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 3B475C433FE for ; Tue, 28 Dec 2021 21:30:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237358AbhL1VaP (ORCPT ); Tue, 28 Dec 2021 16:30:15 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]:32725 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236380AbhL1VaP (ORCPT ); Tue, 28 Dec 2021 16:30:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1640727011; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=A/YdqQbiYan/8puYBvi5XsqHp47yRlJpMdsMFPVf0MI=; b=Q+NK/Z9G+5/MEUvHMUidRXZ1iLqUp8yCyyW5228ng0UhrVZ3aNwxyFyhDAEMSAs/8ilE42 tHt97ld62YdcRDQ4Nm42L85DC+Dc0w4VePFinqR3tsQ0J4QL2+eCQOfT0Q6gce7zkciUe0 jfJsR5gmgB5vtossIuB3QauqsDKiJas= Received: from mail-qv1-f69.google.com (mail-qv1-f69.google.com [209.85.219.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-215-3A3vF876NFqmBuMcQvEsKA-1; Tue, 28 Dec 2021 16:30:10 -0500 X-MC-Unique: 3A3vF876NFqmBuMcQvEsKA-1 Received: by mail-qv1-f69.google.com with SMTP id 13-20020a0562140d0d00b00411590233e8so15473470qvh.15 for ; Tue, 28 Dec 2021 13:30:10 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=A/YdqQbiYan/8puYBvi5XsqHp47yRlJpMdsMFPVf0MI=; b=niKoJq9CwxGlJKqmAxF9pkXK7+FwbfGSRAWcdMy6HJOAO+5wDnSvAehpGsEMiUqcRt p3j1eYJLuqhSjCu0c3ERnqP3c2A8JJEiWxW/QEp0ahhwU9zVPh5zLQpqCUh3VJ6K08jm t4fFG32UJRPCd6SDLc8EPS4mFYp5eteqrjtcxIx5ZwgUhNlvPryEd3ValB5KTOzcOiJe 10x1xYvKvsJ7caFWdFkgGFNhPIJff7Fgmg4mZJAyTNRo43/wG8rWqIuFwKMf1IfgTD/m llwQvGmYYTvgKL+yzRykv645rF6XJDJsz1bSSSruZ8onoFNuFanBd8bZ/GZtEfVhZHpx wzOA== X-Gm-Message-State: AOAM533JQdirTNbWm9MOc7lQ+iTn8HKi5e6KpbFEHgoxjkAFW9RVG1BE SMYBTCpUmLTdVoY8zj46Y2Kg+7biarKjoTvEaKU4fHR+YwxohU9wmkPmEIGo+5fgkakF7tPI6jn UFMBUHCf/aAMYHlIyYmXnHQ== X-Received: by 2002:a05:6214:21ae:: with SMTP id t14mr20997602qvc.36.1640727010237; Tue, 28 Dec 2021 13:30:10 -0800 (PST) X-Google-Smtp-Source: ABdhPJzfEjMfPqR60C5of2U4nOV8i5dTSbhNYRsXcPJ5AM9RUqI3+1pyKKK7TeYmr4kflXNZSC7gQg== X-Received: by 2002:a05:6214:21ae:: with SMTP id t14mr20997592qvc.36.1640727010045; Tue, 28 Dec 2021 13:30:10 -0800 (PST) Received: from localhost (pool-68-160-176-52.bstnma.fios.verizon.net. [68.160.176.52]) by smtp.gmail.com with ESMTPSA id u6sm16668245qki.129.2021.12.28.13.30.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Dec 2021 13:30:09 -0800 (PST) Date: Tue, 28 Dec 2021 16:30:08 -0500 From: Mike Snitzer To: Ming Lei Cc: Christoph Hellwig , Jens Axboe , linux-block@vger.kernel.org, dm-devel@redhat.com Subject: Re: [PATCH 0/3] blk-mq/dm-rq: support BLK_MQ_F_BLOCKING for dm-rq Message-ID: References: <20211221141459.1368176-1-ming.lei@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Dec 22 2021 at 11:16P -0500, Ming Lei wrote: > On Tue, Dec 21, 2021 at 08:21:39AM -0800, Christoph Hellwig wrote: > > On Tue, Dec 21, 2021 at 10:14:56PM +0800, Ming Lei wrote: > > > Hello, > > > > > > dm-rq may be built on blk-mq device which marks BLK_MQ_F_BLOCKING, so > > > dm_mq_queue_rq() may become to sleep current context. > > > > > > Fixes the issue by allowing dm-rq to set BLK_MQ_F_BLOCKING in case that > > > any underlying queue is marked as BLK_MQ_F_BLOCKING. > > > > > > DM request queue is allocated before allocating tagset, this way is a > > > bit special, so we need to pre-allocate srcu payload, then use the queue > > > flag of QUEUE_FLAG_BLOCKING for locking dispatch. > > > > What is the benefit over just forcing bio-based dm-mpath for these > > devices? > > At least IO scheduler can't be used for bio based dm-mpath, also there should > be other drawbacks for bio based mpath and request mpath is often the default > option, maybe Mike has more input about bio vs request dm-mpath. Yeah, people use request-based for IO scheduling and more capable path selectors. Imposing bio-based would be a pretty jarring workaround for BLK_MQ_F_BLOCKING. request-based DM should properly support it. I'm on vacation for the next week but will have a look at this patchset once I'm back. Thanks, Mike