Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751989AbWCBVZg (ORCPT ); Thu, 2 Mar 2006 16:25:36 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751641AbWCBVZg (ORCPT ); Thu, 2 Mar 2006 16:25:36 -0500 Received: from smtp.osdl.org ([65.172.181.4]:9376 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751634AbWCBVZf (ORCPT ); Thu, 2 Mar 2006 16:25:35 -0500 Date: Thu, 2 Mar 2006 13:25:12 -0800 (PST) From: Linus Torvalds To: Douglas Gilbert cc: Kai Makisara , Matthias Andree , Mark Rustad , linux-scsi@vger.kernel.org, Linux Kernel Mailing List Subject: Re: sg regression in 2.6.16-rc5 In-Reply-To: <44074CA1.3000007@torque.net> Message-ID: References: <4404AA2A.5010703@torque.net> <20060301083824.GA9871@merlin.emma.line.org> <4405F6F1.9040106@torque.net> <44074CA1.3000007@torque.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1442 Lines: 34 On Thu, 2 Mar 2006, Douglas Gilbert wrote: > > As more information has come to light, the worst case > "big transfer" of a single SCSI command through sg (and > st I suspect) is 512 KB **. With full coalescing that figure > goes up to 4 MB **. I am also aware that some users > increase SG_SCATTER_SZ in the sg driver to get larger > "big transfer"s than sg's current limit of (8MB - 32KB) **. > That facility has now gone (i.e. upping SG_SCATTER_SZ will > have no effect) with no replacement mechanism. > > So I'll add my vote to "revert this change before lk 2.6.16" > with a view to applying it after some solution to the "big > transfer" problem is found. Considering that the old code was apparently known-broken due to not honoring the use_clustering flag, I would say that the more likely thing is that very few people use sg in the first place, and we should wait and see what the reaction is to actually fixing a real bug. Doing more than page-sized transfers can be hard/impossible in virtualized environments, for example. In contrast, upping the limits should be fairly easy, I assume. Same goes for if some driver disables clustering even though it shouldn't. No? Linus - 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/