Date: Thu, 19 Aug 1999 00:41:29 -0500 From: Russell Cattelan <cattelan@thebarn.com> To: "Alton, Matthew" <Matthew.Alton@anheuser-busch.com> Cc: "'Hackers@FreeBSD.ORG'" <Hackers@FreeBSD.ORG>, "'fs@FreeBSD.ORG'" <fs@FreeBSD.ORG> Subject: Re: BSD XFS Port & BSD VFS Rewrite Message-ID: <37BB9909.53D356FE@thebarn.com> References: <0740CBD1D149D31193EB0008C7C56836EB8AFC@STLABCEXG012>
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Glad to hear somebody is willing to dive in to XFS. Right now I am one of three people working on the XFS to linux port, so I have pretty good view of what is currently happening. When is it going to be ready? Don't hold your breath. Officially SGI has said by the end of the year, technically... whew frankly I can't even guess. I would hope within a month or so we will have the basics of a FS. There are a lot of hurtles to overcome. XFS is a very very complex file system that relies on some of the more advanced features of IRIX. The buffer cache and chunk cache (chunking buffers together to do large IO) are two examples that come to mind. SGI is rewriting the buffer cache (calling it the page cache) such that is will be able to support XFS. chunk cache... ? not sure what we are going to do with that. We have been having several discussions about the best way to "interface". IRIX uses VFS,VNODE,BEHAVIOR which is similar to the BSD's interface but of course very IRIX specific. Linux's vfs/vnode is different from either. Realizing this, a lot of our discussions have been around how to go at making a new/modify existing interface layer that might be more "universal" i.e. not irix not linux not bsd not etc.... specific. In reading Terry's & Bill's comments seems there is a a lot of room for improvement. Initially we trying to make as few changes as possible to XFS to get an initial implementation running on linux. After we get things running we will start to analyze where the problems exist, and decide what direction in terms of interface to take at that time. I would like any constructive input people have on this matter. I have a pretty good chance of setting design direction. Be waned: SGI at the moment is committed to linux, development directions will favor that platform. They are not against other OS's being XFS'atized but SGI is in the business of selling hardware/solutions based on that hardware and linux one of the OS they have decided to use for their intel based boxes. Also as far as the GPL issue goes, get over it! I understand the issues and agree with many of the points. My suggestion lets find a way to work with the GPL (i.e. loadable kernel module / softupdates model) If somebody has a very very good argument/solution to the licensing debate let me know, I can present it to the people dealing with the lawyers. The license issue has slowed the release of the actual code more than anything else, and will not be revisited again without great pain. > I am currently conducting a thorough study of the VFS subsystem > in preparation for an all-out effort to port SGI's XFS filesystem to > FreeBSD 4.x at such time as SGI gives up the code. Matt Dillon > has written in hackers- that the VFS subsystem is presently not > well understood by any of the active kernel code contributers and > that it will be rewritten later this year. This is obviously of great > concern to me in this port. I greatly appreciate all assistance in > answering the following questions: > > 1) What are the perceived problems with the current VFS? > 2) What options are available to us as remedies? > 3) To what extent will existing FS code require revision in order > to be useful after the rewrite? > 4) Will Chapters 6,7,8 & 9 of "The Design and Implementation of > the 4.4BSD Operating System" still pertain after the rewrite? > 5) How important are questions 3 & 4 in the design of the new > VFS? > > I believe that the VFS is conceptually sound and that the existing > semantics should be strictly retained in the new code. Any new > functionality should be added in the form of entirely new kernel > routines and system calls, or possibly by such means as > converting the existing routines to the vararg format &etc. > > Does anyone know when SGI will release XFS? > > -- Russell Cattelan cattelan@thebarn.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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