for the entire 48 minutes. >Thus, if you touch the snapshot file (by for example doing a "stat" >on it), then the process doing the stat will hang for 48 minutes. Isn't there some way we can loosen this aspect up ? Either by having stat know about it and return approximate info or simply by failing ? (I pressume that making the sleep interruptible would break all sorts of standards) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe The race to the root problem in general could be largely solved by changing lookup (VOP_LOOKUP really) to release the lock that it holds on the directory before blocking on the next component in the case where it is doing a lookup without intent to create. If we did this, then a single locked node would have lookups pile up on itself, but could not cascade to the root. A related change would be to do an interruptable locking request on the node so that if one did an `ls -l foo' where foo was say a locked snapshot, it would be possible to interrupt it. ~Kirk