From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 93FE6C43334 for ; Mon, 20 Jun 2022 06:29:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235858AbiFTG3L (ORCPT ); Mon, 20 Jun 2022 02:29:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53220 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238464AbiFTG2g (ORCPT ); Mon, 20 Jun 2022 02:28:36 -0400 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 96DC363FE; Sun, 19 Jun 2022 23:28:32 -0700 (PDT) Received: by verein.lst.de (Postfix, from userid 2407) id 9D91C6732D; Mon, 20 Jun 2022 08:28:28 +0200 (CEST) Date: Mon, 20 Jun 2022 08:28:28 +0200 From: Christoph Hellwig To: Hannes Reinecke Cc: Damien Le Moal , John Garry , axboe@kernel.dk, jejb@linux.ibm.com, martin.petersen@oracle.com, brking@us.ibm.com, hch@lst.de, linux-block@vger.kernel.org, linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, chenxiang66@hisilicon.com Subject: Re: [PATCH RFC v2 03/18] scsi: core: Implement reserved command handling Message-ID: <20220620062828.GA10753@lst.de> References: <1654770559-101375-1-git-send-email-john.garry@huawei.com> <1654770559-101375-4-git-send-email-john.garry@huawei.com> <88d192b5-741b-7104-7f72-0178aa18bafb@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <88d192b5-741b-7104-7f72-0178aa18bafb@suse.de> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 20, 2022 at 08:24:24AM +0200, Hannes Reinecke wrote: > So my idea for SATA is simply _not_ to use reserved tags. > Any TMF functions (or the equivalent thereof) should always be sent as > non-NCQ commands. And when doing so we're back to QD=1 on SATA anyway, so > there _must_ be tags available. Consequently the main reason for having > reserved tags (namely to guarantee that tags are available for TMF) doesn't > apply here. At least in the non-elevator case (which includes all passthrough I/O) request have tags assigned as soon as they are allocated. So, we absolutely can have all tags allocated and then need to do a TMF.