From owner-freebsd-geom@freebsd.org Fri Nov 24 13:08:10 2017 Return-Path: Delivered-To: freebsd-geom@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 1CDC2DE50D9 for ; Fri, 24 Nov 2017 13:08:10 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: from mail-io0-x22f.google.com (mail-io0-x22f.google.com [IPv6:2607:f8b0:4001:c06::22f]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id C8A9B73C3E for ; Fri, 24 Nov 2017 13:08:09 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: by mail-io0-x22f.google.com with SMTP id i38so29543369iod.2 for ; Fri, 24 Nov 2017 05:08:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bsdimp-com.20150623.gappssmtp.com; s=20150623; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc; bh=wOUgQZRszG2Cc8EXcF4I4ct1fBYHQfUdMYXIWs+F+kM=; b=isUkA4ECI3JesPLAYxUKKYXeVMi2zrx/o0OP8GdV9QaT6lGbmir4UFVIyNYDzeWoK4 +Gh2PDDBVRyQhALliKCbNPQLYwW5g0o4avQoA84U/EKvj8J3LcVpDh5H8n2iVv+rwCd5 T+fNeh0gVujBdYv16TG9dlsP8zhzc4MEl+yoGn3W+a1c4UdBEQuocPLoe46snTPi73fw wTCbX1qijQhDWL/aQz2REYg8qYM77zxui9siy77UlEQPzKF2nGzNCbDj8mlmgbX2fAY/ wLWvj0afhHXsnq32X67GK7ksGpZ2PMec9riGRPI7fCJvhW1zTI+msQ2pYO78iaOaYVcv S3bg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:cc; bh=wOUgQZRszG2Cc8EXcF4I4ct1fBYHQfUdMYXIWs+F+kM=; b=iXUcyquR3YgrG0a+JQGyt68Kovlq18Cl7yggq7ALk5wwPCyj7f8ob0Wbu/2lgU12rD MVg1uBy2LD534B4PUPNS4NAtUoAAmUvtUOU226AtZ1bQ5pHnxBCkP3/yGeZ0kTGpLWPM aZhfssjCpuZEYVZHpi7VVmHcw0oN25qzzxpiUaLMiUIsBZ8tWrNR5s3t9gNJKwIG6WY5 SSa9nby+X5bArjuZWV5joZqpRVNoVfUWIJtk99wru6z2jq7W0wwrTyJdCcgik0vZITUq 15fdDFG+1xy0JXG6XnbnF5Snp4tRLWdIbZrNXhS5Ij/6lCTVLhHRSYs673OHcX1GkbDl vT7w== X-Gm-Message-State: AJaThX7GCM4tEEZ079Dp6SCDBinz3o7koEfIlHs4+mPwuQ5e5fG1VsMz hganxeA7zvqEs5nXBvVntaC5fmy1uhzBvCtrHWlMSQ== X-Google-Smtp-Source: AGs4zMY4MoBgdZFANsotjdt+Pxukf0cEindNxrZgT9zCGlGViUGX63RvX4ZZmzK0IC5ZT5xNwZUl0/rOkuCUehmtndY= X-Received: by 10.107.104.18 with SMTP id d18mr28887141ioc.136.1511528888799; Fri, 24 Nov 2017 05:08:08 -0800 (PST) MIME-Version: 1.0 Sender: wlosh@bsdimp.com Received: by 10.79.108.204 with HTTP; Fri, 24 Nov 2017 05:08:08 -0800 (PST) X-Originating-IP: [2603:300b:6:5100:f964:7c3e:d2:aac5] In-Reply-To: <391f2cc7-0036-06ec-b6c9-e56681114eeb@FreeBSD.org> References: <391f2cc7-0036-06ec-b6c9-e56681114eeb@FreeBSD.org> From: Warner Losh Date: Fri, 24 Nov 2017 06:08:08 -0700 X-Google-Sender-Auth: tj7KN5Upw_bTsDr4uHtec8Eefns Message-ID: Subject: Re: add BIO_NORETRY flag, implement support in ata_da, use in ZFS vdev_geom To: Andriy Gapon Cc: FreeBSD FS , freebsd-geom@freebsd.org, Scott Long Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.25 X-BeenThere: freebsd-geom@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: GEOM-specific discussions and implementations List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 24 Nov 2017 13:08:10 -0000 On Fri, Nov 24, 2017 at 3:30 AM, Andriy Gapon wrote: > > https://reviews.freebsd.org/D13224 > > Anyone interested is welcome to join the review. > I think it's a really bad idea. It introduces a 'one-size-fits-all' notion of QoS that seems misguided. It conflates a shorter timeout with don't retry. And why is retrying bad? It seems more a notion of 'fail fast' or so other concept. There's so many other ways you'd want to use it. And it uses the same return code (EIO) to mean something new. It's generally meant 'The lower layers have retried this, and it failed, do not submit it again as it will not succeed' with 'I gave it a half-assed attempt, and that failed, but resubmission might work'. This breaks a number of assumptions in the BUF/BIO layer as well as parts of CAM even more than they are broken now. So let's step back a bit: what problem is it trying to solve? Warner