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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4F8ADC433EF for ; Wed, 27 Oct 2021 13:16:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2E7EF60F6F for ; Wed, 27 Oct 2021 13:16:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237051AbhJ0NSs (ORCPT ); Wed, 27 Oct 2021 09:18:48 -0400 Received: from mail-pf1-f177.google.com ([209.85.210.177]:45642 "EHLO mail-pf1-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236464AbhJ0NSs (ORCPT ); Wed, 27 Oct 2021 09:18:48 -0400 Received: by mail-pf1-f177.google.com with SMTP id f11so2681383pfc.12; Wed, 27 Oct 2021 06:16:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=RxGdKvpK4OULd8cS2o0dRz2hnuGIH9NxZACigE+2c3o=; b=0hJU7OYJ57SKm6TwWg4o2uMAwYWTRHCwQSnuTi0wm+q8s7W4ISGRbtFrTdGnao6/MF 5NLbmDusZsIolJaSmyIEJTR4fuiP78zt0r6JE5ptppO8yRbGIPqnNJGDb+oS8wqqtNKW ElQu8ZdMJjyUHqreYagz1pA2VXTL0e1a26Hnp703fLgIqnIFVTBeTC7svX1eeMOC5kjF +mDnfpo8Er2QpSI+AI00KSvriZfKMpyLyohnW2WXivC5oI9uvkK6Twzh7tw8YznkMRm7 q2uQX9Dm1yWRKYa4NdgXB7rZihrQA0MUKQOAALVPExwrmW/j8lka025VzliWzF9CE0nX XF5Q== X-Gm-Message-State: AOAM532vmPS+bUvm9uZI7FzBNASr0o6hP9GrSIYeQwXl/U1i1MUen0nS fn9uwab6qx/vygDr7b583J9gBeML1eo= X-Google-Smtp-Source: ABdhPJwQuj8Y+OK3dVAEU+H0eFs40hz4YLj2tBsARNnGsRdeT2i6wXcAZBZ2XmC0rwYKEQ5bCsuDKg== X-Received: by 2002:aa7:8246:0:b0:44b:4870:1b09 with SMTP id e6-20020aa78246000000b0044b48701b09mr33249471pfn.82.1635340581882; Wed, 27 Oct 2021 06:16:21 -0700 (PDT) Received: from [192.168.51.110] (c-73-241-217-19.hsd1.ca.comcast.net. [73.241.217.19]) by smtp.gmail.com with ESMTPSA id t22sm7404113pfg.63.2021.10.27.06.16.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Oct 2021 06:16:20 -0700 (PDT) Subject: Re: [PATCH] scsi: ufs: mark HPB support as BROKEN To: Christoph Hellwig Cc: "Martin K. Petersen" , James Bottomley , Jens Axboe , Jaegeuk Kim , alim.akhtar@samsung.com, avri.altman@wdc.com, linux-scsi@vger.kernel.org, linux-block@vger.kernel.org References: <20211026071204.1709318-1-hch@lst.de> <99641481-523a-e5a9-db48-dac2b547b4bd@acm.org> <7ed11ee1f8beca9a27c0cb2eb0dcea4dbd557961.camel@HansenPartnership.com> <870e986c-08dd-2fa2-a593-0f97e10d6df5@kernel.dk> <4438ab72-7da0-33de-ecc9-91c3c179eca7@acm.org> <36729509daa80fd48453e8a3a1b5c23750948e6c.camel@HansenPartnership.com> <679b4d3b-778e-47cd-d53f-f7bf77315f7c@acm.org> <20211027052724.GA8946@lst.de> From: Bart Van Assche Message-ID: Date: Wed, 27 Oct 2021 06:16:19 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20211027052724.GA8946@lst.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 10/26/21 10:27 PM, Christoph Hellwig wrote: > On Tue, Oct 26, 2021 at 01:10:47PM -0700, Bart Van Assche wrote: >> If blk_insert_cloned_request() is moved into the device mapper then I >> think that blk_mq_request_issue_directly() will need to be exported. > > Which is even worse. > >> How >> about the (totally untested) patch below for removing the >> blk_insert_cloned_request() call from the UFS-HPB code? > > Which again doesn't fix anything. The problem is that it fans out one > request into two on the same queue, not the specific interface used. That patch fixes the reported issue, namely removing the additional accounting caused by calling blk_insert_cloned_request(). Please explain why it is considered wrong to fan out one request into two. That code could be reworked such that the block layer is not involved as Adrian Hunter explained. However, before someone spends time on making these changes I think that someone should provide more information about why it is considered wrong to fan out one request into two. Thanks, Bart.