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 AF6C7C43334 for ; Wed, 13 Jul 2022 09:04:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235971AbiGMJEC (ORCPT ); Wed, 13 Jul 2022 05:04:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49058 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235975AbiGMJD5 (ORCPT ); Wed, 13 Jul 2022 05:03:57 -0400 Received: from mail-wr1-f45.google.com (mail-wr1-f45.google.com [209.85.221.45]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 898B232ECF; Wed, 13 Jul 2022 02:03:52 -0700 (PDT) Received: by mail-wr1-f45.google.com with SMTP id bu1so13364749wrb.9; Wed, 13 Jul 2022 02:03:52 -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=D4vlOUSuSK+FhTh9wftzc20mzgHbEI0vkhcBDU8k6o0=; b=61Ehp2S/6mBp04O9832ppzlcal3T/AMVdXruNV078bPFFWj4PQxgHxf/cxsYPYeIS6 LOE4xvBRhtyzt2u8nSCD5htUKiVzURhHw/fPcGr0SlMr2x85SFVyOrvyCvs+Anfi/uKk Ff+GvrUlMV5E9i+fmv5OoncNmIbzRiTWDNF3P088ze/WcLIa4jjRT+qPqk4hETJOn1pX dzWx2HLofeWl1xdMHArzjnu9hRvTmDeOJ/V5NS8fIqMGJ8Mta3xIuTOlIxHoD9KbXbu4 Ltb1Qe9UlvtWgYt3bvAQ/newE9YUnF+LFR2N+RDQBCHn5dJPhROO1xJjRD+v29KkbtrX DmoQ== X-Gm-Message-State: AJIora85+EfsDxnhZl2wM+NLILSYUCYeqoPklLg62fufPLzHt3Pg3xUM LvtdzEhvXwXQpY4tGLvq0NY= X-Google-Smtp-Source: AGRyM1sUOndfxHpFDhmMn2Ko7HTQ1cbOP4ustw2mw9OA5suipI6Gdfvjnx8Gk5ApYqYcu1YToSzZJQ== X-Received: by 2002:adf:fb83:0:b0:21d:649a:72d9 with SMTP id a3-20020adffb83000000b0021d649a72d9mr1986938wrr.688.1657703031143; Wed, 13 Jul 2022 02:03:51 -0700 (PDT) Received: from [192.168.64.180] (bzq-219-42-90.isdn.bezeqint.net. [62.219.42.90]) by smtp.gmail.com with ESMTPSA id i2-20020a05600011c200b0021d68a504cbsm10344745wrx.94.2022.07.13.02.03.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 13 Jul 2022 02:03:50 -0700 (PDT) Message-ID: Date: Wed, 13 Jul 2022 12:03:48 +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 4/4] nvme-multipath: add multipathing for uring-passthrough commands Content-Language: en-US To: Kanchan Joshi Cc: hch@lst.de, kbusch@kernel.org, axboe@kernel.dk, 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> <20220711110155.649153-5-joshi.k@samsung.com> <3fc68482-fb24-1f39-5428-faa3a8db9ecb@grimberg.me> <20220711183746.GA20562@test-zns> <5f30c7de-03b1-768a-d44f-594ed2d1dc75@grimberg.me> <20220712042332.GA14780@test-zns> <3a2b281b-793b-b8ad-6a27-138c89a46fac@grimberg.me> <20220713053757.GA15022@test-zns> From: Sagi Grimberg In-Reply-To: <20220713053757.GA15022@test-zns> 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 >> However io_kiocb is less >> constrained, and could be used as a context to hold such a space. >> >> Even if it is undesired to have io_kiocb be passed to uring_cmd(), it >> can still hold a driver specific space paired with a helper to obtain it >> (i.e. something like io_uring_cmd_to_driver_ctx(ioucmd) ). Then if the >> space is pre-allocated it is only a small memory copy for a stable copy >> that would allow a saner failover design. > > I am thinking along the same lines, but it's not about few bytes of > space rather we need 80 (72 to be precise). Will think more, but > these 72 bytes really stand tall in front of my optimism. You don't have to populate this space on every I/O, you can just populate it when there is no usable path and when you failover a request...