Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261784AbUCGJhz (ORCPT ); Sun, 7 Mar 2004 04:37:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261785AbUCGJhz (ORCPT ); Sun, 7 Mar 2004 04:37:55 -0500 Received: from phoenix.infradead.org ([213.86.99.234]:11782 "EHLO phoenix.infradead.org") by vger.kernel.org with ESMTP id S261784AbUCGJhy (ORCPT ); Sun, 7 Mar 2004 04:37:54 -0500 Date: Sun, 7 Mar 2004 09:37:45 +0000 From: Christoph Hellwig To: Dave Kleikamp Cc: Andrew Morton , linux-kernel , linux-xfs@oss.sgi.com, Dave Blaschke Subject: Re: [PATCH] JFS DMAPI Message-ID: <20040307093745.A14680@infradead.org> Mail-Followup-To: Christoph Hellwig , Dave Kleikamp , Andrew Morton , linux-kernel , linux-xfs@oss.sgi.com, Dave Blaschke References: <1078444492.9162.56.camel@shaggy.austin.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <1078444492.9162.56.camel@shaggy.austin.ibm.com>; from shaggy@austin.ibm.com on Thu, Mar 04, 2004 at 05:54:52PM -0600 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2175 Lines: 43 On Thu, Mar 04, 2004 at 05:54:52PM -0600, Dave Kleikamp wrote: > Andrew, > Would you consider adding this patch to -mm? This would add the DMAPI > interface to JFS. This function has long been requested by HSMs > (Hierarchical Storage Managers). It is based on SGI's XFS > implementation, but has been clean up to avoid their vnode interface. Umm, no. There's a reason the XFS code this is based on isn't merged, and the problem is the DMAPI spec. E.g. you still have this utterly incompatible to Linux semantics of providing a mount option to specifiy the canonical name for a mount point as dmapi doesn't understand the concept of multiple mounts for a given fs or namespaces, you still don't get the post-unmount even rights, the handle2path stuff is still as broken, how do you handle the mprotect vs dmapi regions interaction the 2.4 XFS tree has the mprotect vm operation hack for, etc..? So the question is whether IBM just wants to provide this for customers that can live with the incompatbilities or really wants to provide HSM support for mainline. In the first case I'd suggest you clean up the changes to the JFS core to not require ifdefs all over the place and submit that one for mainline inclusion so the dmapi dir can more less be dropped into the tree ala XFS. If IBM actually wants to support proper HSM support for Linux let's go back to the drawing board. Some specific requirements: - move the events from fs-specific code to common code. That we have two filesystems now that want it shows pretty much that fs-specific code is the wrong place. - get rid of the concept of a canoical path in kernelspace. If userspace wants it they can't search the mount tab for the right st_dev to provide dmapi semantics. - clean up the whole ioctl API mess. I think we'd mostly be done with a O_HSM option for open to avoid interactions with the callouts and some generic handle API. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/