From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Garzik Subject: Re: [pnfs] [PATCH 05/28] pnfsblock: expose scsi interface Date: Wed, 12 Mar 2008 18:42:29 -0400 Message-ID: <47D85C55.5060101@garzik.org> References: <1205263929-8346-1-git-send-email-iisaman@citi.umich.edu> <1205263929-8346-2-git-send-email-iisaman@citi.umich.edu> <1205263929-8346-3-git-send-email-iisaman@citi.umich.edu> <1205263929-8346-4-git-send-email-iisaman@citi.umich.edu> <1205263929-8346-5-git-send-email-iisaman@citi.umich.edu> <1205263929-8346-6-git-send-email-iisaman@citi.umich.edu> <47D805DE.9000100@panasas.com> <20080312164306.GA3519@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from srv5.dvmed.net ([207.36.208.214]:52530 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755471AbYCLWmn (ORCPT ); Wed, 12 Mar 2008 18:42:43 -0400 In-Reply-To: <20080312164306.GA3519@infradead.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Christoph Hellwig Cc: Benny Halevy , Fred Isaman , Andy Adamson , pnfs@linux-nfs.org, linux-scsi Christoph Hellwig wrote: > On Wed, Mar 12, 2008 at 06:33:34PM +0200, Benny Halevy wrote: >> This calls for a layering violation. >> >> To fill-in more context, here's an excerpt from the next patch, >> showing how you use shost_class to scan all scsi disks: > > Yes, absolutely. No one outside of few places in the core scsi code > should ever iterate over the scsi disks. > >> My question is how should a proper API between the scsi layer and >> the block layout driver look like? >> >> Can you list your requirements, e.g.: >> - scanning all available devices, >> >> - discovering new devices on the fly >> >> - getting notified for new devices? > > Neither. pnfs shouldn't open block devices from kernelspace at all, > but do it's disovery in userspace. > > Or even better this whole block layout driver crap should go away > completely and the people who have designed it beaten up until they > aren't recognizable anymore. The fact that NFSv4.1 requires SCSI is stupid crap, too. The _design_ is a layering violation. I say we just say "no". NFS _clients_ should not need to know deep device-level details about how to store their data, and should not require SCSI in order to store data. Jeff