From owner-freebsd-fs@FreeBSD.ORG Thu Feb 15 15:04:40 2007 Return-Path: X-Original-To: freebsd-fs@freebsd.org Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id A817616A401 for ; Thu, 15 Feb 2007 15:04:40 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from cyrus.watson.org (cyrus.watson.org [209.31.154.42]) by mx1.freebsd.org (Postfix) with ESMTP id 5008E13C50D for ; Thu, 15 Feb 2007 15:04:40 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from fledge.watson.org (fledge.watson.org [209.31.154.41]) by cyrus.watson.org (Postfix) with ESMTP id 8FC73477DC; Thu, 15 Feb 2007 10:04:39 -0500 (EST) Date: Thu, 15 Feb 2007 15:04:39 +0000 (GMT) From: Robert Watson X-X-Sender: robert@fledge.watson.org To: Tomas Olsson In-Reply-To: Message-ID: <20070215150015.O90799@fledge.watson.org> References: <20070214162938.GA96725@keira.kiwi-computer.com> <20070214173211.L1054@chrishome.localnet> <20070214170808.GC96725@keira.kiwi-computer.com> <20070215044707.GA39168@deviant.kiev.zoral.com.ua> <20070215104537.GC39168@deviant.kiev.zoral.com.ua> <20070215120855.GE39168@deviant.kiev.zoral.com.ua> <20070215134608.GG39168@deviant.kiev.zoral.com.ua> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-fs@freebsd.org, arla-drinkers@stacken.kth.se Subject: Re: Arla on FreeBSD X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Feb 2007 15:04:40 -0000 On Thu, 15 Feb 2007, Tomas Olsson wrote: >> Also, you could look at file handle API, that would save you of path >> lookups after the vnode is looked up first time (look around for vfs_vptofh >> and vfs_fhtovp ops). This API is used by NFS server, so it shall work :). >> > That's an idea. We used that before in another context, but then we ran into > trouble with too many OSes so we dropped it. Depends on how much code one > can share. It has been ages since I looked at the xfs/nnpfs internals, but I thought it already used file handles to identify cache files to the kernel? I seem to recall several of our fh*() system calls were added by Assar specifically in support of Arla work. With regard to cache files -- historically (i.e., last time I looked closely), there was a one-to-one mapping between cache files and files in the Arla working set, and all files were transfered "whole" into the local cache. This was in contrast to AFS's chunking behavior. I assume the cache file changes to support "lines" in the cache are in support of adding chunking to Arla. Is it the case that one file visible in /afs may now be backed by pages coming from different cache files? How does this interact with the vnode pager? I assume you actually end up with two pagers -- one for the file as visible in /afs, and then satisfy the pager's VOP requests by forwarding them to the right one of the cache vnodes? I trust you don't mmap the cache vnode, which would lead to cache consistency issues between any mappings of the /afs vnode vs the cache vnode? Any chance we could attract you to BSDCan to meet in person to discuss this? :-) Thanks, Robert N M Watson Computer Laboratory University of Cambridge