From owner-freebsd-fs@freebsd.org Fri Nov 24 13:08:10 2017 Return-Path: Delivered-To: freebsd-fs@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 1D279DE50DA for ; Fri, 24 Nov 2017 13:08:10 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: from mail-io0-x232.google.com (mail-io0-x232.google.com [IPv6:2607:f8b0:4001:c06::232]) (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 C8B3C73C3F for ; Fri, 24 Nov 2017 13:08:09 +0000 (UTC) (envelope-from wlosh@bsdimp.com) Received: by mail-io0-x232.google.com with SMTP id q101so29487591ioi.1 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=r7yLEAzNHtUXBPZjdsUXJpUvGyBHJPwGEL/uMxUcek4HRHfwVl89SFP+9vlTK9S7ro UIEnjCHr5961NiSAleI8o+SnIYymGlrGm/+kQltV+iB0+TIrWk4b+WRqIy56eIL6XIOW 0Xw+bzKRA1en+e+gb5LzXbSxIipkNLlc9gQQGuPEdYa1CFYzERfkmHtdcA/atodw/y8D InKzXYhUrXhw7Bk0JTk0E4gNlUxK4prxcVixPU5Bt8GanKh+rrOSlv+o8sZnG+2ot0np rxpXJh7S2HGrJ54IgbwEUwED284jn+BvooEssmo8F3Pn7LIEkIrKyu5wLes+3KlHa5J4 S5jQ== X-Gm-Message-State: AJaThX6QJaTSErvrlKg3uZhTb01vGgtvWE8zxqCHvYAt7rn6wZdLSAb0 9DVsyqGEtmaQkEsbZ7jurzwNEG7DlpKwPbeH2hROwQ== 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-fs@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: Filesystems 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