Date: Fri, 21 Jan 2000 16:26:59 -0500 (EST) From: Kelly Yancey <kbyanc@posi.net> To: Brian Beattie <beattie@aracnet.com> Cc: fs@FreeBSD.ORG Subject: Re: UDF, userfs Message-ID: <Pine.BSF.4.05.10001211604320.71794-100000@kronos.alcnet.com> In-Reply-To: <Pine.LNX.4.10.10001211012020.28236-100000@shell1.aracnet.com>
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On Fri, 21 Jan 2000, Brian Beattie wrote: > I have made a couple of posts to hackers, that probably should have gone > here to fs. I and thinking about implementing a UDF filesystem. The plan > I am considering, is to implement a "userfs" to allow me to do most of the > work in a user process. > > I have been thinking about the userfs implementation. I will need some > way for the user process to talk the backend of the userfs kernel code. > The two ways I have thought of are I/O,, probably ioctl's or a new system > call. > > I assume that it is possible, using a module to add an entry to the > syscall table, but I lean more towards a new pseudo device to hang the > ioctl's off of. > > I would be ineterested in any comments. I would also like to hear from > anybody who has thought about a userfs implementation for FreeBSD. > I would love this functionality (I've often considered implementing it myself before being occupied by other projects). A userfs implemention would open the doors to all kinds of filesystems and make development of new filesystems much simpler (as debugging could be done in user mode). Currently, filesystems have to pretend to be NFS (i.e. sharity) to bridge the userland/kernel filesystem boundary. However, it is probably important to note again that I have always gotten distracted before investing significant time into pursuing this (read: I'm no expert :) ). Perhaps you have put more thought into it, but the concern that immediately comes to my mind is how to get VOP function calls from kernel-space to user-space. Some kind of up-call mechanism seems in order. You had suggested a pseudo-device, presumably with the intent to have daemons which implement file systems to read from to catch VOPs and write to to return data. I am curious, however, as to how NFS handles the problem. I have never looked at the NFS implemention in FreeBSD (mostly due to lack of time, and partly out of fear :) ). Assuming that it is not too much of a kludge, it might be better not to reinvent that wheel (which may mean the userfs becomes a NFS wrapper much like sharity is). Anyway, those are my somewhat disjoint thoughts, offered at face value ($0.02). Kelly -- Kelly Yancey - kbyanc@posi.net - Richmond, VA Analyst / E-business Development, Bell Industries http://www.bellind.com/ Maintainer, BSD Driver Database http://www.posi.net/freebsd/drivers/ Coordinator, Team FreeBSD http://www.posi.net/freebsd/Team-FreeBSD/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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