From owner-freebsd-hackers Thu Jan 7 22:08:54 1999 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id WAA08602 for freebsd-hackers-outgoing; Thu, 7 Jan 1999 22:08:54 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from apollo.backplane.com (apollo.backplane.com [209.157.86.2]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id WAA08597 for ; Thu, 7 Jan 1999 22:08:52 -0800 (PST) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.1/8.9.1) id WAA37994; Thu, 7 Jan 1999 22:08:22 -0800 (PST) (envelope-from dillon) Date: Thu, 7 Jan 1999 22:08:22 -0800 (PST) From: Matthew Dillon Message-Id: <199901080608.WAA37994@apollo.backplane.com> To: Alfred Perlstein Cc: freebsd-hackers@FreeBSD.ORG Subject: Re: (mfs idea) Re: questions/problems with vm_fault() in Stable Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :The buffer is just marked as dirty so that the FFS doesn't overwrite it. :MFS _must_ reclaim them into it's own address space to avoid being :overwritten. : :Since i assume that when a buffer is flushed it should then be free :you have to 'give something back' :... I think I understand. The problem is that the system has no clue that the vm_page needs to be returned to MFS. Once MFS gives the page away, that is the end of the matter as far as the system is concerned. Now, of course, we could *make* the system aware that it needs to do something special with the page -- but if we do not create a generally useful mechanism it would be nothing more then a bad hack. Any mechanism that we would create to handle this situation would have to handle moving the page across an arbitrary number of VFS layers, and then either handed back down through the same layers or handed back to the original layer... we cannot assume it will be moved across only two VFS layers. Essentially, the vm_alias mechanism that I described would be able to handle this sort of situation. Could we hack in something simpler? Probably, but it might not be generic enough to be useable in other situations. -Matt Matthew Dillon Engineering, HiWay Technologies, Inc. & BEST Internet Communications & God knows what else. (Please include original email in any response) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message