From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: tag handling refactor V2 Date: Wed, 12 Nov 2014 17:15:38 -0800 Message-ID: <1415841338.7154.33.camel@jarvis.lan> References: <1415634990-3023-1-git-send-email-hch@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from bedivere.hansenpartnership.com ([66.63.167.143]:51866 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753306AbaKMBPk (ORCPT ); Wed, 12 Nov 2014 20:15:40 -0500 In-Reply-To: <1415634990-3023-1-git-send-email-hch@lst.de> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Christoph Hellwig Cc: linux-scsi@vger.kernel.org, Robert Elliott , Hannes Reinecke , "Martin K. Petersen" , Bart van Assche , Jens Axboe , Kashyap Desai , Sreekanth Reddy , Mike Christie , Guennadi Liakhovetski , usb-storage@lists.one-eyed-alien.net On Mon, 2014-11-10 at 16:56 +0100, Christoph Hellwig wrote: > - for those drivers looking at the command tagged information we'd need > to quiesce the LUN. No driver but the 53c700 driver does that, and the > 53c700 does it at a target-level, which despite a comment claiming it's > needed doesn't seem to make sense given the code. I can answer that from ancient memory. The mid-layer tag tracking wasn't sufficient to track the negotiated state of the tags. the 53c700 was constructed before the slave alloc/configure routines came along, so it used a per target tracker for the tag negotiation (i.e. it was all on or all off per target). The reason for the quiesce is so as not to have to try to work out if any LUN has any tagged commands outstanding when changing to untagged. James