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 AC978C433F5 for ; Wed, 27 Oct 2021 15:40:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8AAD560F5A for ; Wed, 27 Oct 2021 15:40:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238707AbhJ0PnP (ORCPT ); Wed, 27 Oct 2021 11:43:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60866 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242768AbhJ0PnO (ORCPT ); Wed, 27 Oct 2021 11:43:14 -0400 Received: from mail-il1-x129.google.com (mail-il1-x129.google.com [IPv6:2607:f8b0:4864:20::129]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 186C1C061745 for ; Wed, 27 Oct 2021 08:40:49 -0700 (PDT) Received: by mail-il1-x129.google.com with SMTP id s3so3480018ild.0 for ; Wed, 27 Oct 2021 08:40:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20210112.gappssmtp.com; s=20210112; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=1V1b8qzpm7KUEUWbM52utQU6szAcV/XqEuLa0wDBSso=; b=ho7pnJHOtwg7DA+HL85whEzTNOdbNGMl4RWqCIl3Ow9CbkQPsK0lBHELBKHAQpCO42 CIL2z7UB0oRxtGXnowDj92d1pFOsT3qwtIMo8a0dxfVK9WV7CaE3i9b4w/+7OuI6wkQX WPuxQKE2aPoChkMB2z8EmY+eNwJP3R23/71wggVL+7koP6uvKIcV8srUCx8hmG3MtBsT p8gPYqx1f6NpPBRAM6ByaJfZ1z32AyJa4faYmLemWN6q2a/hUfvCPcCmsxj1E4l+reis lbgyOcEq9mabnPodPFBM4pnPK5JaXIQrCRjrjmERxWoACPpcwnBh0uvG0stRPcn3nL6r RQ5Q== 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=1V1b8qzpm7KUEUWbM52utQU6szAcV/XqEuLa0wDBSso=; b=RjUf1fUqA04FdU41jU1z8dfm5fycGywXwOVCqG7XVZTLYoZUi+sXL9JEF5InlgdElr vCUCNBkY3szHdEkgauDjtVA4xfKEcm4UH7iNDcV7r2vEBIPKvVqPsyRe7LzPet1AB4up Wrl9WVjsQEWY3FgIKLUax3964lkK5P0+6W5DKDV/0H2KkiO4A5ruMFrmMKWfZKEUYu/F US9w4dKF4Szxo+ywvYEayP3CaZvQiHGjE9STYgoAcT7WN88t4P5oj4MM6g3xCbJsrgr8 IjDCkwLkqMOGPhBbJqQH2iFV5C1WN2LclEKJHV0UVexBPizu9EVsAwQBL6zAsPvCK6NL Ae9Q== X-Gm-Message-State: AOAM533HiwYGecUB60JGggTz4ziL20AQ9XMdk8WEeWNzzp3BPevFidrs FVQm7Nbd9XMYFE5IsxWZBGdVWQ8IUlJkMA== X-Google-Smtp-Source: ABdhPJwyqvDvFLJiP96Yg+atN/QWg96a8D73xASHMazQaiG7s6okBkrAC+ZeWvEorA/DQ/V/hkXVNg== X-Received: by 2002:a92:6408:: with SMTP id y8mr20048661ilb.34.1635349248056; Wed, 27 Oct 2021 08:40:48 -0700 (PDT) Received: from [192.168.1.30] ([207.135.234.126]) by smtp.gmail.com with ESMTPSA id m7sm149192ilu.58.2021.10.27.08.40.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 27 Oct 2021 08:40:45 -0700 (PDT) Subject: Re: [PATCH] scsi: ufs: mark HPB support as BROKEN To: "Martin K. Petersen" Cc: Ming Lei , Keith Busch , Bart Van Assche , Christoph Hellwig , James Bottomley , Jaegeuk Kim , alim.akhtar@samsung.com, avri.altman@wdc.com, linux-scsi@vger.kernel.org, linux-block@vger.kernel.org References: <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> <20211027141231.GA2338303@dhcp-10-100-145-180.wdc.com> <3f43feaa-5c3a-9e4c-ebc1-c982b0723e7e@kernel.dk> From: Jens Axboe Message-ID: Date: Wed, 27 Oct 2021 09:40:42 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 10/27/21 9:35 AM, Martin K. Petersen wrote: > > Jens, > >> But yes, reuse of the existing request is probably another potentially >> viable approach. My worry there is that inevitably you end up needing >> to stash a lot of data to restore the original, and we're certainly >> not adding anything to struct request for that. > > Yeah, I much prefer the reserved tag approach. That was my original > recommendation. > > SCSI error handling does command hijacking and it is absolutely > dreadful. Then let's make sure we nudge it in that direction! It'd be feasible to have less reserved tags, you only need as many as you want to have these special commands inflight. Post that, returning BUSY and just retrying when a request completes should be fine. Hence I'd size the reserved tag pool appropriately depending on what kind of performance is expected out of this, with just 1 reserved tag being enough to give us the guarantees we need for forward progress. I think the plan forward is clear here then: 1) Revert the optimization that requires the use of cloned insert for 5.15. 2) Re-write the optimization using reserved tags, post 5.15 obviously. -- Jens Axboe