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 AABEDC433EF for ; Mon, 11 Jul 2022 17:55:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229690AbiGKRzw (ORCPT ); Mon, 11 Jul 2022 13:55:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58114 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229765AbiGKRzv (ORCPT ); Mon, 11 Jul 2022 13:55:51 -0400 Received: from mail-wr1-f42.google.com (mail-wr1-f42.google.com [209.85.221.42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C00E7CB7B; Mon, 11 Jul 2022 10:55:49 -0700 (PDT) Received: by mail-wr1-f42.google.com with SMTP id d16so7987412wrv.10; Mon, 11 Jul 2022 10:55:49 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=txFXdouWdbSMaKn/caC2kD6TFZVlGEJSQ/STyjeuePM=; b=BxSHKxONkAubYXXEnjLsxUhliMo19FXENBf7GX8pzgiTrD39un4ucSB3FTgPlnvFMD x21E7V76RgBajKzKgWsK60YlRcdy4tHdbPYVuK2kToYD7pYkctPmeTCga3TCLesehC0I xBT7Rk7tJCphu///zn9wM3cC/hpNG08fBFH1j5Nee2hK3TA0J7SITG2y6VuJAMlll3l1 DFkq2YDcXMJorLWbYhezdL/WMkCC0JwAgJOnUYkzMgVuIVphYDcbifmICIRgHUMYcABp yBGZnO1zjzbIfttpyA7MVr7tsVe6epV2FMYJWmJvf9vjpm+VdUKH/1E9SgPHIOepq2Dt 6JBw== X-Gm-Message-State: AJIora/FjRkhHOmAdA3v+cgEunIGBdm4go0Nz+YB4Gh0Lp+JKll3jL7P DMlXQz/KzmOStbzYao01yWk= X-Google-Smtp-Source: AGRyM1sKxx1B26hTHr9NFnILGrSO5IkEVbBifXCrW4nydchvlUTDPmtgCkdme4W/ypt+B+OyHU0BLw== X-Received: by 2002:adf:f946:0:b0:21d:6433:a7bb with SMTP id q6-20020adff946000000b0021d6433a7bbmr18582857wrr.518.1657562148165; Mon, 11 Jul 2022 10:55:48 -0700 (PDT) Received: from [10.100.102.14] (46-117-125-14.bb.netvision.net.il. [46.117.125.14]) by smtp.gmail.com with ESMTPSA id w2-20020adfde82000000b00213ba3384aesm6353066wrl.35.2022.07.11.10.55.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 11 Jul 2022 10:55:47 -0700 (PDT) Message-ID: <43955a42-7185-2afc-9a55-80cc2de53bf9@grimberg.me> Date: Mon, 11 Jul 2022 20:55:45 +0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Subject: Re: [PATCH for-next 3/4] io_uring: grow a field in struct io_uring_cmd Content-Language: en-US To: Jens Axboe , Kanchan Joshi , hch@lst.de, kbusch@kernel.org Cc: io-uring@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, asml.silence@gmail.com, joshiiitr@gmail.com, anuj20.g@samsung.com, gost.dev@samsung.com References: <20220711110155.649153-1-joshi.k@samsung.com> <20220711110155.649153-4-joshi.k@samsung.com> <2b644543-9a54-c6c4-fd94-f2a64d0701fa@kernel.dk> From: Sagi Grimberg In-Reply-To: <2b644543-9a54-c6c4-fd94-f2a64d0701fa@kernel.dk> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org >> Use the leftover space to carve 'next' field that enables linking of >> io_uring_cmd structs. Also introduce a list head and few helpers. >> >> This is in preparation to support nvme-mulitpath, allowing multiple >> uring passthrough commands to be queued. > > It's not clear to me why we need linking at that level? I think the attempt is to allow something like blk_steal_bios that nvme leverages for io_uring_cmd(s). nvme failover steals all the bios from requests that fail (and should failover) and puts them on a requeue list, and then schedules a work that takes these bios one-by-one and submits them on a different bottom namespace (see nvme_failover_req/nvme_requeue_work).