Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933401Ab0KQKBk (ORCPT ); Wed, 17 Nov 2010 05:01:40 -0500 Received: from hera.kernel.org ([140.211.167.34]:53168 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933216Ab0KQKBh (ORCPT ); Wed, 17 Nov 2010 05:01:37 -0500 Message-ID: <4CE3A7E9.3010009@kernel.org> Date: Wed, 17 Nov 2010 11:01:13 +0100 From: Tejun Heo User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9.2.12) Gecko/20101027 Lightning/1.0b2 Thunderbird/3.1.6 MIME-Version: 1.0 To: Jeff Garzik CC: Linus Torvalds , linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org, LKML Subject: Re: [PATCH] libata: remove unlock+relock cycle in ata_scsi_queuecmd References: <20101117062958.GA2894@havoc.gtf.org> <4CE38D70.4010507@garzik.org> In-Reply-To: <4CE38D70.4010507@garzik.org> X-Enigmail-Version: 1.1.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Wed, 17 Nov 2010 10:01:16 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1418 Lines: 37 Hello, Jeff, Linus. On 11/17/2010 09:08 AM, Jeff Garzik wrote: > Looking solely at the SCSI code (ie. ignoring LLD code), it seems > like the magic number zero for serial_number is signaling a boolean > condition "are we an EH command?" > > EH tests this at the very beginning of the abort/reset/explode error > handling sequence, presumably to avoid recursive EH invocations > (scsi_try_to_abort_cmd). > > So maybe an EH expert (Tejun?) can correct me here, but I think we > may be able to completely the lock/get-serial/unlock sequence from > libata, as long as scsi_init_cmd_errh() reliably sets an "I am an EH > command" flag. > > Would be nice if true... Yeah, it's actually nice (for once). libata doesn't use or care about scmd->serial_number at all. The SCSI EH path you mentioned above is not applicable as libata implements its eh_strategy_handler and SCSI only calls scsi_try_to_abort_cmd() for the default EH handler, scsi_unjam_host(). We'll need to test a bit to make sure everything is okay but I'm fairly certain removing it won't break anything fundamental. If something breaks at all, it would be some silly easy-to-fix thing. Thanks. -- tejun -- 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/